F l o r i d a H o s p i t a l f o r C h i l d r e n

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Alicia Kleinhans BSN RN CCRN CEN A guide for PICU nurses. Includes neurology anatomy, physiology, epilepsy and surgical interventions

Pediatric Epilepsy and Neurosurgery

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Table of Contents

Objectives 5

Pediatric Neuro Anatomy & Physiology 6

Pediatric Neurological Assessment 12

Pediatric Epilepsy 18

Surgical Options and Brain Mapping 21

Neurosurgery for Epilepsy 27

Neurosurgery Post-Op Care 29

References 31

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Objectives

Pediatric Neurology is a very challenging system to understand with a great variety of disease processes, trauma, and developmental factors to consider. This self study packet was created to assist the PICU nurse in caring for pediatric epilepsy and neurosurgery patients. After reading the material please complete the post test and return to the unit educator. The objectives are for the learner to gain knowledge and comprehension of this complicated system including:

• Name the major structures of the brain and describe normal CSF flow

• Describe the sympathetic and parasympathetic nervous system

• List the three components of the cranial vault contents

• Define epilepsy

• State treatment for status epilepticus

• Compare anti-epileptic medications

• State post-op treatment for craniotomy patient

• Define the Monroe Kellie Doctrine

• Identify three early signs of increased ICP and state the treatment

• Relate the initial set up for an External Ventricular Drain

• Recite method for contacting physicians regarding neuro-epilepsy patient problems

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Neuro Anatomy and Physiology

The human brain is the most complex and least understood part of the human anatomy. There may be a lot we don’t know, but here are a few interesting facts that we’ve got covered:

• Nerve impulses to and from the brain travel as fast as 170 miles per hour. You can react fast to things around you and a stubbed toe hurts right away due to the super-speedy movement of nerve impulses.

• The human brain cell can hold 5 times as much information as the Encyclopedia Britannica. Scientists have yet to settle on a definitive amount, but the storage capacity of the brain in electronic terms is thought to be between 3 or even 1,000 terabytes. The National Archives of Britain, containing over 900 years of history, only takes up 70 terabytes.

• Your brain uses 20% of the oxygen that enters your bloodstream. The brain only makes up about 2% of our body mass, yet consumes more oxygen than any other organ in the body, making it extremely susceptible to damage related to oxygen deprivation.

• The brain is much more active at night than during the day. Logically, you would think that all the moving around, complicated calculations and tasks and general interaction we do on a daily basis during our working hours would take a lot more brain power than, say, lying in bed. Turns out, the opposite is true.

• Scientists say the higher your I.Q. the more you dream. While this may be true, most of us don’t remember many of our dreams and the average length of most dreams is only 2-3 seconds.

• Neurons continue to grow throughout human life. While it doesn’t act in the same manner as tissues in many other parts of the body, neurons can and do grow throughout your life, adding a whole new dimension to the study of the brain and the illnesses that affect it.

• Information travels at different speeds within different types of neurons. Not all neurons are the same. There are a few different types within the body and transmission along these different kinds can be as slow as 0.5 meters/sec or as fast as 120 meters/sec.

• The brain itself cannot feel pain. While the brain might be the pain center when you cut your finger or burn yourself, the brain itself does not have pain receptors and cannot feel pain. The brain is surrounded by loads of tissues, nerves and blood vessels that are plenty receptive to pain and can give you a pounding headache.

• 80% of the brain is water. Your brain isn’t the firm, gray mass you’ve seen on TV. Living brain tissue is a squishy, pink and jelly-like organ thanks to the loads of blood and high water content of the tissue.

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The neurological system serves three main functions including receiving sensory input from internal and external environments, interpreting the information, responding to stimuli. It can be broken down into two main divisions: central and peripheral. The central nervous system includes the brain and spinal cord. The peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system.

Our focus in this learning module will be on the central nervous system component, the brain. The brain sits inside a cranial vault that most people call the skull. The cranial vault has several different bone plates that are separate in infants but fuse together in early childhood. These bone plates later define the areas of the cranial vault and include the frontal, parietal, temporal and occipital areas (fig 1). Within the cranial vault lie the brain, blood and cerebral spinal fluid.

The Brain:

The adult brain weighs about 3 pounds and is comprised of several components (table 1).

Component Main Function Two cerebral hemispheres make the cerebrum

Receive, interpret and respond to stimuli

Hypothalamus Production and secretion of TRH, Somatostatin, pituitary releasing hormones

Pituitary Gland Secretion of TSH, Growth Hormone, ADH, ACTH, LH and FSH

Corpus Callosum Communication between left and right cerebral hemispheres, eye movement, maintaining the balance of attention and arousal, tactile localization

4 fluid filled ventricles Circulation and re-absorption of CSF, regulation of Intracranial pressure

Choroid Plexus Production of CSF Cerebellum Coordinated movement Brain Stem Exit of cranial nerves from the brain to system,

regulation of breathing and heart rate

Figure 1

Table 1

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Both the brain and spinal cord are covered in three continuous sheets of connective tissue, the meninges. From outside in, these are the

dura mater — pressed against the bony surface of the interior of the vertebrae and the cranium

the arachnoid the pia mater

The region between the arachnoid and pia mater is filled with arteries, vasculature and cerebrospinal fluid (CSF).

The vascular system of the brain is developed differently than vasculature in any other organ in the body. The circulation of blood in the brain is designed to maintain adequate oxygen delivery to the tissues even under extreme circumstances. The brain consumes 20% of all oxygen in the body and computes and responds to almost 7o terabytes of information every day even when you are asleep. It is the one system that controls it all with high metabolic needs so it makes sense that it would need a complicated circulatory system.

Blood is supplied to the entire brain by 2 pairs of arteries: the internal carotid arteries and vertebral arteries. The right and left vertebral arteries come together at the base of the brain to form a single basilar artery. The basilar artery joins the blood supply of the internal carotid arteries in a ring at the base of the brain. This ring of arteries is called the circle of Willis. The circle of Willis provides a safety mechanism...if one of the arteries gets blocked, the "circle" will still provide the brain with blood

Figure 2

Figure 3

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CSF, cerebral spinal fluid is produced in the choroid plexus in the ventricles. It circulates from the lateral ventricles to the foramen of Monro (Interventricular foramen), third ventricle, aqueduct of Sylvius (Cerebral aqueduct), fourth ventricle, foramen of Magendie (Median aperture) and foramina of Luschka (Lateral apertures); subarachnoid

space over brain and spinal cord. It serves to cushion the brain and the spinal cord, provide chemical stability and regulate ICP. The flow of CSF and absorption into the bloodstream rinses the metabolic waste from the central nervous system through the blood-brain barrier. This allows for homeostatic regulation of the distribution of neuroendocrine factors, to which slight changes can cause problems or damage to the nervous system

Different parts of the cerebral cortex are involved in different cognitive and behavioral functions. These areas can be mapped by basic or sophisticated means. The most widely used basic map of cortical areas came from Brodmann, who split the cortex into 51 different areas and assigned each a number. Brodmann areas were originally defined and numbered in 1909 by the German anatomist Korbinian Brodmann based on the organization of neurons he observed in the cerebral cortex using the Nissl stain

The cerebellum (Latin for little brain) plays an important role in motor control. The cerebellum does not initiate movement, but it contributes to coordination, precision, and accurate timing. It has the appearance of a separate structure attached to the bottom of the brain, tucked underneath the cerebral hemispheres.

covered with finely spaced parallel grooves actually a continuous thin layer of tissue (the cerebellar cortex), tightly folded in the

style of an accordion. Within this thin layer are several types of neurons with a highly regular arrangement,

the most important being Purkinje cells and granule cells. complex neural network gives rise to a massive signal-processing capability, but almost

all of its output is directed to a set of small deep cerebellar nuclei lying in the interior of the cerebellum

Figure 4

Figure 5

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It works as a feedback loop for muscle movement. When the cortex sends a message for motor movement to the lower motor neurons in the brain stem and spinal cord it also sends a copy of this message to the cerebellum. Information also gets to the cerebellum from muscle spindles, joints and tendons. This information (proprioception and kinesthesia) lets the cerebellum know about the movements that have been executed, so that it can determine how well motor commands coming from the cortex are being carried out. This is called its comparator function

The brainstem is the region of the brain that connects the cerebrum with the spinal cord. It consists of the midbrain, medulla oblongata, and the pons. Motor and sensory neurons travel through the brainstem allowing for the relay of signals between the brain and the spinal cord. The brainstem coordinates motor control signals sent from the brain to the body. The brainstem also controls life supporting functions of autonomic nervous system

Alertness Arousal Breathing Blood Pressure Digestion Heart Rate

Figure 6

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To examine your patient’s neurological status, it’s important to understand basic functions of the sympathetic and parasympathetic divisions of the autonomic nervous system. The sympathetic division is what produces the “fight or flight” response to stressors on your body.

There are two kinds of neurons involved in the transmission of any signal through the sympathetic division; pre- and post- ganglionic. The shorter preganglionic neurons originate from the thoracolumbar region of the spinal cord (levels T1 - L2, specifically) and travel to a ganglion, often one of the paravertebral ganglia, where they synapse with a postganglionic neuron. From there, the long postganglionic neurons extend across most of the body.[3]

At the synapses within the ganglia, preganglionic neurons release acetylcholine, a neurotransmitter that activates nicotinic acetylcholine receptors on postganglionic neurons. In response to this stimulus postganglionic neurons - with two important exceptions - release norepinephrine, which activates adrenergic receptors on the peripheral target tissues. The activation of target tissue receptors causes the effects associated with the sympathetic division.[4

The effects seen on examination of a patient with a sympathetic response include:

The parasympathetic division works to compliment the sympathetic division and promote “rest and digest.” The parasympathetic nervous system uses chiefly acetylcholine (ACh) as its neurotransmitter, although peptides (such as cholecystokinin) may act on the PSNS as a neurotransmitter. The ACh acts on two types of receptors, the muscarinic and nicotinic receptors. Most transmissions occur in two stages: When stimulated, the preganglionic nerve releases ACh at the ganglion, which acts on nicotinic receptors of postganglionic neurons. The postganglionic nerve then releases ACh to stimulate the muscarinic receptors of the target organ.

Figure 7

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Effects of the parasympathetic nervous system can be seen as opposite to the sympathetic division.

When assessing your patient, keep in mind the two divisions of the autonomic nervous system and their effects on the body. If you recognize a sympathetic or parasympathetic response, you would know how to counteract it.

Pediatric Neurological Assessment

A basic Neurological assessment always begins with the “across the room” assessment of your patient’s level of consciousness. Does the patient appear alert, sitting up in the bed and participating in conversation or activity? Is the patient resting with their eyes closed which requires further examination to determine level of consciousness and Glasgow Coma Score? The definitions for level of consciousness can be confusing to some and are summarized in the following table (table2).

Level of Consciousness Definition Alert Eyes open, follows commands, sucks on a pacifier Confused Not able to think rapidly and clearly; impaired judgement Disoriented Decreased wakefulness, alternates between lethargy and

excitability Lethargis Sleeps often, arouses to shaking or shouting Obtunded Responds to vigorous shaking, increased periods of sleep Stupor Responds only to pain, reflex movements Coma No response, abnormal reflexes, flaccid tone

Figure 8

Table 2

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The Glasgow Coma Scale (GCS) has been the gold standard of neurologic assessment for trauma patients since its development by Jennett and Teasdale in the early 1970s. The GCS was found to be a simple tool to use. Since that time, the scale has been implemented as an assessment tool in many varied clinical areas. There have been modifications made to the scale to be utilized for infants and children whom are not able to verbalize like adults. Since the GCS has been proven reliable and most practitioners can relate a score to a patient’s neurological status, it can be a useful tool for communication among interdisciplinary team members.

A full and complete neurological exam includes all of the following as well as an assessment of cranial nerve functions:

– GCS – Mental state: level of consciousness – Stimulus for arousal: AVPU – Mood: anxious, restless, calm – Behavior: appropriate, paranoid – Speech: clear, slurred, coherent – Extremity strength and movement: weakness or uncoordinated movement (cerebellum) – Gait: steady, unsteady, uncoordinated – Cry: weak, high-pitched – Fontanel: sunken, bulging, flat, soft, tense – Coordinated movement (cerebellar function): finger to nose, heel to shin

Table 3

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Cranial nerve assessment in most cases does not examine all 12 of the cranial nerves. Usually we are focused on cranial nerve II, III, VII and occasionally IV and IX. The correlation to these nerves and our clinical exam are summarized on table 3.

Cranial Nerve Name Assessment II Optic Pupillary reflex III Oculomotor Extraocular movements and pupil constriction IV Trigeminal Corneal Reflex VII Facial Facial Droop IX Glossopharyngeal Gag Reflex

Examining these cranial nerves tells us if there is severe damage, edema, ischemia or masses in the brain pressing on the cranial nerves. For example diffuse increased intracranial pressure will press on the cranial nerves and impede their function. On examination this could be seen as dilated, sluggish or fixed pupils and absence of reflexes in severe cases. Any change in your patient’s cranial nerve assessment is serious and warrants communication with Intensivist, neurologist and/or neurosurgeon on the case as well as clear and detailed documentation.

Pupils should be assessed every 2 hours for ICU patients. There are times when neuro checks are ordered every hour and a full neuro assessment should be completed every time and documented. To assess pupils, we shine a light in the patients’ eyes and look to see size, shape and reaction. Pupils should be equal, round, react to light, in the same direction and not moving. Below are some definitions of things you may find on examination of pupils.

• Bilateral fixed and dilated pupils are secondary to inadequate cerebral perfusion, usually indicate an irreversible injury.

• A unilateral fixed and dilated pupil has many potential causes. A pupil that is dilated and sluggish indicates injury to same side of brain. A pupil that does not constrict when light is directed at the pupil but has intact consensual response is indicative of a traumatic optic nerve injury.

• An ovoid pupil is indicative of early herniation • A core optic pupil is a pupil that appears irregular in shape. This is caused by a lack of

coordination of contraction of the muscle fibers of the iris and is associated with midbrain injuries.

• Coloboma is a hole in one of the structures of the eye, such as the iris, retina, choroid or optic disc. Congenital, presents as a key-hole shaped pupil

• Nystagmus- Involuntary movement of an eye which may be horizontal, vertical, rotary or mixed. Lots of causes.

• Strabismus (aka Disconjugate gaze)- failure of the eyes to turn together in the same direction.

Increased intracranial pressure has varying signs and symptoms dependent upon the degree of pressure. The cranial vault holds three things: brain, blood and CSF. According to the Monroe-Kelli Doctrine, there is a fixed volume within the skull. Head trauma causing bleeding or swelling on one side of the cerebrum or growth of masses in the cranial vault leads to increased pressure in the brain vault. To equalize the pressure there is a shift in volume which may eventually lead to brain herniation. There are many types of trauma to the brain including surgical interventions.

Table 4

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The body can regulate itself to a point when pressure starts to rise inside the cranial vault. It does this by decreasing production of CSF, increasing resorption of CSF and decreasing blood flow through vasoconsrtiction. As a result, cerebral perfusion suffers. When the brain can’t get adequate blood flow, ischemia occurs which promotes more swelling and eventually leads to the brain herniating through the foramen magnum and brain death if it is not recognized and intervention occurs. To maintain cerebral perfusion, we acalculate a cerebral perfusion pressure. This is done by taking the mean arterial pressure (MAP) and subtracting the intracranial pressure (ICP).

The CPP needs to be kept above 60mmHg to maintain perfusion.

Unless a patient has ICP monitoring in place, recognizing signs and symptoms of increased ICP usually falls to the astute observations of the bedside nurse. The following are signs of increased ICP:

• Altered LOC • Headache • Vomiting • Blurred vision • Irritability • Ataxia • Seizures

Late sings of increased ICP include seizures, Seizures, Bulging fontanel, Changes in respiratory pattern, Pupillary changes, Cushing’s triad (Hypertension, Bradycardia, Apnea). Pupil changes are dependent on the type of neurological injury (diffuse or focal) and the part of the brain that is affected (Ex. left sided tumor or stroke= same side pupil enlarged)

There are many treatment options available for increased ICP. Many of these are initiated by nursing. Immediately upon determination of increased ICP, the nurse should raise the head of bed to 30 degrees, maintain the head in midline position, keep the environment quiet with minimal stimulation and notify the intensivist, neurologist and neurosurgeon assigned to the patient. Other interventions available include sedating the patient, giving mannitol, supporting blood pressure with vasopressors or placing the patient in a pentobarb coma.

80%

10%10%

Inside the Brain Vault

Brain Tissue Blood CSF

Figure 9

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Since we know that edema usually peaks at 72 hours, there are times we will expect an increase in ICP and will be monitoring for it with either a filament or an external ventricular drain. With and EVD, you have the availability to drain off CSF in an attempt to decrease the total pressure inside the cranial vault. Monitoring and EVD systems available in PICU include Codman or Integra. EVDs can be placed post-surgical or at the bedside with a ventriculostomy. Due to the nature of our patient population in PICU, all nurses should be well versed in assisting with ventriculostomies and set up of EVDs as well as monitoring.

The nurse should gather all supplies for the neurosurgeon most of which are on the neuro cart in supply room A. Consent must be obtained and witnessed and universal protocol completed with everyone pausing just before the procedure. The nurse gives two patient identifiers, the procedure to be done and any laterality identified. The nurse is responsible for monitoring the patient during the procedure as well as setting up the drainage system to be connected to the EVD. When performing a ventriculostomy, opening pressures should be noted as any opening ICP>20 is considered intracranial hypertension.

To set up the drainage system, preservative free saline should be used to prime the tubing. Ensure there are no air bubbles anywhere in the system. A transducer is placed on the system at the stopcock between the patient and the drip chamber. This is the zero reference point and should be leveled to the Foramen of Monroe. The external landmark for leveling the transducer is the tragus of the ear. The transducer is then slaved to the monitor to give us a number and waveform.

Figure 10

Figure 11

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The neurosurgeon will write orders for what level mmHg it should be set at as well as monitoring parameters. Generally speaking, normal ICP is around 10-12. The main goal is to maintain cerebral perfusion pessure. Normal and abnormal ICP waveforms are seen in figure 13.

Assessment of the system should be completed every two hours or with neuro checks, whichever is more frequent. When assessing the system, check that HOB is at the ordered height, HOB control is Locked Out, there are no air bubbles noted in the system, all connectors in the system are tight and the position of the transducer is at the “Foramen of Monroe.” Observe and document the amount and color of CSF draining into collection chamber. If the amount of CSF drainage is excessive, the neurosurgeon may order replacement fluids.

Troubleshooting problems with an EVD after it has been set up can be tricky. If the EVD is not draining, first, check the tubing to ensure it is not kinked and there are no visible obstructions from blood or tissue. This may necessitate removing some dressing obstructing view of the drain.

Next, bring the transducer, drip chamber and collection bag below the level of the patient’s head. If the patient’s ICPs are low, they may not drain when the drip chamber is set at 20 or even 10mmHg but if the drip chamber is dropped significantly, you should see flow.

Flushing of the EVD by nursing staff is not recommended without neurosurgeon notification and specific orders to do so. In the case of flushing, always flush away from patient, NEVER to the brain.

Figure 12

Figure 13

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Pediatric Epilepsy

A seizure is a sudden outward manifestation of an abnormal and excessive electrical activity of brain cells (neurons). Seizures can be caused by many different diseases and pathologic states including epilepsy.

Epilepsy is defined as a tendency toward recurrent seizures without provocation. At least 2 seizures on separate occasions must be documented to be considered epilepsy. Epilepsy could be caused by many different brain disorders.

Causes of pediatric seizures and epilepsy can be broken down by age. In infancy and early childhood, the most common causes include Birth injury, Inborn errors of metabolism and congenital malformation. For children and adolescents cause are most likely Idiopathic, a genetic syndrome or result of a CNS infection. Adolescents and young adults are at higher risk for traumatic injury and drug intoxication and withdrawal which can cause seizures. Certain other things can precipitate a seizure

Low (less often, high) blood glucose Low sodium Low calcium Low magnesium Stimulant/other proconvulsant intoxication Sedative withdrawal Severe sleep deprivation

When a patient is admitted for new onset seizures, evaluation includes a detailed history and neurological exam, blood tests (CBC, electrolytes, glucose, hepatic, and renal function). A lumbar puncture should be performed only if meningitis or encephalitis is suspected. Blood or urine screen for drugs is also a concern to rule out accidental or purposeful drug ingestion or overdose.

New onset seizure patients should get an electroencepalogram or EEG as well and CT or MRI to diagnose seizures and locate site and or cause. An EEG will show transient abnormalities associated with seizures and epilepsy. These can be seen as spikes, sharp waves or spike-wave complexes. More than ½ of epilepsy shows normal EEG with the first EEG and up to 10% of normal population have abnormal EEG. So remember, an abnormal EEG does not always equal epilepsy!

A CT may be done in acute setting to rule gross abnormality such as tumor, hemorrhage, and stroke, but most of epilepsy patients have normal CT. Therefore, MRI is the imaging test of choice for epilepsy patients. If the initial MRI was normal, there is no need for repeated testing unless the seizures are poorly controlled and surgery is considered.

Medical treatment of first seizure is controversial. It is not considered epilepsy and might be an isolated event but:

16-62% will recur within 5 years Relapse rate is reduced by antiepileptic drug treatment Abnormal imaging, abnormal EEG increase relapse risk Quality of life issues are important

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Treatment of Epilepsy

When it comes to treatment of epilepsy, there are several classes of anti-epileptic drugs (AEDs) to choose from. Dependent upon:

◦ Epilepsy syndrome (Type/frequency/severity of seizure) ◦ Anti-epileptic Drug (AED)

Mechanism of action / Spectrum of activity Side effect profile (tolerability) Drug interactions Dosage form

◦ Patient Age Co-morbidities Concomitant medications (drug interactions) Previously failed therapies

Many times, the antiepileptic drug is chosen based on the type of seizure. For Partial Epilepsy with or without secondary generalization a narrow spectrum anti-epileptic drug is typically chosen. Therapy for Partial and Generalized Epilepsy would be a broad spectrum drug. Syndrome specific anti-epilepsy drugs include ETX for Childhood absence epilepsy, ACTH for infantile spasms, VIG for infantile spasms in patients with tuberous sclerosis and PYR for pyridoxine dependent seizures (table 5)

Narrow Spectrum Broad Spectrum Syndrome-specific

Phenobarbital (PB)

Phenytoin (PHT)

Carbamazepine (CBZ)

Oxcarbazepine (OXC) Gabapentin (GAB)

Benzodiazepines (BZD)

Valproic acid (VPA)

Levetiracetam (LEV)

Lamotrigine (LTG)

Topiramate (TOP)

Zonisamide (ZON)

Rufinamide (RUF)

Felbamate (FEL)

Ethosuximide (ETX)

Vigabatrin (VIG)

Corticotropin (ACTH)

Pyridoxine (PYR)

Table 5

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Most physicians prefer drug monotherapy. This simplifies treatment, reduces adverse effects is cost effective and more likely to ensure patient compliance. Polytherapy (using multiple drugs at the same time) is not proven to be effective. However, some patients will not have seizures fully controlled on monotherapy or even on polytherapy. If the patient fails more than two drugs, they should consider seeing a specialist. At Florida Hospital for Children we have pediatric epilepsy specialists whom focus on helping seizure patients to be seizure free through a multitude of diagnostics and interventions. We will go more into detail on that in the coming pages.

Many anti-epileptic drugs had interactions with other medications, toxicities and adverse effects. It is important to keep in mind that giving an anti-epileptic medication is not a cure all. Many AEDs have serum levels drawn to monitor optimum therapeutic levels and reduce toxicities. These levels are meant to be guidelines and are not hard and fast rules. There is limited data to support specific ranges and there are broad generalizations and individual differences. Therapeutic ranges are however helpful in: providing initial target in patients with infrequent seizures, understanding unexpected seizures or side effects, especially with polypharmacy and verifying compliance.

Many toxicities occur when initiating the medications. It is important to follow titration guidelines when initiating therapy. Some toxicities are dose related and decreasing the dose or serum concentration may eliminate the adverse drug reaction. Some toxicities require discontinuation of medication. There are antidotes for one category of AEDs: Flumazenil for benzodiazepines. Some dose related toxicities include:

Phenobarbital o Respiratory depression (correlates with serum concentration)

Phenytoin o Ocular disturbances (blurred vision, diplopia, nystagmus) o Central nervous system (ataxia, coma, dizziness, drowsiness, dyskinesias, lethargy,

slurred speech) Carbamazepine

o Diplopia Topiramate

o Metabolic acidosis (decreasing the dose may be effective)

When to discontinue AEDs due to toxicity may be difficult to determine. If the AED is preventing the patient from having seizures then which is the bigger evil: the toxicity or the seizures? A general guideline to follow is to always discontinue immediately if the toxicity is life threatening such as Steven Johnson’s Syndrome. If the toxicity is not life threatening then we must weigh the risks versus the benefits. Quality of life is one issue to consider.

Discontinuation of anti-epileptic medications can be considered on a patient who has been seizure free for >2 years (implies overall >60% chance of successful withdrawal). Favorable factors for discontinuation would be control achieved easily on one drug at low dose, no previous unsuccessful attempts at withdrawal, and normal neurologic status and EEG.

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There are other lifestyle modifications and/or procedures that can be done to help control the amount and frequency of seizures. Some easily modified practices include getting adequate sleep, avoiding alcohol and stimulants, stress reduction and a good diet. Some patients will be on a ketogenic diet. Ketogenic diets work on the premise of anti-seizure effect of ketosis and acidosis. It is a low carbohydrate, low protein, high fat diet after fasting to initiate ketosis. Ketogenic diets are mainly seen with children, especially those with multiple seizure types. The long-term effects, however, are unknown so it is recommended to follow a ketogenic diet for no more than two years.

Surgical Options and Brain Mapping

When all of the above treatment options have failed, the patient and family should consider seeing a specialist. Pediatric Epilepsy specialists work closely with neurologists and neurosurgeons to develop a plan to get the patient seizure free or at the very least, improve the quality of life. General selection of patients for surgical intervention is based on factors including epilepsy syndrome not responsive to medical management (Unacceptable seizure control despite maximum tolerated doses of 2-3 appropriate drugs as monotherapy) and Epilepsy syndrome amenable to surgical treatment. Once patients have met these basic criteria, the evaluation is extensive.

First, a thorough history is taken. Are the patient’s seizures consistent? What is localization of seizure onset and progression? Next begins the exam phase. Patients will undergo MRI, EEG, neuromedical spectroscopy scan, PET scan, neuropsychological battery, psychiatric evaluation, social work evaluation and possibly intracarotid amobarbital test. Table 6 summarizes the phases of evaluation and treatment and table 6 summarizes these tests and how they are carried out. What we are looking for with all of the tests and what the keys to successful surgical intervention include:

Localization of the “epileptogenic zone” – “where” Demarcation of the “epileptogenic zone” – “how large” Localization of the “eloquent cortex” in relation to the epileptogenic zone – “what to avoid”

PHASE 1 PHASE 2 PHASE 3

Seizure Monitoring Craniotomy for Placement of Intracranial Electrodes

Surgical Treatment

History & Physical Exam Intracranial Electrodes (grids, strips, depth electrodes)

Surgery to remove the seizure focus or special procedures to decrease the frequency or severity of seizures.

Video EEG Telemetry Electrocorticography

Brain Scans (CT, MRI, fMRI, SPECT, Ictal SPECT, PET)

Functional Mapping

MEG

Neuropsychological Testing

Visual Field Exam

Table 6

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Test How is it done? MRI uses magnetic fields and radio waves to produce high quality two-

or three-dimensional images of brain structures without use of ionizing radiation (X-rays) or radioactive tracers. Is useful in identifying masses in the brain or areas of low blood flow.

Functional MRI procedure that measures brain activity by detecting associated changes in blood flow. Tracks change in magnetization between oxygen-rich and oxygen-poor blood. Since the brain does not store glucose, blood flows into active brain areas to transport more glucose, also bringing in more oxygen. The blood-flow change is localized to 2 or 3 mm within where the neural activity is. This is used to map the brain to identify regions linked to critical functions such as speaking, moving, sensing, or planning

Electroencephaolgram (EEG) records the oscillations of brain electric potentials from perhaps 20 to 256 electrodes attached to the scalp. Video EEG is used for pediatric epilepsy patients to record the physical effects of the seizure as well as electrical spikes and location of seizure focus.

Magnetoencephalography (MEG) Recording of neuronal induced magnetic fields non-invasively at the scalp (similar to EEG recording of electrical potentials). The advantage of measuring the magnetic fields produced by neural activity is that they are likely to be less distorted by surrounding tissue (particularly the skull and scalp) compared to the electric fields measured by EEG

NM Spectroscopy Scan suited for imaging brain activity during a seizure. When the patient has seizure activity, a radioisotope is injected. The brain will have increased blood flow to area of seizure origin. Gives a snapshot of cerebral blood flow highlighting seizure focus.

Positron Emission Tomography (PET) Scan

produces a three-dimensional image of functional processes in the brain and assesses regional metabolism. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer). Three-dimensional images of tracer concentration within the brain are then constructed by computer analysis. Seizure focus should have decreased metabolism between seizures and increased metabolism during seizure.

Intracarotid Amobarbital test (aka Wada Test)

used to establish cerebral language and memory representation of each hemisphere. A barbiturate (which is usually sodium amobarbital) is introduced into one of the internal carotid arteries via a cannula or intra-arterial catheter from the femoral artery. The drug is injected into one hemisphere at a time. The effect is to shut down any language and/or memory function in that hemisphere in order to evaluate the other hemisphere. Then the patient is engaged in a series of language and memory related tests.

Table 7

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After all of this testing, the patient moves to Phase 2 and undergoes craniotomy for grid placement. Electrode placement is the first of at least 2 steps for some of the epilepsy surgeries we will be doing. I say “at least 2 steps” because at times the removal of the seizure focus can sometimes take more than 1 surgery, and sometimes there is more than 1 seizure focus. The majority of the patients however, will only have 2 surgeries: 1 for electrode placement, and one for the removal of the electrodes and resection of the seizure focus.

On occasion, a patient might have bilateral craniotomies for electrode placement. This will occur if EEG strongly suggests involvement of one side, but additional testing done during phase 1 (PET, spect, etc) suggests involvement of the opposite side or bilateral involvement.

The numbered “dots” are called “contacts” and they are embedded in a flexible silicone sheet so they will lay flat along the brain surface. The contacts can be arranged in a grid as shown here, or in strips of 2 or more contacts. The actual layout of the electrode array can be customized for each patient and the number and arrangement of electrodes placed will be determined by the epileptologist.

The average “skin-to-skin” time for a unilateral craniotomy for placement of subdural electrodes is about 2 hours. During this surgery, the epileptologist and the epilepsy team will be present in the operating room to direct the positioning of the implanted electrodes, record EEG from the electrodes placed, and to photograph the surgical site for reference as in the above picture.

A CT scan will be done upon completion of the surgical procedure. The epilepsy team will use this CT scan to help “diagram” the surgical plan. PICC line placement will also be done at the end of the procedure. This will add about an hour on to the in-operating room time for a total of 4-5 hours.

Figure 14

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The electrode arrays are often referred to as “grids” or “strips” based on the shapes they come in. The contacts in each array are individually numbered. The contacts can receive information from the brain surface regarding the origin and spread of a seizure (where does the seizure start and how does it spread after it starts?).

The contacts can also be used to stimulate the brain surface during testing by the epileptologist to help determine functional areas of the brain (where does speech production originate from or where in the brain causes movement of an arm, hand, or the face?).

When the neurologist and surgeon discuss seizures they can use the contact numbers as points of reference…”the seizure starts under contacts 13 and 14” or “motor control for the mouth is under contacts 6 and 7. “

After the epilepsy team have finished, the surgical site is closed. A dural expansion material (Alloderm) is sewn to the patient’s own dura to create more room for the electrodes and to allow for a relaxed dural closure. Cells from the patient’s own dura will grow into this material. It is not removed during the second surgery. The dura is then closed and the electrodes secured at their dural exit site.

The ends of the electrodes, also called lead wires, are brought through individual holes around the skin incision and secured at their skin exit site. Having the electrodes secured at 2 locations makes it difficult, but not impossible, to cause displacement or removal of the electrode by pulling on the lead wires. Because the lead wires provide direct communication between the subdural space and the “outside world” and CSF leak through the electrode exit sites or incision increases the risk for infection.

The bone is “floated” over the dura, meaning that it is not attached with any plates to the surrounding bone. This allows more room for the electrodes and any swelling that might occur as a result of electrode placement. The head is wrapped. A CT scan is done while the patient is still sleeping to confirm electrode location.

Now that the grids are in place, the patient is sent to PICU for at least 24 hours and phase two Electrocorticography and Functional Mapping can now take place.

For most patients, pain medications (typically Toradol and a narcotic based oral medication) will be scheduled to be given together every 6 hours. These will be tapered on a kid-dependent basis, but most patients will be off all scheduled pain meds by post-op day 3 or 4. Morphine or dilaudid will also be offered on an as-needed basis.

Figure 15

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Zofran will also be scheduled every 6 hours, ideally given at the same time as the scheduled pain medication. Most patients will only need anti-emetics for 48 hours, but some need them scheduled the entire time the electrodes are in place. Phenergan will also be ordered as a PRN medication.

As always…medication needs are patient dependent and the above is subject to change based on patient allergies, etc.

Electrocorticography (intracranial EEG)

When the patient arrives in PICU an EEG tech will connect the electrodes and instruct parent on use of “event” button. The patient is there so we can get information to determine where the seizure is coming from with the goal of hopefully being able to remove the portion of their brain causing the seizures. The parents of these kids have typically spent years trying to find a medication to control the seizures so the idea of letting them seize or taking the child off their medication to see the seizures can be scary. Reassure the parents: “We want your child to have seizures so we can figure out where they are coming from.”

Generally speaking, the goal is to capture at least three seizures on EEG and video to make sure they are either all originating from the same place or several areas. This will determine the type of surgical intervention which will best help the patient. It is most helpful for the nurse to follow these guidelines when the patient with electrodes in place has a seizure. When a seizure occurs:

Turn room light on. Stay out of the way of the camera. Pull covers back and say out loud what you see:

o Eye deviation- which way? o Head turned- which way? o Facial twitching- which side? o Extremity movement- which side? What extremity?

Roll patient onto side.

By talking out loud and describing what you see, the neurologists can form a mental picture of what you see if the camera is unable to see these details. Physical findings during a seizure may give useful information when determining where a seizure starts.

Most patients will remain in the PICU for the entire duration of intracranial EEG monitoring. Vital signs & neuro checks should be done every hour for the 1st night. This should be a full neuro assessment as that starting on page 11 of this book. If there are issues regarding changes in the patient’s neurological status, both the intensivist and the neurosurgeon need to be notified. Some examples are:

Pupils unequal. Face, arm, and/or leg weakness not previously present and noted by neurosurgery or nursing. Speech difficulties that were not previously noted Fluid leak you suspect might be CSF Any signs of increased ICP Any signs of infection including temp >101.5 and nuchal rigidity even in the absence of fever

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Infection (i.e. meningitis, empyema) is the greatest concern while the electrodes are in place. Fever is typically the heralding sign that infection is present. Infection can occur even in the absence of CSF leak. Threshold for electrode removal is low…if a fever occurs while electrodes are in place, it may be a surgical emergency! The patient more than likely will be headed to the operating room for electrode removal without resection if the patient has no indicators of infection from another source (i.e. urine, lungs) or if the patient is clinically deteriorating.

While the patient has electrodes in place, at least once daily dressing changes should be done. Inspect incision and each electrode exit site. Clean the incision and electrode exit sites with betadine. Apply antibiotic ointment to the incision(s) and electrode exit sites. Rewrap head. Notify neurosurgery of any fluid leak from incision or electrode exit site.

Direct Cortical Stimulation Mapping

As mentioned previously, the contacts can also be used to stimulate the brain surface during testing by the epileptologist to help determine functional areas of the brain. This is called direct cortical stimulation testing or mapping. For this, the epileptologist will come to the patient’s room and stimulate different contacts watching the patient to see what reaction there is. Electrical stimulating currents applied to the cortex are relatively low, between 2 to 4 mA for somatosensory stimulation, and near 15 mA for cognitive stimulation

The functions most commonly mapped through DCES are primary motor, primary sensory, and language. The patient must be alert and interactive for mapping procedures, though patient involvement varies with each mapping procedure. Language mapping may involve naming, reading aloud, repetition, and oral comprehension; somatosensory mapping requires that the patient describe sensations experienced across the face and extremities as the epileptologist stimulates different cortical regions. Motor reactions can be seen and documented.

To put all the pieces together and form a plan for surgical intervention, Pre-op OT, PT, and/or Speech assessments are completed at this time. The epileptologist takes all the information and maps which areas are seizure foci, which areas are functional foci and develops a plan for intervention. The patient can now move on to phase 3.

Figure 16

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Neurosurgery for Epilepsy

Neurosurgery for pediatric epilepsy patients can be potentially curative. If the seizure focus can be clearly defined and does not overlap with functional areas, a resection of epileptogenic region (“focus”) can be done without causing significant new neurologic deficit. The type and amount of tissue resected depends upon the findings from mapping and can include Lobectomy, Topectomy (partial lobectomy), Lesionectomy (removal of a seizure focus visible on MRI) or Hemispherectomy

If the patient’s seizure activity originates from several foci in the brain or cannot be separated from functional areas, a palliative surgery can be done to decrease the severity and frequency of seizures.

With patients in this category, the treatment will be patient specific. Some patients may have a palliative procedure to help control the seizures, and present again at a later date needing additional surgery. Ideally, you want to find a seizure focus, remove it, and render the patient seizure free with the goal of getting them off medication. This will not be possible for every patient. But for every patient the goals of “improved function” and “better quality of life” and “improved seizure control” should be addressed. Having a patient go from 10 seizures per day on 3 medications to no seizures on 3 medications is an improvement. When the kids get older and want to drive, the length of time they are seizure free on or off medications will determine whether or not they will even be able to get behind the wheel of a car. Florida’s laws say that an applicant should be seizure free for 2 years before being approved for licensing, but that may be reduced to 6 months if presented to the medical review board.

If no single focus could be identified or if multiple areas of seizure onset some options available include Electrode removal:

Without any additional procedure Corpus callosotomy Multiple subpial transection (MST) Resection of the most active seizure focus PLUS callosotomy or MST.

Figure 17

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As mentioned above, this is done to improve the patient’s quality of life and increase safety. For example, if a patient experiences “drop Seizures” where the seizure activity is so diffuse and severe the patient drops to the floor, a palliative surgery such as a corpus callosotomy can be done to decrease the spread of seizure activity across the brain and subsequently decrease the severity of the seizure.

The corpus callosum as discussed in neuro anatomy section of this book, is the located between the two hemispheres of the brain. It functions as the main pathway connecting the two hemispheres. Division (partial or complete) of the corpus callosum front to back can prevent seizure spread from one hemisphere to the other. Kind of like a major highway connecting 2 cities. If you remove that highway as a means from point A to point B you might not be able to get there.

Nothing is removed when doing this procedure…the corpus callosum is divided. An approximately 4 inch incision is made over the coronal suture. Next, a ventriculostomy is placed into lateral ventricle to help relax cerebral hemispheres. Lastly, the Corpus Callosum is divided with blunt dissection and suction. Ventriculostomy is removed at completion of case, skin closed, head wrapped and MRI completed.

Other palliative neurosurgical procedures include a partial resection of epileptogenic region and/or a MST (multiple subpial transaction). A multiple subpial transection involves the surgeon making a series of shallow cuts (transections) into the brain's cerebral cortex. These cuts are thought to interrupt some fibers that connect neighboring parts of the brain, but they do not appear to cause long-lasting impairment in the critical functions that these areas perform. Multiple subpial transections can help to reduce or eliminate seizures arising from vital functional areas of the cerebral cortex

No matter what type of resection is done, all patients undergo a craniotomy and have the same post-op course and concerns as any craniotomy patient. Remember that this is a long day for parents so keep them updated. The time frame includes 3-4 hours operating time plus an additional 3 hours for anesthesia induction, possible intra-op MRI, post-op MRI, extubation and transport to recovery.

Upon arrival to PICU, ensure the room is set up properly, get vitals and a new baseline neuro assessment. New neuro assessments are especially important in post-resection patients as it is important to note any new deficits and, if present, confirm with the surgery team whether these are expected post-operative deficits.

Figure 18

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Post-op Care for Craniotomy

Prior to the arrival of a post-op epilepsy patient, ensure that the room is ready for them. Some checklist items are:

Working suction tubing and appropriately sized tip. Oxygen tubing and mask correctly sized for patient size. Working HR/SpO2 monitors with new leads. Padded and functional hospital bed. Working patient controls (TV, nurse call button). Working patient camera

Most of these items are expected to be present and working in any ICU bed. The padding on the hospital bed is an extra measure taken for the epilepsy patients to reduce the chance they might get hurt when they have a seizure.

Head wrap is typically discontinued by neurosurgery on post-op day 1 or 2. Nurses should complete and instruct parents to perform wound care with Betadine and antibiotic ointment application once daily. Pain management and anti-emetics schedule for patients is the same as after electrode placement. Some comfort measures we can do for our patients include ice packs for eye(s)/cheek to decrease masseter or jaw pain. A typical complaint after craniotomy is that “It hurt to chew.” The reason for this is that when performing a craniotomy, the temporalis muscle, which is one of the “chewing” muscles, is divided. It is reapproximated at closing, but can still cause pain.

There may be functional deficits relating to the procedure done…or what area of the brain had the resection. Any time we expect a possible post-op deficit, we will discuss this and expected recovery with the family. Sometimes it will come down to the that family deciding to accept the possibility of a planned, long term deficit in order to achieve better seizure control. Uncommon but it has happened.

The nurse must diligently monitor the patient for neurological deficits, any CSF leak, any signs of increased ICP or infection. Any of these warrant a notification to the intensivist and neurosurgeon.

Figure 19

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Disconnection syndrome may occur with callosotomy patients and is unique to this procedure. Not all who have this procedure will experience it. It may be delayed in onset. (12-24 hours post-op)and is more common in complete divisions.

Typical findings of disconnect syndrome include mutism where the patient knows what they want to say but they can’t get the words to come out. Many of the patients who have this procedure done will be neurologically devastated even before the surgery. Their speech might be limited to vocalizing (yelling, babbling) instead of talking. In this population the vocalization will initially be less or non-existent but will return over days to weeks. The patients who experience disconnection won’t recognize they have 2 arms and 2 legs. Their brain only “sees” one side…it can look like a stroke as the patient will not have any spontaneous movement of one side of their body. It’s not that they can’t…their brain just doesn’t recognize that it can. If you pinch the patients finger, they will withdrawal from that painful stimulus…this is a reflex response.

Patients who experience disconnection syndrome will return to their baseline level of activity in days to weeks. They might require inpatient rehabilitation if the symptoms persist past days.

Expected hospital stay after resection varies:

Without deficits = 3-5 days then home =/- outpatient therapy. With deficit(s) but can eat, walk = 3-5 days + outpatient therapy. With deficit(s) and unable to walk (but could walk before surgery) and/or eat safely = variable

inpatient stay at FH (5-7 days) then transfer to inpatient rehab.

The goal is always to increase the quality of life for pediatric patients experiencing seizures.

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