Online Module: Online Module: HydrocephalusHydrocephalus

HydrocephalusHydrocephalus Derived from Greek words:Derived from Greek words:

““Hydro” – waterHydro” – water ““Cephalus” – headCephalus” – head

As the name implies, it refers to a As the name implies, it refers to a general condition whereby there is general condition whereby there is excess Cerebro-Spinal Fluid (CSF) excess Cerebro-Spinal Fluid (CSF) within the intracranial space and, within the intracranial space and, specifically, the intraventricular spaces specifically, the intraventricular spaces within the brain…causing dilation of the within the brain…causing dilation of the ventricles, and a wide range of ventricles, and a wide range of symptoms.symptoms.

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For our purposes, we will be dealing For our purposes, we will be dealing with hydrocephalus in the older with hydrocephalus in the older child/adult population. child/adult population. Hydrocephalus in the younger Hydrocephalus in the younger population, especially neonates and population, especially neonates and children without fixed sutures, children without fixed sutures, represents an excellent avenue for represents an excellent avenue for further reading, in case you are asked further reading, in case you are asked to elaborate on it for extra points! to elaborate on it for extra points!

Facts and PhysiologyFacts and Physiology The majority of CSF is produced by the The majority of CSF is produced by the

choroid plexus choroid plexus within the brain through within the brain through a metabolically active process (i.e. a metabolically active process (i.e. requires ATP) whereby sodium is requires ATP) whereby sodium is pumped into the subarachnoid space, pumped into the subarachnoid space, and water follows from the blood vessels.and water follows from the blood vessels.

Choroid plexus is primarily located in the Choroid plexus is primarily located in the lateral ventricles (temporal horn roofs, lateral ventricles (temporal horn roofs, and floors of bodies), posterior 3and floors of bodies), posterior 3rdrd ventricle roof, and caudal 4ventricle roof, and caudal 4thth ventricle ventricle roof.roof.

Facts and PhysiologyFacts and Physiology The average adult brain produces between The average adult brain produces between

450 and 600 cc’s of CSF every day.450 and 600 cc’s of CSF every day. Normally, production = resorption.Normally, production = resorption.

At any given moment, there is only ~150 At any given moment, there is only ~150 cc’s of CSF present in the average adult; of cc’s of CSF present in the average adult; of this, only ~25 cc’s is within the brain this, only ~25 cc’s is within the brain ventricles!ventricles! So, the CSF volume turns over three to four So, the CSF volume turns over three to four

times every day, with only a very small fraction times every day, with only a very small fraction of the CSF being in the ventricles at any given of the CSF being in the ventricles at any given time, even though the majority of it is produced time, even though the majority of it is produced there!there!

Important concept to Important concept to build onbuild on

The CSF production/resorption The CSF production/resorption system exists in a delicate balance system exists in a delicate balance under normal conditions.under normal conditions.

The CSF pathwayThe CSF pathway

From the From the lateral ventriclelateral ventricle (remember, (remember, there are two…one on each side), CSF there are two…one on each side), CSF travels through the travels through the foramen of Monroforamen of Monro into the into the 33rdrd ventricle ventricle (midline), then (midline), then passes through the Cerebral passes through the Cerebral Aqueduct [of Aqueduct [of Sylvius]Sylvius] into the into the 44thth ventricle ventricle. It then . It then exits the 4exits the 4thth ventricle through either of ventricle through either of two two Foramina of LuschkaForamina of Luschka (“L” is for (“L” is for Lateral/Luschka) or the single Lateral/Luschka) or the single Foramen of Foramen of MagendieMagendie (“M” is for Midline/Magendie). (“M” is for Midline/Magendie).

CSF pathway (cont’d)CSF pathway (cont’d)

After exiting the 4After exiting the 4thth ventricle, the ventricle, the CSF flows through the CSF flows through the subarachnoid subarachnoid spacespace over and around the brain and over and around the brain and spinal cord, and is eventually spinal cord, and is eventually reabsorbed into the venous (blood) reabsorbed into the venous (blood) system through numerous system through numerous arachnoid arachnoid granulationsgranulations along the dural venous along the dural venous sinuses (especially the superior sinuses (especially the superior sagittal sinus).sagittal sinus).

CSF pathway (cont’d)CSF pathway (cont’d) Arachnoid granulations contain Arachnoid granulations contain

arachnoid villi, which function as arachnoid villi, which function as pressure-dependent one-way valves that pressure-dependent one-way valves that open when the ICP is ~3 to 5 cm H20 open when the ICP is ~3 to 5 cm H20 greater than dural venous sinus pressure.greater than dural venous sinus pressure.

Remember – CSF production is a Remember – CSF production is a metabolically active process which uses metabolically active process which uses ATP, whereas CSF resorption is a passive ATP, whereas CSF resorption is a passive process that is driven by the pressure process that is driven by the pressure gradient between the intracranial space gradient between the intracranial space (ICP) and the venous system (~CVP).(ICP) and the venous system (~CVP).

HydrocephalusHydrocephalus

Two major distinctions:Two major distinctions: Communicating Hydrocephalus (CoH)Communicating Hydrocephalus (CoH)

Also known as “non-obstructive” Also known as “non-obstructive” hydrocephalushydrocephalus

Non-communicating Hydrocephalus Non-communicating Hydrocephalus (NCH)(NCH) Also known as “obstructive” hydrocephalusAlso known as “obstructive” hydrocephalus

Hydrocephalus Hydrocephalus terminologyterminology

It is important to understand the It is important to understand the difference between “Communicating” and difference between “Communicating” and “Non-communicating” hydrocephalus.“Non-communicating” hydrocephalus. If the CSF pathway is “open from start to If the CSF pathway is “open from start to

finish,” meaning CSF can travel freely from finish,” meaning CSF can travel freely from the choroid plexus to the arachnoid the choroid plexus to the arachnoid granulations, then you have “no obstruction” granulations, then you have “no obstruction” and a and a communicatingcommunicating hydrocephalus. hydrocephalus.

If the CSF can’t travel freely from start to If the CSF can’t travel freely from start to finish, then you’ve got an “obstruction” and finish, then you’ve got an “obstruction” and non-communicatingnon-communicating hydrocephalus. hydrocephalus.

Let’s look first at Let’s look first at Communicating Communicating Hydrocephalus…Hydrocephalus…

CoHCoH

In the vast, vast majority of cases, In the vast, vast majority of cases, this represents a problem with CSF this represents a problem with CSF resorption; simply put, it cannot resorption; simply put, it cannot keep the pace with CSF production.keep the pace with CSF production. Normal CSF production = resorptionNormal CSF production = resorption Comm. Hydrocephalus CSF production Comm. Hydrocephalus CSF production

> resorption> resorption As a result, the ventricular system As a result, the ventricular system

dilates uniformly, and ICP rises.dilates uniformly, and ICP rises.

Still building…Still building…

Remember that the normal system Remember that the normal system exists in a fairly delicate balance. A exists in a fairly delicate balance. A major insult is not required to upset major insult is not required to upset this balance; sometimes, a very this balance; sometimes, a very slight disturbance is enough to tip slight disturbance is enough to tip the scales such that, over time, the scales such that, over time, communicating hydrocephalus communicating hydrocephalus results.results.

CoHCoH

Very rarely, there is overproduction Very rarely, there is overproduction of CSF (rather than under-of CSF (rather than under-absorption) which leads to absorption) which leads to disruption of this balance, and disruption of this balance, and development of communicating development of communicating hydrocephalus.hydrocephalus.

This is rare, but Choroid Plexus This is rare, but Choroid Plexus Papillomas have been known to Papillomas have been known to present this way.present this way.

CoHCoH

Signs/SymptomsSigns/Symptoms In young children whose cranial sutures In young children whose cranial sutures

have not yet fused, you can see have not yet fused, you can see disproportional increase in head disproportional increase in head circumference compared to the rest of circumference compared to the rest of the face/body.the face/body.

In children with fused sutures/adults, In children with fused sutures/adults, hydrocephalus manifests with symptoms hydrocephalus manifests with symptoms of increased intracranial pressure;of increased intracranial pressure; H/A, N/V, papilledema, gait disturbance, 6H/A, N/V, papilledema, gait disturbance, 6thth

cranial nerve palsy, upgaze difficulty, etc.cranial nerve palsy, upgaze difficulty, etc.

CoH etiologyCoH etiology

Infection (incidence after bacterial Infection (incidence after bacterial meningitis can approach 30%)meningitis can approach 30%)

Subarachnoid Hemorrhage (blood Subarachnoid Hemorrhage (blood and blood breakdown products cause and blood breakdown products cause scarring of arachnoid granulations)scarring of arachnoid granulations)

Post-operative Post-operative Head traumaHead trauma Etc.Etc.

Still building…Still building…

Although we usually think of Although we usually think of Communicating Hydrocephalus as Communicating Hydrocephalus as being a “gentle” disruption of the being a “gentle” disruption of the balance between CSF production and balance between CSF production and resorption that occurs over time, resorption that occurs over time, sometimes there can be a sizeable sometimes there can be a sizeable insult that causes an acute disruption insult that causes an acute disruption of the balance, and CSF resorption is of the balance, and CSF resorption is suddenly (and dramatically) reduced.suddenly (and dramatically) reduced.

Still building…Still building… Given the high turnover of CSF in the Given the high turnover of CSF in the

normal individual, you should quickly normal individual, you should quickly recognize that a dramatic decline in CSF recognize that a dramatic decline in CSF resorption ability can represent an resorption ability can represent an emergency. If a significant number of emergency. If a significant number of arachnoid granulations are impaired, say, arachnoid granulations are impaired, say, by subarachnoid blood (such as from a by subarachnoid blood (such as from a ruptured aneurysm), hydrocephalus can ruptured aneurysm), hydrocephalus can develop very quickly. Neurological decline develop very quickly. Neurological decline in such a situation can be rapid, with in such a situation can be rapid, with patients becoming sleepy, then obtunded, patients becoming sleepy, then obtunded, then requiring intubation.then requiring intubation.

Let’s pause the Let’s pause the CoH discussion, CoH discussion,

now, and turn our now, and turn our focus to Non-focus to Non-

communicating communicating Hydrocephalus Hydrocephalus

(NCH)(NCH)

NCHNCH

Non-communicating hydrocephalus Non-communicating hydrocephalus occurs whenever there is ANY occurs whenever there is ANY physical obstruction to the normal physical obstruction to the normal flow of CSF before it leaves the flow of CSF before it leaves the ventricles.ventricles.

NCH causesNCH causes

Many, many causes:Many, many causes: Aqueductal stenosisAqueductal stenosis Tumors/Cancers/MassesTumors/Cancers/Masses CystsCysts InfectionInfection Hemorrhage/hematomaHemorrhage/hematoma Congenital malformations/conditionsCongenital malformations/conditions Etc.Etc.

The bottom line…NCHThe bottom line…NCH Non-communicating hydrocephalus can Non-communicating hydrocephalus can

result from CSF flow obstruction at any result from CSF flow obstruction at any point along the intraventricular pathway.point along the intraventricular pathway.

Processes that have developed over Processes that have developed over longer periods of time (i.e. masses, etc) longer periods of time (i.e. masses, etc) usually cause gradual development of usually cause gradual development of symptoms.symptoms.

Acute processes (i.e. intraventricular Acute processes (i.e. intraventricular bleed) can cause acute obstruction with bleed) can cause acute obstruction with rapid mental status decline (just like we rapid mental status decline (just like we discussed previously).discussed previously).

RadiographyRadiography The earliest consistent The earliest consistent

radiographical finding radiographical finding indicative of indicative of development of development of hydrocephalus is hydrocephalus is dilation of the dilation of the temporal horns of the temporal horns of the lateral ventricles lateral ventricles (arrows). In most (arrows). In most younger and middle-younger and middle-aged patients, these aged patients, these should be almost should be almost invisible.invisible.

→↓

This is an abnormal scan!

Hydrocephalus treatmentHydrocephalus treatment Treatment for Hydrocephalus remains Treatment for Hydrocephalus remains

surgical.surgical. Acute hydrocephalus, whether communicating Acute hydrocephalus, whether communicating

or not, usually necessitates urgent or emergent or not, usually necessitates urgent or emergent placement of an External Ventricular Drain placement of an External Ventricular Drain (EVD - catheter passed through the patient’s (EVD - catheter passed through the patient’s scalp and skull into lateral ventricle, that scalp and skull into lateral ventricle, that drains CSF to a collection system kept at the drains CSF to a collection system kept at the patient’s bedside).patient’s bedside).

EVD cannot be maintained indefinitely; usually, if EVD cannot be maintained indefinitely; usually, if the patient is unable to tolerate weaning/clamping the patient is unable to tolerate weaning/clamping of the EVD prior to removal, a permanent shunt will of the EVD prior to removal, a permanent shunt will be required.be required.

Hydrocephalus treatmentHydrocephalus treatment For communicating hydrocephalus, the For communicating hydrocephalus, the

mainstay of treatment is shunt mainstay of treatment is shunt placement.placement. Ventriculo-peritoneal is most used.Ventriculo-peritoneal is most used. Lumbar-peritoneal sometimes utilized, Lumbar-peritoneal sometimes utilized,

though overdrainage is a problem.though overdrainage is a problem. Acute communicating hydrocephalus Acute communicating hydrocephalus

patients (i.e. SAH) can sometimes be patients (i.e. SAH) can sometimes be managed with EVD with successful weaning managed with EVD with successful weaning and no shunt placement, but a significant and no shunt placement, but a significant number of these patients eventually need number of these patients eventually need shunt placement weeks or months later.shunt placement weeks or months later.

Non-communicating Non-communicating HydrocephalusHydrocephalus

NCH treatment also surgical, but NCH treatment also surgical, but sometimes shunt can be avoided by sometimes shunt can be avoided by removing the obstructing lesion.removing the obstructing lesion. Colloid cyst at anterior 3Colloid cyst at anterior 3rdrd ventricle causing ventricle causing

ball/valve obstruction of Foramen of Monro.ball/valve obstruction of Foramen of Monro. Pineal region tumor causing compression of Pineal region tumor causing compression of

cerebral aqueduct.cerebral aqueduct. Ependymoma blocking 4Ependymoma blocking 4thth ventricular CSF ventricular CSF

outlets.outlets. Many, many more!Many, many more!

NCH treatmentNCH treatment

In addition to surgical removal of In addition to surgical removal of obstructive lesion and shunt placement, obstructive lesion and shunt placement, Third Ventriculostomy is an option for Third Ventriculostomy is an option for non-communicating hydrocephalus.non-communicating hydrocephalus. Often performed in conjunction with VP Often performed in conjunction with VP

shunt placement.shunt placement. Hole is surgically opened in floor of third Hole is surgically opened in floor of third

ventricle so CSF flows out into the ventricle so CSF flows out into the interpeduncular cistern and pre-pontine interpeduncular cistern and pre-pontine space (bypasses cerebral aqueduct).space (bypasses cerebral aqueduct).

Previously shunted Previously shunted patientspatients

Take note: Every patient with a Take note: Every patient with a history of VP shunt placement who history of VP shunt placement who presents with a headache is NOT presents with a headache is NOT automatically having a shunt automatically having a shunt malfunction/infection.malfunction/infection. Yes, you should consider that in your Yes, you should consider that in your

differential, but still work it up differential, but still work it up appropriately. After all, the vast majority appropriately. After all, the vast majority of patients with headaches don’t have VP of patients with headaches don’t have VP shunts.shunts.

Previously shunted Previously shunted patientspatients

Nevertheless, VP shunts can and do fail Nevertheless, VP shunts can and do fail for any of a number of reasons.for any of a number of reasons. The incidence of shunt failure is as much as The incidence of shunt failure is as much as

40% the first year (most in the first few 40% the first year (most in the first few months), and then 5% per year after the first months), and then 5% per year after the first year.year.

50% of shunts fail by 5 years from placement.50% of shunts fail by 5 years from placement. Mechanical failure from occlusion/disconnection, Mechanical failure from occlusion/disconnection,

migration, overdrainage/underdrainage, infection, migration, overdrainage/underdrainage, infection, skin erosion, etc.skin erosion, etc.

One last thing to One last thing to discuss…discuss…

Normal Pressure Normal Pressure HydrocephalusHydrocephalus

Normal Pressure Hydrocephalus (NPH) Normal Pressure Hydrocephalus (NPH) - This is a distinct clinical entity that - This is a distinct clinical entity that was first described in 1965.was first described in 1965.

This is important and you MUST know it This is important and you MUST know it because it is one of the rare preventable because it is one of the rare preventable and/or reversible causes of dementia.and/or reversible causes of dementia. Under-recognition leads many patients with Under-recognition leads many patients with

NPH to be diagnosed with Alzheimer’s or NPH to be diagnosed with Alzheimer’s or age-related dementia and they never seek age-related dementia and they never seek (or receive) treatment.(or receive) treatment.

NPHNPH Classic triad: “Wet, Wobbly, and Classic triad: “Wet, Wobbly, and

Wacky!”Wacky!” Urinary incontinenceUrinary incontinence Gait disturbance (usually the first symptom to Gait disturbance (usually the first symptom to

present) – wide stance; short, shuffling stepspresent) – wide stance; short, shuffling steps Rather quickly-progressive dementiaRather quickly-progressive dementia

Communicating hydrocephalus on CT/MRICommunicating hydrocephalus on CT/MRI Lumbar Puncture (LP) Lumbar Puncture (LP)

Normal opening pressureNormal opening pressure Symptoms improve with CSF removalSymptoms improve with CSF removal

NPH treatmentNPH treatment

Procedure of choice for patients felt Procedure of choice for patients felt to be suffering from NPH is VP shunt to be suffering from NPH is VP shunt placement.placement. LP shunts tend to overdrain.LP shunts tend to overdrain.

NPH prognosisNPH prognosis Chance of outcome is improved if symptoms Chance of outcome is improved if symptoms

have been present for shorter period of have been present for shorter period of timetime Meaning that failure to recognize these patients Meaning that failure to recognize these patients

delays their treatment and lessens their delays their treatment and lessens their chances!chances!

Least likely symptom to improve with Least likely symptom to improve with shunting is dementiashunting is dementia It’s always a worse sign once mentation gets It’s always a worse sign once mentation gets

involved!involved! Most likely symptom to improve is Most likely symptom to improve is

incontinenceincontinence

NPH: Bottom LineNPH: Bottom Line

Good history taking and time with Good history taking and time with patients and family is key to nailing this patients and family is key to nailing this diagnosis. Just because they’ve got the diagnosis. Just because they’ve got the classic triad doesn’t mean it may not be classic triad doesn’t mean it may not be Alzheimer’s (it often will be); but if you Alzheimer’s (it often will be); but if you keep NPH on your differential and keep NPH on your differential and consider it rather than writing off all consider it rather than writing off all dementia as Alzheimer’s, you will have dementia as Alzheimer’s, you will have the opportunity to make a fantastic the opportunity to make a fantastic difference in the lives of many patients.difference in the lives of many patients.