Acute Flaccid Paralysis (Afp)

7/25/2019 Acute Flaccid Paralysis (Afp)

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Pediatrics lect. 7Dr. Samah Abu-Rahma

11-11-2009

ACUTE FLACCID PARALYSIS (AFP)

GENERAL

AFP (acute flaccid paralysis)is a universal abbreviation because it is

very imp. as it can be caused by several disorders such as botulism, polio...

AFP is the acuteonset of generalized flaccid weaknessin the absenceof symptoms of encephalopathy, it implicates the motor unit so we meana lower motor neuron.

AFP is a top emergency because children who come with acute flaccidparalysis can transition from inability to walk to being in a respiratoryfailure within hours. it is very important to have a triage system and aprofessional idea about where the problem is..if it's polio,nerve problemor muscle problem, how involved the respiratory system is.. before youleave the patient you have to have a management plan because many times

respiratory failure could be incipient (early) that goes unnoticed unlessyou think about it and look for it .>> We divide it into:

o Hyperacutegeneralized weakness : unusual , happens within hours.S b t n li d kn ss : s ll h pp ns 2 3 d s

Please note that boxes with a dashedline contain information from the

slides NOT mentioned by the doctor.


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- Flaccid leg weakness without involvement of the arms could also arise

from cerebral disorders, but other signs of cerebral involvement are alsousually present, particularly cognitive involvement

THE INITIAL COMPLAINTAlmost always noticed in the lower extremities because

1.

many disorders that we will mention soon are ascending startingfrom the lower extremities.

2.

symptoms of leg weakness are more easily to pick up and moreobvious than arm weakness...for example the parents may tell youthat their child's gait has changed, he can't walk or can't stand

up. before they notice that he can't comb his hair or can't pickthings from his closet) . although it's generalized weakness butproblems are more easily noticeable in the lower extremities so youhave to ask about signs of weakness in other sites. When you hear alow extremity complaint , that does not mean it's confined to thatregion.

WITH PROXIMAL MUSCLE WEAKNESSo

You can see the waddling gaitwhich is characteristic forproximal muscle weakness ; when you stand on one foot ,abductors will stabilize you, if you have weak abductors( ) ;the patient uses circumduction tocompensate for gluteal weakness

o

Difficulty in going upstairs due to hip extensor weakness.o

Difficulty in going downstairs if the patient hasQuadriceps weakness and cannot extend his knee
http://en.wikipedia.org/wiki/Glutealhttp://en.wikipedia.org/wiki/Circumduction


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o Repeated ankle spraining because of lateral instability.

o

Children with foot drop will lift the knee high in the air so the footwill clear the ground.o

Older children will complain of specific disabilities. For example thechild will till you he can't comb his hair or he can't open the door.

o limb weakness is often associated with weakness of muscles of the

head and neck, so you should ask about bulbar weakness (gait,

general power) then you ask about upper extremities.o

Inquire about diplopia, drooping eyelids (ptosis), difficulty chewingand swallowing, facial expressions, and voice changes (nasal speech) ,red urine in case of myositis , we will have myoglubinurea .. all theseyou should ask about in the history of someone with muscleweakness ( Hx of present illness).

PHYSICAL FINDINGSo

Look for atrophy or hypertrophy.o

Look for Fasciculations ; spontaneous contractions in single ms fibero

Palpate muscles for tenderness and texture.o

Joint contractures ; children with myopathy will have fixedcontractures of the limbs then weakness in muscles ,myotonia.o

Strength and tendon reflexeso

Watch the child sit, stand, and walk. He usually has :

Hunched shoulders Exaggerated lumbar lordosis ; he is trying to shift his center

of gravity so he won't fall down.

Toe walking ; also found with those who have DuchenneMuscular Dystrophy (DMD)because achilles tendon is verytight.

Waddling


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>> It is an indication of proximal muscle weakness. In textbooks it is

always mentioned with DMD but any proximal muscle weakness also willgive positive Gower's sign.>> It is part of Motor system examination; you ask the patient to sit down& then to stand up.

HYPERACUTE WEAKNESSo

Symptoms evolve very quickly and children reach the maximumweakness within 24 hours .

o Diagnosis here depends mainly on history and physical examination ;you can't find any lab or electrophysiological abnormality . forexample if you cut the ulnar nerve, there will be ulnar side weakness

but normal nerve conduction studies(normal distal stump) .Soaccurate history is essential to assess peripheral causes becauseelectrodiagnosis (EMG, NCS) may not be helpful.

=Note=EMG (electromyogram) ----- NCS ( nerve conduction study)o

Etiologies : *periodic paralysis, intoxications (organophosphatepoisoning) , or psychogenic.

=Note= Guillain Barre syndromemay have a hyperacute course.*Hyper/hypokalemic paralysiswhich are familial disorders can causehyperacute presentation

PERIODIC PARALYSISIt is a temporary paralysis but NOT associated with respiratory failure,

either hyperkalemic or hypokalemic channelopathy.The doctor said:" youdon't have to memorize them,they are not uncommon &you may see them."Familial hyperkalemic periodic paralysis

Autosomal dominant Weakness severity is variable usually lasts less than an hour after


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GUILLAIN-BARRE SYNDROME (GBS)

GENERAL>> Guillain-Barre syndrome is the commonest cause of acute flaccidparalysis (AFP) in healthy children.>> It is an acute inflammatory demyelinating polyradiculoneuropathy

(AIDP)as the name implies (

! ) :*Acutenot chronic , usually has subacute presentation*inflammatory; inflammation at the nerve root so we call it*polyradiculoneoropathy; the maximum inflammation is in the nerve rootsof the spinal cord leading most of the time to*demyelination.

>> Acquirednot genetic.>> monophasic; just one phase of increasing weakness then plateau thenimprovement, so it is not a chronic recurrent illness.>> roughly Symmetrical, progressive ascendingweakness, associated withareflexia (common , complete loss of reflexes), variable sensorycomplaints( numbness, pain, parasthesia).

>> the hallmark is elevated CSF protein without pleocytosis=Note=GBS is one of rare causes of acellular hyperprotienemia in CSF.

?WHYdo we have high protein level ?because of dumping of myelin products into the CSF as a result of

proximal demyelination.

and this is very important as we can distinguish it from infections wherewe have high cell count & high protein level.

PATHOPHYSIOLOGY


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>> The main lesions are acute

inflammatory demyelinating with acuteaxonal degeneration in some cases,particularly those followingcampylobacter infection there arespecific autoantibodies against myelinin the serum , associated with disease

following campylobacter infection orfollowing RSV infection (respiratorysyncytial virus).

FORMS OF GBS

1.

Acute inflammatory

demyelinating polyneuropathy

(AIDP):the prototype and themost common form in developedcountries. It has the best px

2.

Pure sensory3.

Mixed axonal and demyelinating4. Pure axonal the worstprognosis5-Miller Fisher syndrome:is similar to GBS but it comes as a triad of

1- external ophthalmoplegia ( inability to move pupils),2-ataxia (unstable wide based gait)

3-areflexia with muscle weakness.~It is part of differential diagnosis of ataxia not weakness.~

-Acute inflammatory demyelinating polyneuropathy (AIDP):theprototype and the most common form in developed countries


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CLINICAL FEATURES OF GBS

>> Two to four weeks after a benign febrile illness.>> Common presentations are tingling, sensory sensations,paresthesias in the fingers and toes, pain (is a commonpresentation in children (79%),particularly low back pain(common), muscle pain.>> Symmetrical ascending(starting from longer nerves then ascending to

shorter nerves)muscle weakness in the lower extremities, that a scendsover hours to days to involve the arms, and in severe cases it will involverespiratory muscles leading to respiratory failure so the patient has to beon ventilator.

>>Cranial nerves are affected in 30% of the cases, most commonly the

facial nervewith bilateral facial palsy.

>>More than 90% of patients reach the nadir (the maximum deficit) oftheir function within 2-4 weeks then a period of plateau, after that thepatient starts to improve because it is a self limiting disease. BUT westart treatment by immune modulation to hasten/accelerate improvement.

PHYSICAL EXAMINATION>> You will find symmetrical weakness with diminished or absent deeptendon reflexes.>> Vibration & position sensation are commonly affected in 40% of cases.

>> 50% of patients will have evidence of autonomic dysfunction; as theautonomic nerves are small peripheral nerves so they could be involved:

- Cardiac arrhythmias -Orthostatic hypotension,hypertensionParalytic ileus Urinary retention


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Cerebrospinal fluid Electrophysiologic studies

(NCS)-test CSF after the first week ofsymptoms because in the firstweek, CSF may be normal.-CSF typically revealsnormal pressure, normal cell

count, and elevated protein~the more severe the diseasethe more protein in the CSF~

-Most specific and sensitive testsfor diagnosis.-Normal (NCS) after 10days-2wksof illness make the diagnosis of GBSunlikely.

-Evidence of evolving multifocaldemyelination.

?WHEN should we suspect this is NOT GBS?

The problem is not missing diagnosis of GBS but it's diagnosing it insomeone who doesn't have it. Everyone automatically assumes that anyonewith acute flaccid paralysis has GBS and misses other importantdifferential diagnoses (mis-label them as GBS).

~~ GBS is highly unlikely if...

1.

marked asymmetry of weakness this is seen with polio NOT GBS2.persistent bladder or bowel dysfunction (weakness, urinary

retention or inability to urinate) early sign of spinal cord patho.3.leukocytosis in CSF (infection) seen in polio4.sharp sensory level seen in spinal cord dysfunction (sensory level

is related to the spinal cord NOT the brain because the brain is

divided into right and left; for example, loss of sensation below T5,normal sensation above T5). So any patient with weakness musthave testing for sensory level to rule out spinal cord pathology.

5.pupillary abnormalities seen in botulism, which causes weakness


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The#1 cause of death is autonomic dysfunction, while the 2

nd

mostcommon cause of death is respiratory failure. Because medical care hasbecome so advanced, no one should die of respiratory failure - it would bea travesty (ridiculous )! It is very important to remember that goodsupportive care can prevent death following autonomic dysfunction orrespiratory failure.

When do we worry about respiratory failure due to GBS?

The risk factors include:1) Cranial nerve involvement2)

Short time from preceding respiratory illness acute case ofrespiratory infection or gastroenteritis 3 days before GBS

(signifies severe autoimmune reaction).3)

Rapid progression over 90% of baseline

health status. The degree of recovery depends on the severity ofinflammation (only few children recover fully). For example, children withmild demyelination recover fully while those with axonal pathology recoveronly partially. 50% of children are ambulatory by 6 months and 70% walkwithin a year of onset of the disease Remember that GBS has a chronic


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respiratory failure may be the same during a certain year (both may be

able to walk with assistance)!TRANSVERSE MYELITIS

GENERALThe major differential diagnosis of GBS is a spinal cord

problem, the most common being transverse myelitis(inflammation of the spinal cord).Like GBS, it is also a post-infection (viral) or post-vaccination autoimmune disease.

PATHOPHYSIOLOGY

Transverse myelitis is an acute demyelinating disorder of the spinal cordthat usually evolves over days, but may have a hyperacute presentation.It may be associated with demyelination in other parts of the CNS.

CLINICAL FEATURES

Symptoms progress rapidly (peak within 2 days). Recovery usually beginsafter a week of onset of the illness

1)

Mean age of onset is 9 years2)Patients present with ascending weakness.3)In the initial phase of the disease, reflexes may be depressed or

lost (like GBS) because of spinal shock or involvement of the nerve

roots. With time, these reflexes become brisk.4)Thoracic level of myelitis (usually)5)

Sensory level6)Asymmetrical leg weakness7) *E l bl dd & b l i l t ( i )


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in cases of weakness without bulbar involvement you must consider and

rule out spinal cord involvement.

DIAGNOSIS#1 MRI of the spine(diagnostic tool of choice)In patients with transverse myelitis, the MRI usuallyshows swelling (inflammation) of the spinal cord.However, at times it is normal.

How quickly must you do an MRI for a patient whopresents with lower limb weakness (to detect sensorylevel)? Should you do it immediately, tomorrow orpostpone it for a couple of days??? The MRI shouldbe performed IMMEDIATELY on admission because

it is needed to rule out a mass lesion of the spinal cord (exclusion of acutecord compression is essential). If a lesion is detected, then surgicalintervention must follow (ex. epidural mass, tumor, abscess, hematoma,etc). Any delay in its management may lead to development ofirreversible paraplegia or irreversible damage to the spinal cord.

MANAGEMENTTo treat a patient with transverse myelitis, immediately give him/her highdoses of IV steroids(followed by tapering doses ofprednisone).

OUTCOME

Unfortunately, transverse myelitis has a poor prognosis. Only 50% makea full recovery, 40% recover incompletely, and 10% do not recover (thesepatients continue to suffer from severe neurological dysfunction).Prognosis depends on the severity of the inflammation detected in theMRI ( ti t ith ild d h b tt i th ti t


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virus to consider in AFP (most likely to cause severe paralytic disease) is

the polio virus. You must rule out polio myelitis in any patient presentingwith GBS (due to our strict vaccination program, polio has beeneradicated from HKJ, but it continues to be a worldwide disease).Coxsackie and echoviruses are more likely to cause aseptic meningitis.

PATHOPHYSIOLOGY

Enteroviruses are RNA viruses that inhabit the GI tract of humansThey are neurotropic and produce paralytic disease by irreversiblydestroying the motor neurons of the brainstem and spinal cord. Theyspecifically target the anterior horn cells (the most important part of themotor neuron).

CLINICAL FEATURESPoliomyelitis usually occurs as epidemic inthe spring and summer.

1)

Initially, the patient suffers frombrief illness characterized by fever,

malaise and GI symptoms. Becausethe cause of this AFP is infectious,the patient displays symptomstypical of someone with an

infection(toxic appearance, fever,meningismusmeningeal signs , and

pleocytosis in CSF as if thepatient has paralytic meningitis orCNS infection). To rule out poliomyelitis it is very important to do *lumbar puncture(LP) if patientpresents with AFP t xic appearance fever & menin eal si ns


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DIAGNOSISThe most important steps in the diagnosis of polio myelitis are:

1) Clinical suspicion(v. imp)2)*LPCSF leukocytosis is seen in the acute phase (because it is an

infection). Elevated CSF protein may also be seen.3)CBC shows leukocytosis (because it is an infection)

4)

Virus recovery from stool & stool analysis is essential.5)

Serological testing. Obtain stool, blood and throat samples for viralserology, demonstrating a 4-fold rise in IgG is helpful but notalways easy. Positive IgM antibodies is diagnostic

MANAGEMENTTreatment of polio myelitis is mainly supportive for pain and othersymptoms until the patient's condition improves

1)

Mechanical ventilation may be needed in bulbar involvement2)Pain management for paresthesias3)Physical therapy

OUTCOMEThere are different types of polio.

Bulbar polio, only the cranial nerves are involved. This can be lifethreatening because it may lead to respiratory dysfunction

(prolonged periods of apnea), swallowing dysfunction, and otherproblems. So, they may require mechanical ventilation.Extraoccular muscles are spared

Paralytic polio, rarely seen (due to introduction of polio vaccine)


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respiratory failure (before the introduction of steroids and mechanical

ventilation)!PATHOPHYSIOLOGYMG is an autoimmune, T-cell mediated disease directed at proteins in thepost-synaptic membrane. It causes *fluctuating muscle weaknessand*fatigability of muscles(v. imp hallmark of disease ex. child is normal inthe morning but becomes increasingly tired by the end of the day until

he/she can no longer walk OR he/she develops ptosis after lookingupwards for 30 seconds and can no longer open his/her eyes).

Because it is linked with certain HLA haplotypes, MG has also beenassociated with other autoimmune diseases(ex. Grave's disease) andgenetic factors may play a role (family history).

CLINICAL FEATURESThere are 2 clinical forms of MG:

Ocular myasthenia Generalized myasthenia

The most common presentation of someone withMG is *ptosis(v. imp ocular finding). Ptosisacquired secondary to MG may be unilateral orbilateral. Pupils are spared.50% of patientswith ocular myasthenia have generalizedsymptoms within 2 years.

1)

>50% of patients present with occular weakness and ptosis2)

15% present with bulbar weakness: dysphagia, dysarthria3)


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2)nerve conduction studies - NCS (ex. repetitive nerve stimulation

reveals characteristic abnormal pattern in 60% of patients withMG, may be difficult to perform in children)3)serological tests and antibody assays (ex. anti-acetylcholine

receptor antibodies, positive in 85% of cases)

MANAGEMENT

1)

Myasthenic crisisis the involvement of respiratory muscles withsevere, increasing, generalized muscle weakness. It is a serious lifethreatening condition that requires ICU admission and respiratorysupport, in addition to MG specific treatment (high dose steroids,IVIGIV immunoglobulins, plasmapheresis, and oral anti-cholinesterases).

2)

Children with generalized myasthenia, with positive antibodiesshould undergo thymectomyas soon as possible for thymoma orthymus hyperplasia (about 1 in 10 MG patients have a thymoma.There is a true "cause and effect" association between MG andthymomas because thymus is responsible for production of T-cells).

BOTULISM

GENERALBotulism is another cause of AFP. Unlike polio myelitis, we still see casesof botulism. There are different types of botulism:

1)

Food borne botulism: ingestion of pre-formedbotulinum toxin (very rapid progression ofdisease and appearance of symptoms). Mostcommon sources include: *expired canned


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PATHOPHYSIOLOGY

C. botulinum is a heterogeneous group of gram-positive, rod-shaped, sporeforming, obligate anaerobic bacteria. Spores of C. botulinum are heat-resistant (can only be destroyed by heating to 120C for five minutes)

Factors favoring toxin production: Restricted O2exposure (anaerobic or semianaerobic environment)

Low acidity (pH >4.6) water temperature of 25 to 37C for ideal growth

Botulism - PathogenesisThe toxin disperses widely via the vascular system and binds to a specificreceptor (synaptotagmin II) on the presynaptic sides of peripheralcholinergic synapses at ganglia and neuromuscular junctions. After gainingentrance to the cell's cytoplasm, the toxin produces an irreversibledisruption in stimulation-induced acetylcholine release by that presynapticnerve terminal. Return of synaptic function requires sprouting of a newpresynaptic terminalabout 6 months

CLINICAL FEATURESLike MG, botulism is a neuromuscular junction disease associated with*pure motor weaknessand is pre-synaptic (NOT post-synaptic). Pre-synaptic function returns to normal after 6 months. Severity of symptomsis variable (some people have mild weakness, others require ventilation)

1)

Acute onset bilateral cranial neuropathies associated withsymmetric descending weaknessare very common

2)Symmetric neurologic deficits.3)NO fever(unlike polio)4) P i i i (NO h l h )


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Symptoms of food-borne botulismusually appear quickly (within 12 to 36hours) after ingestion of the preformed toxin. Prodromal symptomsinclude: nausea, vomiting, abdominal pain, diarrhea, and dry mouth. Resp.difficulties requiring intubation & mechanical ventilation are common.

Cases of wound botulismhave been described involving abrasions,lacerations, open fractures, surgical incisions, and even closed hematomas.

This type does NOT have the prodromal GI symptoms common to food-borne botulism and has a longer incubation period of approximately 10days. Fever may be present.

DIAGNOSIS1)

Food borne toxin: toxin in blood, stool, vomitus & suspected foods

2)

Repetitive nerve stimulation (NCS) reveals a pattern characteristicof pre-synaptic neuromuscular junction disease.

3)Serum analysis for toxin by bioassay in mice, demonstration oftoxin in the blood is diagnostic

4)Adult enteric and infantile botulism: isolation of spores from stool

5)Triage:classification of patientsaccording to type and severity of injury,usually in times of war or crisis, todetermine whom to treat first and whomto send home (ex. mild, moderate,severe or life-threatening injury).

*CSF in botulism is completely normal

MANAGEMENTManagementof botulism is supportive and includes:


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Treatment:

1) Antitoxin therapy(equine serum botulism antitoxin or human-derived botulinum Ig) reduces fatality rates compared to untreatedpatients, but it must be given 24 hours of the onset of theillness. Antitoxin treatment initiated after 24 hours of symptomonset is useless and (according to the slides, it does NOT shortenthe duration of symptoms, but may decrease fatality rates).

2)

Antibiotics: Penicillin G (3 million units IV every four hours inadults) provides effective coverage of other clostridial species

***Aminoglycosides are contraindicatedbecause they affect theneuromuscular junction and may increase weakness.

OUTCOMERespiratory failureis the #1 cause of death in patients with botulism

RAPIDLY PROGRESSIVE WEAKNESS

GENERALRapidly progressive weakness is an emergency. This is how you evaluate

any patient who presents with AFP:1) Assure integrity of ABCs (v. imp)airways, breathing & circulation2)

Support and stabilize patient3)Focused hx to determine exact cause (is it GBS? MG? Botulism?)4)Attempt to localize weakness5)

Labs and studies appropriate for patient

6)

Triage the patient (ex. decide whether to send the patient to ICUvs. mild GBS so admit as regular patient?)

DIAGNOSIS


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MANAGEMENT

Do labs to check for early respiratory failure:1)

*Forced Vital Capacity (v. imp to determine respiratory status

of patient) Check FVC as soon as the patient is admitted. If itis normal (70 cc/kg) at admission, repeat test after 2 hours thenevery 4-5 hours if it remains normal. If the FVC is initiallyabnormal, then you must recheck it after 1 hour. Admit the patient

to the ICU if the patient's condition continues to deteriorate andconsider intubation when it decreases to 25 cc/kg.

2)CXR3)ABG4)

Further triage according to severity of illness

AFP-pearls- SUMMARY Acute and subacute weakness or rapidly progressive weakness is a


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DISEASE GENERAL PATHOPHYSIOLOGY CLINICAL FEATURES DIAGNOSIS MANAGEMENT OUTCOME

GBS- acute inflammatory

demyelinating

polyradiculoneuropathy

- post infectious

- autoimmune disease

- self limiting disease

- Symmetrical ascending

- low back pain muscle pain

- bilateral facial palsy.

- elevated CSF proteinw/o pleocytosis

- Electrophysiologic

studies (NCS)

- clinical , by exclusion

- Steroids are NOT

effective and C/I

- Critical care

- good px, esp.

children

-Demyelinatinggood px

- Axonal

worst px

- death due to

auton.dysfx +

RS.failure

Transverse

myelitis

-

Spinal cord inflamm- post-infection (viral)

- post-vaccination

- autoimmune dis.

- acute demyelinating

disease

- ascending, asymmet.

weakness of limbs

- bladder & bowel dmg

- Back pain

- or tendon reflex

- MRI of spine- IV steroids

+prednisone- Poor px

Polio

myelitis

- Enterovirus

(coxsackie/echovirus)

- Feco-oral

- RNA viruses

Neurotropic

- dmg ant. horn cells

of motor neurons

- febrile illness

- meningismus

- pleocytosis in CSF

-

paralytic dis.

- Clinical suspicion

- CSF= WBC & ptn

- stool analysis (virus)

-

+ve IgM,IgG

- Supportive

- Bulbar polio =

life threatening

- Paralytic

polio= rare

MG- Myasthenic crisis:

resp. ms + general

muscle weakness

- Autoimmune, Tcell

- Dmg post-synapse

- HLA haplotypes

- family history

- ocular vs. generalized

MG

- fatigability of ms

- ptosis

- hx & pe

- NCS nerve stim.

- anti-acetylcholine

receptor abs

- steroids, IVIG,

plasmapheresis

- oral anti-

cholinesterase

- thymectomy

- death due to

respiratory

failure

Botulism

- NM jn disease

-

pre-synaptic- food borne/

infant/wound

- C. botulinum

heterogeneous

-

Gram +ve rod- heat-resist spore

- obligate anaerobes

- motor weakness

-

acute bilat.neuropath- symmetric desc.

- Autonomic dysfn

- toxin (blood/stool/

vomitus)

-

NCS nerve stim.- Toxin in serum

- Spores from stool

* Normal CSF

- Anti-toxin Ry

-

Penicillin G*C/I aminoglycoside

-

Resp. failure

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Acute Flaccid Paralysis (Afp)