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-ABPMR Board Review > Systemic nerve and muscle disease > Flashcards

Systemic nerve and muscle disease Flashcards

1
Q

Peripheral Polyneuropaties - how to characterize

A
  1. acute or gradual onset (e.g. GBS/AIDP v DM PN)
  2. demyelinating or primarily axonal (e.g., decreased CV, increased latency, +/- CB; or decreased amplitude); or both
  3. sensor, motor, or both
  4. diffuse and symmetric or mutlifocal and asymmetric

most are symmetric and symptomatically/electrodiagnostically worse distally

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2
Q

DM PN - pathophysiology, Px, PE

A

most common form of PN

Hx elevated A1C and poor blood glucose control → narrowing ov vasa nevorum → length-dependent dying back of PNs (axonal loss)

Px: gradual onset numbness/tingling w burning pain in stocking and glove distribution

PE: claw toes and hand muscle atrophy, areflexic achilles reflexes

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3
Q

DM PN - NCS/EMG

A

primarily axonal (dying back of n) → decreased amplitude

NCS: decreased amplitude on SNAP/CMAPs; may have prolonged latency if demyelinating component (CB, temporal dispersion)

EMG: if axonal process (dying back) → decreased recruitment distal > proximal; polyphasicity (reinnervation)

findings typically symmetric

evaluate at least 3 limbs

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4
Q

GBS/AIDP - pathophysiology, Px, concerns, Tx

A

recent GI/respiratory infection → rapidly progressive motor polyneuropathy d/t immune system confusing myelin for foreign protein → acute onset ascending paralysis (e.g., over days) with ascending areflexia

quick Dx → quick Tx (IVIG/plasmapheresis) → better prognosis; concern for respiratory compromise

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5
Q

GBS/AIDP - NCS

A

NCS: 1st change is absent or delayed F waves; H reflexes may also become abnormal early on

abnormal F and H waves → suggests proximal lesion e.g., polyradiculopathy

demyelinating process
SNAP: prolonged latency, reduced amplitude w sural sparing (sural n. large w more myelin than median/ulnar)
CMAP: prolonged latency, decreased CV, +/- CB w abnormal temporal dispersion; usually amplitude is normal

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6
Q

GBS/AIDP - key prognostic factor on NCS

A

if distal CMAP amplitude is <20% upper limit of normal → bad prognosis

demyelination so severe that axonal loss is ocurring

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7
Q

GBS/AIDP - EMG

A

mainly demyelinating process → normal EMG if no axonal loss has taken place

if severe w lots of CB → decreased recruitment

several weeks after onset → may see fibs/sharps (active denervation) d/t secondary axonal loss

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8
Q

CIDP v AIDP

A

CIDP essentially relapsing-remitting AIDP

Px and EDS findings similar except symptom progression is much slower (months)

Tx: plasmapheresis, IVIG, steroids (unlike AIDP)

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9
Q

critical illness neuropathy EDX

A

axonal sensorimotor polyneuropathy following critical illness, Tx rehab

NCS: abnormal SNAPs and CMAPs (low amplitude d/t axonal loss)

EMG: LDLA (long duration, large amplitude), decreased recruitment (machine gun), fibs/sharps
few axons → fewer motor units doing all the work for muscle contraction

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10
Q

CMT etiology px

A

many subtypes; duplication of PMP 22 gene

gradual distal > proximal weakness, fewer sensory abnormalities

b/l foot drop, Champagne bottle legs d/t calf and anterior compartment muscle wasting → weak dorsiflexion

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11
Q

deletion of PMP 22 gene

A

gives HNPP - hereditary neuropathy with liability to pressure palsy

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12
Q

CMT 2

A

gives you axonal polyneuropathy → EDX: decreased amplitude SNAPs/CMAPs; active denervation/reinnervation on EMG

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13
Q

CMT 1

A

demyelinating → EDX prolonged latency, decreased CV, without conduction block or abnormal temporal dispersion

usually uniform demyelination w CMT

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14
Q

AIDP v CMT 1 EDX

A

CMT 1 demyelinating - uniformly therefore universally prolonged latency and decreased CV (without conduction block or abnormal temporal dispersion)

v AIDP - focal demyelination → conduction block at normally non entrapment sites

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15
Q

HIV neuropathy

A

polyneuropathy
typically distal axonal
symmetric
sensory > motor

NCS: abnormal amplitudes of SNAPs/CMAPs
EMG: abnormal spontaneous activity in distal > proximal muscles

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16
Q

Mononeuritis Multiplex

A

“mononeuritis multiplexonal” → axonal proccess

axonal peripheral n. injury (e.g., median neuropathy)
combined w other single peripheral n. injuries

Px: acutely, asymmetrically; weakness, numbness/tingling

usually d/t underlying vasculitis which damages axons (e.g., Diabetes, Wegener Granulomatosis, polyarteritis nodosa, lupus)

NCS/EMG: abnormalities in respective peripheral nerves, axonal features generally

17
Q

MG - EDX

A

NCS: normal routine studies
abnormal repetitive nerve stimulation

EMG: normal, perhaps increased jitter (variability of neighboring muscle fibers) on single fiber EMG

Tx: thymectomy, pyridostigmine (ACh-esterase inhibitor), plasmapheresis/IVIG

18
Q

LEMS - EDX

A

r/o small cell lung ca

NCS: low amplitude CMAPs bc hard to get response
normal RNS

EMG: increased jitter and blocking on single fiber EMG

Tx: rehab, corticosteroids, anticancer therapy, plasmapheresis/IVIG

19
Q

botulism - EDX

A

NCS: decreased/absent CMAP, abnormal RNS

EMG: active denervation w decreased recruitment, increased jitter on single-fiber EMG

Tx: antitoxin, rehab, respiratory support

20
Q

RNS - EDX indications, findings/Dx

A

when NMJ disorder suspected

normal people: CMAP looks fine

NMJ disorder: CMAP amplitude will decreased
>10% decrement between 1st and 4th waveforms is positive for NMJ disease

RNS can be given at low rate or high rate

21
Q

low v high rate RNS

A

low: muscle stimulated at 2-3 Hz; NMJ dz will cause amplitude decrement

high: muscle stimluated at 10-50 Hz
Ca builds up in neuron → facilitates normal NMJ transmission → normal CMAP
all NMJ dz will show some CMAP repair, but with LEMS it will show huge increase in CMAP amplitude (300%)

22
Q

post exercise facilitation v exhaustion

A

similar to RNS

facilitation: like high rate RNS
after low rate RNS → maximal contraction, 60 seconds → repair of CMAP

exhaustion: CMAP decreased the more a person exercises overall
after low rate RNS → CMAP does not show decrement → if still suspect NMJ dz → repeat low rate RNS q1min x5mins → one test should show CMAP decrement

23
Q

anterior horn cell dz - EDX

A

PE: usually LMN signs, sometimes UMN present (ALS, PLS, HSP)

in general, SNAPs normal as well as latency/CV (not demyelinating but axonal loss)

must demonstrate abnormalities in 3 out of 4 spinal segments (cervical, thoracic, lumbosacral)

e.g., SMA, ALS, poliomyelitis, post-polio syndrome

24
Q

SMA - Px/course/EDX

A

mutations in SMN1 gene →

SMA1 (Werdnig-Hoffman): floppy infant, dies of resp failure

SMA2: weak 1 year old, wheelchair as toddler, can sit independently and stand w ADs, dies of respiratory failure

SMA3: gradually weakning ~10 year old, can walk independently, normal life expectancy

labs: elevated CK

EDX: normal SNAPs, abnormal CMAPs, LDLA MUAPs w decreased recruitment

Tx: rehab, nusinersen, Zolgensma

25
Q

ALS -Px/EDX

A

60 year old, progressive weakness w UMN/LMN signs (pure motor), no bowel/bladder abnormalities

NCS: normal SNAPs, possibly normal CMAPs d/t reinnervation

EMG: LDLA MUAPs, decreased recruitment, fibs/sharps, increased jitter and fiber densitiy

show denervation in 3 of 4 spinal segments

Tx: rehab, submaximal exercise, riluzole (anti-glutamate)

26
Q

poliomyelitis - EDX

A

pure motor anterior horn degeneration following polio infection

NCS: normal SNAPs, decreased amplitude CMAPs

EMG: LDLA MUAPs, fibs/sharps, decreased recruitment

Tx: supportive

27
Q

post-polio syndrome

A

clinical Dx, no EDX required

Px: new onset progressive weakness

Hx: prior recovery from polio 15 years ago

remaining anterior horn cells get burnt out

if EDX:
NCS: normal SNAPs, low amplitude CMAPs
EMG: giant MUAPs, decreased recruitment, fibs/sharps

28
Q

myopathy - Dx/EDX

A

muscle Bx can show type I (aerobic) or type II (anaerobic) muscle fiber atrophy
type II atrophy usually w steroid myopathy

EMG only evaluates type I fibers → will appear normal with steroid myopathy

EDX:
NCS: normal SNAPs, abnormal CMAP amplitude d/t atrophied muscles
EMG: SDSA polyphasic MUAPs (myopathic motor units); muscle so atrophied and small that takes early/increased recruitment to summate for muscle contraction
myotonic discharges divebomber sound

29
Q

Gottron papules

A

purple patches over MCPs/PIPs/DIPs

associated w heliotrope trash

inflammatory myopathy (e.g., dermatomyositis, polymyositis)

Hx viral infection/cancer

30
Q

dermatomyositis/polymyositis - Px/Dx/EDX

A

Hx viral infection/cancer
“type 3 not me” type 3 = cancer

proximal weakness +/- heliotrope rash and Grotton papules (purple patches of MCP/PIP/DIP)

labs: elevated CK, ESR, LDH; perifasicular atrophy on muscle Bx

NCS: normal SNAPs and CMAPs

EMG: abnormal MUAPs (SDSA w increased/early recruitment)

Tx: corticosteroids, plasmapheresis/IVIG

31
Q

statin myopathy

A

stop offending agent, can slowly reintroduce or switch to other statin

proximal muscle pain (myalgias), Hx statin use, often iso CYP450 inhibitors

NCS: normal SNAPs and CMAPs

EMG: normal

32
Q

steroid myopathy

A

causes type II muscle atrophy (Bx)

NCS/EMG: normal

33
Q

critical illness myopathy

A

Hx: patients in ICU; weakness and atrophy in both proximal and distal muscles with normal sensation; thus not critical illness neuropathy or AIDP

labs: elevated CK (muscle dz)

NCS: normal SNAPs, low amplitude CMAPs

EMG: SDSA MUAPs, sometimes fibs/sharps, with normal/early recruitment

-ABPMR Board Review (19 decks)

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