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Board prep - Neuromuscular focus Flashcards

1
Q

Describe corynebacterium neuropathy and treatment

A

Diptheria

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2
Q

Differentiate GBS from the. following:
- polio
- tick paralysis
- porphyria
- diptheria

A

Rules of GBS:
- Abdominal pain should PRECEDE but not occur simultaneously with weakness
- GBS is a pure nerve d/o&raquo_space; you should not see AMS
- CSF finding is albuminocytologic dissociation: high protein, LOW wbc

Diptheria may have more of descending quality

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3
Q

CIDP criteria duration

A

More than 2 months (>56 days)

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4
Q

Describe CIDP features

A

Usually motor + sensory

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5
Q

Describe Lewis-Sumner syndrome (MADSAM)

A

Variant of CIDP which affects asymmetrically the UPPER extremities first
Multifocal conduction block
Responds well to IVIG
Often confused with mononeuropathy multiplex - look for demyelinating features

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6
Q

Describe DADS

A

Distal Acquired Demyelinating Syndrome often associated with IgM monoclonal gammopathy particularly anti-MAG

Poor response to treatment

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7
Q

What are first-line treatment options for CIDP? How is this different from GBS?

A

Oral/IV prednisone (unlike GBS/AIDP!!!)
IVIG
Others: azathioprine, cyclosporine, methotrexate

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8
Q

Interpret this motor - NCS

A

Looking at distal to proximal there is a significant reduction in the size of CMAP c/w a conduction block (drop >50%)

Whenever you see a conduction block think about multifocal motor neuropathy

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9
Q

Speed associations:

Conduction block - dx?

A

Multifocal motor neuropathy

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10
Q

What are some features of multifocal motor neuropathy?

A

Male-predominant autoimmune disorder with weakness exceeding atrophy, often upper limb before lower limb and distal more than proximal

Often mimic of ALS because MMN is VERY treatable. Patients with MMN don’t have any upper motor neuron findings

Like GBS steroids are INEFFECTIVE (unlike CIDP)

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11
Q

Multifocal motor neuropathy with conduction block associated antibody

A

Anti-GM1 (only present in 50%) but another way to differentiate from ALS

GM1 antibodies word of warning - markedly elevated antibodies highly associated with MMN

Intermediate and low range antibodies can be associated with aLS

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12
Q

How to clinically differentiate multifocal motor neuropathy and vasculitis neuropathies?

A

MMN - motor ONLY
Vasculitic neuropathy - motor AND PAIN, +weight loss, fatigue, arthralgias

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13
Q

Describe vasculitic neuropathies

A

BURNING
Asymmetric presentation of motor + sensory
Most patients >50yo

Clinical example: 52yo man presents for L wrist drop and subsequently develops R foot drop. He reports significant pain, weight loss, and fatigue. Reflexes are reduced. Focal atrophy of muscle examination. EMG/NCS is notable for asymmetric neuropathy with sensory and motor involvement.

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14
Q

Differentiate the following vasculitides:
- Polyarteritis nodosa
- Microscopic polyangiitis
- Churg-Strauss
- Wegener’s granulomatosis

A
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15
Q

10-30yo patient with:
- High arched feet
- Hammer toes
- Absent reflexes
- Inverted champagne bottle leg
- Prominent steppage gait
- EMG - markedly slow conduction velocities

A

Charcot-Marie-Tooth type 1
Autosomal DOMINANT disorder
Hereditary sensory and motor neuropathy (HSMN)
DEMYELINATING

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15
Q

Charcot-Marie-Tooth type 1A gene and inheritance

A

PMP-22 DUPLICATION (chr 17)

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15
Q

CMT type 1a vs type 1b

A

CMT type 1a is the more classic and favorite of the boards. Clinically type 1a and type 1b are almost indistinguishable. Type 1b has more “axonal” electrophysiologic features and more likely to be associated with Adie’s pupil

Genetics:
1a: AD PMP-22 duplication (chr 17)
1b: AD myelin protein zero (MPZ) duplication (chr 1)

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16
Q

Describe HNPP

A

Multiple mononeuropathies often with family hx usually precipitated by positioning

Important to differentiate from vascultitis neuropathies and mononeuritis multiplex:
- not painful
- starts in adolescence
- no other sx features of vasculitic neuropathy
- On US HNPP have sausage feature unlike vasculitic hypoechoic and enlarged

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17
Q

Describe CMT type 2

A

axonal!
Still AD
MFN2

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18
Q

Describe CMT type X

A
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19
Q

Differentiate CMT types by inheritance, gene, and neuropathy type:
- CMT 1a
- CMT 1b
- CMT 2
- CMT type X

A
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20
Q

Describe Refsum disease

A
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21
Q

What type of neuropathy is suggested by this nerve biopsy?

A

This is onion bulb sign reflecting demyelination and remyelination with multiple layers of Schwann cells around the axon

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22
Q

Clinical clues for a DEMYELINATING polyneuropathy

A

Early generalized loss of reflexes
Disproportionately mild muscle atrophy in presence of weakness
Neuropathic tremor
Palpably enlarged nerves

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23
What is the following NCS demonstrating? What type of neuropathy should that trigger?
Temporal dispersion which is indicative of ACQUIRED DEMYELINATION (all the fibers aren't getting together at the same time)
24
What is a SLOW conduction velocity in nerves of arms? Nerves of legs?
Arms <35m/s Legs <30m/s Board questions probably going to give you velocities in the 10s because there is no way axonal process could cause velocities that slow
25
Neurophysiologic findings in demyelinating neuropathy (5)
- MARKED slowing of conduction velocity (<50%, ie 10s) - Distal latencies are MARKEDLY prolonged (>130%) Acquired demyelination only - conduction block and temporal dispersion Because the axon is still intact, there is little muscle atrophy Unmyelinating fibers are unaffected so temp and pain sensation are typically spared
26
Describe the NCS findings below
Proximally higher amplitude with dramatic decrease to <50% = conduction block which is always indicative of ACQUIRED demylination
27
Polio vs GBS
CSF in polio has WBC CSF in GBS has albuminocytologic dissociation
28
GBS and MFS associated antibodies
GM1 Abs = GBS C. jejuni infection GQ1b is associated with C. Miller-Fischer variant in almost all parients (ataxia, areflexia, ophthalmoplegia)
29
GBS Neurophysiologic features and predictor of prognosis
Within the first few days, NCS may be normal but will have abnormalities FASTER then protein in CSF (up to 1 week) First finding is often delayed, absent, or impersistant F waves due to proximal demyelination at the root level SNAP response is classically slowed but may see "sural sparing" because proximal pathology CMAP - slowing more than amplitude loss, temporal dispersion, conduction block EMG - reduced recruitment but otherwise normal MUAPS (reinnervation has not occured yet) **best predictor prognosis is CAMP amplitude same as worse prognosis with axonal variants
30
Pharyngeal brachial cervical GBS variant Ab association
GT1a Abs May mimic MG
31
Describe tick paralysis
American dog tick poisoning include fever, chills and tender lymph nodes. In addition, American dog ticks can cause tick paralysis, which can lead to respiratory distress and muscle weakness.
32
Porphyria
5 P's of porphyria Pain Psychiatric Peripheral neuropathy Pink urine Precipitated - drugs, alcohol, severe fasting
33
F wave latencies reflect what?
F wave is a late response that follows the motor response (M) and is elicited by supramaximal electrical stimulation of a mixed or a motor nerve. (example of antidromic transmission) F waves provide a means of examining transmission between stimulation sites in the arm and the leg and the related motor neurons in the cervical and lumbosacral cord. Involved early in GBS thought to be due to proximal demyelination at the root level
34
Describe the following CIDP variants: - MADSAM (Lewis-Sumner syndrome) - DADS
35
What is a major difference between AIDP and CIDP in terms of treatment?
AIDP is NOT steroid responsive. AIDP/GBS should be treated with IVIG CIDP IS responsive to steroids. Can sue steroids +/- IVIG
36
Describe features of tetanus
C. tetani toxin is internalized by retrograde axonal transport to alpha motor neurons cell bodies in brainstem and spinal cord Migrates to presynaptic membrane and blocks release of inhibitory glyvine and GABA. Disinhibits spinal reflex arc and increases the firing rate of alpha motor neurons producing rigidity. Sx: Trismus, risus sardonicus, opisthotonus, hypersympathetic state Cranial-caudal presentation because short nerves are affected faster. 1-2 weeks after exposure
37
Mechanism of stiff person syndrome
GAD-65 blocks glutamate decarboxylase leading to excessive glutamate and LESS gaba (More excitation and LESS inhibition anterior horn cells)
38
Stiff Person Syndrome features
39
Describe a normal NEUROMUSCULAR synapse
action potential reaches the terminal button of a motor neuron Ca influx ACh is released K channels open allowing +charge out and reset of resting potential
40
Describe location of action of the following dz in neuromuscular synapse: - Botulism - Myasthenia gravis - Organophosphates - Lambert Eaton P/Q Ca Ch Abs - Neuromyotonia
41
What are the expected EMG/NCS findings in Lambert-Eaton syndrome?
At baseline, LOW CMAP with facilitation (increment) of CMAP amplitudes after 30Hz repetitive stimulation (feature of presynaptic disorders - also seen in botox)
42
Botulism forms (5)
1. Classic - food - pre-formed 2. Wound - bacteria produces toxic 3. Infant - ingested spores produce the toxin 4. Hidden - adult form of infant 5. Iatrogenic w/ treatment
43
What is botulism impact on pupils?
Botulism toxin blocks acetylcholine release thereby blocking pupillary constriction
44
Features of Lambert-Eaton
Does NOT affect eyes As more action potentials come down eventually enough Ca channels open so that Ach can be released (Augmentation effect) Note that 3,4-diaminopyridine (Ampyra) blocks potassium facilitating Ca channel open
45
Lambert-Eaton syndrome characteristic EMG
Low baseline CMAP with increment upon stimulation - Facilitation of CMAP
46
Describe neuromyotonia aka Isaac syndrome
Autoimmune condition of stiffness + continuous muscle twitching + EMG high frequency trains ("pinging" and after discharges (due to delayed muscle relaxation)
47
EMG sound - rain on a roof
Fibrillation potentials - single muscle fibers firing spontaneously in the absence of innervation In neurogenic disorders, such as radiculopathies, mononeuropathies, or motor neuron disease, loss or degeneration or axons leads to denervated muscle fibers. In myopathic diseases, functional denervation of individual or segments of muscle fibers occurs as the fiber becomes separated from the endplate zone due to muscle necrosis and fiber splitting.
48
Synthesis and break down of acetylcholine
49
Nicotinic and muscarinic receptor distribution
50
Where do the following toxins work in the neuromuscular junction? - tetrodotoxin (puffer fish) - magnesium - botulism - lathrotoxin (black widow) - scorpion venum - tick paralysis (depate) - b-bungarotoxin (snakes) - mushrooms - curare
51
Tick paralysis vs GBS
52
Organophosphate poisoning What are they at risk for years later??
Years later they are at risk for delayed peripheral neuropathy even with limited exposure (organophosphate induced demyelinating polyneuropathy) After discharges almost pathognomonic on EMG Potentially fatal - bronchorrhea and bronchospasm SLUDGE or DUMBBELSS S - salivation L - lacrimation U - urinary incontinence D - diarrhea and diaphoresis G - gi upset E - emesis D - diaphoresis U - urination M - miosis B.- bradycardia B - bronchorrhea E - emesis/excitation L - lacrimation S - Salivation S - seizures
53
Describe ciguatera symptoms
Exposed to fish in a question stem think about ciguatera vs mercury... if lots of symptoms, ciguatera
54
Anticholinergic toxidrome symptoms...
55
Scalloped tongue with ptosis should make you think...
MuSK variant of myasthenia gravis
56
Describe MuSK antibody myasthenia gravis
57
EMG findings for myasthenia gravis
CMAP NORMAL at baseline and decrement with repetitive stimulation because not enough ACh can bind so responses get smaller and smaller
58
Practice recommendation for thymectomy for MG
If think there is a thymoma - get it our
59
Pyridostigmine can exacerbate what respiratory condition...?
ASTHMA Because of risk of bronchospasms
60
Respiratory precautions MG
61
Key points of congenital MG
Inherited NOT autoimmune Can be delayed but sx usually present at birth Most AR NO ROLE for immunosuppression
62
Transient neonatal myasthenia
63
What is the significance of Ab levels in MG ?
Antibody levels are patient-specific reflections of disease activity (NOT absolute) If one patient's Ab levels have decreased, that suggests stability
64
Key myopathy features
65
What are some patient factors and comorbidities that cause elevated CK levels?
66
Myopathies with: - Normal CK - Elevated CK
67
EMG features myopathy
The number of functioning muscle fibers in a motor unit DECREASES so the smaller unit results in shorter duration and amplitude MUAP but you recruit other small muscle fibers and have polyphasic appearance
68
Neuropathic vs myopathic EMG features
Neuropathic - large Myopathic - small, polyphasic
69
True or false: Fibrillations does not automatically imply neurogenic process
True: Use motor recruitment and clinical story to help you
70
General myopathic changes on biopsy
71
Myopathy vs neuropathy
72

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