Neuromuscular

Question 1

Giant Axonal Neuropathy

Cause, symptoms

Answer 1

GAN mutation gigaxonin

• Child with ataxia , CNS and PNS disease w/ optic atrophy, UMN signs, and peripheral neuropathy. HAVE VERY CURLY HAIR. Tightly packed axons on pathology

Similar to Metachromatic leukodystrophy

Question 2

NCS (motor, sensory)/EMG findings in:

Axonal Neuropathy
Demyelinating Neuropathy
Myopathy
Upper motor Neuron
Reinnervation

Answer 2

Axonal Neuropathy
- decrease in amplitudes of SNAPs and CMAPs
- decreased recruitment = less MUPs firing more rapidly

Demyelinating Neuropathies
- increased latency and decreased conduction velocity of SNAPs and CMAPs
- can cause decreased amplitudes if conduction block is between stim and recording sites
- genetic demyelination would not have conduction blocks or temporal dispersion

Myopathy
- -rapid recruitment, faster, smaller amplitude MUPs that may be polyphasic

UMN
- decreased recruitment = normal morphological MUPs at slower rate

Reinnervation
- MUPs polyphasic, increased amplitude and duration (less motor units controlling more fibers)

Question 3

Nerve conduction Study Components

Fwave? H-reflex?

Answer 3

Sensory Conduction study: Stimulate sensory nerve and record elsewhere

SNAP
Amplitude (mV)= # of axons conducting between stim and recording sites
Sensory Latency (onset and peak, ms) = Time between stimulation and recording
Conduction Velocity = Velocity of AP conduction between stim and recording (aka distance/latency)

Motor Conduction Study: Stimulate motor nerve and record on muscle belly

CMAP
Amplitude (mV)= # of axons conducting between stim and recording muscle
Sensory Latency (onset and peak, ms) = Time between stimulation and recording
Conduction Velocity = Velocity obtained at 2 different sites is divided by the difference in latency at the two sites to determine conduction velocity between two stim sites and avoid confounds with NMJ (aka distance/[latency1 - latency2])

Fwave - obtained after supramaximal stim of motor nerve. AP travels back up motor nerve axon in reverse, then reflects and comes back to muscle
H reflex - equiv of DTR at S1 obtained by stimulating tibial nerve at knee and recording at soleus. AP goes up sensory nerve, to spine, and back down to muscle like normal reflex arc

Question 4

Needle EMG Components, when are they changed?

Answer 4

Motor Unit Potentials (MUPs) - fire when muscle activates
Amplitude
Duration
Configuration
Recruitment - Number of MUPs with increasing force of contraction

Insertional Activity - muscle activity during needle insertion
^ in myotonic disorders, denervated muscle
v in paralysis, and when muscle replaced by fat/soft tissue

Spontaneous Activity - when muscle at rest. All are abnormal.
Fibrillation Potentials
Fasiculation Potentials
myokymia
Myotonic potentials

Question 5

NCs/EMG findings in:

1. Radiculopathy

Answer 5

Radiculopathy = Normal NCS (postganglionic fibers spared). EMG shows axonal damage
2. Myasthenia Gravis - 10% decrement in CMAP amplitude after 2Hz repetitive stim. SFEMG abnormal
3. LES: incremental improvement with > 50% rapid 20Hz stim. Normal NCS/EMG

Question 6

NCs/EMG findings in:

2. Myasthenia Gravis
3. LES

Answer 6

Myasthenia Gravis - 10% decrement in CMAP amplitude after 2Hz repetitive stim. SFEMG abnormal
LES: incremental improvement with > 50% rapid 20Hz stim. Normal NCS/EMG

Question 7

Familial Amyloid polyneuropathy

Types, symptoms, diagnosis

Answer 7

FAP1 = 20-40s, poly neuropathy loss of pain and temp, dysautonomia, renal, GI, or heart involvement

FAP2 = mostly carpal tunnel in families and slow polyneuropathy, no dysautonomia

Congo red stain = green birefringence on polarized light/ Primary AL type amyloid.

Question 8

Charcot-Marie-Tooth (Hereditary Sensorimotor polyneuropathies)

Types, causes, Symptoms

Answer 8

CMT 1 = AD, demyelinating. Progressive weakness, atrophy, mild sensory loss, arched feet, palpable enlarged nerves, fami hx, onion bulb nerves (also in CIDP)

CMT2 = AD axonal, progressive weakness, no nerve hypertrophy

CMT3 = AR and AD forms, severe pain and weakness as infant w/ nerve hypertrophy

CMT 4 = AR, mixed axonal and demyelinating, severe forms

CMT X = demyelinating, similar to CMT1

Question 9

Nerve/root with:

Foot drop spared eversion
Foot drop lost eversion
Foot drop lost inversion

Answer 9

Foot drop spared eversion = deep peroneal (extensors out, but inversion from superficial fibular suppling peroneus longus and brevis spared)

Foot drop no spared eversion = common peroneal

Foot drop lost inversion = L5 radiculopathy (eversion is tibialis posterior from tibial nerve)

Question 10

Hypokalemic periodic paralysis vs Hyperkalemic periodic paralysis

Causes, symptoms, treatment

Answer 10

HYPO
- AD, CACNA1S or SCN4A
- paroxysmal weakness, hyporeflexia, hours to days, triggered by exercise, carbs, alcohol, cold, stress.
- acetazolamide and avoiding stressors

HYPER
- AD, SCN4A
- resting after exercise, fasting

Question 11

Dystrophic Myotonia Type 1 and 2

Symptoms

Answer 11

DM1
- AD CTG repeat, ptosis, facial weakness, frontal balding, Myotonia and DISTAL muscle weakness, cataracts, cardiac involvement

DM2
- AD CCTG expansion in zinc finger protein 9 gene with intranuclear inclusions, myotonia and PROXIMAL muscle weakness

Question 12

FSHD

Cause, symptoms

Answer 12

Facioscapulohumeral Dystrophy

AD deletion of D4Z4. Starts w/ weakness in face and shoulder, eventually progresses t whole body

Question 13

Myotonia Congenita

Paramyotonia congenita

Causes. symptoms?