Anatomy
What is the only muscle exclusively innervated by the C5 nerve root
Rhomboids
How will SNAPs be affected in ALS?
Unaffected. ALS is a motor neuron disease
What type of fibers does needle EMG test?
Type 1a (large, myelinated)
Distinguishing characteristic of conduction velocity changes between acquired and congenital neuropathies
uniform slowing across non entrapment sites is typical of a congenital process
What is the pathophysiology of Lambert Eaton?
Autoimmune reaction with antibodies against PRESYNAPTIC v-gated Ca channels -> prevents influx of Ca -> decreased vesicle release of ACh into synaptic cleft
What is the most proximal muscle innervated by the common peroneal nerve?
Short head of the biceps femoris?
Which muscle is classically evaluated with the H-reflex
Gastrocnemius
Electrical correlate of S1 tendon ankle reflex
A 28 year old male sustained a work related accident when he was carried into a table saw by a chain on the medial proximal leg. What are the descriptive characteristics of the first MUAPs that are seen in the earliest evidence of reinnervation?
low amplitude, highly polyphasic, fast firing rate
- nascent MUAP
Durkan's test- compression at the wrist on the median nerve for 30 s. Developed in 1991. Sensitivity 87% vs phalen 85% with specificity both at 96%. Together 94% and 96% respectively.
Which drug class is most commonly associated with drug-induced Parkinsonism
- Related to anti-dopaminergic action causing extrapyramidal side effects
Which of the following is innervated by a nerve other than the obturator nerve? And what nerve?
Adductor magnus, longus, brevis
Adductor magnus is partially innervated by the sciatic nerve
What type of neuropathy is seen in electrodiagnostic testing in alcoholic neuropathy?
Axonal sensory motor polyneuropathy
Which of the following MUAP characteristcs would be unexpected in apatient with high suspicion for myopathy: low amplitude, long duration, polyphasicity, early recruitment
Long duration
What is the optimal rise time of MUAP?
500 microseconds
What is the net effect of pregnancy on the course of multiple sclerosis? (increases, decreases, neutral)
Neutral
Decrease in relapse during pregnancy
+
Higher than normal relapse during first 3 months post-partum
Where is the suprascapular nerve entrapped if there is isolated infraspinatus weakness?
Spinoglenoid notch
In the newborn, nerve conduction velocities are approximately what percentage of adult values?
50% due to incomplete myelination.
You find CRDs in numerous muscles in a patient. In your knowledge you know that CRDs have the highest odds ratio in which of the following: plexopathy, mononeuropathy, polyneuropathy, motor neuron diseases, and myopathy.
Bonus: what is the pathophysiological key word that may appear on boards describing the pathophysiology of CRDs
Myopathy
Ephaptic: coupling of adjacent nerve fibers caused by the exchange of ions between the cells. "Pacemaker"
You are seeing a patient in the ICU with acute proximal weakness. He has normal sensory and motor NCS with exception of an absent F wave. What is one caveat that needs to be present for the absent F wave to have clinical significance?
A healthy man and a healthy woman have a child diagnosed with Duchenne Muscular Dystrophy. What is the chance that their next child will have Duchenne Muscular Dystrophy?
25%
DMD is X-linked recessive. Man does not carry gene and woman is a carrier.
Causes absence of dystrophin, a protein responsible for connecting the cytoskeleton of muscle fibers -> progressive muscle weakness
What are the 5 classic entrapment locations of the median nerve?
Ligament of strutters - medial epicondyle to
Bicipital aponeurosis - attachment to ulna
Pronator teres
Anterior interosseous nerve
Carpal tunnel
How does a cold limb affect the amplitudes of CMAPs and SNAPs? What is the physiologic explanation of this?
Increases the amplitudes of CMAPs and SNAPs
Na channels are open longer during depolarization
You have somehow obtained a MR neurography prior to needle EMG stating inflammation in the posterior division of the lumbosacral plexus. Which muscle should not be affected? Iliopsoas, gracilis, vastus medialis, sartorius
gracilis: anterior division off the L2-L4 anterior rami of the obturator nerve
All others are femoral nerve -posterior division
A patient asks you to explain the pathophysiology and likelihood of nerve recovery. You luckily have a laboratory report done intraoperatively stating, "Axon severed but endoneurium intact". What is the Seddon and Sunderland classification?
Seddon: grade 2 - axonotmesis
Sunderland: grade 2: highest optimal grade for recovery
Which type of spinal muscular atrophy (SMA) has the latest presentation?
Which type of SMA has the worst prognosis?
(Type I, II, III)
Loss of lower motor neurons with progressive muscle wasting
Type I (Werdnig Hoffman) - onset 0-6mo, "floppy baby", respiratory failure, most do not live past 2yo
Type II (Dubowitz) - onset 6-18 months, variable severity, dec life expectancy but can live to adult hood
Type III (Kugelberg-Welander) - onset >12 months, able to walk at some time, life expectancy generally unaffected