Technical
Waveforms & Abnormalities
Clinical Diagnoses
Innervations
Miscellaneous
100
What type of nerve fibers does EDX evaluate?
What are Ia (large, myelinated) fibers?
100
What waveform abnormality would you expect to see with axonal loss?
What is a reduction in amplitude?
100
60yo M presents with weakness, dysphasia, and fasciculations. NCS SNAP and CMAP normal; EMG with abnormal activity, delayed recruitment, long duration large amplitude MUAP, and CRDs. What is the most likely diagnosis?
What is ALS?
ALS is a motor neuron disease; commonly affects males after the 6th decade.
First signs: asymmetric atrophy, weakness, and fasciculations; dysphagia and dysarthria. Pseudobulbar signs: difficulty chewing, swallowing, and speech, along with unprovoked emotional outbursts. UMN and LMN signs.
Sensation is spared.
100
What is the pure sensory nerve off the femoral nerve?
What is the saphenous nerve?
100
This term refers to the electrode known as "the green one" in nerve conduction studies.
What is the ground electrode?
Red electrode - Recording
Black - Reference
200
How do we define innervation ratio (IR)?
What is the amount of muscle fibers belonging to a single axon?
200
What is the common electrodiagnostic finding in GBS?
What is abnormal F waves?
200
Patient presents with difficulty making an "OK" sign as well as a fist. There are no sensation abnormalities. NCS with normal medial SNAP and normal median CMAP. EMG with abnormal activity to the FPL, normal APB. What is the diagnosis?
What is anterior interosseus syndrome (AIN) syndrome?
FPL and FDP weakness.
EMG with abnormal findings in AIN muscles. NCS possible abnormal CMAP to the PQ.
200
What is the origin of the nerve that innervates the lateral forearm?
What is the LAC, off the musculocutaneous nerve?
200
What is the timeframe for Wallerian degeneration for motor and sensory axons?
Distal motor axons - 7 days
Distal sensory axons - 11 days
300
What happens to amplitude and latency with a decrease in temperature?
Latency is prolonged
Amplitude is increased
300
In which condition will you see myokymic discharges?
What is radiation plexopathy?
300
40yo F presents with proximal fatigue and weakness, primarily in lower limbs, worse with rest but improved with exercise.
NCS with normal SNAP, CMAP with low amplitude and incremental response with high-rate repetitive nerve stimulation.
What is Lambert-Eaton syndrome?
300
What is the muscle innervated by the common fibular nerve?
What is the short head of biceps femoris?
300
This type of injury affects the axon of a nerve but not the supporting connective tissue that results in Wallerian degeneration?
a. Neurotmesis
b. Axonotmesis
c. Neuropraxia
What is axonotmesis?
Neurotmesis - complete transection
Axonotmesis - nerve crush injury
Neuropraxia - nerve compression injury
400
This term describes when the electrical impulse travels in the opposite direction of normal physiological conduction.
What is antidromic?
400
In which conditions can you see early motor recruitment versus reduced recruitment?
Early recruitment - myopathic
Reduced recruitment - neuropathic
400
Patient presents with proximal muscle weakness; started on a new medication a few weeks prior to presentation. NCS and EMG findings normal. What is the most likely diagnosis?
What is steroid myopathy?
Onset: weeks to years post use
Risk increased if on 30mg/day
EMG may be abnormal with small polyphasics in very severe cases
Treatment: stop steroid, rehab
400
This muscle is NOT dually innervated?
a. Flexor pollicis brevis
b. Gracilis
c. Biceps femoris
d. Lumbricals of the hand
What is the Gracilis?
FPB - Median and ulnar
Gracilis - Obturator
Biceps femoris - Short head (common fibular); Long head (Tibial branch of the sciatic)
400
Why are SNAPs normal in radiculopathy?
Lesions proximal to the DRG preserve the SNAP waveform despite clinical sensory abnormalities.
Postganglionic injury results in Wallerian degeneration of both motor and sensory axons. There is physical separation of the axon from the cell bodies in the DRG and the ventral portion of the SC. CMAP and SNAP responses are diminished or absent.
500
What happens when the low frequency filter is raised?
Peak latency reduced
Amplitude is reduced
Reducing the high-frequency filter prolongs the peak latency and reduces the amplitude
500
A connection of the recurrent branch of the median nerve in the hand to the deep motor branch of the ulnar nerve producing an all ulnar innervated hand is known as what?
What is Riche-Canniue anastomosis?
500
Patient is a 50yo M with asymmetric weakness in his fingers, quadricep muscles, and foot drop that has been slowly progressing. Labs with increased CK. EMG with abnormal activity and early recruitment.
What is inclusion body myositis?
Asymmetric, slowly progressive, painless weakness in proximal and distal muscles. Patients often notice falling, tripping, and difficulty gripping objects as first symptoms. Atrophy present.
Affects adults 45-55 years, peaks at 70
Increased CK. Muscle biopsy with eosinophilic inclusion bodies and rimmed or cytoplasmic/basophilic vacuoles.
NCS: +/- abnormal SNAP and CAMP.
EMG: abnormal activity, early recruitment, +/- short duration, small amplitude MUAP
No treatment. Not responsive to steroids.
500
What are the muscles innervated by the AIN?
FDP (digits II and III)
Flexor pollicus longus
Pronator quadratus
500
What are the expected conduction velocity variations by age?
CV for a newborn is 50% of that of an adult. AT 1 year, it is 80%. Equal to an adult by 3-5 years.