Practice exam questions

Practice exam questions The resting membrane potential of nerve and muscle is: - ANS -90 to -70 mV A bundle of nerve fascicles are bound together by a connective tissue called: - ANS perineurium What best describes the connective tissue sheath surrounding EACH individual fascicle in a peripheral nerve? - ANS endoneurium In examining a patient with brachial plexopathy, the deltoid and triceps are weak, but the biceps and pronator trees are normal. The lesion is best localized to the: - ANS posterior cord The immediate influx of sodium ions into the muscle or nerve is a characteristic of what? - ANS depolarization What are the standard filter settings for motor conduction studies? - ANS 2 Hz- 10 kHz Inadvertently reversing the anode and cathode in an orthodromic sensory nerve conduction study will result in what? - ANS a latency increase Common mode rejection involves what: - ANS suppression of signals recorded equally by both active and recording electrodes. The unit of charge is what? - ANS Coulomb What measurement is most helpful for accurately calculating the conduction velocity of the fastest axons in a sensory nerve? - ANS onset latency The measurement of negative peak duration of a compound muscle action potential waveform will yield the most information regarding: - ANS temporal dispersion Physiologic temporal dispersion affects the sensory nerve action potential (SNAP) more than the compound motor action potential (CMAP) for the following reasons: - ANS relatively short-duration SNAP's Both H-waves and F-waves are what? - ANS are of value in disorders of the nerve roots and proximal segments. After a crush injury, what is the rate that an injured nerve can regenerate? - ANS 1 mm a day What pathway does the R2 component follow in the blink reflex? - ANS The R2 component follows a polysynaptic pathway through the pons and lateral medulla. When performing an H-wave recording on the tibial nerve, what do you look for in the foot? - ANS plantarflexion (downward, away from the leg) Recording a Blink Reflex study measure a portion of what nerves? - ANS Trigeminal, Facial, and the nucleus in the brainstem. Is the H reflex sensory or motor response? - ANS mixed motor and sensory response In a Blink Reflex study, the R1 synapses in what area? - ANS pons. Is myasthenia gravis pre or post synaptic? - ANS post synaptic Myasthenia gravis would show what on a repetitive stimulation? - ANS decremental response What is Lambert- Easton myasthenia syndrome? - ANS Presynaptic neuromuscular junction disorder Pseudofacilitation seen on repetitive nerve stimulation studies demonstrate what? - ANS demonstrate no significant change in waveform area. A patient presents with proximal weakness, fatiguability, dry mouth and transient sensory paresthesias. This patient is most likely suffering from what? - ANS lambert eaton myasthenic syndrome In a patient with myasthenia gravis, nerve stimulation immediately following brief maximal exercise (10-15 seconds) most likely produce what? - ANS Transient normalization of the decremental response at 2 Hz stimulation. In which disorder would you see low baseline CMAP amplitudes, accompanied by incremental responses to brief exercise or rapid repetitive stimulation? - ANS Lambert- Eaton myasthenic syndrome A 40 year old woman complains of diplopia and difficulty climbing stairs in the late afternoon. The most helpful diagnostic test would be what? - ANS Facial nerve repetitive stimulation at 2 to 3 Hz. In myasthenia gravis, what is there a decrement of in the muscle fiber? - ANS receptors This disease worsens with heat and exercise. It affects the post-synaptic neuromuscular junction resulting in a decremental response on repetitive nerve testing. - ANS Myasthenia Gravis The recording electrode for the superficial peroneal nerve (sensory, antidromic) action potential is located: - ANS anterior (medial) to the lateral malleolus The sciatic nerve receives innervation from what nerve roots? - ANS L4-S3 A 22 year old patient strikes a tree while sledding. The nerve conductions studies 3 weeks after the accident show absent median and ulnar motor responses on the affected side. Which of the following would point to a brachial plexus injury over a root avulsion. - ANS an absent ulnar sensory response. Which of the following anterior rami come together to form the lumbosacral plexus? - ANS L1-S3 The anterior rami roots of L2-L3-L4 divide into divisions and the posterior divisions unite to form what nerve? - ANS Femoral When performing a peroneal motor nerve conduction study, excessive stimulation at the popliteal fossa most commonly results in what problem? - ANS Activation of the tibial nerve. Which nerve is a pure sensory nerve that is derived from L2-L3 nerve roots? - ANS Lateral Femoral Cutaneous What sensory nerve conduction response will best help distinguish between true neurogenic thoracic outlet syndrome and cubital tunnel syndrome? - ANS Medial antebrachial cutaneous. The study that is most helpful differetialting a brachial plexus lesion from nerve root avulsion is what? - ANS Sensory nerve action potential amplitude. An example of an acute inflammatory demyelinating polyneuropathy is: - ANS Guillain-Barre syndrome the fourth dorsal interosseous muscle is innervated by the: - ANS deep branch of the ulnar nerve. Maintaining the elbow in extension while performing an ulnar motor conduction study can result in what? - ANS The calculated conduction velocity being slower than the actual conduction velocity. In a patient with severe neurogenic thoracic outlet syndrome, which of the abnormalities would be expected on the affected side? - ANS reduced amplitude of the ulnar SNAP. Which of the following is the most desirable technical condition for reliable repetitive nerve stimulation studies? - ANS Skin temp should be at least 33 degrees C Martin Gruber anastomosis is seen when there is a: - ANS crossover of median fibers to ulnar fibers in the forearm. Left ulnar motor nerve conduction studies performed in a 36 year old man with a history of a C8 radiculopathy reveal an initial positive deflection of the compound muscle action potential after wrist stimulation. What is the likely cause? - ANS Misplacement of the active electrode. What is the single most important step to avoid contamination in the EMG lab? - ANS washing hands An anomalous accessory peroneal nerve, when present, innervates the: - ANS extensor digitorum brevis Sensory nerve action potential will be increased by: - ANS lowering the skin temp to below 29 degrees What is the most common outcome of repetitive nerve stimulation on a cool limb (cooler than 30 degrees celsius?) - ANS decreased decremental response During motor nerve conduction studies, failure to place the recording electrode over the motor point most often results in a waveform that is: - ANS triphasic, initial positive deflection. a safety risk can be avoided by doing what? - ANS pluggin all equipment attached to the patient into the same outlet.