1. (C ): This is most commonly a technical problem, for example, amplifier turned off, electrode placement, skin impedance, previous sural nerve biopsy, edema, or ankle deformity. One should check the integrity of the circuit before attributing the abnormality to a disease. Amyotrophic lateral sclerosis (ALS) is a motor neuron disease and sensory nerves are usually preserved. Tarsal tunnel syndrome (planter nerve entrapment) would not affect the sural sensory response. (Preston and Shapiro 1998, p. 6)

2. (A): Dorsal root ganglion contains the cell bodies of large myelinated sensory 1A fibers. It consists of bipolar cells with two separate axonal projections. The projections of dorsal root ganglion enter the spinal cord at the entry zone of the dorsal funiculus. Peripheral projections of the DRG eventually become the sensory fibers in the peripheral nerve. (Preston and Shapiro 1998, p. 9)

3. (A): Only large fast conducting fibers are myelinated. Myelination of the peripheral nerves is the function of the Schwann cells and every segment is myelinated by a single Schwann cell. The myelination is absent near the neuromuscular junction and at nodes of Ranvier. (Preston and Shapiro 1998, p. 12)

4. (D): When the nerve is stimulated proximally the CMAP area, amplitude, and duration are similar to those of the distal stimulation waveform. CMAP amplitude is usually measured from baseline to the negative peak and less commonly from the first negative peak to the next positive peak. CMAP duration is a measure of synchrony (simultaneous firing of individual muscle fibers). Conduction velocity is a measure of the speed of the fastest conducting motor axons, which is calculated by dividing the distance traveled by the nerve conduction time from a proximal to a distal stimulation site. One cannot calculate a true distal motor conduction velocity by using a distal motor latency and a distance; as the velocity measurement would include the conduction time through the neuromuscular junction and along the muscle fiber. (Preston and Shapiro 1998, p. 26)

5. (B): Cool temperatures result in slowing of conduction velocity, which is prominent in large rather than small myelinated fibers. For motor and sensory studies, conduction velocity slows between 1.5 and 2.5 m per second for every 1C drop in temperature and distal latency prolongs by approximately 0.2 ms per degree. Cooling of the limb results in a larger amplitude and longer duration potential, associated with a longer distal latency and slower conduction velocity. (Preston and Shapiro 1998, p. 85)

6. (A): Placing ground electrode between the stimulator and the recording electrodes helps reduce the stimulus artifact. Reducing electrodes impedance will decrease the stimulus. Rotating the anode of the stimulator while maintaining the position of the cathode will decrease the stimulus. Keeping the stimulator and recording electrode cables separate and kept as far as possible will help reduce the influence of stimulus artifact. (Preston and Shapiro 1998, p. 90)