| Popis: |
Sensory nerve action potentials are a valuable component of any neurophysiological assessment of the peripheral nerves. In the proper clinical environment these potentials can be invaluable in localizing lesions either proximal or distal to the dorsal root ganglia. They are among the most sensitive measures of peripheral nerve dysfunction and are more sensitive than motor conduction studies in most forms of peripheral neuropathy. Additionally, the responses may be able to provide some information about the pathophysiology of the neuropathy, suggesting demyelination or axonal loss in some cases. Because sensory nerve action potentials are much smaller than compound muscle action potentials (being microvolts in size, compared to millivolts of the compound muscle action potential), they are technically more difficult to perform and require greater expertise and caution. Temperature will have a greater impact on sensory potentials than motor potentials, with cooler limb temperatures leading to longer latencies, slower conduction velocities, and larger amplitudes. Background electrical interference may be a problem when recording sensory nerve action potentials. As a result, responses are commonly averaged three to five times to minimize the effect of the background noise on the waveforms. Distance from the electrical generator and interelectrode distance will also impact the appearance and size of the nerve potential waveform. All of these variables should be standardized wherever possible. |
