Role of somatosensory evoked potentials in the diagnosis of peripheral nerve lesions: recent advances.

Short-latency somatosensory evoked potentials (SEPs) have become an important tool in the investigation of peripheral nerve lesions. Electrically evoked SEPs are most suitable because they provide results with small variations and are readily repeatable. Techniques for testing 10 different upper and lower limb nerves, dermatomes, cutaneous fibers of trigeminal nerve, and nerves supplying urogenital areas are now available. The established, principal areas of application are in the investigation of brachial plexus lesions, proximal injuries of individual nerves in upper and lower limbs, and painful dysesthesias and in the differential diagnosis of pain caused by psychogenic causes or organic lesions. The techniques have proven to be of value in demonstrating early proximal abnormalities in polyneuropathies. Abnormalities have occurred in trigeminal nerve lesions, urogenital dysfunctions, hereditary ataxias, and rare neuropathies. Unexpected abnormalities have also been reported in motor neuron disease, myotonic muscular dystrophies, and other conditions. Applications in the diagnosis of spondylopathic root lesions are not satisfactory; the techniques' usefulness in the investigation of these lesions does not extend beyond aiding the selection of patients for other diagnostic modalities, such as myelography, computed tomography (CT), and nuclear magnetic resonance (NMR) imaging. The usefulness of SEP techniques in the diagnosis of peripheral nerve lesions will remain, even if advances in organ imaging techniques can provide more specific information about the level and magnitude of lesions in the central nervous system. SEP techniques are an important complement to the other well-established methods, such as clinical testing, electromyography, and nerve conduction studies.