Evaluation of Radiculopathies by Segmental Stimulation and Somatosensory Evoked Potentials

Abstract

SUMMARY:Thirty-six patients with suspected or myelographically proven radiculopathies were investigated with motor and sensory conductions, F-waves, needle electromyography, and somatosensory evoked potentials (SEPs). SEPs were elicited by cutaneous nerve stimulation representative of input from individual cervical and lumbosacral dorsal roots. A myelographic defect was present in 83% of 30 patients who had myelograms. Overall 78% of patients had one or more abnormal electrophysiologic tests, the needle EMG giving the best diagnostic yield (75%). F-waves and SEPs were abnormal in 43% and 57% of cases respectively. Motor deficit correlated best with abnormal EMGs, whilst abnormal SEPs occurred most frequently when sensory deficit predominated. Prolonged latency of the SEP occurred rarely, reduced amplitude or abnormal morphology being the most useful characteristics. SEPs evoked by cutaneous nerve stimulation are a useful addition to conventionally available electrophysiological methods of evaluating radiculopathies, especially in the absence of motor deficit.

Measurement of Knee Tendon Reflex Latencies in Lumbar Radicular Syndromes

“…In a study of radiculopathies using soma tosensory potentials, which were evoked after segmental stimulation [10], a high diagnostic yield was obtained. However, we do not think that measurement of somatosensory evoked potentials should be the method of first choice for patients suffering from a ra dicular syndrome.…”

“…Measurement of 11 rellexes [4,6). F waves [7][8][9], and somatosensory evoked potentials [10] can be helpful in this respect. The elic iting of H rellexes.…”

AAEM Minimonograph 32: The electrodiagnostic examination in patients with radiculopathies

“…Eisen and coworkers found that 16 (57%) of 28 patients studied by this technique had abnormal scalprecorded responses, but NEE had the best diagnostic yield (75%). 28 The most common SEP abnormalities were reduced amplitude and poor morphology; latency abnormalities were uncommon. Using a similar technique, Perlik and associates evaluated the L4, L5, and S1 segments of 27 patients with low-back pain, unilateral radicular symptoms, and abnormal computerized tomography (CT) scans.…”

Diagnostic validity of somatosensory evoked potentials in subgroups of patients with sciatica

“…Sensitivity to diagnose P1 latency prolongation in mixed sensorimotor nerves has been assumed to be reduced in monoradicular nerve root compromise because the evoked response may be conducted through a normal neighboring nerve root and the P1 latency may be normal [7,8,19,20]. The segmental specificity of the sensory nerves used for stimulation in the present study is better than that of mixed nerves, but is not perfect [5,18,19,40].…”