A Proximal Conducting Technique of Sural Nerve

OBJECTIVE: The sural nerve is a sensory nerve in the lower extremity which is formed by the union of the medial sural cutaneous nerve of tibial nerve and the communicating branch of the common peroneal nerve. The objective of this study is to standardize the electrodiagnostic technique of proximal conduction of sural nerve and to investigate the usefulness of the technique in evaluation for the patients with peripheral neuropathy. METHOD: Fifty eight extremities in 29 normal adults without the clinical signs and symptoms of peripheral neuropathy were evaluated with sural nerve conduction study. The active recording electrode was placed over 14 cm proximal to the lateral malleolus, and the reference electrode was placed over 4cm distal to the active electrode. The antidromic evoked responses were recorded with stimulation at points 7, 14, 21 cm proximal to the recording electrode and directly over the sural nerve. RESULTS: The mean values of proximal conduction study of sural nerve in normal adults were 2.40 1.03 msec for peak latency, 11.55 +/-7.31 microvolt in amplitude with stimulation at 7 cm proximal to the recording electrode; 3.43 +/-0.78 msec for peak latency, 10.87 5.86 microvolt in amplitude with stimulation at 14 cm; 4.51 +/-0.83 msec for peak latency, 8.78+/- 4.10 microvolt in amplitude with stimulation at 21 cm. CONCLUSION: A method of proximal conduction study of sural nerve was introduced which could be used as a valuable technique for the evaluation of peripheral neuropathy.

Clinical Features and Electrodiagnostic Findings of Ulnar Neuropathy at the Elbow

OBJECTIVE: To evaluate the clinical and electrodiagnostic findings of ulnar neuropathy at the elbow. METHOD: Sixty-two patients with ulnar neuropathy at the elbow were reviewed retrospectively to establish causes, severity and type of neuropathy, symptom, sign, operation name and operative findings. RESULTS: 1) Of total 62 cases, 41 were male and 21 were female and the most often were in their forties and fifties. 2) The main cause of the neuropathy is bone deformity caused by previous fracture or dislocation (43.6%). 3) The symptoms observed were motor weakness (66.1%), sensory change (79%) and muscle atrophy (35.5%). 4) Forty-nine cases showed abnormality in nerve conduction study and needle electromyography study, and 9 cases showed abnormality only in the needle electromyography study. 5) On needle electromyography, sparing of flexor carpi ulnaris was shown in 50 cases (80.6%). 6) Operative treatment was performed in 15 cases. Among them, electrodiagnostic and operative diagnosis coincided in only 12 cases (80%). CONCLUSION: We conclude that above clinical and electrodiagnostic findings are useful for the diagonosis ulnar neuropathy at the elbow with consideration of etiology, localization and for the selection of operative treatment.

Clinical Significance of the R3 Response of the Blink Reflex in Medullar and Cervical Spinal Cord Lesions

OBJECTIVE: To compare the R3 response of the blink reflex in medullar and spinal cord lesion and to investigate whether the reflex arc of the R3 response descend to the cervical spinal cord or not. METHOD: We have studied 3 patients with medullar lesion and 5 patients with cervical spinal cord or vertebral lesion. Normal ranges of the R3 response refer to the results suggested by Moon et al. RESULTS: In 3 patients with medullar lesion, two patients with lateral medullar lesion showed delayed R3 latency or no evoked potential. Four patients with cervial spinal cord lesion showed no R3 response. In one patient with disc protrusion R3 was normal. CONCLUSION: Our results support the hypothesis that the reflex arc of the R3 response descend to the cervical spinal cord.

Significance of Intraoperative Monitoring with Median Nerve Somatosensory Evoked Potentials during Operation for Cerebral Aneurysm

OBJECTIVE: Intraoperative somatosensory evoked potentials (SEPs) are widely used for the early detections of cerebral ischemia during temporary occlusive procedures of the parent vessels in aneurysm surgery. This study intended to evaluate the usefulness of median nerve SEPs during intracranial aneurysm surgery. METHOD: Between September 1995 and June 1997, we monitored 42 aneurysm patients in Uijongbu St. Mary's hospital. Median nerve SEPs were detected on scalp and cervical spine during surgery. We measured latencies, amplitudes of N20 and N13 waveforms and central conduction time (CCT, N20-N13). We analyzed pre- and post-surgical radiologic findings and changes of neurologic signs. RESULTS: The delayed latencies, CCT, and reduced amplitudes of median nerve SEPs during intraoperative monitoring were closely related to neurological deficits after surgery. CONCLUSION: Intraoperative SEPs are useful in preventing clinical neurological injury during surgery of intracranial aneurysm and in predicting which patients will have unfavourable outcomes.

The Clinical Significance of Residual Latency in Diagnosis of Diabetic Neuropathy

OBJECTIVE: To determinate the reference values of residual latencies of motor nerves and to evaluate the early diagnostic value of residual latency. METHOD: The subjects were 129 diabetes mellitus patients and 60 controls with no known neurological disorders. The patients were divided into two groups based on the conventional nerve conduction study: Group 1, 75 patients without neuropathy; Group 2, 54 patients with neuropathy. The group 2 patients were subdivided into 4 sub- groups on the basis of conduction velocity and residual latency of the median nerve. Residual latencies were measured in all subjects and glycosylated hemoglobin percentages (HbA1c) were measured in the diabetes patients. In group 2, each nerve conduction parameter was correlated with the duration of diabetes and HbA1c. The duration of diabetes, HbA1c, and amplitude of median nerve response were compared between the subgroups of group 2 patients. RESULTS: Motor residual latencies obtained from the controls were 1.93+/-0.28 msec, 1.53+/-0.24 msec, 2.46+/-0.43 msec, 2.21+/-0.53 msec in median, ulnar, deep peroneal and posterior tibial nerves, respectively. In group 1, motor residual latencies of median & deep peroneal nerves were significantly delayed compared with those of the controls. In group 2, motor residual latencies of median, ulnar, deep peroneal and posterior tibial nerves were significantly delayed more than those of the controls and group 1. In group 2, increased HbA1c correlated to the decreased conduction velocities of median, deep peroneal, posterior tibial nerves but not to the residual latencies. In the subgroup of group 2 (2-D), the nerve involved more distally showing lower compound muscle action potential and higher HbA1c. CONCLUSION: Residual latency measurement can be a useful diagnostic method for the early detection of diabetic neuropathy.