The Value of the Dermatomal Somatosensory Evoked Potentials in Patients with Lumbosacral Radiculopathy

OBJECTIVE: The purposes of this study were to evaluate the diagnostic value of dermatomal somatosensory evoked potentials (DSEPs) in the unilevel/unilateral lumbosacral radiculopathies. METHOD: The study was performed on 41 patients with herniated lumbosacral disc which was confirmed by magnetic resonance imaging, and the patients with clinical lumbosacral radiculopathies (L5 radiculopathy in 33 cases and S1 radiculopathy in 8 cases). Stimulation sites were over the dorsum of the foot on the distal fifth metatarsal bone for the S1 dermatome and at the interdigital web space between first and second toe for the L5 dermatome. Recordings were made at Cz' and reference to Fz. Conventional nerve conduction study, needle EMG and H-reflex were also examined. RESULTS: While the needle EMG showed abnormalities in 32 patients (78.0%), the abnormalities of DSEPs were in 13 patients (31.7%): 33.3% for the L5 radiculopathy and 25.0% for the S1 radiculopathy, respectively. Moreover, there was no significant relationship between the abnormal findings of needle EMG and DSEPs (p>0.05). The H-reflexes were abnormal in 6 of 7 patients (85.7%). And then two of them were found abnormal in S1 DSEPs. CONCLUSION: The conventional needle EMG appears to be the more useful electrophysiological technique in the diagnosis of lumbosacral radiculopathies. The ultimate diagnostic value of DSEPs in lumbosacral radiculopathies is doubtful and controversial.

The Usefulness of Sympathetic Skin Response in Patients with Chronic Renal Failure

OBJECTIVE: The sympathetic skin response (SSR) was measured in patients with chronic renal failure (CRF) for diagnosis of uremic polyneuropathy and its correlations with nerve conduction study (NCS) and clinical autonomic symptoms were investigated. METHOD: The SSR was measured in 15 patients with CRF on regular hemodialysis, aged 26 to 67 years. With median nerve stimulation at the wrist using the extremity without arteriovenous fistula, the SSR was recorded from both palm and sole simultaneously. The responses were interpreted as normal (presence) or abnormal (absence). Routine nerve conduction study was also performed in the same extremities and clinical autonomic symptoms were investigated. RESULTS: Nine of fifteen patients (60.0%) had symptoms suggestive of autonomic dysfunction: the most frequent findings were orthostatic dizziness and sweating problem. The SSR was absent in four of fifteen patients (26.7%). There is no significant relationship between SSR and autonomic symptoms (P>0.05). The nerve conduction study was abnormal in eight of fifteen patients (53.3%), and the SSR was absent in two of seven patients with normal NCS. There is no significant relationship between NCS and SSR (P>0.05). CONCLUSION: Although the proportion of abnormal SSR was small, it may be a valuable method in the assessment of uremic polyneuropathy in conjunction with routine nerve conduction study in CRF patients.

The Diagnostic Value of the F-wave in Patients with Lumbosacral Radiculopathy

OBJECTIVE: The purpose of this study was to examine the sensitivity and characteristics of F-wave abnormalities detected by various parameters in patients with lumbosacral radiculopathies and to evaluate the relationship of F-wave with needle EMG. METHOD: The study was performed on 37 patients with lumbosacral disc herniation, which was confirmed by MRI and the patients with clinical lumbosacral radiculopathies (single lesion of L5 in 28 cases, S1 in 1 case, double lesion of L5 and S1 in 8 cases). F-waves were recorded by stimulating peroneal and tibial nerves at the ankle. Minimal latency (F min), maximal latency (F max), latency difference between F min and F max (F dif), mean duration (F dur) and side to side difference between sides in F min and F max were measured. Conventional nerve conduction study and needle EMG were also examined. RESULTS: The abnormal parameters of F-wave were so varied that the results could not lead any apparent conclusions as to which parameters were the most sensitive. However, F min and F dur seemed to be abnormal more frequently than F max and F dif. While the needle EMG showed abnormalities in 28 patients (75.7%), at least one of the different F-wave parameters was found to be abnormal in 18 patients (48.6%). Moreover, no significant relationship was observed between the abnormal findings of EMG and F-wave (p>0.05). CONCLUSION: The conventional needle EMG appears to be the more useful electrophysiological technique in the diagnosis of lumbosacral radiculopathies. Concerning the additional usefulness of F-wave, further study will be necessary.