Effects of spontaneous chronic hypoglycemia on central and peripheral nervous system in insulinoma patients before and after surgery: a neurophysiological follow-up.

To investigate the effects of spontaneous chronic hypoglycemia on the peripheral and central nervous system, a multimodal neurophysiological evaluation [median somatosensory (mSEP), brain stem auditory (BAEP), and visual (VEP) evoked potentials recordings] was performed in seven insulinoma patients before and 3 and 6 months after surgical removal of tumor. Before surgery, mSEP findings showed abnormal reduction in peripheral wrist-Erb conduction velocity in three patients as well as a pathological increase in Erb-N13, N13-N20, and Erb-N20 conduction times in five cases. BAEP and VEP recordings gave pathological results in two patients. Moreover, during hypoglycemia, the III-V and I-V interpeak latencies of BAEPs were significantly prolonged (P < 0.01 and P < 0.005, respectively) compared to recordings in euglycemia. After 6 months, a mSEP recovery, even if partial was noted in four patients, BAEPs were normalized in one case, and VEPs were unmodified. Compared to presurgery data, these recordings showed a significant (P < 0.05), but incomplete, shortening of BAEPs (III-V and I-V interpeak latencies) and mSEPs (Erb-N13 and Erb-N20 conduction times). Our findings demonstrate that multiple and selective neurophysiological abnormalities are present in insulinoma patients, confirm that hypoglycemia impairs suddenly brain stem function, and show that after tumor removal, long recovery times for improvement of some neurophysiological anomalies are requested.