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Brain stem auditory evoked responses (BAERs) were recorded in 50 normal adult subjects at various click rates. Attention was paid to absolute latencies, interwave latencies, interear interwave latencies, absolute amplitudes, and various amplitude ratios. The variability of waves VI and VII suggests that the clinical utility of these waves is restricted-their absence is not necessarily due to a CNS lesion. The wave IV-V complex appears with six different patterns. These variations must therefore be considered normal; none should be misconstrued as indicative of disease of the CNS. Repeated studies over a period of two to nine months showed no statistically significant changes in amplitude or latency measurements with the passage of time. Knowledge of these normal values and their variations, as a precondition for establishing criteria for abnormality, is essential to the interpretation of BAERs in clinical situations.

Late response (H reflex and F response) and sural conduction studies were used in addition to conventional motor and sensory conduction to detect peripheral neuropathy in 30 randomly selected patients with chronic renal failure (18 receiving hemodialysis), five of whom had no clinical evidence of peripheral neuropathy; 30 age-matched control subjects were also studied. Conventional motor (median, ulnar, peroneal, and tibial) and sensory (median and ulnar) nerve conduction studies showed abnormalities of motor conduction in 25 (83%) and of sensory conduction in 26 (87%) patients. Abnormalities of sural nerve conduction and of late responses were present in all 30 patients. Five patients (17%) who had normal routine motor conduction showed abnormalities of late responses in the same nerve distribution. All electrophysiologic abnormalities were significantly more evident in lower limbs. Studies of late responses and sural conduction, in addition to improving the diagnostic yield, provide a method whereby effects of dialysis and medical management can be followed quantitatively in patients whose neuropathy would otherwise be undetectable.

Fifty-one patients with clinically pure optic neuritis (ON) and 149 with possible, probable, or definite multiple sclerosis (MS) were tested with pattern shift visual evoked responses (PSVER) and compared with a group of 43 normal subjects. Attention was paid to response latency, intereye latency difference, as well as differences in amplitude or duration of the major positive peak (P100). Abnormal PSVER cannot be recorded from everyone with confirmed ON. Abnormal responses were recorded from 91% of all patients (including those with MS) who had a history of ON, 57% of all MS patients, and 36% of patients without a history of ON or an abnormal eye examination. Measurements of amplitude and duration proved to be of little value in this setting. Though abnormalities of PSVER are not "specific" for ON or MS, because they also result from other disease processes, they afford more reliable, quantitative documentation of abnormal conduction in visual pathways than any other clinical test.

A study of data on 30 patients with cervical spondylosis was carried out to determine whether short-latency somatosensory-evoked responses (SEPs) to median, ulnar, radial, and peroneal nerve stimulation provided additional information to that obtained by electromyography (EMG), late responses, and peripheral conduction studies. Peripheral studies, EMG results and SEPs were within normal limits in ten patients with pain, but without objective neurological deficit. By contrast, of ten patients who had objective signs of root compression, conventional EMG results were normal in nine, but abnormalities of the SEPs from radial nerve stimulation were obtained in only five patients, and were normal from ulnar and median nerve stimulation. In ten patients with clinical features of myelopathy, seven had abnormal median SEPs and all had abnormal peroneal SEPs, whereas EMG results were abnormal in only five patients. It is suggested that SEPs and EMG are both of limited use in patients with only symptoms of root compression. In patients with signs of root compression, EMG is the most sensitive procedure; however, some additional information can be obtained from superficial radial SEPs. In patients with cervical myelopathy, SEP was the most useful procedure, especially when upper and lower limbs were studied.