Alterations of visual evoked responses in patients with hydrocephalus

Visual evoked responses elicited by a flash stimulus were measured in patients with hydrocephalus documented by CT scan or pneumoencephalography. In infants under one year of age, responses were found to be abnormal in all of the five patients examined. Abnormalities consisted of either alterations of waveform with reduction in the normal number of phases present or delays in latency of the initial response components. In many subjects, both latencies and waveforms were abnormal. In two adult patients studied, latencies of the initial components were normal but alterations in waveform occurred. Although findings were usually present at stimulus frequencies of .5Hz, the use of faster stimulation rates enhanced the abnormalities present. In some patients asymmetry of evoked potentials was associated with an underlying asymmetry of the ventricular system as demonstrated by CT scan or pneumoencephalography. Following treatment of the hydrocephalus by shunting procedures, changes in the VERs were noted within the first week following the operative procedures. Those consisted of shortened latencies and alterations of the waveforms toward a more normal appearance. The findings suggest that the visual evoked response may be a useful tool in the diagnosis and management of patients with hydrocephalus.