THE LIGHT-FLASH-EVOKED RESPONSE AS A POSSIBLE INDICATOR OF INCREASED INTRACRANIAL-PRESSURE IN HYDROCEPHALUS

Surgical treatment of in fantile hydrocephalus by shunt implantation m ay result in suboptimal intracranial pressure. Major neurological impa irments and death are usually prevented by shunt treatment, but minor sequelae may persist or develop. The introduction of adjustable shunts has improved the possibilities of optimizing shunt function and minim izing the risk of such impairments. However, it is still impossible to determine the intracranial pressure without invasive measurements. Cl inical findings and procedures such as computed tomography (CT) are no t always enough to allow a conclusion as to whether a child's signs an d symptoms are the result of suboptimal intracranial pressure (shunt d ysfunction) or are of another etiology. With the aim of reducing the n umber of invasive pressure measurements and CT scans, we investigated the effect of increased intracranial pressure on the visual evoked res ponse (VER). Binocular light flash stimuli of supramaximal intensity w ere used and VER recordings were performed from Oz and Ct. The VER res ults from a group of 31 infants and children with hydrocephalus and 2 children with pseudotumor cerebri were compared with responses from a control group of 35 healthy children. The results show that a subpoten tial, P' (P-prime), usually just preceding P1 (P100), had an increased latency (>96 ms) in all hydrocephalic children before surgery. The P' latency in this group was usually even above 110 ms. The latencies of other VER potentials were also increased but not as consistently as P '. After surgical intervention the VER latencies decreased and usually normalized. The P' latency in four children in the control group was just above the borderline latency, but was less than 110 ms. In the re maining 31 children the VER P' latency was 96 ms or below. The VER pro vides information about the physiological condition of the visual syst em and seems to be related to intracranial pressure. The method was fo und to be useful in the clinical examination of hydrocephalic children . In addition, the VER may be used to monitor patients' clinical condi tion and the effect of treatment, e.g., in cases of pseudotumor cerebr i or traumatic brain injury.