[Experimental study on reversibility of neuronal function in rats with congenital hydrocephalus]

To evaluate the usefulness of cerebral evoked potential examination in determining the severity of hydrocephalus and its prognosis, we measured brainstem auditory evoked potential (BAEP), somatosensory evoked potential (SEP), and visual evoked potential (VEP) in rats with HTX congenital hydrocephalus. In addition, changes in cerebral evoked potentials were measured before and after shunt operation, and the reversibility of neuronal function was evaluated. In control rats without hydrocephalus, SEP appeared in the latter half of the first week after birth, and VEP and BAEP in the former half of the second week. The peak latency tended to gradually decrease with growth. Significant differences were observed in SEP in the latter half of the second week after birth and in VEP in the former half of the third week between the group with hydrocephalus and the control group. However, BAEP did not significantly differ between the two groups. These results suggest that impairment of cerebral function is more marked than that of brainstem function in rats with HTX congenital hydrocephalus, and SEP is the most useful for evaluating the progression of this disease. Ventriculo-peritoneal shunt was performed in the rats with hydrocephalus in the latter half of the second week, when the N1 latency of SEP began to be prolonged, or in the latter half of the third week. Outcomes markedly differed between the two groups. However, the N1 latency of postoperative SEP was shortened in both groups. These results strongly suggest that the reversibility of neuronal function in hydrocephalus evaluated by SEP examination is well preserved until the terminal stage. Cerebral evoked potential examination, especially, SEP examination may be useful for evaluating the degree of impairment in neuronal function in hydrocephalus.