[Extraventricular obstructive hydrocephalus]

In extraventricular obstructive hydrocephalus (EVOH) there is an impaired outflow from the subarachnoid space usually at the level of the basal cisterns or arachnoid granulations. Subarachnoid haemorrhage, suppurative meningitis, and neoplastic or inflammatory exudates may fibrose or occlude the subarachnoid space. Following early reports that the response to shunt procedures was universally excellent, CSF shunting operations were performed on a large scale. Presence of the typical clinical triad, identified underlying aetiology, predominance of gait disorder, short duration of illness, absence of atrophy on CCT scan, typical lumboventricular perfusion picture, and improvement after high-volume lumbar puncture usually predict a beneficial response to surgery. The case presented here, however, indicates a favourable outcome of shunt surgery even in idiopathic EVOH with long duration of illness and without substantial clinical improvement after high-volume lumbar puncture. Thus, in clinically progressive idiopathic EVOH, shunt surgery should be considered in spite of a high complication rate, since there are no promising therapeutic alternatives for this syndrome.