Seventy four consecutive patients diagnosed as normal pressure hydrocephalus (NPH) and operated with a ventriculo-peritoneal shunt were followed prospectively for an average of 2.1 years. The mean age was 64 years. The effect of the operation was estimated by calculating 6 indices expression social functioning, neurological signs, gait ability, continence, psychometric performance and psychiatric condition. Ninety-six % had mental symptoms, 95% gait disturbances and 75% incontinence. Improvement was observed in 78% after shunt surgery, while 22% deteriorated. Psychiatric improvement was seen in 80% and 76% improved in gait ability. Improvement was highest in the group caused by subarachnoid hemorrhage (98%) while 73% with idiopathic NPH improved. Old age was not correlated to poorer response, while long-standing pre-operative symptoms yielded worse results. No single symptom or sign could predict a positive outcome of the operation. Eleven % of the patients could leave long-term care institutions and there was a 36% reduction of aid in daily living. Complications to shunt surgery were observed in 50% of the patients and shunt related mortality was 1%. Shunt malfunction was the most frequent complication (31%) followed by infection (19%). Epilepsy developed in 9% after surgery. All shunt complication except one appeared within the first year after surgery.

This study demonstrates no factual support for existence of a transmantle pressure gradient in nonacute communicating or noncommunicating hydrocephalus.

Relative regional cerebral blood flow (rrCBF) was measured by single-photon emission tomography (SPET), using technetium-99m-d,l-hexamethylpropylene amine oxime (HMPAO) as flow tracer, in 23 patients with normal pressure hydrocephalus (NPH). 1000 MBq 99mTc-HMPAO was given intravenously and the rrCBF calculated as regional/cerebellar count level ratios. The patients were examined before and 3-12 months after ventriculoperitoneal shunt surgery. rrCBF was also determined in ten healthy aged matched volunteers who served as controls. The NPH patients had decreased rrCBF in the hippocampal regions and in the frontal and parietal white matter as compared to the controls. The frontal/parietal rrCBF ratio correlated with both psychiatric disability and the preoperative degree of incontinence. Decreased flow in frontal white matter, frontoparietal and hippocampal grey matter and a low frontalparietal grey matter flow ratio preoperatively correlated with improvement in both Mini Mental State score and psychiatric disability after shunt surgery. After shunt surgery the rrCBF increased in the mesencephalon, frontal grey and white matter, parietal white matter and hippocampus. The flow increase in hippocampal regions and frontal white matter correlated with improvement in psychiatric symptomatology. The results of this study regarding the frontal and hippocampal rrCBF patterns, and the clinical correlation, support the hypothesis that CBF changes in these regions are of pathophysiological and prognostic importance in NPH.