Abstract
Normal pressure hydrocephalus (NPH) often complicates after the rupture of intracranial aneurysms (NPH developed in 17.4% of our series). To clarify the pathophysiology and indication of shunting, intracranial pressure (ICP), cerebral blood flow (CBF) and radio nuclide cisternography were studied in patients who developed hydrocephalus after subarachnoid hemorrhage (SAH).
Patients developing hydrocephalus after SAH were divided into three stages, i.e., the acute stage (within one week after SAH), pre-NPH state and NPH state. Pre-NPH and NPH state patients had enlarged ventricles and periventricular lucency on CT scans and delayd absorption of CSF and/or complete block of the subarachnoid space with ventricular filling on cisternography. The ICP base-line in continuous ICP recordings was at a level of less than 15 mmHg in NPH patients, and at a level of more than 15 mmHg in pre-NPH state patients. ICP curves in the acute stage of patients who were drowsy after SAH showed pressure variations superimposed on an increased ICP base-line. The pressure variations were recurring increases in ICP in the range of 20 ?? 40 mmHg and resembled the B and C-waves of Lundberg. ICP curves in pre-NPH and NPH state patients showed plateau waves or B-waves. The plateau waves seen in these patients usually ranged between 30 ?? 50 mmHg and lasted for 5 ?? 10 minutes, i.e., the waves were smaller and briefer than those seen with increased intracranial pressuer from brain tumors. A few NPH patients showed a continuously low and flat ICP curve. ICP in these patients were recorded more than six months after SAH.
Changes in CBF were analysed. Mean values of 42.9 ml/ 100 gr/min were obtained in acute stage patients. Pre-NPH and NPH state patients showed flows of 35.1 and 28.7 ml/100 gr/min, respectively. Marked reduction in CBF (23.8 ml/ 100 gr/min) was found in NPH patients with the low and flat ICP pattern. Thus, CBF was markedly reduced in patients with NPH in spite of the lowered ICP.
The shunting procedure brought about remarkable recovery in pre-NPH and NPH state patients who showed pressure waves in continuous ICP recordings and a CBF of over 25 ml/ 100 gr/min.
