Acta Neurochir (Wien) (1987) 86:93-97 :Acta Neurochirurgica 9 by Springer-Verlag 1987 Absence of Hydrocephalus in Spite of Impaired Cerebrospinal Fluid Absorption and Severe Intracranial Hypertension K. Hansen, F. Gjerris, and P. S. Sorensen University Clinic of Neurosurgery, Rigshospitalet, Copenhagen, Denmark Summary Four patients are described presenting papilloedema, increased pressure and reduced CSF absorption--caused by either spinal tumours, leptomeningeal carcinomatosis or encephalitis. Remarkably they all had a normal CT without signs of hydrocephalus. A 24-hour intracranial pressure monitoring showed a mean pressure of 30- 35mmHg, recurrent plateau waves and high occurrence of B waves. Conductance to CSF outflow studied by a constant perfusion test was severely reduced 0.010-0.026mlmin l mmHg ~l (normal > 0.12 ml mm Hg -1 rain--l). Despite these findings no ventricular enlargement was seen on serial CT scans. The reason therefore remains unknown. Disappearance of papilloedema and a variable clinical improvement followed shunt-insertion. Introduction Ventricular dilatation is generally expected to de- velop in patients with increased intracranial pressure (ICP) caused by impaired CSF circulation or ab- sorption. However, normal sized ventricles despite raised ICP and impaired CSF absorption have been reported in a few patients with a high spinal protein content 12, 15 and is a constant finding in patients with benign intracranial hypertension (BIH) 9. The reason for the absence of ventricular dilatation remains obscure. We report 4 patients with significantly increased ICP and CSF absorption block of different aetiology but surprisingly no hydrocephalus on CT. Patients and Methods The 4 patients were treated in the Department of Neurosurgery, Rigshospitalet, Copenhagen during the years 1980 and 1983. Estimation of ventricular dilatation was based on serial CT and calculation of the Evans' ratio normally below 0.31. ICP was monitored continuously for 24 hours either via an intraventricular cannula (Statham P 37) (cases 1 and 3) or via an epidural transducer (Philips) (cases 2 and 4). Mean ICP was calculated and occurrence of plateau and B waves registered. CSF absorption was measured by a constant pressure perfusion method: lumbo-ventricular in case 1, lumbo-lumbar in case 2 and 4 and ventriculo-ventricular in case 3. The lumbo-ventricular perfusion method has been described by Borgesen etal.1, while the other procedures are variations of the same. The CSF absorption capacity is expressed as the conductance to CSF outflow normally more than 0.12 ml mm Hg -1 rain-1. CSF was examined for pleocytosis including tumour cells and protein content. The clinical features including ICP recordings, CSF outflow conductance and CSF examination are summarized in Table 1. A sample of a ICP recording (case 2) is shown in Fig. 1. Case ] A 22-year-old man had complained of a gradually increasing headache, nausea, blurred and double vision for about a month. On admission he was mentally alert and except for bilateral sixth nerve palsies and papilloedema the neurological examination was normal. ACT revealed no mass lesions, normal sized ventricules, cisterns, cortical sulci and no periventricular lucency. During the following week he deteriorated with increasing headache and drowsiness. ICP monitoring showed an increased mean pressure of 35 mm Hg, plateau waves and constant occurrence of B waves. Lumboventricular perfu- sion test indicated a decreased CSF absorption. CSF examination was normal, except a very high protein concentration. This finding lead to the suspicion of a spinal turnout. A X-ray film of the total vertebral column showed scalloping of the posterior aspects of the vertebral bodies and dilatation of the lumbo-sacral spinal canal. Myelography disclosed a 1 cm tumour behind the vertebral body of S 3. At laminectomy it was removed almost completely and histolog- ical examination showed a myxopapillary ependymoma Kernohan type 1. After the operation the patient deteriorated gradually with increasing headache, drowsiness, beginning dementia and rising spinal protein. Two months after admission a ventriculo-atrial Hakim medium pressure shunt was implanted followed by slight