Abstract
To clarify the pathogenesis of two different types of adult-onset normal-pressure hydrocephalus (NPH), we investigated cerebrospinal fluid distribution on the high-field three-dimensional MRI. The subarachnoid spaces in secondary NPH were smaller than those in the controls, whereas those in idiopathic NPH were of similar size to the controls. In idiopathic NPH, however, the basal cistern and Sylvian fissure were enlarged in concurrence with ventricular enlargement towards the z-direction, but the convexity subarachnoid space was severely diminished. In this article, we provide evidence that the key cause of the disproportionate cerebrospinal fluid distribution in idiopathic NPH is the compensatory direct CSF communication between the inferior horn of the lateral ventricles and the ambient cistern at the choroidal fissure. In contrast, all parts of the subarachnoid spaces were equally and severely decreased in secondary NPH. Blockage of CSF drainage from the subarachnoid spaces could cause the omnidirectional ventricular enlargement in secondary NPH.
Highlights
Total number Mean age Male Evans index >0.3 Z-Evans index >0.4 Callosal angle
Fifty-two patients were diagnosed with iNPH, 15 patients were diagnosed with secondary NPH (sNPH), and 31 participants were allocated to the control group
An opening of the inferior choroidal point, which we here newly define as a direct pathway linking CSF spaces between the inferior horn of the lateral ventricles and the ambient cistern at the inferior choroidal point of the choroidal fissure, was observed in 39 of 52 patients (75%) with iNPH but in only 2 of 11 (13%) with sNPH and in none of the controls (Table 1)
Summary
Total number Mean age (years) Male Evans index >0.3 Z-Evans index >0.4 Callosal angle
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