Normal pressure hydrocephalus

[kunfu]

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Goljan in the latest edition of RR on pg 570 says normal pressure hydrocephalus has increased subarachnoid space volume.

First Aid 2010 on pg 404 makes a point of saying normal pressure hydrocephalus does not result in increased subarachnoid space volume.

Any thoughts? I don't understand the pathogenesis enough to work this one out.

 

[radiodoc99]

• exact cause unknown but theories include
  • ventricular dilation may be caused by disorder of decreased cerebrospinal fluid (CSF) absorption, but mechanism leading to NPH is unknown
  • arachnoid granulations fail to maintain baseline CSF removal, perhaps due to fibrosis or scarring
  • pressure gradient develops between subarachnoid space and ventricles, leading to decreased CSF production and higher but still normal baseline pressure
• ventricles become distended, periventricular parenchyma compressed, sometimes causing periventricular pattern of ischemia