A 64-year-old man was referred to us for suspected normal pressure hydrocephalus (NPH), according to the clinical history of gait disturbance and urge incontinence, and radiologic evidence of a supratentorial hydrocephalus, with enlarged pericephalic spaces (figure 1). A new MRI revealed a 4-cm prepontine arachnoid cyst (figure 2). An endoscopic ventriculo-cystostomy was performed with a prompt improvement of symptoms.
Figure 1 First MRI examination
The first MRI examination revealed the presence of supratentorial ventriculomegaly out of proportion to sulcal atrophy, rounded frontal horns, and transependymal CSF flow in the form of periventricular high signal on T2-weighted FLAIR images.
Figure 2 T2-weighted images
(A, B) Preoperative T2-weighted images revealing a space-occupying suprasellar prepontine arachnoid cyst (arrows), displacing superiorly the third ventricle floor, the pituitary stalk and the optic chiasm, and, posteriorly, the mammillary bodies. (C, D) Postoperative T2-weighted images demon-strating a more horizontal orientation of chiasm and third ventricle floor. The cyst has shrunk (arrows).
Eighty-five percent of prepontine arachnoid cysts occur in children; most of them present with acute/subacute signs of increased intracranial pressure. The possibility of diagnosing these lesions in adults has been reported; only two cases have been described in the elderly, none of whom had symptoms of NPH.1,2
ACKNOWLEDGMENT
The authors thank Daniele Petricca for help with illustrations.
Footnotes
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Disclosure: The authors report no conflicts of interest.
Series editor: Mitchell S.V. Elkind MD, MS, Section Editor
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