Which imaging measure supports a diagnosis of normal pressure hydrocephalus?

Which imaging measure supports a diagnosis of normal pressure hydrocephalus?

• A. Enlarged sulci without ventriculomegaly.
• B. Demyelinating plaques in periventricular white matter.
• C. Mass effect with midline shift.
• D. Ventriculomegaly with an Evans index >0.3, ventricles enlarged out of proportion to sulci.

Answer: (D)

Imaging for normal pressure hydrocephalus is focused on showing ventriculomegaly that stands out compared with the cortical sulci, quantified by the Evans index. The Evans index is the ratio of the maximum width of the frontal horns to the maximum inner diameter of the skull. When this index is greater than 0.3, it supports hydrocephalus. In normal pressure hydrocephalus, the ventricles enlarge disproportionately to the sulci, so you see prominent ventricular enlargement with relatively preserved or less-widened cortical sulci. This pattern helps distinguish NPH from brain atrophy (where sulci are markedly enlarged) and from other conditions like demyelinating plaques or mass lesions, which don’t show this specific ventricular-to-sulcal disproportion.

Imaging for normal pressure hydrocephalus is focused on showing ventriculomegaly that stands out compared with the cortical sulci, quantified by the Evans index. The Evans index is the ratio of the maximum width of the frontal horns to the maximum inner diameter of the skull. When this index is greater than 0.3, it supports hydrocephalus. In normal pressure hydrocephalus, the ventricles enlarge disproportionately to the sulci, so you see prominent ventricular enlargement with relatively preserved or less-widened cortical sulci. This pattern helps distinguish NPH from brain atrophy (where sulci are markedly enlarged) and from other conditions like demyelinating plaques or mass lesions, which don’t show this specific ventricular-to-sulcal disproportion.