Imaging: Both computed tomography (CT) and magnetic resonance (MR) may demonstrate findings suggestive of the NPH. The most commonly described finding suggesting NPH is enlargement of the ventricles out of proportion to sulcal atrophy, commonly referred to as ventriculosulcal disproportion and/or ventriculomegaly. As with many imaging tests, the suggestion of NPH based on imaging is not diagnostic of the disease and clinical correlation with history, symptoms, and physical exam is warranted. If there is uncertainty, a neurological consult may be warranted.

While findings of ventriculomegaly are the most commonly described features suggestive of NPH on imaging, other findings on MR can also lead to a suggestion of NPH. Additional MR findings include:

• Abnormal CSF flow, specifically increased flow through the cerebral aqueduct.
• Abnormal brain signal about the ventricles, suggestive of transepependymal CSF flow.
• 50-60% of patients with NPH will have periventricular and deep white matter lesions.
• MR Spectroscopy (MRS) can demonstrate lactate peaks in the lateral ventricles in NPH patients, but not in those with other types of dementia.
• Diffusion Tenor Imaging (DTI) is an MR technique which can be used to evaluate white matter pathology, and some studies have demonstrated that white matter changes can help distinguish between NPH and various dementias (8).

Nuclear medicine studies have also been used to evaluate NPH. Indium-111 DTPA (diethylene triamine penta-acetic acid) can be instilled in the CSF via a lumbar puncture. Normally, the tracer is resorbed over the convexities in 2-24hrs. In NPH, reflux of the tracer into the ventricles is seen with lack of tracer accumulation over the convexities 24-48 hours after instillation. Patients with this appearance may respond better to shunting than patients with a normal or equivocal In-111 DTPA study (9). Other nuclear medicine studies such as 18F-FDG PET also may be used to evaluate for NPH, but are reserved for a more advanced clinical evaluation.