Imaging should show an enlargement to at least one of the temporal horns of lateral ventricles, and impingement against the falx cerebri resulting in a callosal angle ≤ 90° on the coronal view, showing evidence of altered brain water content, or normal active flow (which is referred to as "flow void") at the cerebral aqueduct and fourth ventricle.MRI scans are the preferred imaging. The distinction between normal and enlarged ventricular size by cerebral atrophy is difficult to ascertain. Up to 80% of cases are unrecognized and untreated due to difficulty of diagnosis. Imaging should also reveal the absence of any cerebral mass lesions or any signs of obstructions. Although all patients with NPH have enlarged ventricles, not all elderly patients with enlarged ventricles have primary NPH. Cerebral atrophy can cause enlarged ventricles, as well, and is referred to as hydrocephalus ex vacuo. The Miller Fisher test  involves a high-volume lumbar puncture (LP) with removal of 30–50 ml of CSF. Gait and cognitive function are typically tested just before and within 2–3 hours after the LP to assess for signs of symptomatic improvement. The CSF infusion test and the lumbar test are similar tests to Miller Fisher test. The tests have a positive predictive value over 90%, but a negative predictive value less than 50%. The LP should show normal or mildly elevated CSF pressure. CSF should have normal cell contents, glucose levels, and protein levels. Treatment
Ventriculoperitoneal shunts
For suspected cases of NPH, CSF shunting is the first-line treatment.
Among individuals with dementia, the incidence of NPH is thought to be between 2 and 6%. See also
Low pressure hydrocephalus

References
External links
The Normal Pressure Hydrocephalus Center at Johns Hopkins Bayview Medical Center
Normal Pressure Hydrocephalus at Cleveland Clinic
normal_pressure_hydrocephalus at NINDS
When it really is NPH at Likvor
Hydrocephalus in Adults at Spina Bifida Resource Center