Magnetic Resonance Differential Diagnosis of Normal Pressure Hydrocephalus and Alzheimer Disease

Abstract

Background: Normal pressure hydrocephalus (NPH) is a progressive sub-acute or chronic disorder with a triad of clinical manifestations: 1) cognitive impairment 2) gait impairment 3) urinary incontinency. Radiological findings in NPH include: ventricular enlargement, periventricular signal changes, periventricular edema, increase Evans Index (at least 0.3), temporal horn enlargement and callosal angle of greater than 40°. One of the most important differential diagnoses of NPH is Alzheimer disease (AD). However, ventricular enlargement is common in a variety of dementing disorders and urinary and gait abnormalities are also common in the elderly. In this study, we want to compare the size of lateral ventricles, third ventricle, temporal horn, peri hippocampal fissure, Evans index and callosal angle in NPH and AD patients.

Materials and Methods: In this study 45 participates divided into 3 groups: 1) NPH 2) AD 3) Control. At first all of participates received MMSE questionnaire. MRI findings of 3 groups compared with each other. We graded lateral ventricles, third ventricle, peri hippocampal fissure and temporal horn for size as a follows: 0=normal 1= mildly dilated 2=moderately dilated 3=markedly dilated. We also measured Evans index and callosal angle.

Results: Significant differences between the two groups were found for the size of lateral ventricles, third ventricle, perihippocampal fissure, temporal horn and callosal angle. However, there were no significant differences in Evans index between NPH and AD group.

Conclusion: The degree of dilatation of peri hippocampal fissure and callosal angle appears to be sensitive and specific markers to differentiating AD from NPH because of very small overlap between two groups. Also we cannot found Evans index as a specific marker for diagnosis of NPH as reported in the past studies.