Normal pressure hydrocephalus

Discussion:

Gradually deteriorating neurologic condition with developing characteristic clinical triad, which is called the "triad of Hakim-Adams" is typical for elderly-onset normal pressure hydrocephalus (NPH).

Imaging findings allow for correct recognition of the condition and predict a good response to CSF shunt placement in 70-80% of cases. Besides this imaging in dementia with a neurologic deficit is mandatory to exclude other potentially treatable diseases, such as tumor, stroke and various inflammatory and/or infectious processes.

Typical imaging symptoms of NPH include:

  1. Marked dilatation of ventricles
  2. Disproportional size of basal and Sylvian and parasagittal CSF fissures: basal and Sylvian being wide while parasagittal being narrow if present at all.
  3. Wide aqueduct with a significant signal void in it from high-speed flow on T2-weighted images.
  4. Lack of downward bending of the 3rd ventricle floor, indicating of normal ventricular pressure.
  5. Periventricular edema, which is not consistently present, but more often visible in decompensated cases with a significant neurologic deficit.
  6. Narrow callosal angle of less than 90 degrees.
  7. Increased Evan's ratio, more than 0.3.

Proposed diagnostic criteria for NPH are:

  • disproportional widening of cerebral ventricles (Evan's index more than 0.3)
  • no visible CSF flow occlusion
  • and onу or more of the following:
    • callosal angle ≤ 90 degrees
    • periventricular edema
    • signal void in aqueduct and/or 4th ventricle

The difficulty of distinguishing NPH from other disorders with cerebral atrophy is one of the reasons why more than 80% of NPH cases go unrecognized and under- or even untreated. Modern means to distinguish cerebral atrophy and NPH include both imaging and non-imaging methods, the former are phase-contrast dynamic MRI study of cerebrospinal fluid flow, MR-imaging with measurement of diffusion tensor and diffusional kurtosis, diffusivity histogram analysis, 

Since clinical and imaging findins in the patient were consistent with NPH, he was shunted and after shunt placement, his condition rapidly improved. Tetraparesis regressed and he started to walk by himself, cognitiion have been also markedly improving. 

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