Normal pressure hydrocephalus

Case contributed by Dr Andrei Tsoriev

Presentation

Male patient with gradually developed gait disturbance up to progressing tetraparesis, urinary incontinence, and progressive dementia.

Patient Data

Age: 64
Gender: Male
Modality: MRI

Significant dilatation of all cerebral ventricles, transverse diameter of the third ventricle being 17 mm. Periventricular edema: band-like duffuse signal increase on T2-weighted and FLAIR images along the walls of lateral ventricles. Accented CSF flow signal void in aqueduct on T2-weighted axial images with dilatation of cerebral aqueduct. Lack of ventricular obstruction. Disproportional widening of basal and Sylvian CSF fussures and ventricles and narrowing of medial parasagittal fissures. Lack of deformation of the 3rd ventricle's floor, indicating normal interventricular pressure, pointing at "normal pressure hydrocephalus". Callosal angle is 74 degrees, Evan's index is 0,36. No abnormal contrast enhancement, excluding meningeal and/or arachnoidal lesions, which may cause aresorbtive hydrocephalus.

 

Modality: Annotated image

Several signs of normal pressure hydrocephalus:

Case Discussion

Gradually deteriorating neurologic condition with developing characteristic clinical triad, which is called '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 responce to CSF shunt placement in approximately 70-80% of cases. Besides this imaging in dementia with neurologic deficit id mandatory to exclude other potentially treatable disease, 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 fussires: basal and Sylvian being wide while parasagittal being narrow if present at all.
  3. Wide aqueduct with significant signal void in it from high speed flow on T2-weithted 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 significant neurologic deficit.
  6. Narrow callosal angle (see annotated image) which is less than 90 degrees.
  7. Increased Evan's ratio, more than 0,3.

Proposed diagnostic criteria for NPH are:

Disproportiomal widening of cerebral ventricles (Evan's index more than 0,3)

No visible CSF flow occlusion

And onу or more of the following:

  • Callose 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 was rapidly inproving. Tetraparesis regressed and he started to walk by himself, cognitiion have been also markedly improving. That is why this case considered proven: surgical proof.

 

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Case Information

rID: 34294
Case created: 13th Feb 2015
Last edited: 12th Jan 2016
Inclusion in quiz mode: Included

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