Presentation
Male patient with gradually developed gait disturbance up to progressing tetraparesis, urinary incontinence, and progressive dementia.
Patient Data
- significant dilatation of all cerebral ventricles, transverse diameter of the third ventricle is 17 mm
- periventricular edema: band-like diffuse 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 fissures 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, Evans' index is 0.36
- no abnormal contrast enhancement, excluding meningeal and/or arachnoidal lesions, which may cause resorptive hydrocephalus
- incidental development venous anomaly with cavernous hemangioma in the right hemisphere of the cerebellum
Several signs of normal pressure hydrocephalus:
- narrow callosal angle of 74 degrees
- coronal T2: periventricular edema (green arrows)
- sagittal T1: wide cerebral aqueduct (red arrow) and normal floor of the 3rd ventricle (green arrow)
- axial T2: increased flow void in the aqueduct (green arrow)
- axial T2: narrow parasagittal CSF fissures (green arrows)
- axial T2: wide Sylvian fissures (green arrows)
Case 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:
- marked dilatation of ventricles
- disproportional size of basal and Sylvian and parasagittal CSF fissures: basal and Sylvian being wide while parasagittal being narrow if present at all
- wide aqueduct with a significant signal void in it from high-speed flow on T2-weighted images
- lack of downward bending of the 3rd ventricle floor, indicating normal ventricular pressure
- periventricular edema, which is not consistently present, but more often visible in decompensated cases with a significant neurologic deficit
- narrow callosal angle of less than 90 degrees
- 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 the cerebral 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 findings 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, cognition have been also markedly improving.
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