Approach to Normal Pressure Hydrocephalus (NPH)

Normal-pressure hydrocephalus (NPH) is a neurological condition in which excess cerebrospinal fluid (CSF) occurs in the ventricles, and with normal or slightly elevated cerebrospinal fluid pressure. As the fluid builds up, it causes the ventricles to enlarge and the pressure inside the head to increase, compressing surrounding brain tissue and leading to neurologic and psychiatric symptoms. The etiology of NPH remains poorly understand and diagnosis and management remains controversial to this day.[1]

Comorbidity

Diagnostic Criteria for NPH

Adapted from: Fasano, A., Espay, A. J., Tang‐Wai, D. F., Wikkelsö, C., and Krauss, J. K. (2020). Gaps, controversies, and proposed roadmap for research in normal pressure hydrocephalus. Movement Disorders, 35(11), 1945-1954.
International Guidelines (2005) Japanese Guidelines (2012)
Clinical features (Probable) Gait/balance disturbance and at least 1 of the following:
a. Cognitive impairment
b. Urinary incontinence/urgency
At least 2 of the clinical triad:
a. Gait disturbance
b. Cognitive impairment
c. Urinary incontinence
Clinical features (Possible) Symptoms of either:
a. Incontinence and/or cognitive impairment in the absence of gait/balance disturbance
b. Gait disturbance alone
Same as probable
Brain imaging (Probable) Ventriculomegaly (EI > 0.3) and at least 1 of the following:
a. Narrow callosal angle
b. Enlargement of the temporal horns
c. Periventricular signal changes not attributable to ischemic changes or demyelination
Ventriculomegaly (EI > 0.3) and narrowing of the sulci over the high convexity, or presence of disproportionately enlarged subarachnoid space hydrocephalus (DESH)
Brain imaging (Possible) Ventriculomegaly (EI > 0.3) Ventriculomegaly (EI > 0.3)
Duration of symptoms >3 months N/A
Age >40 years >60 years
Comorbidities No other condition Other neurological condition possible (but “mild”)
Opening pressure 70–245 mm H2O ≦200 mm H2O
  • The classic NPH triad consists of gait deviation, dementia, and urinary incontinence (commonly referred to as “wet, wacky, and wobbly” or “weird walking water”). However, this true pathognomonic triad is only present in less than 25% of cases.[4] Gait deviations are present in nearly all patients and usually the first symptom.
  • Notably, the urinary symptoms often begins as polyuria or urgency rather than true incontinence.[5]
  • Individuals with NPH can have non-specific symptoms including psychiatric syndromes.

A typical assessment for NPH includes neurological exam, cognitive testing (e.g., commonly with the MoCA), Tinetti-Gait and Balance (T-G&B) analysis, and MRI brain with fast imaging employing steady-state acquisition (FIESTA) sagittal cuts and cerebrospinal fluid (CSF) flow studies.[9]

  • A classic “magnetic gait” can be seen in NPH, and this gait is often described as if one's feet were “stuck to the ground.”[10]
  • Disproportionately Enlarged Subarachnoid-space Hydrocephalus (DESH) is a feature of NPH that is often not well known or recognized.[11]
    • It is characterized by a pattern of “tight high-convexity and medial subarachnoid spaces, and enlarged Sylvian fissures with ventriculomegaly (on coronal imaging view), this is also described as sulcal effacement.[12]
    • In contrast, a normal appearance involves the presences of my grooves (sulci) on coronal view.
    • Radiological reports may report “ventriculomegaly” if there are dilated ventricles, but this should only be called if DESH is present, otherwise, it should be called generalized volume loss
  • It can also be misinterpreted as cortical atrophy and misdiagnosed as neurodegenerative disease.[13]
  • Combined with the clinical signs, DESH appears to be an imaging finding for NPH that can in predict whether the NPH will be shunt responsive.[14]
    • It is thought that even in shunt-responsive patients, improvements are primarily with gait, but cognition may not consequently improve as well.[15]
  • Remember however, that ventricles do increase in size with age.[16]
  • A trial of a large volume lumbar puncture and observing for improvement in gait and cognition is one way of treating NPH temporarily
  • A ventriculoperitoneal (VP) shunt is the preferred long-term treatment solution for patients that can tolerate surgery
    • VP shunts are a thin plastic tube that helps drain extra cerebrospinal fluid (CSF) from the brain