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The diagnosis and treatment of idiopathic normal pressure hydrocephalus

Abstract

Idiopathic normal pressure hydrocephalus (INPH) is a syndrome that is characterized by gait impairment, cognitive decline and urinary incontinence, and is associated with ventriculomegaly in the absence of elevated cerebrospinal fluid (CSF) pressure. There is significant variation in the clinical presentation and progression of this disorder, and its diagnosis often represents a challenge for neurologists and neurosurgeons. Various supplemental tests, including the CSF tap test, external CSF drainage via spinal catheter, and CSF outflow resistance determination, can improve the accuracy of predicting a response to surgical treatment. CSF shunting provides significant symptom improvement in the majority of appropriately evaluated patients. In 2005, an international study group published evidence-based guidelines for the diagnosis and management of INPH. This review will highlight the clinical presentation, radiographic findings, supplemental prognostic tests, differential diagnosis, surgical treatment and outcomes of INPH.

Key Points

  • Idiopathic normal pressure hydrocephalus (INPH) is characterized by gait disturbance, cognitive deterioration and urinary incontinence, and is associated with ventricular enlargement in the absence of elevated cerebrospinal fluid (CSF) pressure

  • INPH may represent a unique reversible form of neuronal injury, the mechanism of which is not well understood

  • Only a few epidemiological studies on INPH are available, so the incidence and prevalence of this disorder are difficult to determine

  • An essential part of the evaluation of patients with suspected INPH is neuroimaging with either CT or MRI to assess ventricular size

  • Because INPH is a disease of the elderly population, a diverse differential diagnosis of the individual symptoms should be considered, including neurodegenerative diseases, vascular etiologies and urological disorders

  • Treatment for INPH is surgical diversion of CSF, which is accomplished by implanting a shunt to drain CSF from either the intracranial ventricular system or the lumbar subarachnoid space to a distal site, where the CSF can be reabsorbed

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Figure 1: Neuroimaging of two patients with idiopathic normal pressure hydrocephalus.
Figure 2: Development and noninvasive treatment of bilateral subdural hygromas following placement of a programmable shunt for idiopathic normal pressure hydrocephalus.

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Correspondence to Michael A Williams.

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Competing interests

In the 12 months prior to the submission of this manuscript (March 2006), MA Williams and D Rigamonti received financial support for hydrocephalus research from Medtronic, and Dr Williams received honoraria from Medtronic for speaking on the topic of adult hydrocephalus. MA Williams is an unpaid volunteer member of the Medical Advisory Board of the Hydrocephalus Association.

Supplementary information

Supplementary Box 1

Description of idiopathic normal pressure hydrocephalus (INPH) classification: probable, possible and unlikely categories. (DOC 37 kb)

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Gallia, G., Rigamonti, D. & Williams, M. The diagnosis and treatment of idiopathic normal pressure hydrocephalus. Nat Rev Neurol 2, 375–381 (2006). https://doi.org/10.1038/ncpneuro0237

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