Normal-pressure hydrocephalus

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By Peter Hedera MD and Robert P Friedland MD

The only established treatment of normal-pressure hydrocephalus is a CSF-diverting operation. However, the selection of patients to potentially benefit from a shunt is controversial. It varies from a rigorous approach to offering the benefit of the doubt. An operation should be considered in patients with a history of dementia for less than 2 years and prominent gait impairment; patients with isolated gait impairment are particularly good candidates for an operation (Graff-Radford and Godersky 1986). Concurrence of cerebrovascular disease predicts poor response to shunt placement (Boon et al 1999). Patients who have a high risk of surgical complication may be treated by repeated high-volume lumbar punctures (Lim et al 2009).

Marked cortical atrophy is not a contraindication for operation, as many patients with normal-pressure hydrocephalus are older. Patients with amelioration of symptoms after lumbar puncture or temporary lumbar drainage are likely to respond positively to a shunt. Invasive monitoring can reduce uncertainty in atypical cases. Resistance to outflow higher than 18 mmHg/ml per minute has the highest positive predictive value for significant improvement (Boon et al 1997). Quantitative MRI CSF flow measurement with a CSF stroke volume of more than 42 microliters has also been reported to be useful in predicting outcome of shunting (Bradley et al 1996).

Indication for the shunt procedure in patients without the typical clinical picture or with a long history of symptoms is difficult. However, patients should be monitored for new symptoms; in particular, demented patients who develop characteristic gait impairment should also be considered for shunt operation (Poca et al 2005). There is no conclusive evidence that any type of shunting procedure or valve opening pressure has superior results. However, results of the Dutch normal-pressure hydrocephalus study suggest that patients with low-pressure shunts have a tendency for better outcome than patients with medium-pressure valves (Boon et al 1998). Shunt siphoning with restoration of the ventricular size should be considered in patients with shunt-nonresponsive hydrocephalus (Bergsneider et al 1999).

Production of CSF can also be reduced by acetazolamide or digoxin. Patients with high perioperative risk may benefit from a pharmacological approach. Treatment with 125 to 375 mg per day of acetazolamide improved periventricular hyperintensities and gait parameters in a small group of patients with normal pressure hydrocephalus (Alperin et al 2014). However, conclusive clinical studies are not available in normal-pressure hydrocephalus patients treated with these compounds.

In This Article

Historical note and nomenclature
Clinical manifestations
Clinical vignette
Pathogenesis and pathophysiology
Differential diagnosis
Diagnostic workup
Prognosis and complications
References cited