Frequency and amplitude of elevation of cerebrospinal fluid resting pressure by the Valsalva maneuver.

BACKGROUND Patients are referred to ophthalmologists to evaluate for papilledema when they are found to have elevated cerebrospinal fluid (CSF) pressure. However, some of these patients have no clinical history consistent with intracranial hyper-tension. We aimed to determine how often and how high patients with normal opening pressure could artificially elevate their CSF pressure to a pseudo-pathologic level by performing a Valsalva maneuver. METHODS We measured CSF pressure at rest and after a Valsalva maneuver in 15 consecutive normotensive patients referred for CSF analysis to determine the frequency and amplitude of elevation of pressure. Manometry was performed in the standard lateral decubitus position with legs and knees extended and abdomen relaxed and then again during a Valsalva maneuver with hip flexion and bearing down against a closed glottis. RESULTS All 15 normotensive patients elevated their CSF pressure to levels greater than 25 cm water. One patient reached a maximum pressure of 47 cm water. INTERPRETATION Artifactual elevation of CSF pressure may therefore occur frequently. Caution is advised before accepting a diagnosis of intracranial hypertension in those lacking this syndrome. These patients require repeat CSF pressure measurements to either verify or refute previous recordings.