Brugia Malayi - Clark Science Center - Smith College

Otoacoustic Measurements on Patients with Idiopathic Intracranial
Hypertension before and after Lumbar Puncture
Mary McGrath and Alina Pechacek
Astronauts have returned from long missions at the International Space Station having shown signs of elevated intracranial
pressure (ICP). Distortion product otoacoustic emissions (DPOAEs) are known to change systematically with ICP. 1 The goal
of this study is to map known ICP to DPOAE so that DPOAEs may be used in future space missions to assess the ICP of
astronauts.
This study compares the DPOAE, reflectance, and impedance measurements of subjects before and after the draining of
cerebral spinal fluid (CSF) during a lumbar puncture (LP). The main populations studied were patients with idiopathic intracranial
hypertension (IIH), a condition that results in increased global ICP due to imbalanced in and out flows of CSF, which is relieved
by draining the CSF during an LP. This study has two sets of measurements on each subject, for each of which the ICP of the
subject is known. Subjects were limited to ages between eighteen and 65. IIH patients were referred to St. Luke’s Episcopal
Hospital from local neurologists for an LP. Control subjects were recruited from St. Luke’s Episcopal Hospital’s in-patients
needing an LP for diagnostics.
The LP begins with the subjects either sitting up or lying on their side with their back in a convex position. Once the needle
is in place, the subject is asked to lie on their side with legs extended and head in line with the spine to ensure accurate pressure
readings. After the opening pressure has been read, the middle ear pressure (MEP) is taken using a tympanometer. An ER10C
probe with a foam tip is then inserted into the ear and given time to expand before starting reflectance and DPOAE measurements
using the Mimosa HearID system. The CSF is then drained and the closing pressure is read. Finally the middle ear pressure,
reflectance and DPOAE measurements are repeated.
The collection of data for this study is still in progress, as only a portion of the total number of subjects for the study as
stated in the IRB were able to be recruited during our 8 week, direct involvement in the study. A significant portion of time
was spent training doctors and a research nurse how to properly use the equipment to continue taking measurements after our
departure to complete the study.
The preliminary data shows some of the expected changes in DPOAE magnitude and phase associated with a known change
in ICP. (Supported by the National Science Foundation)
Advisor: Susan Voss
References:
1
Marchbanks, R. J. and Reid, A. (1990). Cochlear and cerebrospinal fluid pressure: Their inter-relationship and control mechanism. Int. J. Audiol., 24, 179-187.
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