Chronic Hydrocephalus Clinical Trial
Official title:
Validation of a New Non Invasive Method of Indirect Measurement of the Intracranial Pressure Variations
The intracranial pressure (ICP), defined by the hydrostatic pressure of the cerebrospinal
fluid (CSF), is a key parameter for diagnosing and treating several neurosurgical diseases.
Continuous ICP monitoring has an important place in neuro-intensive care for patients with
severe head trauma and severe meningeal hemorrhage.
Until now the assessment of ICP requires invasive methods, with a pressure transducer either
within the ventricular CSF or within the brain parenchyma. The pressure sensor placement is
performed in a neurosurgery department. These invasive methods have also disadvantages:
highest risk of infections, catheter misplaced, and risk of bleeding. All these justify the
development of a non invasive method. The Biophysics Laboratory (School of Medicine of
Clermont-Ferrand) described that the intra-labyrinthic pressure (ILP) modify the functional
activities of the outer hair cells in the cochlea.
Cochlear activities' recording is non-invasive and technically simple. A probe is gently
inserted into the outer portion of the external ear canal.
Anatomical studies showed communication between the subarachnoid spaces and the
perilymphatic compartment by the cochlear aqueduct. Thereby, increases in ICP are
transferred to increases in intra-cochlear pressure, which is detected as modifications in
cochlear activities.
CSF dynamic tests, as constant flow infusion test, are conducted in patients in the
diagnosis of the idiopathic adult hydrocephalus syndrome. Artificial CSF is infused through
a lumbar needle, into the CSF space at a constant rate, and the corresponding rise in ICP is
registered and analyzed.
The objective of this study is to assess prospectively the accuracy and the precision of a
new method for non invasive ICP measurement (using cochlear activities) compared with
invasive gold standard CSF pressure measurement during CSF dynamic tests.
The purpose of this study is to examine the evolution of the electrophysiological cochlear
activity (cochlear microphonic potential, CMP), with a non invasive method, during invasive
ICP monitoring. The data analysis will determine relationship between ICP variations and CMP
variations.
Patients, from the neurosurgery department, investigated for 'normal pressure' chronic
hydrocephalus are involved in CSF dynamic test. This complex protocol, including infusion
test and invasive CSF monitoring, is needed in order to confirm the diagnosis. CSF dynamic
tests, a socalled 'perfusion test', are performed in an operating theater, the patient had
to be awake but sedated. During perfusion test, electrophysiological cochlear activities are
measured with a gold tiptrode (Etymotic Research, Elk Grove Village, Ill) gently inserted
into the ear canal.
Electrophysiological cochlear activities, so called electrocochleography (ECochG), are a non
invasive and totally passive method used in routine in ENT department. The response measured
in ECochG is the cochlear microphonic potential (CMP), generated by the outer hair cells
following by presenting tone burst at 1kHz. CMP is recorded with the help of an Echodia®
hand-held equipment.
Previously animal studies have shown that the phase of CM is sensitive to ICP changes and CM
phase shifts exhibit the same time course as those of otoacoustic emissions (DPOAEs).
The phase changes of CM can indeed be used as a non-invasive tool for monitoring
intralabyrinthine and intracranial pressures.
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Intervention Model: Single Group Assignment, Masking: Single Blind (Subject)