Background: It is well known that uncorrected hearing loss can lead to increased feeling
of exhaustion, social isolation and decreased quality of life. Sensorineural hearing loss
originates from a damage to the cochlea in the inner ear or to the cochlear nerve and
progresses with increasing age. Severe-to-profound hearing loss (STPHL) is defined as
hearing levels 70 dB or worse on the better ear. The Swedish registry for adult patients
with STPHL has showed that 30 % of the patients suffer from vertigo or dizziness often or
always. The reasons for this are not established.
Apart from the cochlea the inner ear harbors the vestibular system consisting of the
semicircular canals and the two otolithic organs, utriculus and sacculus. The vestibular
system is the sensory system that helps us maintain balance. This study aims to
investigate if patients with STPHL ie cochlear injury also have impaired vestibular
function ie damage to the vestibular system.
The function of the vestibular system can be measured in three main ways. The
semicircular canals can be assessed with caloric irrigation and video head impulse test
(vHIT). The function of the sacculus and utriculus can be determined by the recording of
vestibular evoked myogenic potential (VEMP). The sacculus is assessed by cervical VEMP
(cVEMP) and the utriculus by ocular VEMP (oVEMP).
In patients with sensorineural STPHL the damage is most often located in the cochlea in
the inner ear. The hypothesis in this study is that these patients also have a
deteriorated function in the vestibular system. The aim of this study is to investigate
whether the vestibular function between persons with STPHL
Method: This study will be conducted in the county of Värmland in Sweden, a county with
approximately 280,000 inhabitants. Auditbase is the hearing data software used in
Värmland where all audiograms are stored. By conducting a database search The
investigators have identified all patients in Värmland with severe-to-profound hearing
loss.
Patients aged 50-85 years have been extracted from the initial pool of patients. Ethical
approval has been gained from the Ethics Review Authority in Sweden. An invitation will
be sent to these patients. Only patients with a strict sensorineural hearing loss will be
included in the study. Patients with a cochlear implant will be excluded. After a signed
informed consent has been retrieved from the patient a time for testing will be
scheduled.
The patient will undergo testing with caloric irrigation, vHIT and VEMP. Prior to testing
patient will undergo an otoscopy to verify an intact eardrum.
The tests are described in detail below.
Caloric irrigation: Bi thermal caloric irrigation is performed with 30 and 44 degree
water. Eye movements are recorded with goggles that prevent visual fixation.Nystagmus is
recorded for ten seconds prior to irrigation. Irrigation then follows for a total of 30
seconds. Nystagmus is then recorded during one minute followed by 10 seconds with
fixation and finally 10 seconds without fixation. Slow phase velocity (SPV) is
automatically calculated for each irrigation. Since both ears are measured with cold and
warm water four SPV-values are recorded.
VHIT: This test is carried out in a well-lit room with the patient seated in a
height-adjustable, rotatable chair. Fast head thrusts are performed in the direction of
the semicircular canal. A high speed camera detects the head movement and the
corresponding eye response is recorded. This gives a measurement of the vestibulo-ocular
reflex in the tested canal. If the eye response matches the speed of the head movement
the resulting gain value will be close to 1. With a slower eye response the gain value
will decrease indicating impaired function in that canal.
VEMP: Utricular and saccular function can be measured by VEMP. Sound (500 Hz toneburst,
124 dB SPL) is presented in one ear at a time and the evoked myogenic potential in the
sternocleidomastoid and the superior oblique muscles can be measured respectively. This
gives a measurement of the function of the sacculus (cVEMP) and utriculus (oVEMP). The
measurements that can be performed and analyzed are: response (yes/no), latency to the
response and, amplitude of the response.
The results of the tests will be used to compare whether there are any detectable
differences between patients with STPHL and the control group without STPHL.