The input device for our sense of
balance is called ' The vestibular Apparatus'. It consists of three
semicircular canals at right angles to each other. They are located in
the inner ear. The inner ear measures the size of a dime and is located
behind the temporal bone on each side of the skull. The semicircular
canals are filled with fluid and lined on all sides with sensors called
'Otoconia'. these sensors are stimulated by the turbulance and motion
of the fluid inside the canals that send a signal to the cerebellum
which it interprets as our position in space. As we age some of
these Otoconia wear down, break off and float in the endolymph. They
are referred to as Canaliths, to indicate perhaps their degenerated and
calcified composition.They
then randomly collide with the walls of the canal causing a disturbance
in the signal and brief moments of dizziness lasting up to 5 minutes.
Turning the head in bed and looking up are the most common motions that
lead to this disturbance. The most important semicircular canal is the
Posterior one. It has a flat section near the bottom, and is oriented
in the longitudinal plain approximately 55 degrees medial to the
sagittal( nose to occiput ) plain, such that when we turn our head 55
degrees to one direction, the ipsilateral ( same side ) posterior
semicircular canal becomes parallel to the sagittal plain. The flat
part of the canal is located at the bottom 30 degrees below the horizon
such that it becomes horizontal when we put our chin down 30
degrees. The painstaiking description of the geometry of the
posterior semicircular canal is crucial to understanding the theory and
treatment of ' The Canalith repositioning Techniques' used to clear the
posterior Canal off the loose otoconia.
The reason that this is stated as a theory is that these canaliths have
never been observed in autopsies, but have been proven by successful
therapeutic maneuvers. The most impressive of these experiments was
conducted at the National Neurology Hospital in London, England, not to
be confused with London, Kentucky. Patients were strapped in
rotating chairs. In the treatment arm, the chairs were rotated 360
degrees backwards a couple of times. In the control group, the chairs
were rotated forward two complete circles. 9 of eleven patients in the
treatment group were cured versus 1 of 10 patients in the control
group. This successful experiment both proves the Canalith theory and
establishes an effective treatment. The reason the forward
rotation was the control group is because the Posterior semicircular
canal has a closed end anteriorly( see diagram below ), where the
particles have nowhere to
go, posteriorly however, the canal connects to a large resevoir called
the utricle, so that posterior rotation leads to travel and deposition
of these particles into the utricle, with little possibility of getting
back to the canal again. More practical maneuvers were described
by Epley and Semont for administering in the office setting. Most
recently a German group devised home exercises that proved quite
successful in abolishing vertigo. Click on the following link to view
the home treatment exercises for BPPV. Hold each position for 30
seconds. Repeat the exercises 3 times per session 3 times per day until
symptom resolution.