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Full text of "Diseases Of The Nose Throat And Ear"

z/z                                          THE EAR

stopped, i.e. the equivalent of an acceleration to the left, the endolymph and
cupola will continue to move to the right, the impulse rate from the left
horizontal canal will reduce and the rate from the right canal will increase.
There will be a sensation of rotation to the left, although the head and body
are at rest; there will be nystagmus with the slow phase to the right and the
quick phase to the left. It will be seen that destruction of one labyrinth with
abolition of the resting impulse rate will produce imbalance of impulses
arriving in the central nervous system from the two sides, resulting in the
same effect as vestibular stimulation, i.e. sensation of rotation, nystagmus,
righting reflexes and, if the stimulation is large enough, nausea, vomiting,
pallor of the skin and sweating. Rotation carried out in this way using
controlled accelerations may be used for testing semicircular canal function
but it has the disadvantage of stimulation of the canals of both sides at the
same tune.

FUNCTIONAL EXAMINATION OF THE VESTIBULAR APPARATUS

A careful history of the case must first be taken as regards dizziness, its
duration, severity, mode of onset, and effect of sudden changes in the position
of the head. Was the dizziness associated with nausea and vomiting ? Are the
attacks periodic, and are they associated with any known cause? In which
direction did external objects appear to move? Was the dizziness sufficiently
severe to cause falling? To which side did the patient tend to fall ?

SPONTANEOUS NYSTAGMUS

The patient's head is kept steady in the upright position, and he is told to look
straight forward and then to follow the finger of the examiner held 2 feet
away and moved to the right and left and also up and down. Spontaneous
nystagmus hi any of these positions is noted. In some normal people slight
spontaneous (fixation or fatigue) nystagmus may be observed on looking to
the extreme right and to the extreme left; this nystagmus is equal hi both
directions.

NYSTAGMUS

Nystagmus is of three main typesócentral, ocular and vestibular. Central
nystagmus is generally associated with other signs of intracranial disease.
Ocular nystagmus is usually accompanied by other signs of ocular disease and
is commonly an oscillatory movement. Vestibular nystagmus is accompanied
by vertigo and usually some loss of hearing. It is a rhythmic associated
movement of the eyes and consists of a slow movement of the eyes in one
direction followed by a quick return hi the opposite direction. The slow
movement or component of the nystagmus is the one produced by ear
stimulation. The recovery, or quick movement, is usually held to be of
cerebral origin, but the reflex arc for vestibular nystagmus hi man and other
animals consists of: labyrinth, vestibular nerve, vestibular nucleus, abducens
nucleus, abducens nerve and external rectus muscle. It is perhaps unfortunate
that the direction of the nystagmus has been named according to the direction
of the quick component, Le. nystagmus to the right means that the quick jerk