Loss of vestibular reflex

Introduction In addition to causing a certain sense of position and movement, the afferent impulses of the vestibular organs can also cause changes in various posture-regulating reflexes, nystagmus, and autonomic nervous functions. These phenomena are collectively referred to as vestibular reflexes. Excessive stimulation or prolonged stimulation of the vestibular organs can cause symptoms such as nausea, vomiting, dizziness and pale skin, called vestibular autonomic response. For people who are oversensitive to vestibular organ function, general vestibular stimulation can also cause vestibular autonomic response, which is prone to motion sickness and seasickness. The most special vestibular response is a special movement of the eye caused by the rotation of the body, called nystagmus. Ocular tremor is mainly caused by stimulation of the semicircular canal. Clinical otitis can be used to determine whether the vestibular function is normal. The eye movements for evaluating vestibular eye reflexes include: nystagmus electrogram, spontaneous nystagmus examination, evoked nystagmus examination, visual eye system function examination, and semicircular canal function test. The vestibular eye reflex disappears when the brain is dead.

Cause

brain death. Such a condition refers to a criterion for declaring death by using a brain stem or a brain stem to permanently lose function of the central nervous system as a frame of reference. The brainstem function is normal. The coma is only due to severe damage or sudden inhibition of the cerebral cortex. The patient can have spontaneous breathing, heartbeat and brainstem response, while brain death has no spontaneous breathing and is permanent and irreversible.

an examination

Related inspection

Closed eye walking test

Vestibular eye reflex - vestibular eye reflex (temperature test):

Observe the 1-3 minutes after the water is injected into the external auditory canal. If there is no nystagmus, the vestibular eye reflex disappears. Even if there is no obvious nystagmus, it is impossible to judge that the vestibular eye reflex disappears with slight eye movement. This experimental method is different from the temperature experiment used in the ENT department, which is alternately stimulated with cold water at 20 ° C or hot and cold water at a body temperature of ± 7 ° C.

Differential diagnosis

"Ocular dipping" refers to a slow downward movement that occurs in a patient with normal reflex horizontal gaze, and then a more rapid upward movement of both eyes. Eyeball subsidence is especially common in patients with diffuse hypoxia that damages the cerebral cortex and may be persistent upward or downward gaze. When the thalamus and the midbrain are damaged, the eyes may turn downwards and inwards.

The examination of the "doll eye" or the movement of the head eye is to firstly rotate the head from the side to the other side or to rotate the head vertically, and to induce a reflective eye movement opposite to the direction of the head movement. These responses are brainstem reflexes that originate in the labyrinth, vestibular nucleus, and neck proprioceptors. Visual gaze controlled by the cerebral hemisphere in awake people normally suppresses these reflexes. The neuronal channel of reflex horizontal motion requires the integrity of the paranuclear region and is performed by the medial longitudinal bundle (MLF) in cooperation with the contralateral ocular nerve.

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