Loss of corneal reflex

Introduction Corneal reflex examination method: the patient looks at one side, and the examiner gently touches the outer and lower sides of the contralateral cornea with a thin bundle of cotton bristles, from the outside to the inside, so that the patient is not seen. The reflex is caused by contraction of the bilateral orbicularis oculi muscles, and bilateral blinking action occurs. The same side is called direct corneal reflection, and the opposite side is called indirect corneal reflection. Reflective arc: Corneal-trigeminal ocular branch - middle cerebral plexus sensory nucleus - reticular structure - thalamus - cerebral cortex - cortical medullary bundle - bilateral lateral nucleus - bilateral lateral nerve - bilateral orbicularis oculi muscle. Loss of corneal reflexes indicates that the nerves or brain that formed the cornea are damaged or have been diseased.

Cause

The cause of corneal reflex disappeared:

Corneal reflexes can be affected by a variety of lesions. There are three common situations in which corneal reflex disappears:

(1) Reflex arc afferent neuropathy: The lesion of the trigeminal ocular branch, except for the sensory area of the branch (the forehead skin), is accompanied by a decrease or disappearance of corneal reflex. When the lateral trigeminal nerve damage causes corneal paralysis, there is no reaction on both sides, and the bilateral reaction can still be caused when the contralateral corneal reflex is performed. The common cause of attenuated corneal reflex is the early symptoms of the first damage of the trigeminal nerve. As the lesion progresses, the corneal reflex disappears. Since the cerebellum is also distributed by the first branch of the trigeminal nerve, corneal reflexes may be weakened in the early stage of the cranial fossa, such as cerebellar hemorrhage, cerebellopontine angle cholesteatoma. It has been reported that ipsilateral corneal reflexes are weakened and/or disappeared, which is an important indication for localization diagnosis.

(2) Efferent neuropathy of corneal reflex (peripheral facial paralysis): The efferent nerve of corneal reflex is facial nerve. When peripheral facial neuropathy occurs, the cornea can not be closed after blinking. In a broad sense, corneal reflexes also disappear. When the lateral nerve is paralyzed, the ipsilateral corneal reflex disappears and the contralateral reflex exists.

(3) One-sided cerebral hemisphere lesions: unilateral corneal reflexes are weakened or disappeared, often as part of partial numbness, and in many cases of hemiplegia, the cornea may be the only numb area. Some people think that there is a corneal reflex center in the parietal lobe, which may be explained. If the bilateral corneal reflexes weaken or disappear, it indicates extensive damage on both sides of the brain (such as deep coma, cerebral edema, cerebral hypoxia), and invades the intracerebral reflex arc of corneal reflex.

In addition, damage to the trigeminal nerve will also disappear from corneal reflex.

an examination

Related inspection

Ultrasound examination of the eyeball and eyelid by CT in the eye and temporal region

Examination and diagnosis of corneal reflex disappearance:

Corneal reflex: The examinee looks inward and upward, and the physician uses a fine cotton swab to gently touch the patient's cornea from the outer edge of the cornea. Normally, the eyelid of the subject is quickly closed, called direct corneal reflex.

Stimulation - lateral cornea contralateral eyelid closure reaction indirect corneal reflex.

Reflex arc: trigeminal nerve branch pons facial nerve nucleus - the orbicularis muscle responds.

Both direct and indirect corneal reflexes disappeared seen in patients with trigeminal neuropathy (afferent barrier).

Direct reflex disappears, indirect reflexes exist, and are seen in the side of the nerves (escape obstacles).

Corneal reflexes disappear completely: seen in patients with deep coma.

The trigeminal nerve has different parts and can have different performances:

When the trigeminal nerve is damaged more than half a month, the general sensory loss of the skin and tongue, mouth and nasal mucosa of the affected side may occur; the corneal reflex disappears; the affected side chews the tendon, and the mandible is biased toward the affected side when the mouth is opened.

When the trigeminal nerve is damaged below the semilunar ganglion: the performance of each single injury may occur. When the ocular nerve is damaged, the skin sensation is more than the affected side, and the corneal reflex disappears. When the maxillary nerve is damaged, it can reach the affected side and upper lip skin. Sensory disturbance of the maxillary teeth, gums and hard palate mucosa; the mandibular nerve can cause general sensory disturbance of the affected mandibular teeth, gums and anterior tongue 2/3 and mandibular skin, and dyskinesia of the ipsilateral masticatory muscle.

Differential diagnosis

Discrimination of corneal reflexes and confusing symptoms:

The reaction to light disappears: the change in the pupil's disappearance of light reflection. When the pupil is illuminated by a flashlight, the change is small, and the pupil increase is not obvious after the light source is removed. This condition is called the pupil is unresponsive to light. When the pupil does not respond to light reflection, it is called the reaction to light disappears.

Eye-head reflex disappears: one of the brainstem reflections, which includes horizontal cephalic and vertical ocular reflexes. When making horizontal cephalic reflexes, the head should be turned quickly and sharply to the left and right sides by 90°. When the eye is reflected, the head should be turned quickly and sharply to the chest. The normal reaction is the rotation of the eye in the opposite direction of the head rotation. If there is cervical trauma, this reflection should not be made.

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