Corneal reflex, absent
Corneal reflex, absent: Excerpt from Professional Guide to Signs & Symptoms (Fifth Edition)
The corneal reflex is tested bilaterally by drawing a fine-pointed wisp of sterile cotton from a corner of each eye to the cornea. Normally, even though only one eye is tested at a time, the patient blinks bilaterally each time either cornea is touched—this is the corneal reflex. When this reflex is absent, neither eyelid closes when the cornea of one is touched. (See Eliciting the corneal reflex, page 194.)
The afferent fibers for this reflex are located in the ophthalmic branch of the trigeminal nerve (cranial nerve V); the efferent fibers are located in the facial nerve (cranial nerve VII). Unilateral or bilateral absence of the corneal reflex may result from damage to these nerves.
History and physical examination
If you can’t elicit the corneal reflex, look for other signs of trigeminal nerve dysfunction. To test the three sensory portions of the nerve, touch each side of the patient’s face on the brow, cheek, and jaw with a cotton wisp, and ask him to compare the sensations.
If you suspect facial nerve involvement, determine whether both the upper face (brow and eyes) and lower face (cheek, mouth, and chin) are weak bilaterally. Lower-motor-neuron facial weakness affects the face on the same side as the lesion, whereas upper-motor-neuron weakness affects the side opposite the lesion—predominantly the lower facial muscles.
Because an absent corneal reflex may signify such progressive neurologic disorders as Guillain-Barré syndrome, ask the patient about associated symptoms, such as facial pain, dysphagia, and limb weakness.
Medical causes
Acoustic neuroma
This tumor affects the trigeminal nerve, causing a diminished or absent corneal reflex, tinnitus, and unilateral hearing impairment. Facial palsy and anesthesia, palate weakness, and signs of cerebellar dysfunction (ataxia, nystagmus) may result if the tumor impinges on the adjacent cranial nerves, brain stem, and cerebellum.
Bell’s palsy
A common cause of diminished or absent corneal reflex, Bell’s palsy causes paralysis of cranial nerve VII. It can also produce complete hemifacial weakness or paralysis and drooling on the affected side. The affected side also sags and appears masklike. The eye on this side can’t be shut and tears constantly.
Brain stem infarction or injury
An absent corneal reflex can occur on the side opposite the lesion when a brain stem infarction or injury affects cranial nerve V or VII or their connection in the central trigeminal tract. Associated findings include decreased level of consciousness, dysphagia, dysarthria, contralateral limb weakness, and early signs and symptoms of increased intracranial pressure, such as headache and vomiting.
In a massive brain stem infarction or injury, the patient also displays respiratory changes, such as apneustic breathing or periods of apnea; bilateral pupillary dilation or constriction with decreased responsiveness to light; rising systolic blood pressure; widening pulse pressure; bradycardia; and coma.
Guillain-Barré syndrome
In this polyneuropathic disorder, a diminished or absent corneal reflex accompanies ipsilateral loss of facial muscle control. Muscle weakness, the primary neurologic sign of this disorder, typically starts in the legs, then extends to the arms and facial nerves within 72 hours. Other findings include dysarthria, dysphagia, paresthesia, respiratory muscle paralysis, respiratory insufficiency, orthostatic hypotension, incontinence, diaphoresis, and tachycardia.
Herpetic keratoconjunctivitis
This disorder may cause corneal anesthesia, usually unilaterally. Other findings include regional adenopathy, blepharitis, and vesicles on the eyelid.
Trigeminal neuralgia (tic douloureux)
A diminished or absent corneal reflex may stem from a superior maxillary lesion that affects the ophthalmic branch. The patient with trigeminal neuralgia characteristically experiences sudden bursts of intense pain or shooting sensations, lasting from 1 to 15 minutes, in one of the divisions of the trigeminal nerve, primarily the superior mandibular or maxillary division. An attack may be triggered by local stimulation, such as a light touch to the cheeks, exposure to hot or cold temperatures, or eating or drinking hot or cold food or beverages. Areas around the patient’s nose and mouth may be hypersensitive.
Special considerations
When the corneal reflex is absent, you’ll need to take measures to protect the patient’s affected eye from injury, such as lubricating the eye with artificial tears to prevent drying. Cover the cornea with a shield and avoid excessive corneal reflex testing. Prepare the patient for a computed tomography scan or cranial X-rays.
Pediatric pointers
Brain stem lesions and injuries are the most common causes of an absent corneal reflex in children; Guillain-Barré syndrome and trigeminal neuralgia are less common causes. Infants, especially those born prematurely, may have an absent corneal reflex due to anoxic damage to the brain stem.
Pictures
Book Source Details
- Book Title: Professional Guide to Signs & Symptoms (Fifth Edition)
- Author(s): Springhouse
- Year of Publication: 2006
- Copyright Details: Professional Guide to Signs & Symptoms (Fifth Edition), Copyright © 2006 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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