Complications
When the eyelids fail to close properly, the lubricating tear film and cornea-protective blink response become ineffective. Additionally, parasympathetic dysfunction to the lacrimal gland in the acute phase may result in reduced tear production. The combination of these factors may result in keratoconjunctivitis sicca (dry eye) and exposure keratopathy, which may lead to ulcerative keratitis (corneal ulcer) through physical (e.g., corneal abrasions) or infectious mechanisms, which may in turn cause blindness.
Such complications are best prevented through the use of a transparent eye shield (not a patch) during the day, artificial tears as needed during waking hours, and an ophthalmologic lubricant ointment together with taping of the eyelids closed at bedtime.[71] Eye patches are contraindicated because the eye may easily open under the patch and subsequently be subjected to corneal abrasion.
Strong consideration for early upper eyelid weight placement or tarsorrhaphy (both of which are reversible) should be given to patients who lack Bell's phenomenon (protective reflex in which the globe rotates upward and outward with attempts at eye closure) or those whose prognosis for early rapid return of function is poor.
Indications for ophthalmologic consultation include: only seeing eye affected, suspicion of exposure keratitis, and decreased or absent corneal sensation.
This may occur during the acute flaccid phase of Bell's palsy and rarely persists.
It is more common in older adults because of canthal tendon laxity that occurs with aging.
The likelihood is 16% to 29% in the absence of treatment.[3]
The suspected mechanism is increased neural irritability and aberrant regeneration of motor axons.
Physical therapy for patient education, soft-tissue mobilization, biofeedback, and neuromuscular retraining may be effective.
Botulinum toxin administration into hyperactive muscles is effective.
Gustatory hyperlacrimation (crocodile tears or Bogorad syndrome) is believed to occur as a long-term complication of Bell's palsy due to aberrant regeneration of preganglionic parasympathetic fibers carried within the facial nerve that supply the lacrimal gland and mucosal glands of the nasal cavity and palate (via the greater superficial petrosal nerve) and the submaxillary, sublingual, and minor salivary glands of the oral cavity (via the chorda tympani nerve).
Botulinum toxin to the lacrimal gland has demonstrated effectiveness in the long-term management of this complication.
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