What is the pathophysiology of benign essential blepharospasm (BEB)?

Updated: May 20, 2019
  • Author: Robert H Graham, MD; Chief Editor: Edsel Ing, MD, MPH, FRCSC  more...
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Answer

Blepharospasm is now recognized as a neuropathologic disorder, rather than psychopathologic, as was once believed. The cause of blepharospasm is multifactorial. Although it is likely that a central control center for coordination and regulation of blink activity exists, somewhere in the basal ganglia, midbrain, and/or brain stem, it is unlikely that a single defect in this elusive control center is the primary cause of this disease. [2, 3, 4, 5, 6, 7, 8, 9]

Blepharospasm is a network defect in dynamic circuit activity, rather than a defect at a specific locus. [10, 11] Fayers et al have found a decrease in corneal sensitivity in patients with blepharospasm, implying an impairment in cortical processing of sensory input, with a resultant loss of blink reflex inhibition. [12]

If the central control center fails to regulate blinking in blepharospasm, it is believed to be only one component of an overloaded, defective circuit. This circuit forms a blepharospasm vicious cycle, which has a sensory limb, a central control center located in the midbrain, and a motor limb. The sensory limb responds to multifactorial stimuli, including light, corneal or eyelid irritation, pain, emotion, stress, or various other trigeminal stimulants. These stimuli are transmitted to the central control center, which may be genetically predisposed or weakened by injury or age. This abnormal central control center fails to regulate the positive feedback circuit. The motor pathway is composed of the facial nucleus, facial nerve, and orbicularis oculi, corrugator, and procerus muscles. Other facial muscles also may be involved.

The photophobia associated with blepharospasm may be related to dry eyes and the melanopsin-containing intrinsically photosensitive retinal ganglion cells.


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