Benign Essential Blepharospasm
Benign essential blepharospasm (BEB) is a bilateral focal dystonia that affects approximately 30 of every 100,000 people. The condition is characterized by increased blinking and involuntary spasms of the periocular protractor muscles (Video 12-7). The spasms generally start as mild twitches and progress over time to forceful contractures. Other muscles of the face may also be involved with blepharospasm. Unlike hemifacial spasm, BEB typically abates during sleep. The involuntary episodes of forced blinking or contracture may severely limit the patient’s ability to drive, read, or perform activities of daily living. Women are affected more frequently than men. The age of onset is usually older than 40 years. BEB is a clinical diagnosis, and neuroimaging is rarely indicated in the workup. BEB must be differentiated from reflex blepharospasm, which can occur secondary to dry eye syndrome and other medical conditions.
Benign essential blepharospasm. Courtesy of Pete Setabutr, MD.
The cause of BEB is unknown; however, it is probably of central origin, in the basal ganglia. BEB can be managed by medical or surgical approaches. Neurotoxin injections are the primary treatment for blepharospasm. (See BCSC Section 5, Neuro-Ophthalmology.)
Botulinum toxin injection
Repeated periodic injection of one of the botulinum toxin type A formulations is the treatment of choice for BEB (Fig 12-25). Injection of these agents at therapeutic doses results in chemical denervation and localized muscle paralysis. Botulinum toxin injection is typically effective, but the improvement is temporary. Average onset of action is in 2–3 days, and average peak effect occurs at about 7–10 days following injection. Duration of effect also varies but is typically 3–4 months, at which point recurrence of the spasms and need for reinjection is anticipated. Complications associated with botulinum toxin injection include bruising, blepharoptosis, ectropion, epiphora, diplopia, lagophthalmos, and corneal exposure. These adverse reactions are usually transient and result from spread of the toxin to adjacent muscles.
Figure 12-25 Injection patterns of botulinum toxin type A for benign essential blepharospasm (red) and hemifacial spasm (unilateral red sites plus blue).
(Modified from Dutton JJ, Fowler AM. Botulinum toxin in ophthalmology. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 2007, module 3.)
Treatment with surgical myectomy is reserved for patients with severe spasm who do not respond adequately to botulinum therapy. Meticulous removal of the orbital and palpebral orbicularis muscle in the upper (and sometimes lower) eyelids can be an effective and permanent treatment for blepharospasm. Complications of surgical myectomy include lagophthalmos, chronic lymphedema, and periorbital contour deformities. Limited upper eyelid protractor myectomy is helpful in patients with less severe disease. Recurrence of spasm is not uncommon after myectomy, and treatment with reduced dosage of botulinum toxin is indicated.
Many patients with BEB have an associated dry eye condition that may be aggravated by any treatment modality that decreases eyelid closure. Artificial tears, ointments, punctal plugs or occlusion, moisture chamber shields, and tinted (FL-41) spectacle lenses may help minimize discomfort from ocular surface problems.
Surgical ablation of the facial nerve
Though effective in treating BEB, selective facial neurectomy has been largely abandoned. Recurrence rates as high as 30% and frequent hemifacial paralysis from facial nerve dissection limit this treatment’s appeal. The results obtained with facial nerve dissection are, therefore, less satisfactory than those of direct orbicularis oculi myectomy. Some surgeons have had greater success with microsurgical ablation of selected branches of the facial nerve.
Muscle relaxants and sedatives
Muscle relaxants and sedatives are rarely effective in the primary treatment of BEB. Oral medications such as orphenadrine, lorazepam, or clonazepam are sometimes effective in suppressing mild cases of BEB, prolonging the interval between botulinum toxin injections, or helping to dampen oromandibular dystonia associated with BEB. Psychotherapy has little or no value for the patient with blepharospasm.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.