Benign essential blepharospasm (BEB) is a focal cranial dystonia, characterized by excessive involuntary contractions of the eyelid muscles leading to eyelid closure in the absence of any other ocular or adnexal cause which is usually bilateral, although it may be unilateral and brief at onset. The initial symptoms include unpleasant sensations, eyelid fluttering or increased blink rate to stimuli, which progresses to chronic involuntary bilateral spasms of the eyes, often so severe as to make the patient functionally blind. These symptoms are absent during sleep.
The prevalence of BEB is estimated at 36 per 10,00,000 individuals in the general populations. BEB affects women 2-3 times more frequently than men and more so in people over 50 years of age. It was noted on postmenopausal women with thyroid dysfunction and those using phenothiazines are more prone to BEB .
The exact pathogenesis of BEB is unknown, but abnormalities in the basal ganglia and corticostriatal pallidothalamic loop have been considered and also abnormal auditory brainstem response potentials have been noted. Over a period of time, as the condition progresses, spasm may involve the mid-face and neck muscles. This condition is referred to as Meige syndrome (MS). The symptoms of MS typically peak in the sixth decade of life and are seen more common in women than in men (3:2 to 2:1 ratio), with a prevalence of 5 to 10 cases per 100,000 people.
Hemifacial spasm (HFS) is a unilateral condition characterized by involuntary tonic and clonic contractions of muscles innervated by facial nerve. It occurs twice as often in women than in men with an overall prevalence of 10 per 100,000 and it usually appears in the fourth to seventh decade of life. HFS are attributed to an aberrant artery (anterior inferior cerebellar, posterior cerebellar, or vertebral) compressing seventh cranial nerve near its origin from the brainstem. HFS can be surgically corrected by microvascular decompression surgery but it potentiates the serious adverse effects.
Till date, the best method available for the initial treatment of BEB, MS and HFS is chemodenervation by Botulinum toxin type A (BTX). It retards the release of acetylcholine from the presynaptic terminals, thus blocks neuromuscular transmission at peripheral cholinergic nerve endings. It takes about 24-72 hours for onset effect after injection although it may be delayed for 2-3 weeks. It takes 3-5 days to achieve the plateau effect and the effect usually lasts for three months.
The dose of BTX is 1.25-5 units per injection site initially and may be increased if the response is not sufficient. Recovery of muscular function occurs in about three months by axonal sprouting and formation of new neuromuscular junctions.
Antibodies formed to the toxin may lead to the failure of appropriate response in 2-5% cases. This occurs when high doses are used at frequent intervals.
Adverse effects to the botulinum toxin include ecchymosis, ptosis, keratitis, epiphora, diplopia and ocular irritation. These are transient and usually do not last more than three weeks. Other less common side eff ects include transient increase in intraocular pressure, flulike syndrome and secondary biliary colic.
As we see many of patients with BEB and Hemifacial spasm in TIO, we have done one year prospective study on treatment outcome of Injection Botulinum toxin in Blepharospasm. It was a hospital based, prospective, interventional study conducted on patients diagnosed as Benign essential blepharospasm (BEB), Meige syndrome (MS) and Hemifacial spasm (HFS) by oculoplastic surgeon at Oculoplasty department OPD, Tilganga Institute of Ophthalmology, from December 2018 to November 2019. After taking all standard precautions for botulinum toxin injections, 6 to 8 sites for injecting 2.5 to 5 IU of the toxin were given. All the patients were evaluated before and after injections according to Jankovic spasm grading and improvement in functional impairment scale and followed on one week, one month, three month and when the symptoms reappeared.
A total of 43 patients who completed all the follow ups and fulfilled all the criteria were included. There were 13 (30.2%) males, with mean age of 58.38 years ± 10.437, 30 (69.8%) females with mean age of 60.30 years ± 10.557. There were 32 (74.4%) cases of BEB, 9 (20.9%) HFS and 2 (4.7%) MS. There was involvement of right eye (OD) in 3 (7.0%), left eye (OS) in 7 (16.3%) and both eyes (OU) in 33 (76.7%). The involved patients were from all parts of Nepal, 13 (30.3%) from within Kathmandu valley. They were mostly by farmer in occupation comprising 20 (46.5%).
The mean Jankovic severity score was 3.51 ± 0.51 (range 3-4). The mean improvement in functional score was 2.60 ± 0.54 (range 1-3), was statistically significant (p-value <0.001). All patients experienced decrease in spasm within one week and relieved from symptoms after Botulinum toxin injection, is statistically significant. The average eff ective period was a minimum of 93 days, maximum of 189 days with a mean of 127.55 ± 19.860 days. There was no significant change in the IOP on the follow-ups compared to the pre-injection level, all within the normal ranges. Improvement in the levator function was observed on the right eye which was statistically significant (p-value 0.012). We have found that our patients had dry eyes on Schirmer’s test I testing.
Four patients had minimal side effects of - injected site redness and hematoma at one site which appeared on the day of injection and completely resolved by one week by itself. No patient complained of any systemic side effects. 38 patients had repeated injections after reappearance of symptoms.
The limitations of our study included no study on repeat injections, fairly good numbers of patients were enrolled due to lack of promise to regular follow-ups and low patient compliance. The only drawback of botulinum toxin is that the effect of injection wears off in an average of 12 weeks and it has to be repeated every 3-4months which is financially burdensome. This needs the patient’s motivation and understanding the lasting duration of toxin effect, affordability, availability of injection in the centre.
Conclusion: Botulinum toxin type A is the first line treatment of choice for Blepharospasm, Hemifacial spasm and Meige syndrome and is effective and safe for temporary treatment available today. Its duration of effect ranges from 93 to 189 days with significant improvement within 1 week and minimal local side effects.
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