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Dr.Prerana, Dr.Ram kishore shandilya,Dr.ANIMESH SAHU,Dr.Narendra Patidar

Introduction

Benign essential blepharospasms are idiopathic tonic clonic contractions of the eyelid closing muscles mainly the orbicularis oculi. It is a type of focal dystonia with unknown etiology though some studies have linked it to degenerative changes in the basal ganglia1. Hemifacial spasms are segmental myoclonus of muscles supplied by facial nerve due to its compression by the anamolous branch of the basilar or cerebellar artery2,3, space occupying or a brainstem lesion.Apraxia of lid opening (ALO) is the inability to open the eyes after voluntary closure of the eyelids. ALO can interfere with normal lid opening, which results in significant vision interference and adversely affects activities of daily living. Various treatment options are available such as medical therapy, microvascular surgical decompression but botulinum toxin remains the gold standard treatment. It temporarily paralyses the muscle by blocking acetylcholine release at the neuromuscular junction.4-8

Focal dystonia result in undue pressure on the eyelids causing changes in the corneal morphology specially the astigmatism value and the tear film. With application of botulinum toxin, eyelid pressure is released and its effect has been measured in previous study using conventional corneal topography and pentacam with single botox application, respectively9. In this study, we intend to see the long term changes in the corneal morphology using pentacam.

Subjects and Methods

The study was conducted in Orbit and Ocular services OPD at Shri Sadguru Netra Chikitsalaye, Jankikund, Chitrakoot. It was a  prospective consecutive observational clinic based study from September 2016 to April 2018. 33 eyes of  21 patients were included between  40-80 years of age group suffering from facial dystonias (BEB, hemifacial spasms, apraxia of eyelid opening) causing impairment of daily activity. Patients having allergies to botulinum toxin or to any component of the drug, previous treatment with botulinum toxin A, corneal surface-altering diseases, strabismus, contact lens wear, pregnancy, breastfeeding, neuromuscular junction or peripheral neuropathic diseases and the use of aminoglycosides or other agents that could interfere with neuromuscular transmission were excluded.

History, ocular examination, systemic examination, pretreatment measurement schirmer’s test with topical anaesthesia, TBUT test, Jankovic’s severity grading (0- no spasm, 1-mild spasm; barely noticeable, 2-mild spasm; no functional impairment, 3- moderate spasm; moderate functional impairment, 4- severe spasm; severe functional impairment.), corneal parameters included the spherical equivalent, best-corrected visual acuity, tear breakup time (TBUT), Schirmer test under topical anesthesia, corneal power measurements, pachymetric measurements, and corneal volume measurements using Oculus pentacam were done.Single application of measured units (2.5 units/ 0.1ml)of botulinum toxin A injections were then given at predetermined sites. The patients were followed up after 1month, 3month and 6month respectively.

Statistical analysis was done by using descriptive and inferential using student’s paired t test and software used in the analysis were SPSS 22.0 version and GraphPad Prism 6.0 version and p<0.05 was considered as level of significance.

Results

A total of 21 patients were enrolled in the study of which 13 were males and 8  were females. Mean age was 54.42±8.84years with male predominance of 61.9%.BTX-A injection relieved spasm in all patients with significant difference post treatment ꭓ2value =50.23 p<0.001at 6months. Few patients however started showing pretreatment spasm levels after 1 and 3months but was statistically insignificant.Corneal astigmatism decreased significantly 1st, 3rd and 6th month, 0.51D ± 0.32 p=0.029,  0.39D ±0.22 p=0.01, 0.42D ±0.22 p=0.032 respectively, with against the rule astigmatism shift according to vector analysis by Moon et al10 . Schirmer’s score significantly decreased  1st (13.45 ± 6.22 p=0.002) 3rd(11.73 ±4.73 p=0.01) and  6th(12.01 ±4.73  p=0.024) month. TBUT increased post injection  1st, 3rd and 6th month but was statistically insignificant. No changes were seen in other corneal parameters.

Discussion:

It is well known thatbotulinum toxin A has a temporary effect and require repeated applications. Even then it is the most commonly used therapy due to its efficacy and safety2. Many studies have been previously done showing its effectiveness.

In this study, facial dystonia significantly improved with application of botulinum toxin A injection from pretreatment to 6months of duration. A few patients showed reoccurrence of spasms after 3 months but was statistically insignificant possibly because of the presynaptic stimulus of the neighboring schwann cells leading to axonal sprouting thus, innervating the nearby denervated endplates.

Corneal astigmatism in patients with facial dystoniasoccurs due to undue tension of eyelids on the cornea resulting in changes in the corneal surface, due to flattening on the periphery of the cornea in superior vertical meridian, and conversely steepening in the corneal center11,12.Lavy et al13, reported  a change in corneal astigmatism for the management of lagophthalmosafter implantation of a metallic device in the eyelid.Suat and Guler14, described increase in corneal astigmatism in patients with congenital ptosis in a single eye as compared with the healthy eye. Moon et al10, reported change in corneal astigmatism after injection of botulinum toxin in patients with blepharospasm and hemifacial spasm and also noticed an against the rule shift in astigmatism which reverted back to pretreatment values after 6months. This study also shows a decrease in corneal astigmatism after 1,3, 6 months with against the rule shift.

Schirmer values significantly decreased in this study till 6months. This may be due to decrease in production of tears with age as most patients in this study are >50 years. Another reason might be the pharmacological effect of botulinum  toxin A on lacrimal gland tear production by its effect on autonomic nervous system as a similar picture is seen in cases of botulism. Other clinical features include mydriasis, accommodation paresis, decreased salivary secretion, and decreased lacrimation15.

Tear breakup time (TBUT) increased post treatment but was statistically insignificant. One reason may be the paralytic effect of lacrimal pump mechanism which prevents drainage of tear and improves availability on the ocular surface. Park et al16,reported that the TBUT increased significantly, along with lower lid tear meniscus height and dacryoscintigraphy, after BTX-A injections in patients with essential blepharospasm. Thus, botulinum toxin has a dual effect in decreasing tear production and also increasing the availability on the ocular surface.

No definite changes were seen in pachymetry values after 1,3,6 months post injection.

The differences in results of BTX-A therapy between the literature and this study might be due to different injection techniques, because both the number and distribution of injections can vary, also small sample size, limits the study.

To conclude, this study is the first one to be conducted in India using Scheimpflug imaging in patients with facial dystonia. Botox has an effect on spasm severity and tear film with little changes in corneal parameters except corneal astigmatism.

References

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  2. Kraft SP, Lang AE. Cranial dystonia, blepharospasm and hemifacialspasm: clinical features and treatment, including the use of botulinum toxin. Can Moo Assoc J 1988;139:837-44.
  3. Adler CH, Zimmerman RA, Savino PJ, et al. Hemifacial spasm: evaluation by magnetic resonance imaging and magnetic resonance tomographic angiography. Ann Neurol 1992;32:502-6.
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  11. Kang KH, Baek SH, Lee KS. Corneal astigmatic change in corneal topography after upper eyelid surgery. J Korean Ophthalmol Soc. 2002; 43:1113–1122.
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  13. Lavy JA, East CA, Bamber A, et al. Gold weight implants in the management of lagophthalmos in facial palsy. Clin Otolaryngol Allied Sci. 2004;29:279–283.
  14. Suat HU, Guler Z. Corneal topography in patients with congenital ptosis. Eye. 1999;13:550–554.
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  16. Park DI, Shin HM, Lee SY, et al. Tear production and drainage after botulinum toxin A injection in patients with essential blepharospasm. Acta Ophthalmol. 2013;91:108–112.

 

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