Long-term safety of botulinum toxin in a patient of myasthenia gravis with hemifacial spasm

Dear Sir, We recently came across an intriguing case report by Zoccolella et al. (2023)[1] describing a 73-year-old male with ocular myasthenia gravis (MG) who developed a left hemifacial spasm. The condition was managed successfully by administering 50 IU of abobotulinum toxin-A (BTX type A) without significant side effects. Interestingly, we previously reported a similar case involving a patient with MG and left hemifacial spasm treated with botulinum toxin (BTX).[2] Our patient has had MG for the past 10 years and is on a regimen of pyridostigmine 60 mg thrice daily and azathioprine 50 mg once daily. He has been receiving BTX therapy (Botox, Allergan, USA) for left hemifacial spasm since 2017 (a total of 17 times to date). The average dose required is approximately 24 IU, with effects commencing within 2–5 days and lasting 2.5–3.5 months. Notably, the patient has not experienced any significant exacerbation of MG throughout the treatment, aside from occasional transient left-sided partial ptosis. There have been no signs of lethargy, fatigue, or worsening of MG following BTX administration. Currently, our patient is classified under MGFA Class II. Our findings align with the conclusions drawn in this case report by Zoccolella et al. (2023),[1] further reinforcing the safety profile of BTX therapy, even with prolonged usage. A review of the literature for known cases of MG who had received BTX for various indications yielded a total of six cases [Table 1]. Among the patients who maintained stability following BTX therapy, four were female, and their ages were 23–51 years. Three of these patients tested positive for acetylcholine receptor (AChR) antibodies, while one tested negative for both AChR and muscle-specific kinase antibodies. Additionally, two patients had undergone thymectomy. These four individuals exhibited either clinical stability or mild weakness upon exertion and did not require intravenous immunoglobulin (IVIG) treatment. However, two male patients of ages 17 and 73 years, representing extreme age ranges, experienced deterioration after BTX therapy. One of these patients required fortnightly IVIG for managing MG, while the other needed 3,4 diaminopyridine in conjunction with pyridostigmine.Table 1: All cases of myasthenia gravis that have been treated with botulinum toxin (BTX)On the basis of the above review, we can gauge that patients with controlled MG in a minimally symptomatic state can be administered BTX. We must keep such patients in close follow-up to look for signs of worsening. We believe that sharing such experiences and observations can contribute to the growing body of evidence supporting the efficacy and safety of BTX in conditions along with MG. Even so, we suggest that practitioners should be cautious when deciding to use BTX in patients with MG comorbidity. Author contribution A. Research project: Dr. Kshitij Bansal Conception: Dr. Vinay Goyal Organization: Dr. Tanushree Chawla Execution; Anunmozhimaran Elavarasi B. Statistical analysis: Dr. Chanchal Goyal Design: Dr. Chanchal Goyal Execution: Dr. Chanchal Goyal Review and Critique: Dr. Chanchal Goyal C. Manuscript preparation: Dr. Kshitij Bansal Writing of the first draft: Dr. Kshitij Bansal Review and Critique: Dr. Vinay Goyal Ethical compliance statement The authors have reviewed the journal’s ethical publication guidelines and attest that this submission adheres to them. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.