Objective:

To present a case of facial diplegia as a rare adverse effect of botulinum toxin injections for chronic migraine.  

Background:

OnabotulinumtoxinA injections are well-tolerated FDA-approved treatment of chronic migraine, with reported side effects included neck pain, brow asymmetry and eyelid droop. Adverse effects to alternative neurotoxins, incobotulinumtoxinA, are not well-studied in randomized controlled trials. Nonetheless, they are often used for treatment of chronic migraine off-label.   

Design/Methods:

Case Report 

Results:

A 55 year old female with chronic migraine received botulinum toxin injections for treatment with a positive therapeutic response She had previously received 7 sessions with onabotulinumtoxinA using the FDA-approved PREEMPT protocol, and was switched to incobotulinumtoxinA due to institutional formulary change. Approximately 12 days after her third treatment with incobotulinumtoxinA, she gradually developed weakness of her facial muscles that she perceived to be facial swelling due to an allergic reaction. She had trouble closing her eyes, chewing food, and with facial expression. After visits to the emergency department and her PCP, patient followed up with neurology where she was noted to have complete facial diplegia with minimal facial movement. She started to improve after 3-4 weeks, and, her weakness completely resolved by 8 weeks. Further treatment with incobotulinumtoxinA was not pursued, and the patient was switched to a monoclonal cGRP antibody with good response. The patient was felt to have had an facial diplegia as a idiosyncratic reaction to incobotulinumtoxinA, 150 kiloDalton toxin injections with the use of standardized PREEMPT protocol.  

Conclusions:

To our knowledge, this is the first reported case of complete facial diplegia occurring as an indiosyncratic reaction to botulinum toxin therapy for chronic migraine. Importantly, this occurred with use of incobotulinumtoxinA, which is an off-label but often used substitute for chronic migraine and has a lower molecular weight (150 kiloDalton) compared with onabotulinumtoxinA (900 kiloDalton).