Unwanted Muscle Weakness following Botulinum Neurotoxin A Administration in Spinal Cord Injury with Literature Review

Abstract

Botulinum neurotoxin A (BoNTA) is rapidly gaining acceptance for management of spasticity secondary to spinal cord injury (SCI). Due to its increased usage, more undesirable effects and complications have come in light. Unwanted distant and/or generalised muscle weakness is possible following BoNTA administration in SCI population causing temporary neurological and functional decline. Physicians should carefuly perform a clinical assessment of every patient individually for risks stratification. Additional studies for adult population evaluating adverse-effects of high dose of BoNTA treatment for spasticity management are indicated. 20 Introduction: S pasticity is a velocity-dependent increase in tonic stretch reflexes with exaggerated tendon responses. 1 It is one of the most common consequences of spinal cord injury (SCI). One year post-injury, about 78% of patients demonstrate spasticity with more than half requiring pharmacological interventions. 2 Botulinum neurotoxin is gaining rapid acceptance for spasticity management due to several advantages. It avoids sedation, common with oral antispasticity medications. No surgical intervention is required. It provides an option of focal spasticity management. It is equally effective as phenol 3 but technically simpler to administer, less painful, and without any side-effects like dysesthesia. Due to its increased usage, more undesirable effects have come in light. Here, I have described a case elucidating distant and generalised muscle weakness as a potential sideeffect of botulinum neurotoxin A (BoNTA) in a patient with SCI with brief literature review.

Adverse Clinical Effects of Botulinum Toxin Intramuscular Injections for Spasticity

“…71 Possible factors include misdiagnosis, insufficient dose, first injection cycle placebo, problems with toxin storage and preparation, and administration. 20,71 Although 41% of the studies reviewed here either used no guidance or anatomical landmarks and palpation, we do not have information regarding guidance technique used to inject BoNTA in the AEs reported to Health Canada. Electrical stimulation, EMG, and ultrasound are well-established, precise, and beneficial guidance techniques.…”

“…Minor AEs like minor falls, sitting imbalance, and minor gait abnormalities reported after BoNTA treatment may be related to the muscle weakness caused by the toxin. 20 For example, Pittock et al (2003) reported over-weakening of muscles with BoNTA injections resulting in a deterioration of the step length discrepancy observed in their patient population. 23 Non-responsiveness to treatment with BoNTA Non-responsiveness to BoNTA could be as a result of a variety of factors reviewed elsewhere.…”

“…3,11,19,21,[31][32][33][34][35] Neurologic AEs (epilepsy, seizure, convulsions, dystonia, paraesthesia, and hyperaesthesia) 3,11,16,21,23,26,33 and gait abnormalities and falls were reported in seven studies each. 1,16,18,20,23,25,32 Infection related AEs (flu like symptoms, abscess, infection, fever) were reported in five studies. 1,20,25,27,36 Respiratory AEs (cough, dyspnoea, respiratory distress, upper respiratory tract infection, chest infection, and orthopnea) were reported in six studies.…”

“…1,16,18,20,23,25,32 Infection related AEs (flu like symptoms, abscess, infection, fever) were reported in five studies. 1,20,25,27,36 Respiratory AEs (cough, dyspnoea, respiratory distress, upper respiratory tract infection, chest infection, and orthopnea) were reported in six studies. 1,3,16,24,25,31 General AEs (mild discomfort, dizziness, nausea, tooth disorder, somnolence, insomnia, and altered blood test results) were reported in eleven studies.…”

“…40 It has been suggested that total toxin injected in muscles throughout the body may increase weakness 41 , whereas others contest this view. 11 Though considered, reversible 11,20 severe acute local weakness of the injected muscle can be counterproductive because it can lead to muscle imbalance and further loss of function. 7 Although dosage guidelines exist in treating children with spasticity, 38,42 similar guidelines are missing for treatment with BoNTA in adults with spasticity.…”