Clinical commentary: Systemic and subclinical adverse effects of repeated botulinum toxin a injections to decrease spasticity in adults affected by stroke undergoing rehabilitation

Abstract

This is a clinical commentary that expands on an initial attempt to classify possible adverse effects (AE) of repeated and long-term use of Botox A (BTX) to manage post-stroke spasticity into three types, local, systemic and subclinical AE. Clinical manifestations of non-local, systemic AE from widespread diffusion of BTX are presented to help clinicians and researchers recognize changes that may develop in post-stroke patients. Subclinical AE of muscle atrophy and bone degradation may hinder return of motor control and increase certain risk factors. Even with increased trend in the use of BTX, very little is written about long term effects of repeated BTX injections for post-stroke spasticity coupled by fewer clinicians who report what they find in actual practice. Although published studies infrequently report AE, it will be an error if it is attributed to an extension of the disease process in stroke.

Efficacy and Safety of Botulinum Toxin Type A in Spasticity Caused by Spinal Cord Injury: A Randomized, Controlled Trial

“…In seizure disorders and patients with cardiovascular history, baclofen should be used with caution [ 24 ]. Subclinical and systemic adverse effects of botulinum toxin type A are not commonly reported [ 25 ]. With respect to adverse effects of interventions, botulinum toxin type A has selectivity for spasticity caused by spinal cord injury.…”

Non‐cosmetic dermatological uses of botulinum neurotoxin

“…More recent studies are now investigating the possibility of patients producing neutralizing antibodies to BoNT after multiple treatments as evidenced by reduced efficacy in dystonia following repeated injections . Antibody production is related to younger age of commencing BoNT and higher units of injection (per dose and cumulatively) .…”

Anomalies of motor unit amplitude and territory after botulinum toxin injection

“…Reduction of contraction force and surface electromyography (EMG) activity is often obvious within two/four weeks after the injection as reported in humans [14]. However, denervation of muscle fibers is potentially detrimental to those fibers in the long term and thereby leads to loss of contractile tissue and a reduction of overall voluntary capacity [15,16]. Such detrimental results have been reported in both human and animal studies in the recent past [13], but have not been thoroughly characterized in humans at the MU level.…”