Introduction
Central pontine myelinolysis (CPM) was first defined in 1959 as demyelination of the pons center due to osmotic imbalance in malnourished patients (1). It most commonly occurs due to hyponatremia and its rapid correction (2). Typically, CPM is clinically characterized by acute quadriparesis, dysphagia, and dysarthria. Cranial nerve involvement, ocular involvement, sensory changes, and mental impairment can also be seen. The most common and dramatic symptom is motor abnormalities.
Among various treatment options, chemodenervation with botulinum neurotoxin type A (BoNTA) is the preferred method for focal spasticity management (3). Over the last 30 years, accumulating evidence has proven the efficacy of BoNTA therapy (4,5), which usually starts on the second to third day of application, reaching the maximum level within three to four weeks and lasting for approximately three months (6). BoNTA injection is considered safe; however, its widespread use and increasing evidence raise safety concerns (7). Studies have reported local side effects due to BoNTA injection, such as pain at the injection site, edema, ecchymosis, hyperesthesia, and headache, which are generally well tolerated (8,9). Systemic side effects include nausea, weakness and fatigue, generalized weakness, dysphagia, respiratory distress, rash, and flu-like symptoms (9). Side effects vary according to the application and usually depend on the diffusion of the toxin from the muscle where the drug has been administered to the adjacent muscles (10). In our case, a systemic side effect was observed far from the local injection site.
In this paper, we present patient with CPM, a rare disease, who developed ARDS on the third day after BoNTA application to the spastic gastrocnemius muscle group-who did not have any past BoNTA interventions- and required intubation in the intensive care unit due to this complication. Our main purpose is to warn BoNTA practitioners about possible post-injection complications and to draw their attention to the possibility of such an acute and dramatic pulmonary involvement. To our knowledge, this is the first case reported in the literature to develop an acute pulmonary complication after BoNTA injection into spastic lower extremity muscles.