(Kiosk 6) Tongue Fasciculations as a Novel Side Effect from Gabapentin in a Pediatric Brain Injury Patient

Case Diagnosis: Tongue fasciculations as a side effect from gabapentin in a pediatric patient

Case Description or Program Description: A 14-month-old girl with a past medical history significant for Dandy-Walker malformation and hydrocephalus, status post ventriculoperitoneal (VP) shunting was undergoing inpatient rehabilitation for hypoxic brain injury in the setting of VP shunt malfunction and seizures. She was treated with gabapentin for agitation and neuroirritability at a dose of 75mg TID. Symptoms persisted and dose was increased to 100mg TID. Two days later, she was noted to have tongue protrusion and fasciculations. Reduction back to initial dose of 75mg resulted in the resolution of the observed motor symptoms.

Setting: Pediatric Inpatient Rehabilitation

Assessment/Results: The gabapentin dose of a 14-month-old female experiencing neuroirritability and agitation was increased from 75mg TID to 100mg TID. Subsequently, the patient appeared to bite her tongue to help stop movements and she was noted to have dystonic tongue thrusting and fasciculations. After decreasing back to the original dose, fasciculations were no longer observed.

Discussion (relevance): Gabapentin is a frequently prescribed anticonvulsant in adult and pediatric populations for neuroirritability and neurostorming as it inhibits intracellular calcium flow and glutamate release. Despite its common use, the side effect of tongue fasciculations is only scarcely reported. A single, previous case study in the adult population was found to relate gabapentin toxicity to myokymia in bilateral calves, diffuse action tremors, and tongue tremors. To our knowledge, however, there have been no published reports implicating gabapentin as a cause of tongue fasciculations in the pediatric population. The mechanism of action of gabapentin-induced tongue fasciculations is not yet defined. This drug manifestation should be cautioned as this induced motor response, if persistent, may affect swallow ability, advancements in speech therapy, and other modalities of rehabilitation.

Conclusions: This case highlights tongue fasciculations as a newly described side effect of gabapentin in the pediatric population. In the event of its occurrence, decreasing the gabapentin dose appears to resolve the fasciculations within 24-48 hours. Recognizing this manifestation may be useful for pediatric healthcare team members as the clinical presentation may be subtle or complex to verbally express in this population despite its potential to hinder rehabilitation.