Severe Spastic Trismus without Generalized Spasticity after Unilateral Brain Stem Stroke

A 62-year-old female patient diagnosed with left brain stem stroke 2 months ago was admitted to our clinic for rehabilitation. She had no generalized spasticity on both extremities, but could open her mouth only approximately 2 mm between her upper and lower teeth due to severe trismus. On needle electromyography, the left masseter muscle showed paradoxically increased muscle activity during mouth opening. We injected 50 units of type A botulinum toxin (Botox®) into the left masseter muscle, and 20 units into the left temporalis muscle with guidance of ultrasonography. The interincisal distance increased to 8 mm on the 3rd day after injection, and 9 mm on the 4th day. One month later, the interincisal distance increased to 14 mm. The increased interincisal distance was maintained for 13 months after injection, and the quality of hygienic care and compliance of oral stimulation therapy also improved. Keywords: Trismus, Botulinum toxin, Brain stem stroke