1000 Section - Botulinum toxin A in post stroke oromandibular dystonia: a case series

Jaw-closing oromandibular dystonia (JC-OMD) is a rare movement disorder characterized by the involuntary, sustained contraction of the jaw-closing muscles, resulting in restricted mouth opening and functional impairment. Stroke-related JC-OMD is uncommon and underrecognized, particularly following pontine hemorrhage.

Case Description: We report a case series of three patients who developed JC-OMD after pontine hemorrhagic stroke. All patients presented with acute multiple cranial nerve involvement and contralateral hemiparesis. Magnetic resonance imaging revealed pontine hematoma secondary to arteriovenous malformation in one patient and cavernomatosis in two. JC-OMD onset occurred between one and three months post-stroke, with maximum interincisal opening (MIO) limited to 15–17 mm in two patients and completely absent in one. Needle electromyography demonstrated sustained motor unit firing and co-contraction of jaw-closing and jaw-opening muscles, consistent with dystonia. Patients underwent ultrasound-guided botulinum toxin type A (BoNT-A) injections into the masseter and temporalis muscles, followed by structured physiotherapy with mouth-opening exercises. All patients showed clinical improvement within one month, with increased MIO and reduced electromyographic activity. Two patients maintained sustained benefit over a 10-year follow-up, while one patient showed improvement during a three-month observation period. No adverse events were reported.

Discussions:

This case series highlights the effectiveness and safety of BoNT-A chemodenervation combined with physiotherapy in JC-OMD secondary to pontine hemorrhage. The findings support a possible role of pontine motor network disruption, affecting coordination of jaw-opening and jaw-closing muscles, in the pathophysiology of post-stroke JC-OMD.

Conclusions:

JC-OMD following pontine stroke is an underestimated condition. BoNT-A associated with physiotherapy appears to be an effective and durable symptomatic treatment, with sustained benefits observed up to 10 years. Further studies are needed to clarify underlying mechanisms and optimize therapeutic protocols.