Abstract Details

Title Jaw Clonus in Bulbar Onset Motor Neuron Disease

Topic Movement Disorders

Presentation(s) P8 - Poster Session 8 (8:00 AM-9:00 AM)

Poster/Presentation
Number 5-028

Objective N/A

Background Jaw clonus is characterized by rhythmic, oscillatory contractions of the jaw, often induced by stretch. It results from lesions corticopontine tracts, particularly affecting the trigeminal nerve's supranuclear pathways. It is infrequently observed in severe spasticity and hyperreflexia. As its frequency differs from that of ankle and wrist clonus, it is sometimes misidentified as jaw tremor. This phenomenon is typically observed in conditions such as amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), and bilateral pontine infarctions. We present a case of severe spontaneous jaw clonus.

Design/Methods N/A

Results Our patient is a 67-year-old woman who presented with an inability to eat, accompanied by a 6-month history of slurred speech and a 3-month history of progressively worsening dysphagia. Initially evaluated for myasthenia gravis, her electromyography showed no evidence of motor neuropathy or motor neuron disease. She was empirically started on pyridostigmine without improvement.
Clinical examination revealed severe dysarthria and spontaneous jaw clonus when attempting to speak, facial diplegia, tongue fasciculations, and diffuse hyperreflexia with a Babinski sign. Bulbar onset ALS was suspected.
A percutaneous gastrostomy tube was placed for nutrition due to the severity of her jaw clonus Treatment with Baclofen and Clonazepam exhibited no effect. Unfortunately, the patient passed away before botulinum toxin treatment could be initiated.

(The video shows severe clonus of the jaw, which is triggered by any movement, including attempts to speak or stick out the tongue. Patient is holding her jaw with her hand to prevent the shaking).

Conclusions Our case emphasizes the rarity and importance of jaw clonus, as it is often misinterpreted as tremor. Recognizing other pyramidal sign is crucial for narrowing down the differential diagnosis and improving accuracy. Finally, our case highlights the complexities involved in jaw clonus management.

Authors/Disclosures
Armando Martinez Salazar, MD PRESENTER	Dr. Martinez Salazar has nothing to disclose.
Victoria Mazo, MD	Dr. Mazo has nothing to disclose.
I-Hweii A. Chen, MD, PhD, FAAN (University of South Florida)	The institution of Dr. Chen has received research support from Healey Center at Massachusetts General Hospital. The institution of Dr. Chen has received research support from General Hospital Corporation. The institution of Dr. Chen has received research support from Argenx.
Kathleen A. Murray, MD (University of South Florida - JAHVAH)	Dr. Murray has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Guidepoint .

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