Rhythmic Jaw Movements in Amyotrophic Lateral Sclerosis: Is It Clonus or Tremor?

Background: Jaw clonus refers to involuntary, rhythmic jaw contractions induced by a hyperactive trigeminal nerve stretch reflex; however, the movements, when triggered without a stretch, can be confused with a tremor.

Phenomenology Shown: This video demonstrates a patient with amyotrophic lateral sclerosis presenting with rapid rhythmic jaw movements seen at rest, alongside a power spectrum analysis revealing a narrow high-frequency peak of 10 Hz.

Educational Value: Rhythmic jaw movements are seen in many disorders such as Parkinson's disease, essential tremor, tardive syndromes, and cranial myorhythmias; however, a high-frequency movement, regardless of clonus or tremor, can indicate amyotrophic lateral sclerosis when accompanied by typical upper and lower motor neuron signs.

Roussy-Lévy Syndrome: Pes Cavus, Tendon Areflexia, Amyotrophy, Gait Ataxia, and Upper Limb Tremor in a Patient with CMT Neuropathy.

Background: Roussy-Lévy syndrome (RLS) is characterized by postural hand tremor seen in patients with familial autosomal dominant Charcot-Marie-Tooth (CMT) neuropathy.

Phenomenology Shown: This video demonstrates irregular, jerky bilateral kinetic, postural, rest tremor affecting the right > left hand, along with pes cavus and gait ataxia in a patient with CMT disease.

Educational Value: Pes cavus, tendon areflexia, sensory ataxia, and upper limb tremor should prompt consideration of CMT neuropathy.