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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. 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. 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. The presented video abstract shows a patient with amyotrophic lateral sclerosis with rhythmic jaw movements seen at rest. A power spectrum analysis of the rhythmic movements revealed a 10 Hz peak, a frequency higher than those seen in patients with Parkinson's disease, essential tremor, myorhythmia, and tardive syndromes.

Background Repetitive head impact exposure (RHI) is the only known risk factor for chronic traumatic encephalopathy (CTE), a distinct neurodegenerative tauopathy. Most aging studies ask participants about prior traumatic brain injury (TBI), but not common sources of RHI. Understanding the public health footprint of RHI requires targeted questioning of lifetime exposure. To set the stage for our Featured Research Session on CTE, we report RHI prevalence using gold standard methods across independent aging and dementia cohorts. Method The Boston University Repetitive Head Impact Exposure Assessment (BU‐RHIEA) was administered across three cohorts: BU Alzheimer's Disease Research Center (ADRC), UCSF ADRC, and 1Florida ADRC. Participants recruited explicitly with concerns about cognitive effects of prior head trauma were excluded. The BU‐RHIEA queries participation in contact/collision sports (e.g., American football, soccer, ice hockey, boxing) and military service as well as prior TBI. We report RHI and TBI prevalence estimates from the BU‐RHIEA relative to estimates from the National Alzheimer's Coordinating Center Uniform Data Set (NACC UDS). In a subset of participants with frontotemporal dementia, we evaluated the clinical relevance of prior RHI through associations with age of symptom onset and rate of disease progression. Result Data come from 736 participants (age 70.4±9.6, 44.3% male, 43.1% cognitively impaired). Based on NACC UDS, 223 (30.2%) reported any prior TBI (Figure 1). When providing a formal TBI definition, frequency increased to 300 (40.8%). Sport and military history are not known through NACC UDS. Based on the BU‐RHIEA, 221 (30.0%) participants reported any prior contact/collision sport play. Among males, 92 (28.2%) previously played American football and 98 (30.1%) served in the military. In participants with frontotemporal dementia, prior RHI related to younger symptom onset and more rapid cognitive decline (Figure 2). Conclusion There is a high risk of underestimating the scope of RHI influence on brain aging. Among older adults, history of TBI and RHI from popular contact/collision sports is exceedingly common but unrecognized. RHI may contribute to the wide variability observed in the onset and progression of neurodegenerative conditions. Studying head trauma exposure relevant for later‐life brain health, such as sport‐ and military‐related RHI, requires dedicated questioning.

Repetitive head impact exposure (RHI) is the only known risk factor for chronic traumatic encephalopathy (CTE), a distinct neurodegenerative tauopathy. Most aging studies ask participants about prior traumatic brain injury (TBI), but not common sources of RHI. Understanding the public health footprint of RHI requires targeted questioning of lifetime exposure. To set the stage for our Featured Research Session on CTE, we report RHI prevalence using gold standard methods across independent aging and dementia cohorts. The Boston University Repetitive Head Impact Exposure Assessment (BU-RHIEA) was administered across three cohorts: BU Alzheimer's Disease Research Center (ADRC), UCSF ADRC, and 1Florida ADRC. Participants recruited explicitly with concerns about cognitive effects of prior head trauma were excluded. The BU-RHIEA queries participation in contact/collision sports (e.g., American football, soccer, ice hockey, boxing) and military service as well as prior TBI. We report RHI and TBI prevalence estimates from the BU-RHIEA relative to estimates from the National Alzheimer's Coordinating Center Uniform Data Set (NACC UDS). In a subset of participants with frontotemporal dementia, we evaluated the clinical relevance of prior RHI through associations with age of symptom onset and rate of disease progression. Data come from 736 participants (age 70.4±9.6, 44.3% male, 43.1% cognitively impaired). Based on NACC UDS, 223 (30.2%) reported any prior TBI (Figure 1). When providing a formal TBI definition, frequency increased to 300 (40.8%). Sport and military history are not known through NACC UDS. Based on the BU-RHIEA, 221 (30.0%) participants reported any prior contact/collision sport play. Among males, 92 (28.2%) previously played American football and 98 (30.1%) served in the military. In participants with frontotemporal dementia, prior RHI related to younger symptom onset and more rapid cognitive decline (Figure 2). There is a high risk of underestimating the scope of RHI influence on brain aging. Among older adults, history of TBI and RHI from popular contact/collision sports is exceedingly common but unrecognized. RHI may contribute to the wide variability observed in the onset and progression of neurodegenerative conditions. Studying head trauma exposure relevant for later-life brain health, such as sport- and military-related RHI, requires dedicated questioning.

Roussy-Lévy syndrome (RLS) is characterized by postural hand tremor seen in patients with familial autosomal dominant Charcot-Marie-Tooth (CMT) neuropathy. 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. Pes cavus, tendon areflexia, sensory ataxia, and upper limb tremor should prompt consideration of CMT neuropathy. This video abstract depicts a bilateral hand tremor characteristic of Roussy-Lévy syndrome seen in patients with Charcot-Marie-Tooth disease neuropathy. The significance of the abstract lies in the phenomenology and the physiology of the tremor seen in patients with genetically confirmed duplication of PMP22 gene.