Tremor is a cardinal symptom of parkinsonism, occurring early on in the disease course and affecting more than 70% of patients. Parkinsonian resting tremor occurs in a frequency range of 3–7 Hz and can be resistant to available pharmacotherapy. Despite its prevalence, and the significant decrease in quality of life associated with it, the pathophysiology of parkinsonian tremor is poorly understood. The tremulous jaw movement (TJM) model is an extensively validated rodent model of tremor. TJMs are induced by conditions that also lead to parkinsonism in humans (i.e., striatal DA depletion, DA antagonism, and cholinomimetic activity) and reversed by several antiparkinsonian drugs (i.e., DA precursors, DA agonists, anticholinergics, and adenosine A2A antagonists). TJMs occur in the same 3–7 Hz frequency range seen in parkinsonian resting tremor, a range distinct from that of dyskinesia (1–2 Hz), and postural tremor (8–14 Hz). Overall, these drug-induced TJMs share many characteristics with human parkinsonian tremor, but do not closely resemble tardive dyskinesia. The current review discusses recent advances in the validation of the TJM model, and illustrates how this model is being used to develop novel therapeutic strategies, both surgical and pharmacological, for the treatment of parkinsonian resting tremor.

Background: Immune checkpoint inhibitors (ICIs) cause inflammatory immune-related adverse events (irAEs), which are often effectively managed with steroids. Less is known about the best management of irAEs refractory to steroid treatment. Objective: We aimed to assess the efficacy of second-line medications used to treat gastrointestinal (GI) irAEs. Methods: This study was a single-center, retrospective medical record review of patients who received steroids for an ICI GI irAE and at least one dose of infliximab, vedolizumab, or adalimumab for irAE treatment from March 25, 2011 to September 20, 2019, approved by Yale University’s Institutional Review Board. Our primary objective was to assess the efficacy of second-line treatment, measured by the change in the Common Terminology Criteria for Adverse Events Version 5.0 grading system. Results: A total of 39 patients met inclusion criteria. Treatment for steroid-refractory GI irAEs demonstrated a high response rate, with irAE resolution seen in 89.7% of patients. Patients who were specifically initiated on infliximab within 14 days of starting steroids had a higher percent resolution seen in 94.4% of patients. The average time to response, defined as the average days from second-line therapy to reported symptom resolution, was 17 days. Conclusion and relevance: Steroid-refractory GI irAEs can be managed effectively in most patients with immunosuppressive therapy, such as infliximab. Furthermore, initiating second-line immunosuppressive therapy within 14 days of steroid failure resulted in a higher rate of symptom resolution.