A rare case of Holmes tremor in a worker with occupational carbon monoxide poisoning

Parkinsonism and encephalopathy are frequently seen in patients who survive carbon monoxide (CO) poisoning. Neurological findings associated with CO poisoning can emerge immediately after cessation of exposure or following a brief period of pseudo-recovery. When present, the tremor associated with CO poisoning is typical of the postural/intention type. Here, we report on a rare case of toxic encephalopathy with a dominant-hand Holmes-type tremor, characterized by resting, as well as postural and kinetic/intentional components, in a previously healthy 53-year-old man exposed to CO while actively engaged in the process of performing a physically demanding skilled labor task. The unique neuropathological and functional changes that give rise to Holmes-type tremor and how this relates to the selective vulnerability of the inhibitory indirect pathway of the basal ganglia to glutamatergic excitotoxicity mediated by tissue hypoxia are discussed.