Pathogenesis of the Holmes tremor due to cerebellar lesions: A case series with a narrative review.

BACKGROUND: Holmes tremor is a 2- to 5-Hz tremor that occurs at rest, during posture, and with movement. It has been associated with lesions in several central nervous system regions, including the thalamus, brainstem, and cerebellum; however, its precise anatomical origin remains unclear. OBJECTIVE: To investigate the pathogenesis of Holmes tremor associated with cerebellar lesions. PATIENTS AND METHODS: We analyzed two patients treated at our hospital and four previously reported cases of Holmes tremor related to cerebellar lesions. RESULTS: In one of our patients, MRI demonstrated Wallerian degeneration of the dentato-rubro-thalamic pathway (DRTP), and inferior olivary pseudohypertrophy suggested disruption of the dentato-rubro-olivary pathway (DROP). The striato-nigral pathway (SNP) was also suspected to be involved because of the patient's Parkinson's disease. In the second patient, MRI demonstrated Wallerian degeneration of the DRTP, and DROP involvement was also suspected. Among the previously reported cases, all three pathways were suspected to be affected in one patient, whereas combined DRTP and DROP involvement appeared likely in two patients. CONCLUSIONS: These observations suggest that, in cerebellar-lesion-related Holmes tremor, disruption of the DRTP and DROP may contribute to tremor development, in addition to the previously proposed mechanisms involving the DRTP and SNP.