Thalamische Zielpunkte für dystonen Kopftremor – ein systematisches Review

Dystonic head tremor is a rare but debilitating disease, and its etiology is poorly understood. When first-line treatment with botulinum toxin injection is not sufficient, deep brain stimulation is considered. However, there is an ongoing debate about the optimal target point for dystonic head tremor. Especially thalamic targets were explored, but due to low patient numbers, randomized controlled trials are not feasible. We therefore summarized the existing literature that contains data that was collected over several decades in a systematic review.

Literature was selected via Medline using the search term "((dystonic head tremor) OR (isolated head tremor)) AND ((deep brain stimulation) OR DBS) AND (thalamus OR thalamic OR Vim)". Abstracts were screened for interventional studies or case reports of deep brain stimulation involving patients with head tremor. For all relevant abstracts the full text was analyzed.

The search terms retrieved 22 results, of which 6 publications were selected for detailed analysis. Results of 25 patients were reported with overall good response. Tremor was reduced between 60 to 91%, with a decrease in amplitude by 77.5% and dystonia was reduced by 50 to 57%. Overall dystonia was less reduced than tremor. Different rating scales were used throughout publications. All patients with dystonic head tremor had also tremor of the upper extremities. The Vim, the Voa/VLa and Vim/VLp, Voi, inferior base of VL and PSA were targeted alone or in combination. No serious adverse events or permanent side effects were described.

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Thalamic DBS is an efficient therapy option for dystonic head tremor in patients with predominant tremor symptoms. The different nomenclature of the thalamic nuclei can lead to inconsistency. Therefore, exact coordinates and operative technique should be reported. Also, the terms isolated head tremor and dystonic head tremor have not been used in a consistent way. Isolated head tremor was classified as an essential tremor syndrome for some time, but has recently been acknowledged as a dystonic movement disorder. Patients" symptoms need to be described thoroughly and objectified by rating scales. Careful patient selection and genetic testing could improve the overall outcome.