Objective: To discuss the optimal target in deep brain stimulation (DBS) for Holmes tremor (HT)

Background: Holmes tremor is a proximally dominant tremor with low frequency, large and irregular amplitude, occurring at rest, posture and action. It is usually caused by cerebrovascular events, trauma, and MS-related lesions in the mesencephalon or thalamus. Symptoms may appear weeks, months or even years after the underlying cause. Although the exact pathophysiology is still unknown, it is thought that the cerebello-thalamo-cortical, dentato-rubro-olivary and nigrostriatal pathways are involved. HT is mostly resistant to medical treatments, and DBS appears to be the most effective treatment in the management of HT. However, the target selection in DBS for HT is still controversial.

Method: Case report

Results: A 45-year-old male, right-handed patient was referred to our clinic for the complain of tremor in the right hand that has been severe enough to affect daily living activities for 1 week. His medical history revealed left thalamic hematoma 6 months ago that was operated due to detection of cavernoma (Figure 1). Neurological exam revealed severe Holmes tremor in the right upper extremity which interfered with his daily activities. He was on levodopa 600 mg/day, levetiracetam 2000 mg/day, clonazepam 2 mg/day treatments and was fully unresponsive to the medical treatment. Since he was functionally disabled, he underwent left globus pallidus internus (GPi) DBS surgery (Figure 2). Best results were obtained through monopolar stimulation of the contact 3- Case + that improved tremor markedly (2,8 mA; 180 Hz; 60 msec). Approximately 66% improvement was observed on the Fahn‐Tolosa‐Marin Clinical Rating Scale for Tremor (Figure 3&4).

Conclusion: Although thalamic Vim nucleus stimulation seems to be a reasonable target, we were unable to do Vim DBS surgery because of the resection of post-bleeding thalamic cavernoma which is not allowing electrode insertion to the thalamus. Additionally, Vim DBS for HT may also have some limitations including the development of recurrence over time and a limited effect on proximal and intention tremor. 64% and 78% improvement in tremor scale has been reported with pallidal stimulation in some HT cases. A similar improvement was also observed in our case, and we suggest that GPi should be kept in mind as an optimal target of DBS in cases with HT.

Left thalamic hematoma due to cavernoma

Left GPi DBS electrode in CT scan

Tremor Scale in Stim-OFF

Tremor Scale in Stim-ON

References: This case report was presented in WSSFN Congress, Korea in September 4-7, 2022.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/holmes-tremor-treated-with-pallidal-stimulation/