Objective: Deep brain stimulation (DBS) targeting ventralis intermedius nucleus (Vim) is a well-known treatment option for medication-refractory tremor in essential tremor (ET). Common stimulation-induced side effects of Vim-DBS are paresthesia, gait disorders, speech problems. We here described dysgeusia-a rare side-effect of Vim-DBS- leading to weight loss following bilateral Vim-DBS in a patient with ET and discussed the programming strategies.

Background: An 81-year-old man presented to our hospital with bilateral, symmetrical postural and kinetic tremor of both hands. He had ET diagnosis for 30 years which was refractory to medication. He had no cognitive and/or psychiatric problems.

Method: He underwent bilateral Vim-DBS surgery (Boston Scientific® Vercise™).Postoperative DBS-programming employing omnidirectional stimulation bilaterally (i.e. right electrode: C+, (5-6-7)-, 60 μs, 130 Hz, 2 mA; left electrode: C+, 1-, 60 μs, 130 Hz, 2.4 mA) revealed almost complete tremor suppression except for a residual mild postural tremor of the right hand. One week after the initial programming, he was complaining from a metallic, bitter and sour taste in her mouth leading to a decreased oral intake and weight loss.

Results: During the follow-up screening, the active contact was switched to (2-3-4)-, leading to a dorsal stimulation with an increase in the amplitude to 3 mA, resulted with a decrease in dysgeusia without worsening in tremor. The patient presented with paresthesia at his right foot with mild dysgeusia still, leading to a fear of eating that continued the weight loss up to 6 kg after 2 weeks. Following a directional monopolar review, directional stimulation of the left electrode at contact 4-, 3mA, 60 µs and 130 Hz resulted with a complete recovery in dysgeusia and paresthesia without worsening in tremor.

Conclusion: Dysgeusia can be defined as an abnormal feeling of taste such as metallic, sour, bitter, with normal sense of smell and absence of oral paresthesias. It is a rare side-effect of Vim-DBS and supposed to result from stimulating more posterior contacts which are often close to the sensory nucleus of the thalamus and/or medial lemniscus containing the gustatory pathway. Thus, programming strategies such as stimulation of more dorsal contacts or switching to directional steering should be considered to improve stimulation-induced dysgeusia in Vim-DBS for ET.

References: 1. Carlson JD, McLeod KE, Mark JB, McLeod PS, Bremer BA. Dysgeusia in deep brain stimulation for essential tremor. J Clin Neurosci. 2018:50:242-246. doi:10.1016/j.jocn.2018.01.013.
2. Swinnen BEKS, Bot M, Goes KM, Beudel M, Schuurman RP, de Bie RMA. Directional stimulation improves stimulation-induced dysgeusia in DBS for essential tremor. Brain Stimulation 2022; 15 (3): 680-682.
3. Gilard V, Maltête D, Lefaucheur R, Chastan N, Derrey S. Dysgeusia following ventral intermediate nucleus deep brain stimulation for essential tremor. Parkinsonism Relat Disord. 2014 Nov;20(11):1307-8. doi: 10.1016/j.parkreldis.2014.08.020.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/programming-strategies-to-improve-stimulation-induced-dysgeusia-a-rare-side-effect-in-deep-brain-stimulation-for-essential-tremor/