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Letter to the editor
The Application of Deep Brain Stimulation in the Syndrome of Irreversible Lithium-Effectuated Neurotoxicity
Lina Okar1corresp_iconorcid, Peyton Murin1orcid, Anagha Prabhune1orcid, Richard Bucholz2orcid, Pratap Chand1orcid
Journal of Movement Disorders 2025;18(1):101-102.
DOI: https://doi.org/10.14802/jmd.24209
Published online: December 2, 2024

1Department of Neurology, St. Louis University/SSM Health, St. Louis, MO, USA

2Department of Neurosurgery, St. Louis University/SSM Health, St. Louis, MO, USA

Corresponding author: Lina Okar, MD Department of Neurology, St. Louis University/SSM Health, 1008 S Spring Ave, St. Louis, MO 63110, USA / Tel: +1-314-977-2140 / E-mail: Linaokar227@gmail.com
• Received: October 10, 2024   • Revised: November 12, 2024   • Accepted: November 30, 2024

Copyright © 2025 The Korean Movement Disorder Society

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Dear Editor,
Lithium is a commonly used medication for the treatment of psychiatric disorders because of its mood-stabilizing effect. However, despite its common use in clinical practice, lithium has a wide range of adverse effects [1].
Syndrome of irreversible-effectuated neurotoxicity (SILENT) is a rare and long-lasting side effect of acute lithium toxicity. It is characterized by persistent neurological symptoms that occur after acute lithium exposure in the absence of any preexisting neurological conditions. These symptoms should remain present for at least 2 months after the discontinuation of lithium treatment [2]. Common neurological manifestations include cerebellar dysfunction and tremor, which are often irreversible [3,4]. Previous studies have identified deep brain stimulation (DBS) of the ventral intermediate nucleus of the thalamus (ViM) as a possible effective therapeutic strategy for other drug-induced tremors [5]; however, evidence for its use in SILENT is currently limited. Here, we report a case of a successful and persistent response to ViM DBS in a patient with SILENT.
A 64-year-old woman with a history of bipolar disorder presented to the movement disorders clinic with debilitating involuntary movements affecting all the extremities and trunk. The tremors began 2 years before following a 10-day coma due to an accidental lithium overdose. Movements started with bilateral hand tremors that progressed to involve the lower extremities, limiting functional status (wheelchair dependent). Additionally, she reported a decline in her memory, word-finding difficulty, and impaired attention span. Her medical history was remarkable for bipolar disorder, diabetes, hypertension, and alcohol and tobacco use. Her family history was unremarkable. Lithium and aripiprazole were stopped due to tremor without symptom resolution, so medical therapy with carbidopa-levodopa, propranolol, primidone, valproic acid, and duloxetine was attempted. However, her symptoms continued to progress.
Her physical examination was notable for postural and kinetic tremors in all limbs (<4.5 Hz) and the torso, bradykinesia, rigidity predominantly on the right side, positive cerebellar signs (Supplementary Video 1 in the online-only Data Supplement) and ataxic gait. The clinical rating scale for tremor (CRST) scores for Part A (postural and kinetic tremor in the hand), Part B (during writing and water pouring) and Part C (functional disability during eating drinking writing) were all 4 [6].
Owing to an inadequate response to medical therapy, the patient was offered left ViM DBS. The presurgical evaluation, including magnetic resonance imaging of the brain, revealed severe cerebellar hemispheric atrophy on the right side (Figure 1). The results of the neuropsychological evaluation were unremarkable. Left ViM DBS was performed with standard stereotactic coordinates and microelectrode recording and placement of a Medtronic 3387 lead and later, a Medtronic PC nonrechargeable battery without complications. She underwent sequential DBS programming with near complete resolution of the right hand tremor at 6 months (CRST scale score of 1). However, she required interleaved DBS programming between the bottom and top electrodes in the DBS implanted lead to control her hand tremors. The DBS programming parameters are as follows: 1) ViM 1 (left): 0-C+, 2.4 V, 210 PW, 125 Hz; 2) ViM 1 (right): 3-C+, 1.0 V, 60 PW, 125 Hz.
Importantly, this benefit persisted 4 years later (Supplementary Video 1 in the online-only Data Supplement). Additionally, the patient was able to feed herself using her right hand, which was a satisfactory result. Given the good response to left ViM DBS, the patient was offered right ViM DBS; however, she declined. The tremor in the left hand did not improve and persisted after DBS. Therefore, the improvement in the right hand tremor was not due to spontaneous improvement in SILENT.
ViM DBS has shown efficacy in treating tremor disorders, but to the best of our knowledge, this is the first report of its efficacy in SILENT. We also highlight the utility of interleaved DBS programming in this difficult-to-treat condition.
The online-only Data Supplement is available with this article at https://doi.org/10.14802/jmd.24209.
Video 1.
Before deep brain stimulation: The patient has bilateral postural and kinetic hand tremors, is unable to feed herself, has severe dysmetria, and has truncal ataxia. After deep brain stimulation: After left ventral intermediate nucleus of the thalamus deep brain stimulation, the right-hand tremor and dysmetria improved and the patient could feed herself, but truncal ataxia was still presented.

Ethics Statement

No institutional IRB approval was required for this study. Consent was obtained from the patient for videography.

Conflicts of Interest

The authors have no financial conflicts of interest.

Funding Statement

None

Author Contributions

Conceptualization: Lina Okar. Data curation: Pratap Chand. Formal analysis: Peyton Murin. Methodology: Lina Okar. Supervision: Pratap Chand, Richard Bucholz. Validation: Pratap Chand, Richard Bucholz. Writing—original draft: Lina Okar, Anagha Prabhune. Writing—review & editing: Pratap Chand, Richard Bucholz.

The authors would like to acknowledge the Neurology and Neurosurgery department at SSM Health/Saint Louis University. The author would like to thank the patient for providing consent to publish their video. The authors would like to thank Dr. Mehdi Fani for editing the videos.
Figure 1.
MRI brain (T2): Showing brain MRI showing severe bilateral hemispheric cerebellar atrophy that is more prominent in the right cerebellar hemisphere. MRI, magnetic resonance imaging.
jmd-24209f1.jpg
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  • 3. Ott M, Stegmayr B, Salander Renberg E, Werneke U. Lithium intoxication: incidence, clinical course and renal function - a population-based retrospective cohort study. J Psychopharmacol 2016;30:1008–1019.ArticlePubMedPMCPDF
  • 4. Santos CF, Gomes R. Syndrome of Irreversible Lithium-Effectuated Neurotoxicity (SILENT): a review. Eur Psychiatry 2022;65(S1):S717.Article
  • 5. Amerika WE, van der Gaag S, Mosch A, van der Gaag NA, Hoffmann CFE, Zutt R, et al. Medical and surgical treatment for medication‐induced tremor: case report and systematic review. Mov Disord Clin Pract 2022;9:676–687.ArticlePubMedPMCPDF
  • 6. Fahn S, Tolosa E, Marin C. Clinical rating scale for tremor. In: Jankovic J, Tolosa E. Parkinson’s disease and movement disorders. Baltimore-Münich: Urban & Schwarzenberg, 1988;225-234.

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      The Application of Deep Brain Stimulation in the Syndrome of Irreversible Lithium-Effectuated Neurotoxicity
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      Figure 1. MRI brain (T2): Showing brain MRI showing severe bilateral hemispheric cerebellar atrophy that is more prominent in the right cerebellar hemisphere. MRI, magnetic resonance imaging.
      The Application of Deep Brain Stimulation in the Syndrome of Irreversible Lithium-Effectuated Neurotoxicity

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