Isolated neck tremor as a rare tardive effect of long‐term aripiprazole therapy

Aripiprazole, a third-generation antipsychotic, demonstrates the pharmacodynamic characteristics of partial agonism, functional selectivity, and serotonin–dopamine activity modulation, representing the latest paradigm in managing major psychiatric conditions, including Bipolar II disorders.1 Aripiprazole is also associated with a low incidence of tremors and is recommended as an alternative for patients experiencing tremors caused by other antipsychotics.2 Here, we describe a case of isolated neck tremor as a rare tardive effect of long-term aripiprazole therapy. A 34-year-old female with a history of ovarian cystectomy and ongoing treatment for Bipolar II Disorder presented with a 3-month history of head tremors. She had been taking aripiprazole (3 mg/day) for over a decade with no other medications and demonstrated good medication adherence. Her mental state has remained stable over the past few years with the same dose of aripiprazole; apart from the tremors, there have been no relevant physical symptoms. She also denied having dystonic features, such as torticollis and hypertonia, and other extrapyramidal symptoms, including rigidity, hand tremor, reduced arm swing, bradykinesia, difficulty in maintaining posture, or a mask-like face. Working in an office environment, she had no known exposure to specialized chemicals. Additionally, her medical history revealed no instances of international travel or interaction with animals, and there was no evidence of sexual activity involving multiple partners. She was alert and vital signs were stable. Physical examination revealed a resting tremor of the neck, approximately 3 Hz in the anterior–posterior direction (Video S1), with no other significant neurological findings. There were also no signs suggesting other extrapyramidal symptoms, such as Myerson's sign or the retropulsion test. Suspecting drug-induced tremor, aripiprazole was discontinued, leading to the complete resolution of the tremor within a week (Video S1). Therefore, she was diagnosed with isolated tardive neck tremor due to chronic aripiprazole use. Following psychiatric deterioration a month later, aripiprazole was resumed at 3 mg every 3 days, maintaining psychiatric stability without tremor recurrence. Tardive tremor is a relatively rare component of drug-induced extrapyramidal symptoms, accounting for 2.4% of antipsychotic-induced extrapyramidal side effects.3 This condition is commonly observed in patients who have been taking medication for an average period of more than 10 years4; thus, the absence of immediate onset should not preclude the consideration of drug-related side effects. While tremors are commonly present in the limbs, rare cases like this case involve head and neck manifestations.4 Tardive tremors persist even after discontinuation of the causative medication in half of reported cases.5 If no improvement is observed, tetrabenazine should be considered.2 In conclusion, it is crucial to recognize that aripiprazole-induced tremors can occur with long-term use and may exclusively affect the neck. Drug-induced causes should be considered in any new-onset symptoms. Ryuichi Minoda Sada: Conceptualization; writing – original draft; visualization; writing – review and editing. Saki Minoda Sada: Visualization; writing – review and editing; supervision. This research was conducted as part of the All-Osaka U Research in “The Nippon Foundation—The University of Osaka Infectious Disease Response Project.” We would like to thank Editage (www.editage.jp) for English language editing. This study did not receive any specific grants from funding agencies in the public, commercial, or nonprofit sectors. The authors have stated explicitly that there are no conflicts of interest in connection with this article. Ethical approval statement: According to Japanese national guidelines, institutional review board approval is not required for single-patient case reports. Patient consent statement: Informed consent was obtained from the patient for publication of this case report, including any accompanying images and videos. The patient's anonymity has been preserved. Clinical trial registration: None. Video S1 Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.