Objective: The objective of this case presentation is mainly to raise awareness of possible side effects of Carbamazepine in epileptic and non-epileptic patients, even years after the initiation of the drug. It is important to highlight that these movement disorders are reversible when the incriminated drug is stopped.

Background: Drug-induced movement disorders are a worldwide issue and can occur shortly after the initiation or titration of the medication. The challenge in managing these movement disorders is distinguishing an iatrogenic cause from a functional movement disorder, as these two entities may coexist and overlap, and especially as the most common functional clinical manifestations are tremor, dystonia, and myoclonus.

Method: We present the case of a 41-year-old patient with idiopathic generalized epilepsy diagnosed at the age of 18, treated with Carbamazepine (800mg/d) and seizure-free. He presented these last 3 years with hyperkinetic movement disorders affecting his walk and causing clumsiness of the upper limbs. Neurological examination showed truncal and right-arm dystonia, generalized muscle twitches, predominantly at the axial, abdominal and proximal portion of the upper limbs, abrupt and shock-like, in favor of negative myoclonus, worsening with posture and walking. Examination also showed an upper limb resting tremor. The EEG and brain MRI were unremarkable. The antiseizure treatment was switched from Carbamazepine to Levetiracetam (500mg/d), with a complete recovery within 3 weeks.

Results: Dystonia is a rare side-effect of antiseizure medication. It is thought to be caused by either its dopamine-blocking properties or the depletion of GABA concentrations resulting in an increase of the thalamocortical drive. Cases of CBZ-induced hemidystonia and writer’s cramp dystonia have been reported. Cases of CBZ-induced tremor have been reported. Carbamazepine has the widest range of antiseizure-drug-induced abnormal movements, along with lamotrigine, phenytoin, pregabalin, gabapentin and valproate. Factors contributing to the occurrence or exacerbation of movement disorders from one patient to another are not well known.

Conclusion: Carbamazepine can cause a wide range of pharmacological movement disorders, such as myoclonus, tremor, and dystonia, but also parkinsonism and tic-like behavior. No treatment is required, as discontinuation or replacement of the incriminated drug leads to complete disappearance of clinical signs.

References: 1. Zadikoff C, Munhoz RP, Asante AN, Politzer N, Wennberg R, Carlen P, Lang A. Movement disorders in patients taking anticonvulsants. J Neurol Neurosurg Psychiatry. 2007 Feb;78(2):147-51. doi: 10.1136/jnnp.2006.100222. Epub 2006 Sep 29. PMID: 17012337; PMCID: PMC2077655.
2. Magaudda A, Di Rosa G. Carbamazepine-induced non-epileptic myoclonus and tic-like movements. Epileptic Disord. 2012 Jun;14(2):172-3. doi: 10.1684/epd.2012.0504. PMID: 22584239.
3. Rissardo JP, Vora N, Mathew B, Kashyap V, Muhammad S, Fornari Caprara AL. Overview of Movement Disorders Secondary to Drugs. Clin Pract. 2023 Aug 18;13(4):959-976. doi: 10.3390/clinpract13040087. PMID: 37623268; PMCID: PMC10453030.
4. Rissardo JP, Caprara ALF. Carbamazepine-, Oxcarbazepine-, Eslicarbazepine-Associated Movement Disorder: A Literature Review. Clin Neuropharmacol. 2020 May/Jun;43(3):66-80. doi: 10.1097/WNF.0000000000000387. PMID: 32384309.

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