Investigation of the risk of valproic acid-induced tremor: clinical, neuroimaging, and genetic factors

Association of UGT1A6 gene polymorphisms with sodium valproate-induced tremor in patients with epilepsy

BACKGROUND

Individual susceptibility to sodium valproate (VPA)-induced tremors may be due to genetic polymorphisms in the gene encoding the uridine diphosphate glucuronosyltransferase (UGT) enzyme, which affec the drug's clinical efficacy and cause toxic side effects. This study aimed to investigate the association between UGT1A6 polymorphisms and VPA-induced tremors in patients with epilepsy.

METHODS

In total, 128 patients with epilepsy were enrolled. Patients with epilepsy who received VPA were divided into tremor and non-tremor groups. Polymerase chain reaction-restriction fragment length polymorphism was used to investigate the genotype of UGT1A6 polymorphisms.

RESULTS

Carriers of the UGT1A6 A541G mutant genotype conferred a higher risk of tremor than wild-type carriers (odds ratio 2.128, P = 0.045). Logistic regression analysis showed that the A541G mutant genotype was a significant genetic risk factor for VPA-induced tremors. This suggests that individual susceptibility to VPA-induced tremors may result, at least partially, from genetic variation in UGT1A6 A541G.

CONCLUSIONS

Patients with epilepsy carrying the UGT1A6 A541G mutant genotype may have VPA-induced tremors, and early detection of this genotype will help guide the clinical individualizsation of VPA treatment.

A Case of Long-Term Exposure to Valproic Acid Mimicking Tremor-Dominant Parkinson's Disease

Background

Valproic acid is associated with increased risks of tremor and parkinsonism.

Case Report

A 67-year-old man with a diagnosis of epilepsy who had been treated with valproic acid (VPA) for 32 years noticed right-dominant upper-limb resting tremor accompanied by mild rigidity and bradykinesia. He was initially diagnosed with tremor-dominant Parkinson's disease (TDPD), but dopamine transporter single-photon emission computed tomography demonstrated no nigrostriatal degeneration. At 3 months after discontinuing VPA, his symptoms dramatically improved.

Discussion

VPA-induced tremor usually consists of postural or kinetic tremor without asymmetry. Our case indicated that careful evaluation is needed, even in cases of asymmetrical resting tremor and mild parkinsonism resembling TDPD after long term exposure to VPA.

Highlights

We report an atypical case of valproic acid-induced tremor and parkinsonism that mimics tremor-dominant Parkinson's disease. Physicians should not exclude the possible relation to valproic acid in patients presenting unilateral resting tremor and parkinsonism even in the absence of long-term side effects.