BDNF polymorphism and differential rTMS effects on motor recovery of stroke patients

The brain-derived neurotrophic factor (BDNF) gene often shows a single nucleotide polymorphism that is thought to influence synaptic plasticity. It also affects the modulatory effects of repetitive transcranial magnetic stimulation (rTMS) on motor cortex excitability.

This study investigated whether BDNF polymorphism influences the effect of rTMS on the motor recovery of patients with stroke.

Forty-four patients (mean age 53.8 years) experiencing unilateral motor weakness after stroke were recruited. rTMS was applied over the primary motor cortex of the affected hemisphere at 10 Hz with 1000 pulses/day for 10 days. Each patient's motor functions were assessed using the Fugl-Meyer assessment (FMA) and the box and block test (BBT) before, immediately after and 2 months after the intervention. BDNF genotyping was performed via PCR assays of whole blood samples. The patients' data were grouped and analysed into Val/Val and Met allele groups according to the presence or absence of the BDNF polymorphism.

Nine patients (20.5%) were classified into the Val/Val group, and thirty-seven patients (79.5%) were classified into the Met allele group. The patients' baseline motor functions did not differ between the two groups. The FMA and BBT scores showed significant improvement immediately after and 2 months after rTMS in both groups. In addition, the time and groups were found to interact significantly, with the Val/Val group improving to a greater extent than the Met allele group in terms of their FMA and BBT scores.

The findings suggest that the BDNF gene polymorphism negatively influences the effect of rTMS on the motor recovery of upper extremities in stroke patients.