Transcranial magnetic stimulation for diplopia in a patient with spinocerebellar ataxia type 6: a case report

Background In Patients with spinocerebellar ataxia type 6 (SCA6) are often treated by transcranial magnetic stimulation (TMS) over the motor cortex and cerebellum. However, few reports have examined effective therapeutic modalities for diplopia in SCA6 patients. In the current case, we applied single-pulse TMS over the motor cortex and cerebellum to improve ataxia, and observed an unexpected improvement of diplopia. Case presentation A 62-year-old Japanese male with spinocerebellar ataxia type 6 (SCA6) was admitted to our hospital for exacerbation of ataxia. We administered single-pulse transcranial magnetic stimulation (TMS) over the hand motor area and the cerebellum with a circular coil to reduce ataxia. After the initiation of TMS, since diplopia unexpectedly improved, we started a quantitative assessment of diplopia by counting the number of fixation spots that he observed in his visual field. This assessment suggested that TMS had an immediate and cumulative effect on diplopia. We also delivered more localized stimulation only over the motor cortex with a Figure-8 coil, and diplopia improved immediately. Additionally, we administered a sham stimulation before the real stimulation over the motor cortex and the cerebellum. The sham stimulation improved diplopia, and greater improvement was observed with subsequent real stimulation. We also used a Hess chart examination and video recordings of binocular gross appearance to elucidate the changes in ocular movement objectively. However, these examinations did not reveal any obvious oculomotor changes. Conclusions We applied single-pulse TMS to a SCA6 patient with diplopia, which improved without any adverse effects. TMS may have potential for the treatment of diplopia in SCA6 patients.