Low-Frequency Repetitive Transcranial Magnetic Stimulation of Supplementary Motor Area Improves Motor Function in Patients with Parkinson Disease

EBM Focus - Volume 8, Issue 19

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Reference: Neurology 2013 Apr 9;80(15):1400, (level 1 [likely reliable] evidence)

Repetitive transcranial magnetic stimulation (rTMS) has shown efficacy for a wide variety of conditions ranging from stroke to depression to tobacco craving. Its use has been explored for control of motor symptoms in Parkinson disease, but the optimal location and frequency of stimulation are unclear. In previous studies in Parkinson disease, rTMS has generally targeted the primary motor cortex or prefrontal cortex, and high-frequency stimulation has shown greater efficacy than low-frequency stimulation (Mov Disord. 2009 Feb 15;24(3):357). A recent randomized trial evaluated rTMS of the supplementary motor area, comparing 2 different frequencies of stimulation and sham stimulation in 106 patients with Parkinson disease.

Patients (mean age 68 years) with Hoehn-Yahr stage 2-4 Parkinson disease were randomized to low-frequency rTMS (1 Hz) vs. high-frequency rTMS (10 Hz) vs. realistic sham simulation once weekly for 8 weeks and followed for 12 additional weeks. Focal stimulation was applied with a handheld device over the supplementary motor area (3 cm anterior to the leg motor area along the midline). Stimulation sessions lasted 17-20 minutes. All patients continued on their current medications. The primary outcome was change in motor function as measured by the Unified Parkinson’s Disease Rating Scale (UPDRS) part III score. This score includes assessment of speech, tremor, rigidity, posture, gait, and other motor functions, with reduced scores indicating improvement. A change in score of 2.3 points is considered minimal clinically important difference, and a change of 4.5-7 points moderately important.

At the end of follow-up, the mean reductions in motor scores were 6.84 points with rTMS at 1 Hz, 0.71 points with rTMS at 10 Hz, and 2.15 points with sham (p < 0.022, pairwise comparisons not reported). Only the rTMS 1 Hz group showed a significant reduction from baseline. In post hoc analyses, rTMS 1 Hz was associated with significant improvement in posture and gait, and borderline improvement in rigidity and bradykinesia compared to the other groups. There were no significant differences in tremor or speech among groups. There were also no significant differences in depression, apathy scores, or nonmotor symptoms scores among groups. No adverse events were reported in any group.

Repetitive transcranial magnetic stimulation was approved by the FDA in 2008 for treatment of major depression and is widely available for that indication. Its use for other psychiatric and neurologic conditions is still considered investigational.

For more information, see the Parkinson disease topic in DynaMed.