2004 Motor Strength Following Stereotactic Radiosurgery of Metastases in the Primary Motor Cortex

INTRODUCTION: The motor cortex is a highly eloquent region of the brain. Treatment goal focuses on the preservation of functionality. Long-term impact on motor strength is lacking. METHODS: A retrospective review was performed in patients with brain metastases who underwent Gamma Knife SRS between 2012-2020. Demographic, clinical and treatment parameters were evaluated. RESULTS: In 1,151 patients with brain metastases, there were 130 (11.3%) patients with a total of 185 primary motor cortex tumors. Ninety-one (70.0%) patients were female, median age was 63 (range 30–88) years old, and average pre-SRS KPS was 83.7±16.8. Non-small cell lung (42%) and breast (38%) cancers were the most common pathologies. The median margin dose prescribed was 16Gy (range 12–20 Gy). Before SRS, 100 (77%) patients had intact motor strength and 25 (19%) patients experienced motor deficits. In 77 patients with documented motor exams at 6 months, sixty-two (77%) patients showed stable motor function, 11 patients (8%) had improved motor function, and 4 patients (3%) developed new motor deficits after SRS. The rate of tumor control at the median time of follow-up of 6 months was 96%. The overall rate of survival after SRS at 3, 6, and 12 months was 85%, 66%, and 42%, respectively. Seven patients had repeated SRS due to tumor progression. ARE occurred in 3 patients. CONCLUSIONS: SRS can be safely used for metastases located in the motor cortex with low risk of worsening of motor function. Even in patients presenting with peritumoral edema and motor weakness, SRS remains an effective treatment modality and can improve motor function in patients at follow-up.