Motor function after stereotactic radiosurgery for brain metastases in the region of the motor cortex

The authors sought to better define the clinical response of patients who underwent stereotactic radiosurgery (SRS) for brain metastases located in the region of the motor cortex. A retrospective analysis was performed in 2026 patients with brain metastasis who underwent SRS with the Gamma Knife between 2002 and 2012, and multiple factors that affect motor function before and after SRS were evaluated. Ninety-four patients with tumors ≥ 1.5 cm in diameter located in or adjacent to the motor strip were identified, including 2 patients with bilateral motor strip metastases. Motor function improved after SRS in 30 (31%) of 96 cases, remained stable in 48 (50%), and worsened over time in 18 (19%) instances. Forty-seven patients had no motor weakness prior to radiosurgery; 10 (22%) developed new Grade 3/5-4/5 weakness. Thirty (68%) of 44 patients with ≥ 3/5 pre-SRS weakness improved, 6 (14%) remained stable, and 8 (18%) worsened. Three of 5 patients with < 3/5 pre-SRS motor function improved. Motor deficits prior to SRS did not correlate with a worse outcome; however, worse outcomes were associated with larger tumor volumes. The median tumor volume in patients whose function improved or remained stable was 5.3 cm(3), but it was 9.2 cm(3) in patients who worsened (p < 0.05). Tumor volumes > 9 cm(3) were associated with a higher risk of worsening motor function. Adverse radiation effects occurred in 5 patients. Most intact patients with brain metastases in or adjacent to motor cortex maintained neurological function after SRS, and most patients with symptomatic motor weakness remained stable or improved. Larger tumor volumes were associated with less satisfactory outcomes.