cns metastases subjects symptoms treated nervous eligible central neurologically stable cns metastases brain nervous central stable patients treated weeks disease metastases carcinomatous brain meningitis cns nervous central treated participate previously cns metastasis metastases nervous asymptomatic central treated steroids imaging previously carcinomatous meningitis nervous metastases central cns known active untreated clinically nervous central metastases cns known brain active history treated presence meningeal involvement nervous central carcinomatosis metastases signs cns brain clinical carcinomatosis leptomeningeal history cns metastases nervous lymphangitic brain central metastasis metastasis nervous central cns symptomatic known malignancy untreated history active tumors primary brain cns nervous central patients metastases solid seizures neurologically stable metastases brain treated cns nervous central steroids corticosteroids lesions inactive considered cns asymptomatic active treated nervous central small