Hair loss treatment post brain surgery?

Dear Dr I'm a 38 Yr old male suffering from male pattern baldness (receiding temples). I was using minoxidil which helped however last year I had brain surgery for a colloid cyst and hydracaphelus. Since then I stopped using minoxidil and my hair is thinning very quickly. I'm still recovering and wanted to ask is it safe to start using minoxidil again.?