Is a rare tumour the cause of a student’s declining grades?

A 16-year-old school student presents with low mood, headache, and struggling to play the piano
Girl playing piano

Sonia, a 16-year-old high school student, presents with a six-month history of low mood and falling grades at school.

She is a grade eight pianist but now struggles to play grade six pieces. Her previous GP diagnosed depression three months ago and started her on sertraline 50mg daily.