Multi-system atrophy. Coloured magnetic resonance imaging (MRI) scan of an axial (horizontal) view through the head of a 58-year-old male patient with multi-system atrophy (MSA). MSA is a rare, incurable neurological disorder caused by the progressive degeneration (atrophy) of nerve cells in specific areas of the brain. This patient has atrophy of the cerebellum and brain stem (yellow/green cross). Symptoms include difficulty with balance, and arm and leg co-ordination (ataxia). The cause of MSA is not fully understood, but it may be due to a genetic pre- disposition.