Boxers, as with other brachycephalic (short-nosed) breeds, have a predisposition to brain tumours known as gliomas. These tumours start in glial cells (supporting cells) within the brain, and as they grow, cause compression and damage to surrounding brain tissue. Some tumours are slow-growing and relatively benign, while others can be high-grade, aggressive tumours. Aggressive tumours are resistant to current forms of treatment.

Brain tumours primarily occur in older dogs, and signs vary depending on the location of the growth. Seizures, behavioural changes, circling, or general clumsiness indicate damage to the forebrain, while a tumour in the brain stem could trigger head tilting, rapid flicking of the eyes, difficulty swallowing, or unsteady walking.

A veterinary neurologist makes the diagnosis using an MRI or CT (cat) scan, with the most accurate diagnosis being done through biopsy. Once confirmed as a cancerous tumour, treatment for brain tumours involves radiation, and/or chemotherapy, as well as use of other medications to deal with specific symptoms (for example, an anti-seizure medication or steroids). Surgery may be an option depending on the size and location of the tumour.