While symptoms are often non-specific, the following signs and symptoms should be investigated:

• increasing headaches, persistent new headaches, vomiting, unexplained morning headache
• seizure
• blackouts or other alterations in conscious state
• poor coordination
• visual deterioration or other focal neurological symptoms
• progressive weakness
• change in behaviour
• change in memory
• confusion, drowsiness
• speech disturbance
• other unexplained neurological symptoms including major personality/behavioural change.

The presence of multiple signs and symptoms, particularly in combination with other underlying risk factors, indicates an increased risk of high-grade glioma.