• brain metastases
• chemotherapy
• meningeal metastases
• radiotherapy
• spinal cord compression

Ten to 50% of patients with systemic malignancy develop brain metastases during the course of their disease and metastases account for more than half of all brain tumours in adults. The major originating primary tumours are carcinomas typically arising from sites shown in fig 1. The majority of patients have multiple metastases.

A long disease-free interval, with absent systemic metastatic disease and presentation of brain metastases of unknown primary, may require biopsy of the brain lesion if active treatment is appropriate. However, in the context of known metastatic disease histological confirmation is not usually necessary.

Up to one third of brain metastases are discovered on routine staging investigations, the majority presenting with varying clinical features. The diagnosis of brain tumours should be suspected in any cancer patient who develops any new neurological symptoms. Brain metastases present with headaches in 40–50% of patients, with increased frequency with multiple metastases or posterior fossa metastases. Seizures and behavioural symptoms are also common while, in comparison, focal neurological signs are rare as presenting symptoms.

In patients suspected to have brain metastases, contrast enhanced magnetic resonance imaging (MRI) is the best diagnostic test. However, current practice in the UK is to investigate initially with computed tomography (CT). If the CT scan shows multiple metastases then an MRI would not usually add any further information. However, in good performance status patients if a single metastasis is seen on CT imaging an MRI should be performed to exclude multiple metastases before more radical treatment (fig 2).