Tumours of the cerebral hemispheres intrinsic

METASTATIC TUMOURS

Any malignant tumour may metastasise to the brain. Malignant melanomas show the highest frequency (66% of patients); this contrasts with tumours of the cervix and uterus where < 3% develop intracranial metastasis. The most commonly encountered metastatic intracranial tumours arise from the bronchus and the breast; of patients with carcinomas at these sites, 25% develop intracranial metastasis.

In up to 50% of patients, metastases are multiple. Spread usually haematogenous. Occasionally a metastasis to the skull vault may result in a nodule or plaque forming over the dural surface from direct spread.

Common primary sites

- bronchus

- breast

- kidney

- thyroid

- stomach

- prostate

- testis

- melanoma

Intracranial sites V* cerebral hemispheres '/■* cerebellum

(see page 317)

Involvement of the ventricular wall or encroachment into the basal cisterns may result in tumour cells seeding through the CSF pathways - malignant meningitis.

it \ te- ^ _ ^ - Necrotic areas may break down to form cystic cavities containing a pus-like fluid.

Tumour margin - well defined.

Clinical features

Patients with supratentorial metastatic tumours may present with epilepsy, or with signs and symptoms occurring from focal damage or raised intracranial pressure. Cerebellar metastases are discussed on page 317. Malignant meningitis causes single or multiple cranial nerve palsies and may obstruct CSF drainage (see page 497).

Investigations

A CT scan shows single or multiple Metastatic lesions usually well demarcated lesions of variable j j¡Afc&i - j| \ enhance with contrast, size. Often an extensive low density \ A ring-like appearance area, representing oedema, surrounds \ f •ft^^jKt 1 may resemble an abscess-

the lesion. \ /^HflEHvl but the wall is irregular and thickened.

MRI scanning, with and without paramagnetic enhancement, is even more sensitive than CT in detecting small metastatic lesions.

The search for a primary lesion if not already established must include a thorough clinical examination and a chest X-ray. Other investigations including barium studies, intravenous pyelogram (IVP), abdominal CT scans, ultrasound and sputum and urine cytology have questionable value, unless clinically indicated.

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