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VI./4.3.: Workup
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Patients with diagnosed primary tumor presenting with headache, cortical and behavioural changes, focal seizure or slowly progressive focal symptoms first suggest brain metastasis. More commonly, the primary tumor is not diagnosed at the first presentation of the cerebral metastasis. The origin of the metastatic disease should be found even using extensive diagnostic methods, since the treatment is determined by the result. In approximately 15% of patients primary source is not found even with autopsy. In these cases small cell lung cancer may be supposed . Rarely, patients with brain metastasis and diagnosed systemic cancer may have another type of tumor responsible for the metastatic disease.
All patients with neurological symptoms must have investigation with neuroimaging methods. Even nowadays, the first choice of method is the intravenous contrast enhanced CT scan of the brain if in suspicion of cerebral metastasis. Small lesions are not visible in CT scan, which is a limitation of the method, and in many cases multiplicity of the tumor or meningeal infiltration are only diagnosed by MRI. MRI imaging of the brain is the most important radiologic differential method, with the additional use of special sequences of MRI DTI (diffusion tensor imaging), or MRI- spectroscopy. For searching of primary source and postoperative treatment follow-up or predict the dignity of the lesion, PET and SPECT imaging is used.
Cytology examination of the cerebrospinal fluid could be useful in meningeal spread of the tumor. Leptomeningeal infiltration always raise the protein content, but only acute leukemia (crisis) will cause markedly elevated cell count. Giving the adequate amount of cerebrospinal fluid, after sedimentation and specific staining methods, tumor-cells could be found.
EEG is the method of choice in epileptic seizure or in encephalopathies of e.g. paraneoplastic origin.
Bilateral oedema of the optic nerve head is an aspecific sign of increased intracranial pressure. With the easily available neuroimaging methods, bedside examination is not so widely used nowadays.
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Treatment strategy of the patient is determined by the primary source and histology. If known malignancy, re-staging should be done aimed at recurrent primary tumor and systemic metastases. In most cases primary tumor is undiagnosed at the time of presentation of the metastatis.
Usually, radiomorphology gives no clue to the identification of the source, except in tumors commonly bleed, or with specific pattern of contrast enhancement, or characteristic in a location. Detailed physical examination and surveying risk factors (smoking, aethylism, sun and environmental exposure) is needed, the main physical and laboratory findings together should lead the further investigations.
Histology, biopsy is needed after stating. The biopsy site should be chosen as the easiest accessible and most informative one: the primary tumor (skin surface, bronchoscopy, and gastro/colonoscopy), parenchymal organ metastasis or brain metastasis. Biopsy from the brain lesion is indicated if immidiate operation is not an option or if the source of the multiplex brain metastasis cannot be identified another way. If possibility of brain abscess or primary brain lymphoma arises, biopsy is a method of choice to differentiate. Brain biopsy is a stereotactic CT (or MRI) guided technique under local anaesthesia. Choosing the right and most informative area of the biopsy is greatly important, e.g. the necrotic center of the tumor would not give the proper sample. The procedure takes usually 24 hours to complete.
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