Synopsis
Use dexamethasone selectively for symptomatic tumour-related vasogenic oedema, monitor and taper safely, and distinguish this indication from adrenal replacement in pituitary apoplexy and from other neurological steroid protocols.
- Dexamethasone reduces vasogenic oedema and offers temporary symptom relief; it does not treat the tumour, replace surgery or radiotherapy, or improve every asymptomatic scan abnormality.
- Treat the patient, not the MRI: use steroids when neurological or pressure symptoms are attributable to tumour-related oedema, and use the lowest effective dose for the shortest feasible duration.
- Adult brain-metastasis guidance supports 4–8 mg/day dexamethasone for mild mass-effect symptoms and consideration of about 16 mg/day or more for severe symptoms, then taper as rapidly as clinically tolerated; do not generalise this evidence to children or every primary tumour.
Key red flags
Declining consciousness, new anisocoria, posturing, respiratory change or rapid focal deterioration requires emergency imaging and neurosurgical escalation.
A severe acute headache, visual loss, ophthalmoplegia, hypotension or altered consciousness with a pituitary lesion suggests apoplexy and adrenal failure, not routine peritumoural oedema.
Fever, neutropenia, new cough, dysuria or wound change may be masked by glucocorticoids; investigate infection promptly.
Severe agitation, mania, psychosis, suicidal thinking or delirium can be steroid toxicity or intracranial deterioration and needs urgent review.
Marked hyperglycaemia, gastrointestinal bleeding, proximal weakness or new opportunistic infection should prompt treatment reassessment and supportive management.
New neurological worsening during taper may reflect recurrent oedema, tumour progression, haemorrhage, hydrocephalus, seizure or treatment effect; do not assume steroid dependence without reassessment.
Falling consciousness, pupil change, abnormal breathing, rapid motor decline or hydrocephalus requires emergency source control. Dexamethasone can accompany appropriate care but must not delay surgery, CSF diversion or haemorrhage management.
Insomnia, anxiety and irritability are common; mania, psychosis, severe depression and delirium can be dangerous. Distinguish medication timing from tumour, seizure, infection and metabolic causes.
Acute headache, ophthalmoplegia, visual loss and hypotension with a sellar lesion indicate apoplexy and possible ACTH failure. Use the hydrocortisone emergency pathway rather than a generic cerebral-oedema schedule.
Investigation priorities
Measure whether symptoms attributed to oedema improve and detect deterioration requiring urgent source control.
Management branches
An adult has a brain tumour, radiological vasogenic oedema and progressive focal symptoms without immediate herniation.
- Document the neurological baseline, exclude haemorrhage, hydrocephalus, active seizure and infection, and contact the tumour team to link symptom control to definitive treatment.
- Start the lowest effective dexamethasone dose using the applicable product and neuroscience protocol; adult metastatic guidance considers 4–8 mg/day for mild symptoms and higher doses around 16 mg/day for severe mass-effect symptoms.