Brain tumor overview
Brain tumors are classified as primary (arising from brain, meninges, or nerve tissue) or metastatic, and as benign or malignant, with presentation driven largely by location and rate of growth rather than histology alone. Diagnosis rests on contrast brain MRI, and initial management is directed at controlling mass effect, edema, and seizures while pathology guides definitive therapy.
- Topic reviewThe full article, organized the way the exam asks it.
- ABIM-format MCQsVignettes with an explanation for every wrong answer.
- Key factsThe numbers and thresholds worth memorizing, up front.
- AI tutorMedBrain answers the question you're stuck on.
What this article covers
- Overview
Definition: a brain tumor is any abnormal growth within the cranial cavity, arising primarily from brain parenchyma, meninges, cranial nerves, or pituitary/pineal tissue, or secondarily as a metastasis from a systemic cancer.
- Epidemiology
Brain metastases are the most common intracranial tumors encountered clinically, more frequent than any single primary CNS tumor type.
- Risk factors
Previous therapeutic radiation to the head: the only consistent risk factor identified for glioma development, including its most aggressive subtype.
- Pathophysiology
Mass effect: the tumor and any surrounding vasogenic edema occupy space within the fixed cranial vault, displacing normal brain and, if unchecked, raising intracranial pressure (ICP) to the point of herniation.
- Clinical features
Elevated ICP symptom complex: headache that worsens with coughing, sneezing, straining, or the Valsalva maneuver (the classic early-morning headache is actually uncommon), accompanied by nausea…
- Differential diagnosis
Brain abscess: ring-enhancing lesion mimicking a tumor, but with fever, elevated inflammatory markers, and often a source of infection (endocarditis, sinusitis, immunosuppression).
- Diagnosis
Diagnosis is established by imaging characterization followed by tissue pathology when a lesion is not already characteristic and unresectable/high-risk to biopsy: the imaging pattern, location, and…
- Management
First, stabilize if there are signs of mass effect or herniation: elevate the head of the bed to 30 degrees, and if there is peritumoral vasogenic edema, start dexamethasone 10 mg IV once, then 4 mg…
- Complications
Herniation: the most immediately life-threatening complication of an expanding mass or its surrounding edema; see brain herniation syndromes.
- Prognosis
Driven primarily by histologic type and grade, along with resectability, location, and functional status at diagnosis; detailed for major adult and pediatric subtypes in the companion articles.
- Prevention
No established primary prevention exists for sporadic brain tumors, since the only consistent risk factor identified is prior therapeutic radiation exposure, itself usually medically necessary for a separate condition.
Read the whole article
Subscribing to Internal Medicine opens every article, the full question bank and MedBrain, on the web, iPhone and Android.
Related articles
- Brain tumors in adults
In adults, brain metastases (lung, breast, kidney, melanoma) are the most common intracranial tumors, meningioma is the most common primary tumor, and glioblastoma multiforme is the most aggressive primary glioma. Management combines resection when feasible, radiation, and chemotherapy (temozolomide for glioblastoma, methotrexate-based regimens for CNS lymphoma) with corticosteroids and antiepileptics for symptom control.
- Increased intracranial pressure
Sustained intracranial pressure above 20-22 mmHg from mass effect, edema, hydrocephalus, or venous outflow obstruction, diagnosed by clinical signs plus invasive monitoring and treated stepwise with head elevation, hyperosmolar therapy (mannitol or hypertonic saline), CSF diversion, and decompressive surgery when refractory.
- Seizure (first, single, or provoked)
A first or provoked seizure requires a focused history to distinguish it from syncope or a nonepileptic event, urgent glucose and electrolyte testing, brain MRI, and outpatient EEG; an unprovoked seizure with normal imaging and EEG usually does not require antiepileptic drug therapy, since epilepsy is defined only after a second unprovoked seizure or a high-risk first one.
- Malignant spinal cord compression
Malignant spinal cord compression (metastatic epidural spinal cord compression) is an oncologic emergency from vertebral metastasis that requires whole-spine MRI within 24 hours, immediate high-dose dexamethasone, and urgent radiotherapy or surgical decompression to prevent irreversible paralysis.