Oncology · Neurological Oncology
The facts most likely to be tested
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Lung cancer is the most common primary malignancy to metastasize to the brain.
Brain metastases are most frequently located at the gray-white matter junction due to the narrowing of blood vessels.
Contrast-enhanced MRI is the gold standard diagnostic imaging modality for detecting brain metastases.
Multiple lesions at the gray-white matter junction are the classic radiographic presentation of metastatic disease.
Dexamethasone is the immediate first-line pharmacologic intervention to reduce peritumoral edema and alleviate intracranial pressure.
Whole-brain radiation therapy (WBRT) is used for diffuse or numerous brain metastases not amenable to stereotactic radiosurgery, delivered with hippocampal avoidance plus memantine in patients with favorable prognosis; for patients with poor performance status and poor prognosis, best supportive care or hospice is a reasonable alternative to WBRT.
Stereotactic radiosurgery (SRS) is the preferred treatment for patients with a limited number of brain metastases (1–4 lesions, and conditionally up to 10 in selected patients with good performance status and controlled systemic disease).
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A 62-year-old male with a 30-pack-year smoking history presents to the emergency department with a two-week history of progressive headache, nausea, and left-sided hemiparesis. Physical examination reveals papilledema and focal neurologic deficits. A non-contrast CT scan shows multiple hypodense lesions with surrounding edema. Subsequent contrast-enhanced MRI demonstrates multiple ring-enhancing lesions at the gray-white matter junction.
What is the most appropriate initial pharmacologic management to address the patient's symptoms?
Dexamethasone
The patient presents with signs of increased intracranial pressure due to brain metastases; high-dose corticosteroids are required immediately to reduce peritumoral edema.
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Etiology / Epidemiology
Most common intracranial tumor in adults. Lung cancer is the #1 primary source.
Clinical Manifestations
New-onset seizure or focal neurologic deficit. Morning headache with nausea.
Diagnosis
MRI with gadolinium is the gold standard for detection.
Treatment
Dexamethasone for edema; Whole-brain radiation with hippocampal avoidance plus memantine for diffuse disease not amenable to radiosurgery.
Prognosis
Median survival is only ~1 month without treatment (about 2 months with steroids alone).
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Epidemiology & Etiology
Brain metastases are 10x more common than primary brain tumors. The most frequent primary sites are lung, breast, melanoma, and renal cell carcinoma. In patients with a known primary, a new focal deficit is metastatic until proven otherwise.
Pertinent Anatomy
Metastases typically localize to the gray-white junction due to the narrowing of blood vessels. Lesions are often multiple and located in the cerebral hemispheres (80%), followed by the cerebellum.
Pathophysiology
Tumor cells reach the brain via hematogenous spread through the arterial circulation. Once lodged, they induce significant vasogenic edema by disrupting the blood-brain barrier. This edema is the primary driver of increased intracranial pressure and clinical symptoms.
Clinical Manifestations
Patients present with progressive focal neurologic deficits, cognitive decline, or new-onset seizures. Classic morning headache exacerbated by Valsalva suggests increased intracranial pressure. Papilledema on fundoscopy is a critical red flag requiring urgent imaging.
Diagnosis
MRI with gadolinium is the diagnostic test of choice to identify lesion number and size. CT is inferior but used if MRI is unavailable. Biopsy is rarely required if the patient has a known primary and multiple lesions, but may be indicated for a solitary lesion of unknown origin.
Treatment
Immediate management includes Dexamethasone to reduce peritumoral edema. Do not use prophylactic anticonvulsants in patients without a history of seizures. Treatment options include stereotactic radiosurgery for 1-4 lesions or whole-brain radiation with hippocampal avoidance plus memantine (in patients with favorable prognosis) for widespread disease not amenable to radiosurgery.
Prognosis
Prognosis is poor, heavily dependent on the Karnofsky Performance Status and control of the primary tumor. Leptomeningeal carcinomatosis is a devastating complication characterized by diffuse spread through the CSF.
Differential Diagnosis
Primary Brain Tumor: usually solitary, often infiltrative
Brain Abscess: ring-enhancing with central restricted diffusion
Neurocysticercosis: multiple calcified cysts, travel history
Toxoplasmosis: ring-enhancing lesions in HIV/AIDS patients
Multiple Sclerosis: periventricular plaques, relapsing-remitting course