Axial MRI T1 post-contrast. Multiple circumscribed enhancing mass lesions with prominent vasogenic edema.
Brain & Spinal Cord Metastases
Overview
- Brain metastases are the most common form of brain tumor in adults.
- ~ 80% are supratentorial vs ~ 20% are infratentorial.
- They are cited to affect ~ 25% of patients with cancer.
- They typically present with seizures, headaches, focal neurological deficits or signs of increased intracranial pressure.
- Brain metastases that cause significant increase in pressure produce plateau waves, which are sudden, rapid elevations in intracranial pressure (ICP) to 50–100 mmHg that last for 5 to 20 minutes, followed by a rapid decrease of ICP. A vasodilatatory/constriction cascade of cerebral blood flow is thought to produce the sudden changes in ICP.
- Brain METs classically localize to the cerebral hemispheres, especially at the gray/white junction (as does endocarditis).
Metastases to Brain:
- Lung ~ 50%
- Majority of lung metastases are small cell lung cancer; it's ~ 2.5x more likely to be the cause of lung metastases than non-small cell lung cancer.
- Breast ~ 15%
- Melanoma ~ 10%
- Note that nevi, which transform to malignant melanoma typically have irregular borders, are palpable (raised), and have heterogenous color.
- Kidney & Gastrointestinal <15%
- As a helpful heuristic: tumors from below the diaphragm (GI, Renal) typically metastasize as solitary tumors below the tentorium (to the posterior fossa). This is compared to the other tumor types (eg, lung, breast), which tend to metastasize as multiple metastatic lesions throughout the brain.
- Unknown primary site ~ 10%
- Tumors that produce multiple METs:
- Small cell lung cancer and melanoma
- Tumors that produce single METs:
- The remainder: breast, adenocarcinoma of the lung, kidney, thyroid, etc...
Hemorrhagic METs to the Brain
~ 10% of METs will bleed
- Lung cancer
- Given its absolute propensity to metastasize, it's the most common hemorrhagic brain MET.
- Melanoma
- Has highest relative tendency to form hemorrhagic brain MET
- Choriocarcinoma
- Renal cell carcinoma
- Medullary thyroid cancer
Brain METs Treatment
- Single MET:
- Whole-brain radiation therapy (WBRT),
- Then, surgery or stereotactic radiosurgery (SRS),
- Then, salvage chemotherapy
- Multiple METs:
Typically: small cell lung cancer and melanoma
- Whole-brain radiation therapy (WBRT),
- Then, salvage chemotherapy
- Surgery or stereotactic radiosurgery (SRS), if used, is not standard
Metastases to Vertebral Column:
Extradural Extramedullary
Grow from external to the dura mater (ie, the vertebrae)
Most commonly:
- Metastases (most common)
- Breast
- Prostate
- Lung
- Metastases (less common)
- Renal Cell
- Myeloma
- Lymphoma
Helpful mneomonic for key tumor metastases
- BLT with Mustard and a Kosher Pickle
- B: Breast
- L: Lung/Lymphoma
- T: Thyroid
- M: Myeloma
- K: Kidney (Renal cell)
- P: Prostate
- Non-metastatic spine tumors:
- Chordoma
- Sarcoma
Prognostic Indicators
Median survival ~ a few to several months (< 1 year)
- Worrisome (poor) prognostic indicators:
- Age > 50
- Aggressive extracranial (systemic) cancer that responds poorly to chemotherapy
- Brain METs that respond poorly to steroids
- More than 3 metastatic lesions
- Encouraging prognostic indicators:
- Age < 50
- Non-aggressive extracranial (systemic) cancer that responds well to chemotherapy
- Brain METs that respond well to steroids
- Less than 3 metastatic lesions
Differential Diagnosis for Brain METs:
- Glioblastoma
- Primary CNS Lymphoma
- Abscesses
Carcinomatous Meningitis
- Spread of cancer to the meninges, which typically presents with headache, multiple cranial neuropathies and polyradiculopathies, encephalopathy, and spinal meningeal pain; typically a poor prognosis (< 6 month survival).
- Common cancers to cause carcinomatous meningitis:
- Breast adenocarcinoma
- Lung cancer
- Lymphoma
- Melanoma
- GI malignancies
- Leukemia
- Prostate cancer via Batson's plexus: the valveless venous connection between the pelvic and internal cerebral veins, which run through the meninges.
- MRI demonstrates leptomeningeal enhancement
- CSF may show a pleocytosis, elevated protein, and reduced glucose. Although CSF flow cytometry and cytology are helpful if diagnostic, they are insensitive (especially if the CSF is acellular), and often require multiple LPs.
- Treatment:
- Radiation (possibly whole-brain)
- Intrathecal chemotherapy, specifically with intraventricular methotrexate via an Ommaya reservoir.
References
- Daley, M. L., C. W. Leffer, M. Czosnyka, and J. D. Pickard. “Plateau Waves: Changes of Cerebrovascular Pressure Transmission.” Acta Neurochirurgica. Supplement 95 (2005): 327–32.
- Daroff, Robert B., Joseph Jankovic, John C. Mazziotta, and Scott L. Pomeroy. Bradley’s Neurology in Clinical Practice E-Book. Elsevier Health Sciences, 2015.
- Gray, Frangoise, Charles Duyckaerts, and Umberto De Girolami. Escourolle and Poirier’s Manual of Basic Neuropathology. OUP USA, 2013.
- Samuels, Martin A., Allan H. Ropper, and Joshua Klein. Adams and Victor’s Principles of Neurology 10th Edition. McGraw-Hill Education, 2014.
- Tonn, Jörg-Christian, Manfred Westphal, and J. T. Rutka. Oncology of CNS Tumors. Springer Science & Business Media, 2010.
- Yachnis, Anthony T., and Marie L. Rivera-Zengotita. Neuropathology E-Book: A Volume in the High Yield Pathology Series. Elsevier Health Sciences, 2012.