25.3 Neuro-Oncology and Treatment Complications (03.S)
Key Takeaways
- Symptomatic edema from glioblastoma or other primary tumors is treated with dexamethasone and herniation care; antiseizure drugs are not routine primary prophylaxis in a newly diagnosed brain tumor that has never seized (SNO/EANO 2021, consistent with the older AAN parameter).
- Limited brain metastases are often treated with stereotactic radiosurgery; whole-brain radiotherapy is reserved conceptually for numerous metastases, poor performance status, or selected leptomeningeal disease, not as automatic first therapy for a single resectable lesion.
- Metastatic spinal cord compression is an emergency: dexamethasone plus urgent surgical decompression and radiotherapy in selected Patchell-type patients (single site, not highly radiosensitive histology, expected survival, weakness that is still reversible).
- Carcinomatous meningitis needs MRI plus lumbar puncture; cytology yield rises with repeat taps. Paraneoplastic surface-antibody syndromes respond better to immunotherapy plus tumor treatment than intracellular-antigen syndromes such as anti-Hu.
- Radiation complications include somnolence syndrome, necrosis, and SMART (stroke-like migraine after radiation therapy). Chemotherapy pitfalls include ifosfamide encephalopathy (stop drug; methylene blue conceptually), methotrexate neurotoxicity, bevacizumab-associated PRES or hemorrhage, and immune-checkpoint inhibitor neurologic toxicity.
Why 03.S is seven diseases, not one tumor board
The ABPN Neurocritical Care Certification Content Specifications enumerate neuro-oncology (03.S) as seven leaves: primary brain tumors, brain metastasis, spinal cord tumors and metastasis, carcinomatous meningitis, paraneoplastic syndromes, complications of radiation therapy, and complications of chemotherapy. The ICU examination tests herniation care, when not to start an antiseizure drug, cord compression logistics, how to prove leptomeningeal disease, and named toxicities—not the latest trial of tumor-treating fields.
Primary brain tumors
Glioblastoma (GBM), now classified as IDH-wildtype glioblastoma in the WHO 2021 system, is the mass that herniates. Patients present with headache, focal deficit, seizure, or a blown pupil. Dexamethasone treats symptomatic vasogenic edema (practice ranges often start around 4–16 mg/day in divided doses, then taper to the lowest effective dose). Steroids are not a diagnosis and they are not required in an asymptomatic postoperative patient with a small cavity. If primary CNS lymphoma is possible, withhold steroids until biopsy unless the patient is herniating—steroids can melt the lesion and non-diagnostic the tissue.
Antiseizure drugs are not routine prophylaxis. The Society for Neuro-Oncology and European Association of Neuro-Oncology 2021 practice guideline (AAN affirmed) states that in newly diagnosed brain tumors without a seizure, clinicians should not prescribe antiseizure drugs to reduce seizure risk (level A). Perioperative prophylaxis has insufficient evidence. If a seizure has already occurred, treat it. Enzyme-inducing drugs (phenytoin, carbamazepine, phenobarbital) complicate chemotherapy; levetiracetam is a common ICU choice when treatment is indicated.
Herniation care is the same physiology taught elsewhere: airway, head of bed, hyperosmolar therapy, brief hyperventilation as a bridge, and decompressive surgery or tumor debulking when the mass is the problem. Stupp protocol radiotherapy plus temozolomide is oncologic background, not the first hour of care.
Other primary tumors that land in the unit include large meningiomas with edema, pituitary adenomas with apoplexy (covered with endocrine crises), and posterior fossa masses that occlude the fourth ventricle.
Brain metastasis
Brain metastases are more common than primary brain tumors. Steroids again treat symptomatic edema. Hemorrhagic mets (melanoma, renal cell, choriocarcinoma, thyroid) can mimic spontaneous ICH.
Local therapy is stereotactic radiosurgery (SRS) versus whole-brain radiotherapy (WBRT) versus resection:
- SRS is preferred conceptually for limited intracranial disease (few lesions, limited cumulative volume) with reasonable systemic prognosis, including postoperative cavities in selected patients.
- WBRT is used when metastases are numerous, performance status is poor, or as part of leptomeningeal strategies. Hippocampal-avoidance WBRT plus memantine is a modern cognitive-sparing concept, not a requirement to name every gray-matter structure.
- Resect a large, accessible, symptomatic lesion, then irradiate the cavity rather than defaulting to WBRT for a single metastasis.
Do not start WBRT for a single 3 cm cerebellar metastasis in a patient who still has a good performance status without considering surgery or SRS.
Spinal cord tumors and metastasis
Metastatic epidural spinal cord compression (MESCC) is a time-critical myelopathy: back pain, a sensory level, bladder retention, and bilateral weakness. Image the entire spine—skip metastases are common. Start dexamethasone immediately once compression is diagnosed or highly likely. Common practice is a 10 mg intravenous load then about 16 mg/day (for example 4 mg every 6 hours), which has fewer complications than historic 96 mg/day regimens. Taper after definitive therapy.
The Patchell randomized trial (2005) showed that selected patients live more days walking if they receive direct circumferential decompression plus radiotherapy rather than radiotherapy alone. Selection in that trial included a single compressive site, expected survival of at least three months, and exclusion of highly radiosensitive histologies (lymphoma, myeloma, leukemia) that may be treated with radiotherapy and systemic therapy without surgery. Paraplegia lasting many days is less reversible. Unstable spines need surgical opinion even if the cord is not yet crushed.
Primary intramedullary tumors (ependymoma, astrocytoma) present more slowly; the ICU still manages edema, delayed cord swelling after resection, and respiratory failure from high cervical lesions.
Carcinomatous meningitis
Leptomeningeal metastasis (carcinomatous meningitis) presents with headache, communicating hydrocephalus, fluctuating cranial neuropathies, and cauda equina symptoms. MRI may show leptomeningeal enhancement and hydrocephalus; a normal MRI does not exclude the diagnosis.
Lumbar puncture shows high protein, low glucose, and lymphocytic pleocytosis. Cytology is specific but insensitive on a single tap; yield rises with a second or third large-volume sample. Flow cytometry matters for hematologic malignancy. Opening pressure may be high.
Treatment is conceptual: focal radiotherapy to symptomatic sites (cauda, bulky cranial-nerve disease), intra-thecal chemotherapy (methotrexate, cytarabine, thiotepa) via lumbar puncture or Ommaya reservoir in selected patients, systemic agents that reach CSF, and CSF diversion for hydrocephalus. Prognosis is often poor; the examination tests diagnosis and the idea of RT/IT chemotherapy, not a claim of cure.
Paraneoplastic syndromes
Paraneoplastic neurologic disease is antibody-typed:
- Surface antibodies (NMDA, AMPA, GABA-B, LGI1, CASPR2) are more immunotherapy-responsive.
- Intracellular antibodies (Hu/ANNA-1 with small-cell lung cancer: sensory neuronopathy and encephalomyelitis; Yo/PCA-1 with breast or ovarian cancer: purkinje-cell degeneration; Ma2 with testicular germ-cell tumors; CRMP5; amphiphysin) respond less to immune suppression; treat the tumor.
The ICU still gives first-line immunotherapy while the tumor workup runs, especially for surface-antibody encephalitides. Do not promise a Hu encephalomyelitis patient the same recovery as a resected-teratoma NMDA patient.
Complications of radiation therapy
| Timing | Syndrome | What you see | ICU move |
|---|---|---|---|
| Days (during RT) | Acute encephalopathy | Headache, worsening edema, somnolence | Steroids, osmotherapy if mass effect |
| Weeks to a few months | Somnolence syndrome | Profound sleepiness, especially in children after cranial RT; often reversible | Supportive care; do not call this irreversible vegetative state |
| Months to years | Radiation necrosis | Focal deficit, seizures, enhancing lesion mimicking recurrence | Perfusion MRI, PET, or biopsy when it changes therapy; bevacizumab is used for symptomatic necrosis; steroids |
| Delayed, often years | SMART (stroke-like migraine after radiation therapy) | Migrainous headache, seizures, reversible neurologic deficit, unilateral cortical enhancement in a prior radiation field | Supportive care, seizure control; it is not a new MCA occlusion and not automatically recurrent tumor |
SMART is the named trap: a young adult irradiated years ago for a posterior fossa tumor who now has a subacute “stroke” with migraine and striking cortical enhancement. Perfusion is not an arterial cutoff. Treat symptoms and avoid unnecessary thrombolysis or futile redo-craniotomy.
Complications of chemotherapy and immune therapy
Ifosfamide encephalopathy presents with confusion, mutism, seizures, or coma during or shortly after infusion. Stop the drug, support the airway, and give methylene blue (commonly 50 mg IV, repeated) and thiamine as conceptual antidotes; evidence is limited but this is the examination association. Watch for methylene-blue hemolysis in G6PD deficiency and serotonin syndrome when mixed with serotonergic drugs.
Methotrexate neurotoxicity includes chemical meningitis after intra-thecal doses, subacute stroke-like leukoencephalopathy (often fluctuating hemiparesis with diffusion change that is not a single arterial infarct), and chronic leukoencephalopathy. High-dose systemic methotrexate with delayed clearance may need glucarpidase plus leucovorin in the right biochemical setting. Do not call every methotrexate MRI change a new embolic shower.
Bevacizumab (VEGF blockade) causes posterior reversible encephalopathy syndrome (PRES), intracranial hemorrhage, arterial thrombosis, wound-healing failure, and bowel perforation. It is also used therapeutically to reduce GBM or radiation-necrosis edema. The stem will tell you whether the drug is the treatment or the toxin.
Immune checkpoint inhibitors (ICIs) (PD-1, PD-L1, CTLA-4 antibodies) cause immune encephalitis, aseptic meningitis, hypophysitis, myasthenia-like crisis, GBS-like neuropathy, and overlapping myocarditis. Hold the ICI, give high-dose steroids, and add IVIG or PLEX for neuromuscular respiratory failure. Do not restart the drug while the patient is still in myasthenic crisis.
Examination traps
- Starting levetiracetam indefinitely because a glioblastoma was just diagnosed and has never seized.
- Giving WBRT as the only option for a single resectable metastasis.
- Treating MESCC with steroids alone and no surgical or radiation plan.
- One negative CSF cytology closing the leptomeningeal workup.
- Calling SMART an acute large-vessel occlusion.
- Continuing ifosfamide through coma because the MRI is normal.
A 62-year-old with a newly diagnosed hemispheric glioblastoma has never had a seizure. There is moderate vasogenic edema and headache. Which pairing is most consistent with current neuro-oncology practice?
A patient with known prostate cancer develops a T8 sensory level and new urinary retention. MRI shows a single epidural metastasis compressing the cord; he walked yesterday. Which emergency plan is most appropriate?
Three years after cranial radiotherapy for a medulloblastoma, a young adult has a migrainous headache, a fluctuating left hemiparesis, and unilateral cortical gyriform enhancement without an arterial occlusion. Which diagnosis fits best?
During day 2 of ifosfamide, a patient becomes mute and then has a seizure. MRI is unrevealing. Which management statement is correct?