Residency · Residency · Neurology

Neurological Complications of Systemic Cancer

Introduction

Neurological complications affect up to 30% of cancer patients and may involve any level of the neuraxis. They can result from direct tumor effects, treatment toxicity, or immune-mediated mechanisms. Early recognition is essential to minimize disability and guide oncological decision-making.

Brain Metastases

Epidemiology and Pathophysiology

Brain metastases are 10 times more common than primary brain tumors. The most common primary cancers are lung (40-50%), breast (15-25%), melanoma (5-20%), renal cell carcinoma, and colorectal cancer. Spread is hematogenous, with metastases depositing at the gray-white matter junction (watershed zones). A single metastasis is present in 30-50% of cases, with multiple metastases in the remainder.

Clinical Presentation

Brain metastases present with headache, focal deficits, seizures, and cognitive changes. Hemorrhagic metastases are characteristically seen in melanoma, renal cell carcinoma, choriocarcinoma, and thyroid cancer. Posterior fossa metastases may cause obstructive hydrocephalus.

Diagnosis and Management

Contrast-enhanced MRI brain is superior to CT for detecting metastases. Stereotactic radiosurgery (SRS) is preferred for limited (1-4) metastases and spares cognition compared to whole-brain radiation. Whole-brain radiation therapy (WBRT) is used for multiple metastases; hippocampal avoidance and memantine reduce cognitive decline. Surgical resection is appropriate for large, symptomatic, single lesions or when tissue diagnosis is needed. Systemic therapy is increasingly important, with targeted agents and immunotherapy demonstrating CNS penetration (for example, osimertinib for EGFR-mutant NSCLC, tucatinib for HER2-positive breast cancer). Dexamethasone is used for symptomatic vasogenic edema.

Leptomeningeal Disease (Carcinomatous Meningitis)

Leptomeningeal disease involves tumor cells infiltrating the leptomeninges and CSF. The most common primary cancers are breast, lung, melanoma, and hematological malignancies. It presents with multifocal cranial neuropathies, radiculopathies, headache, altered mental status, and hydrocephalus. Diagnosis relies on CSF cytology (sensitivity approximately 50% on first LP, improving to approximately 85% with repeated sampling) and leptomeningeal enhancement on MRI. Treatment includes intrathecal chemotherapy (methotrexate, cytarabine), involved-field radiation, and systemic therapy with CNS penetration. Prognosis is poor with a median survival of 2-4 months.

Spinal Cord Compression

Spinal cord compression from cancer is an oncological emergency requiring diagnosis and treatment within hours. The most common primary cancers are lung, breast, and prostate, along with myeloma and lymphoma. Back pain occurs in more than 90% of cases, typically preceding neurological deficits by days to weeks. The syndrome progresses to a myelopathy with weakness, a sensory level, and bladder dysfunction. MRI of the entire spine with gadolinium is the diagnostic study of choice. Treatment consists of dexamethasone 10 mg IV bolus followed by 4 mg every 6 hours, with urgent radiation therapy or surgical decompression followed by radiation. Ambulatory status at the time of treatment initiation is the strongest predictor of functional outcome.

Treatment-Related Neurotoxicity

Chemotherapy-Induced Peripheral Neuropathy (CIPN)

CIPN affects up to 70% of patients receiving neurotoxic chemotherapy. Causative agents include platinum compounds (cisplatin, oxaliplatin), taxanes (paclitaxel, docetaxel), vinca alkaloids (vincristine), bortezomib, and thalidomide. The pattern is typically a length-dependent sensory-predominant neuropathy. Cisplatin causes a dorsal root ganglionopathy with sensory ataxia. Oxaliplatin produces both acute cold-triggered paresthesias and chronic cumulative neuropathy. Dose reduction or discontinuation is the primary management strategy. Duloxetine has modest evidence for treatment of established CIPN.

Immune Checkpoint Inhibitor Neurotoxicity

Anti-PD-1/PD-L1 and anti-CTLA-4 agents cause immune-mediated neurological complications in 1-5% of patients. Syndromes include myasthenia gravis, Guillain-Barre syndrome, encephalitis, aseptic meningitis, transverse myelitis, and myositis. Myasthenia gravis with concurrent myositis and myocarditis is a potentially fatal triad. Treatment involves holding the checkpoint inhibitor, administering high-dose corticosteroids, and IVIG or PLEX for severe cases.

CAR-T Cell Neurotoxicity (ICANS)

Immune effector cell-associated neurotoxicity syndrome (ICANS) spans a spectrum from tremor and dysgraphia to aphasia, confusion, seizures, and cerebral edema. It is graded using the ICE score (Immune Effector Cell-Associated Encephalopathy score). Management includes dexamethasone, supportive care, and anti-IL-6 therapy for concurrent cytokine release syndrome.

Radiation Neurotoxicity

Acute toxicity (during treatment) causes fatigue and worsening of preexisting symptoms. Subacute toxicity (1-6 months) produces somnolence syndrome and pseudoprogression. Delayed toxicity (beyond 6 months) includes radiation necrosis, leukoencephalopathy, cerebrovascular disease, and secondary tumors. Radiation necrosis may mimic tumor recurrence and is treated with bevacizumab or corticosteroids.

Cerebrovascular Complications

Cancer increases stroke risk through hypercoagulability (Trousseau syndrome), tumor embolism, and treatment effects. Nonbacterial thrombotic endocarditis (NBTE, marantic endocarditis) causes embolic stroke and is associated with mucin-secreting adenocarcinomas. Stroke during L-asparaginase therapy in leukemia results from acquired antithrombin III deficiency. Intravascular lymphoma produces multifocal strokes with constitutional symptoms.

Clinical Pearls

Any cancer patient with new back pain should be urgently evaluated for spinal cord compression with MRI; ambulatory status at diagnosis predicts outcome. Hemorrhagic brain metastases suggest melanoma, renal cell carcinoma, or choriocarcinoma. Checkpoint inhibitor-associated myasthenia gravis can be fulminant; troponin and CK should be checked to assess for concurrent myocarditis and myositis. Repeated CSF sampling increases the sensitivity of cytology in suspected leptomeningeal disease.

References

• Achrol AS, Rennert RC, Anders C, et al. Brain metastases. Nat Rev Dis Primers. 2019;5(1):5.
• Chamberlain MC. Leptomeningeal metastasis. Curr Opin Oncol. 2010;22(6):627-635.
• Loprinzi CL, Lacchetti C, Bleeker J, et al. Prevention and management of chemotherapy-induced peripheral neuropathy in survivors of adult cancers: ASCO guideline update. J Clin Oncol. 2020;38(28):3325-3348.
• Cuzzubbo S, Javeri F, Tissier M, et al. Neurological adverse events associated with immune checkpoint inhibitors: review of the literature. Eur J Cancer. 2017;73:1-8.

For the intern

At 3am, prioritize suspected spinal cord compression and acute cerebral herniation from metastases or edema—these require immediate imaging and dexamethasone (10 mg IV for cord compression, 4-10 mg IV for herniation risk). Hold checkpoint inhibitors if myasthenic crisis or new weakness appears; check troponin and CK urgently for myocarditis. Most other issues—headache without altered mental status, CIPN symptom management, suspected leptomeningeal disease—can be addressed during daylight hours with team discussion and planned MRI or lumbar puncture.

Common pitfalls

• Missing early cord compression: Back pain in cancer patients warrants whole-spine MRI urgently; once paraplegia develops, recovery is rare regardless of treatment. Steroid dosing matters: don't underdose dexamethasone.
• Assuming brain lesions are metastases: Always consider radiation necrosis (if prior RT), infection (especially in neutropenic patients), or progressive multifocal leukoencephalopathy (PML) in lymphoma patients. Biopsy may be needed.
• Underestimating checkpoint inhibitor complications: Myasthenia can present fulminant with respiratory failure; the triad of myositis-myocarditis-myasthenia is life-threatening. Don't restart the drug without oncology/neurology consensus.
• Single negative LP ruling out leptomeningeal disease: Sensitivity improves dramatically with repeat sampling; discuss obtaining 10-15 mL for cytology and consider MRI findings (enhancement, nodules) in conjunction with CSF results.

<image> Create a flowchart-style decision algorithm for evaluating new neurological symptoms in a cancer patient.

Panel 1 (top): "New neuro symptom in cancer patient" branches into three pathways: "Back pain ± weakness," "Headache/seizure/focal deficit," and "Peripheral symptoms."

Panel 2 (middle-left): "Back pain ± weakness" arrow leads to "Urgent spine MRI" box, which branches to "Epidural compression present" → "Dexamethasone 10 mg IV + Radiation/Surgery consult stat" versus "No compression" → "Consider bone mets, pathologic fracture."

Panel 3 (middle-center): "Headache/seizure/focal deficit" arrow leads to "Brain imaging (MRI preferred)" box, which branches to "Mass effect/edema" → "Dexamethasone + urgent neurosurgery consult" versus "Multifocal/meningeal enhancement" → "LP for cytology (consider repeat if negative)."

Panel 4 (middle-right): "Peripheral symptoms" arrow leads to "Pattern recognition" box showing "Length-dependent sensory = CIPN," "Acute weakness = consider checkpoint inhibitor myasthenia/GBS," "Encephalopathy post-CAR-T = ICANS."

Use simple boxes and arrows with minimal text in each box; keep layout clean and vertically oriented for bedside reference. </image>

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