Chapter 24: Neoplastic and Paraneoplastic Disorders of the Nervous System and Neurologic Complications of Chemotherapy and Radiation Therapy

INTRODUCTION

The nervous system can be affected in several ways in patients with neoplastic disease:

• Directly due to primary nervous system tumors or metastases to nervous system structures

• Indirectly due to:

  • Tumors of non–neurologic origin impinging upon nervous system structures

  • Toxicities of chemotherapy and radiation therapy

  • Paraneoplastic syndromes affecting the nervous system

Therefore, in patients with a known history of systemic malignancy, the differential diagnosis of new neurologic symptoms includes direct effects of the cancer itself (metastases to or compression of neurologic structures), complications of treatment (radiation or chemotherapy), and paraneoplastic syndromes. Direct (metastases) or indirect (paraneoplastic) effects of systemic malignancy on the nervous system may also be the presenting feature of a systemic cancer.

INTRACRANIAL TUMORS

Primary or metastastic intracranial tumors may present with headaches, seizures, and/or focal neurologic deficits. Progressive focal neurologic deficits can occur if the tumor affects an eloquent area (e.g., affecting motor, speech, visual, or cerebellar pathways). Diffuse infiltrative lesions or diffuse metastases can present with global cognitive dysfunction and/or personality changes without obvious focal deficits. Some patients with intracranial tumors may present first with a seizure with no preceding history of neurologic dysfunction or headache. Brain metastases may also be discovered in the presymptomatic stage as part of a staging evaluation for a known systemic malignancy.

Particular tumors to consider in particular clinical scenarios include:

• Hearing loss, tinnitus, imbalance: cerebellopontine angle tumor (most commonly vestibular schwannoma or meningioma)

• Bitemporal hemianopia: pituitary tumors, craniopharyngioma

• Unilateral visual disturbance: optic glioma, optic nerve sheath meningioma, or olfactory groove meningioma (olfactory groove meningioma may also cause unilateral loss of smell)

• Multiple cranial neuropathies: skull base lesion, brainstem lesion, or leptomeningeal metastases

In general, steroids are often used for the treatment of peritumoral vasogenic edema in patients whose brain tumors are symptomatic (e.g., headache and/or focal deficits) as a result of the location and size of the mass and its surrounding edema. It should be noted that steroids are part of the treatment for primary nervous system lymphoma and can alter biopsy results if administered prior to biopsy. Therefore, when there is concern for primary central nervous system lymphoma, steroids should ideally be avoided until after biopsy. Antiepileptics should be initiated if seizures occur due to intracranial tumors, although there is no benefit (and there may be harm) to administering prophylactic antiepileptics to patients with brain tumors who have not had seizures.

Brain Metastases

Metastases to the brain from systemic cancer are far more common than primary brain tumors. Brain metastases from lung cancer, breast cancer, melanoma, and colon cancers are most common. Metastases are most commonly found at the gray–white junction, appearing as one or more ring-enhancing lesions on contrast-enhanced neuroimaging (Fig. 24–1). Melanoma, renal cell carcinoma, thyroid carcinoma, and choriocarcinoma have the highest propensity for intratumoral ...