Neurologic Complications
Summary of Key Points
Incidence of Chemotherapy- and Radiation Therapy–Induced Neurotoxicity
• The actual incidence of treatment-related neurotoxicity is unknown, but the frequency is increasing.
• Improvements in supportive care, but not neuroprotective regimens, have allowed dose escalation for many drugs, and thus neurotoxicity often is the dose-limiting factor.
• Increased survival from cancer has resulted in an increasing prevalence of late-onset neurotoxicity.
• Newer treatments directed at tumors in the central nervous system often result in neurotoxicity, particularly with therapies administered directly into the cerebrospinal fluid.
Etiology of Neurotoxicity
• Direct effects on neurons, myelin, and supporting glial cells have been implicated.
• Effects on neuronal cytoskeleton and axonal transport, neuronal metabolism, and neurotransmitter function are the most commonly hypothesized mechanisms of toxicity. Alterations in specific ion channels have been reported in some cases of chemotherapy-induced peripheral neuropathy.
Evaluation of the Patient
• In general, chemotherapy or radiation toxicity should be considered a diagnosis of exclusion.
• Specific diagnostic tests do not exist for treatment-induced toxicity from most agents and regimens in use.
• The diagnosis often is made by recognition of a neurotoxic syndrome temporally related to treatment and by exclusion of other causes of neurologic dysfunction.
