neurologic disorders
Overview of Intracranial Tumors
Cranial Radiation Therapy and Neurotoxicity
Radiation therapy may be directed at the whole head for diffuse or multicentric tumors or locally for well-demarcated tumors. There are two types of localized brain radiation therapy; both aim to spare normal brain tissue: Conformal: Using CT to create a 3-dimensional map of the tumor facilitates precise targeting of the tumor Stereotactic: Using gamma knife or proton beam therapy to deliver multiple focused beams of high energy to the tumor Gliomas are treated with conformal radiation therapy; a stereotactically directed gamma knife or proton beam therapy is useful for metastases. Current recommendations are to treat ≤ 4 metastatic lesions with stereotactic or other focal radiation interventions and to treat> 4 lesions with whole-brain radiation therapy ( Treatment references , Degree of neurotoxicity depends on Cumulative radiation dose Individual dose size Duration of therapy Volume of tissue irradiated Individual susceptibility Because susceptibility varies, prediction of radiation neurotoxicity is imprecise. Symptoms can develop in the first few days (acute) or months of treatment (early-delayed) or several months to years after treatment (late-delayed). Rarely, radiation causes gliomas, meningiomas, or peripheral nerve sheath tumors years after therapy. Typically, acute neurotoxicity involves headache, nausea, vomiting, somnolence, and sometimes worsening focal neurologic signs in children and adults. Acute neurotoxicity largely results from transient swelling and edema; thus, it is particularly likely if intracranial pressure is already high. Using corticosteroids to lower intracranial pressure can prevent or treat acute toxicity. Acute toxicity lessens with subsequent treatments. In children or adults, early-delayed neurotoxicity can cause encephalopathy, which must be distinguished by MRI or CT from worsening or recurrent brain tumor. It may occur in children who have received prophylactic whole-brain radiation therapy for leukemia; they may develop somnolence, which lessens spontaneously over several days to weeks, possibly more rapidly if corticosteroids are used. After radiation therapy to the neck or upper thorax, early-delayed neurotoxicity can result in a myelopathy, characterized by spinal symptoms such as Lhermitte sign (an electric shock-like sensation radiating down the back and into the legs when the neck is flexed). This early-delayed myelopathy typically resolves spontaneously. After diffuse or whole-brain radiation therapy, many children and adults develop late-delayed neurotoxicity if they survive long enough. The most common cause in children is diffuse therapy given to prevent leukemia or to treat medulloblastoma. After diffuse therapy, the most common symptom is progressive dementia; adults may also develop an unsteady gait and focal neurologic symptoms. MRI or CT can show cerebral atrophy and often white matter loss. After localized therapy, neurotoxicity more often involves focal neurologic deficits. MRI or CT shows a mass that may be enhanced by contrast agent and that may be difficult to distinguish from recurrence of the primary tumor. Excisional biopsy of the mass is diagnostic and often ameliorates symptoms. Late-delayed myelopathy can develop after radiation therapy for extraspinal tumors (eg, due to Hodgkin lymphoma). It is characterized by progressive paresis and sensory loss, often as a Brown-Séquard syndrome (ipsilateral paresis and proprioceptive sensory loss, with contralateral loss of pain and temperature sensation). Most patients eventually become paraplegic. 1.Gaspar L, Prabhu R, Hdeib A, et al: Congress of Neurological Surgeons systematic review and evidence-based guidelines on the role of whole brain radiation therapy in adults with newly diagnosed metastatic brain tumors.Neurosurgery84 (3):E159–E162, 2019. doi: 10.1093/neuros/nyy541 2.Vogelbaum MA, Brown PD, Messersmith H, et al: Treatment for brain metastases: ASCO-SNO-Astro guideline.J Clin Oncol40 (5):492–516, 2022. doi: 10.1200/JCO.21.02314 Epub 2021 Dec 21. 3.Long GV, Atkinson V, Lo S, et al: Combinationnivolumabandipilimumabornivolumabalone in melanoma brain metastases: A multicentre randomised phase 2 study.Lancet Oncol19 (5):672–681, 2018. doi: 10.1016/S1470-2045(18)30139-6 Epub 2018 Mar 27. 4.Moss NS, Tosi U, Santomasso BD, et al: Multifocal and pathologically-confirmed brain metastasis complete response totrastuzumabderuxtecan.CNS Oncol11 (3):CNS90, 2022. doi: 10.2217/cns-2022-0010 Epub 2022 Jun 8. 