Cranial Nerve Palsies, Vascular Damage, and Brainstem Injury
Balancing the therapeutic index for radiation therapy to the brain starts with treatment planning and reducing the dose to adjacent critical structures. History taking, clinical examination, and imaging are critical to the diagnosis of complications. Radi
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Aryavarta M. S. Kumar and Simon S. Lo
Learning Objectives • To learn the basic principles of detection and diagnosis of radiation-induced cranial nerve palsies, vascular damage, and brainstem injury. • To learn the incidence of radiation-induced cranial nerve palsies, vascular damage, and brainstem injury. • To learn the management of radiation-induced cranial nerve palsies, vascular damage, and brainstem injury. Radiation therapy to brain and spine tumors can provide effective local control. However, balancing the potential short- and long-term complications from treatment is important. The main strategy toward radiation-associated complications is prevention; however, the following may be used to help the practitioner in assessing and treating a patient who has developed complications. This chapter will specifically cover cranial nerve (CN) injury (except radiation-induced optic neuropathy which is to be covered in Chap. 38), vascular injury, and brainstem injury.
Detection and Diagnosis The detection of radiation injury is primarily based on patient-reported side effects and clinical examination. Establishing a baseline physical examination, and baseline visual field testing if indicated, is important to make comparisons. Close clinical observation is recommended after radiation therapy. Typically, a follow-up visit approximately 1 month after completing radiation therapy is recommended to assess for any short-term side effects. Two to three A. M. S. Kumar Department of Radiation Oncology, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, USA S. S. Lo (*) Department of Radiation Oncology, University of Washington Medical Center, Seattle, WA, USA e-mail: [email protected]
monthly follow-up visits after the initial visit are typical for the first 2 years, but shorter follow-up times are recommended if patients have complications requiring closer monitoring. During the office visit, a complete history and physical examination, along with specific attention to the neurological examination, should take place. Symptoms from cranial nerve deficits will likely be reported by the patient, and the presenting sign will depend on the cranial nerve involved. Similarly, brainstem injury will likely be associated with sensory or motor deficits or gait imbalance. If a patient has a vascular injury, stroke-like symptoms will likely be the presenting signs. In almost all situations, the history and physical examination including a detailed neurologic examination will likely detect the findings. It is possible for radiationinduced cranial nerve or the brainstem injury to occur without a significant presenting symptom, and a careful neurologic examination may elicit those signs. Typically, brain MRI is ordered at follow-up visits to evaluate response to treatment. T1, T2, and FLAIR sequences are important for diagnosis with the frequency determined by tumor type. Typically, contrast enhancement of a cranial nerve on T1 sequence may indicate latent inflammation. Any abnormal enhancement, demyelination, and edema should
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