Radiation Injury
Early (Acute) Effects (1 to 6 Weeks)
Edema, headache, nausea, vomiting, alopecia; hyperpigmentation, desquamation of skin. Complications in 50% for daily dose fractions of 750 cGy; <200 cGy seldom toxic.
MRI: localized swelling of spinal cord or plexus without enhancement. Steroids given prophylactically.
Tissues with fastest turnover rate (skin, bone marrow) affected most often.
Early-Delayed Syndromes (Within 6 Months)
Somnolence, headache in children receiving prophylactic whole-brain radiotherapy. Also irritability, anorexia. Focal signs uncommon. Spontaneous recovery.
Ataxia, dysarthria, nystagmus: irradiation to middle ear area for glomus jugulare tumors.
Severe leukoencephalopathy.
Early-delayed radiation myelopathy: Lhermitte sign (sensation of electrical current radiating down back induced by flexing neck).
Late-Delayed Syndromes (Months to Years)
Radiation Necrosis
About 5% of patients given total doses >5,000 cGy with daily fraction sizes >200 cGy. Median time for symptom onset: 14 months after end of radiotherapy.
Clinical manifestations may simulate those of original tumor.
Imaging: (a) mass lesion at original tumor site or within irradiation path; enhancement mimics original neoplasm, gradually resolving; (b) diffuse white matter changes (hypodensity on CT, increased signal on T2-weighted MRI); usually irreversible.
Distinguishing tumor recurrence from radiation necrosis may be difficult. Radiation necrosis may show hypometabolic areas on PET. Biopsy often needed for diagnosis.
Treatment: steroid therapy or surgical resection. Radiation necrosis rarely progressive, fatal.Related posts:
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