Radiation myelitis is a rare but serious complication of radiation therapy that involves the spinal cord.
It typically occurs after therapeutic irradiation for neoplasms when the spinal cord is included within the radiation field.
The condition is characterized by delayed onset of neurological symptoms, which can include paresthesias, sensory changes, and in severe cases, progressive paresis and paralysis.
The pathogenesis of radiation myelitis: radiation-induced damage to the endothelial cells of the spinal cord’s blood vessels, leading to vascular hyperpermeability, venous exudation, and subsequent ischemic changes.
Radiation-induced damage to the endothelial cells of the spinal cord’s blood vessels results in demyelination and white matter injury, predominantly affecting the lateral funiculi of the spinal cord.
Clinical presentation typically occurs within 6 to 24 months post-radiation therapy, with MRI findings showing characteristic changes such as T2 signal abnormalities and cord expansion.
The risk factors for developing radiation myelitis: higher radiation doses, larger fraction sizes, and concurrent chemotherapy, which can lower the spinal cord’s tolerance to radiation.
In a study of radiation myelitis after hypo fractionated spine SBRT with more than 1900 spinal lesions treated with prescribed doses of 27 to 36 Gy in 3 fractions the risk of grade 3 or higher radiation myelitis was 0.67% at 12 months and 1.1% of 24 months (Jackson CB).
In this study, there were no cases of radiation myelitis with a maximum of 20.8 to 22.2 Gy.
Management of radiation myelitis: no definitive treatment available.
Therapeutic strategies may include corticosteroids, hyperbaric oxygen, and immunomodulatory agents like intravenous immune globulin (IVIG), although their efficacy is variable and often limited.
In some cases, clinical and radiographic improvement has been observed, but the condition can be progressive and irreversible in others.