A 64-yr-old woman with a history of uterine cancer diagnosed in 2016 status post–total abdominal hysterectomy, bilateral salpingo-oophorectomy, and radiation presented with the complaint of back pain. The patient had a history of back pain previously successfully treated with an epidural steroid injection in 2013 and a sacroiliac joint injection in 2020. This recurrence of pain was located in the right buttock and radiated down to the dorsum of the foot. The pain was persistent, 8/10 in intensity, shooting in nature, and accompanied by paresthesia. It was worsened by flexion and twisting movements of the spine. She denied weakness or changes in bowel or bladder function.
A magnetic resonance neurogram was obtained showing a prominent T2 bright signal in the right sciatic nerve just below the level of the right ischium suggesting a local sciatic nerve neuritis (Fig. 1). There was also surrounding thickening of soft tissues on T1-weighted imaging (Fig. 2). These findings suggested scar entrapment of the sciatic nerve at the level of the right ischium. When put in context with the patient’s history of pelvic radiation in 2016 for endometrial carcinoma, the underlying etiology of sciatic neuritis was likely secondary to compression from radiation-induced fibrosis. The patient was treated with a sciatic nerve perineural block under ultrasound guidance.
Radiation fibrosis syndrome is a general term used to describe a myriad of clinical conditions associated with radiation treatment, typically caused by an abnormal accumulation of thrombin in tissue that leads to progressive fibrotic tissue sclerosis. Radiation fibrosis syndrome can present during radiation treatment or years after treatment and can affect any tissue type, including skin, muscles, tendons, viscera, and nerves. Effects can have significant functional implications, such as pain, loss of sensation, and weakness.1 Radiation-induced injury at the nerve root and plexus are well described; however, radiation mononeuritis is a comparatively rare phenomenon.2
The differential diagnosis for back pain is broad. In patients with a history of malignancy and radiation treatment, the differential should include direct effects of malignancy, such as recurrence or metastasis, and complications of cancer treatment, such as radiation fibrosis syndrome. Late mononeuropathy is a relatively rare complication but should be considered in patients presenting with neuropathy after radiation therapy. Imaging modalities, such as magnetic resonance imaging, are indispensable in making the diagnoses.
1. Stubblefield MD: Cancer Rehabilitation: Principles and Practice
, 2nd ed. New York, Demos Medical, 2018
2. Pradat PF, Bouche P, Delanian S: Sciatic nerve moneuropathy: an unusual late effect of radiotherapy. Muscle Nerve