Epidural Hyperintensity.

Clinical History

A 46 year old woman with a history of lower back pain presented refractory to the medical treatment. The symptoms had worsened during the last two months, and they were accompanied with paresthesia of the left lower limb and urine retention.

Imaging Findings

Sagittal T1WI (A), T2WI (B), T2WI STIR (C), and axial T1WI (D) MR sequences. There is a T1 hyperintense, T2 hyperintense, and T2-STIR hypointense epidural collection. Axial T1 WI(D) reveals a hyperintense signal in the epidural space.

Discussion

Background: Epidural lipomatosis is a condition characterized by deposition of unencapsulated adipose tissue in the epidural space [1, 2]. The pathophysiological mechanism behind this disease is not yet well understood, but it has been related to endogenous or exogenous chronic exposure to steroids and obesity [1, 3]. It is classified as an idiopathic disease if the patient doesn't have any identifiable underlying condition [2, 4]. The accumulation mainly involves the lower thoracic and/or lower lumbar levels [1, 4].
Clinical Perspective: Associated symptoms are chronic back pain, lower limb weakness and if it compresses the cauda equina the patient could refer vesical/sexual dysfunction [3, 4]. Because of the clinical and radiologic similarities to other pathologies like vertebral disc herniation, a common lumbago, or metastatic disease, it may lead to misdiagnosis [3]. As radiologists, we need a well structured clinic history, reporting the chronic status of the pathology and risk factors [3].
C. Imaging Perspective: MR is the modality of choice for the diagnosis [1, 4]. Fat accumulation in the epidural space is observed as a high signal intensity on T1 and T2-weighted [2]. The fat suppression sequences play a very important role in the study of these cases, because the low signal on the epidural space confirms the fat excess. On axial MR it is typical to observe a polygonal spiculated, Y-shaped, or stellar deformation of the epidural space, which has a hyper intense signal related to the fat overgrown [2, 4].
Outcome: Conservative strategy is used as an initial approach [1, 4]. A reasonable procedure is to follow the WHO guidelines on the pharmacological treatment of pain. Physiotherapy and exercise have been proven to be effective methods to control the symptoms in some persons. The surgical decompression is reserved for patients in whom conservative measures fail [4]. Individuals with fat accumulation in the lumbar region may have a better recovery after the surgical procedure than patients with thoracic affection [4]. Preoperative steroid doses are also reported to influence the surgical effectiveness, with persons that receive lower doses obtaining better results [4]. Idiopathic epidural lipomatosis has a better prognosis [4].
Take Home Message, Teaching Points: the patient should be informed about epidural lipomatosis, noting that this is a chronic benign condition, without malignant degeneration.

Differential Diagnosis List

Final Diagnosis

Epidural Lipomatosis.

URL:	https://www.eurorad.org/case/13143
DOI:	10.1594/EURORAD/CASE.13143
ISSN:	1563-4086