Epidural Lipomatosis
Epidural lipomatosis is an excessive accumulation of normal fat tissue within the epidural space, the area inside the spinal canal that surrounds the protective covering of the spinal cord and nerves. When the fat builds up in larger amounts than usual, it can press on the spinal cord or nerve roots and contribute to back pain, leg pain, weakness, or symptoms of spinal stenosis. Epidural lipomatosis is most commonly seen in the thoracic and lumbar spine and is often associated with long-term corticosteroid use, obesity, or hormonal conditions.
What is it?
The epidural space is the area inside the spinal canal that sits between the bony walls of the canal and the dura, the protective membrane that surrounds the spinal cord and nerve roots. It normally contains a small amount of fat, along with blood vessels and connective tissue. In epidural lipomatosis, the amount of fat within this space increases significantly, gradually narrowing the room available for the spinal cord and nerves. This excess fat is normal tissue, not a tumor; the problem is that there is too much of it in a confined space.
Epidural lipomatosis most often occurs in the thoracic and lumbar spine, where the epidural fat is normally most prominent. It has several well-recognized causes. Long-term use of corticosteroid medications (such as prednisone) is one of the most common contributors and may relate to medical conditions like autoimmune disease, organ transplant, asthma, or chronic inflammatory disorders. Obesity is another common factor. Endocrine conditions that increase the body’s natural cortisol levels, such as Cushing syndrome, can also lead to epidural lipomatosis. In some patients, no clear cause is identified, and the condition is described as idiopathic.
Symptoms depend on how much the fat narrows the spinal canal and which nerves are affected. Many cases are mild and cause no symptoms, being discovered incidentally on imaging. When symptoms occur, they tend to resemble those of spinal stenosis or radiculopathy: low back pain, buttock or leg pain, numbness, tingling, weakness, and difficulty walking longer distances due to leg discomfort or heaviness (neurogenic claudication). Symptoms typically develop gradually and may worsen with activity, prolonged standing, or extension of the spine. In severe cases, fat compression of the spinal cord or cauda equina can lead to more pronounced neurological problems.
MRI of the spine is the preferred imaging test for evaluating epidural lipomatosis because fat has a characteristic appearance on MRI that allows it to be clearly identified and measured. MRI also shows the degree of spinal canal narrowing and whether the spinal cord or nerve roots are being compressed. CT can also demonstrate excess epidural fat and is useful in patients who cannot have MRI, although it provides less detail of the cord and nerves. Imaging findings are interpreted together with the clinical picture, since modest amounts of epidural fat are common and often do not cause symptoms.
Important to Know
Treatment focuses first on addressing the underlying cause. In patients on long-term corticosteroids, reducing the dose or switching to alternative therapies—when medically appropriate and supervised by the prescribing physician—can lead to significant improvement. Weight loss is often helpful when obesity is a contributing factor, and treatment of any underlying endocrine condition is important. For symptomatic patients, conservative care such as physical therapy, posture and ergonomic adjustments, activity modification, and pain management is often used. Surgical decompression of the spinal canal may be considered in carefully selected patients with significant neurological symptoms or severe spinal cord or nerve compression that has not responded to other treatments.
Because epidural lipomatosis often coexists with other spinal conditions—such as degenerative disc disease, facet arthropathy, or spinal stenosis—imaging findings and symptoms are interpreted as part of the overall clinical picture rather than in isolation.
Red flag symptoms include rapidly worsening leg weakness or numbness, gait or balance difficulty, loss of bowel or bladder control, severe new back pain, fever or chills with back pain, or unexplained weight loss. These warrant prompt medical evaluation, as they may indicate significant neurological compromise or another serious underlying condition.