Spinal epidural lipomatosis (SEL) is an uncommon condition characterized by the abnormal accumulation of fat within the spinal canal. This overgrowth of adipose tissue, which is not surrounded by a capsule, occurs specifically in the extradural space surrounding the spinal cord and nerve roots. The presence of this excess fat reduces the available space, leading to compression of the delicate neural structures inside the spinal column. The resulting pressure on the spinal cord or nerve roots can cause a range of neurological symptoms. This article explains the nature of SEL, its causes, diagnosis, and management strategies.
Defining Spinal Epidural Lipomatosis
Spinal epidural lipomatosis is defined by the excessive, non-encapsulated accumulation of mature fat cells, known as adipose tissue, in the spinal epidural space. This space acts as a sleeve located between the outer covering of the spinal cord (dura mater) and the bony wall of the vertebrae. The term “lipomatosis” refers to the abnormal proliferation of fat tissue.
The overgrowth of this fat reduces the volume of the spinal canal, functionally similar to spinal stenosis. This narrowing causes a mass effect, crowding the spinal cord and the bundle of nerve roots, known as the cauda equina, as they descend through the canal. This compression, particularly in the lower thoracic and lumbar regions where the condition most frequently occurs, can impede the normal function of these neural elements.
Primary Causes and Associated Risk Factors
The development of spinal epidural lipomatosis is strongly associated with conditions that affect the body’s systemic steroid levels. The most recognized cause is the long-term, high-dose use of exogenous corticosteroids, which are prescribed to manage various inflammatory and autoimmune conditions. These steroid medications stimulate glucocorticoid receptors in the fat tissue, promoting the growth and accumulation of adipose cells within the epidural space.
Chronic obesity is another major contributing factor, often recognized as a leading cause, particularly in the absence of steroid use. Obesity can lead to abnormal fat storage, including the deposition of fat in the spinal canal. Less commonly, endogenous causes are responsible, such as Cushing’s syndrome, where the body produces an overabundance of cortisol. Other metabolic disorders and prior spine surgery have also been identified as potential risk factors, with a portion of cases having no identifiable cause, categorized as idiopathic.
Recognizing Symptoms and Confirming Diagnosis
The clinical presentation of spinal epidural lipomatosis often mirrors that of other conditions causing spinal stenosis, making diagnosis based on symptoms alone difficult. Patients frequently experience non-specific back pain, which may be accompanied by pain that radiates into the legs (radiculopathy). This radiating discomfort results from the compression of specific nerve roots as they exit the spinal canal.
Other common neurological complaints include tingling sensations (paresthesia), numbness, and motor weakness in the lower limbs. In severe cases, the pressure can compromise the function of the cauda equina, leading to cauda equina syndrome, characterized by acute symptoms like bladder or bowel dysfunction. Because physical examination findings can be subtle or non-specific, definitive diagnosis relies heavily on medical imaging.
Magnetic Resonance Imaging (MRI) is considered the gold standard because of its superior ability to visualize soft tissues like fat. MRI scans clearly show the excessive, bright signal intensity of the adipose tissue within the epidural space and the degree of compression on the spinal cord or dural sac. While Computed Tomography (CT) scans may also be used, they are less effective than MRI at differentiating between soft tissues and assessing the full extent of nerve compression. Radiologists may use grading systems to classify the severity of the fat accumulation, often noting the characteristic “Y” or “stellate” shape of the compressed dural sac on axial images.
Management Approaches and Treatment
The initial approach to managing spinal epidural lipomatosis is conservative, focusing on addressing the underlying causes of the fat accumulation. For patients taking corticosteroids, a supervised tapering of the medication is often the first step, as reducing the steroid dose can lead to a regression of the epidural fat. Similarly, for patients whose condition is linked to weight, weight reduction is implemented to decrease the volume of the epidural adipose tissue and alleviate symptoms.
Conservative measures are often successful in improving symptoms, provided no severe or rapidly progressing neurological deficits are present. However, if symptoms are severe, such as profound weakness, intractable pain, or signs of cauda equina syndrome, surgical intervention is necessary. The standard surgical procedure is a decompression laminectomy, which involves removing the bony arch of the vertebra to remove the excess fat that is compressing the neural elements. The goal of this surgery is to relieve pressure and restore neurological function.