Lumbar myelopathy is a condition resulting from compression of the spinal cord in the lower back. This pressure disrupts the normal transmission of nerve signals between the brain and body, leading to pain, sensory changes, and difficulty with movement. While “lumbar” refers to the lower back, the anatomy in this region makes the condition distinct from other spinal issues. Understanding this condition involves exploring the lower spine’s structure, the causes of compression, and available treatments.
Understanding the Anatomy of the Lower Spine
The term “lumbar myelopathy” can be misleading. The spinal cord, the primary bundle of nerves from the brain, ends near the first or second lumbar vertebra (L1 or L2). This endpoint is a tapered structure called the conus medullaris. True lumbar myelopathy is the compression or injury of the conus medullaris, the most distal part of the spinal cord.
Below the conus medullaris, the spinal canal contains a bundle of nerve roots that continue downward. This collection of nerves is called the cauda equina, Latin for “horse’s tail.” Compression of these nerve roots results in a related condition known as cauda equina syndrome (CES). The distinction is based on which structures are compressed: the spinal cord tip (myelopathy) or the nerve roots below it (cauda equina syndrome).
A third condition in this area is lumbar radiculopathy, which involves pinching a single nerve root as it branches off the spinal column, often called sciatica. To visualize the difference, think of the spinal cord as a highway. Myelopathy is a blockage at the highway’s end (the conus medullaris), CES is a jam on multiple exit ramps (the nerve roots), and radiculopathy is a blockage on a single exit ramp.
Because the conus medullaris is part of the central nervous system and the cauda equina nerve roots are part of the peripheral nervous system, their compression leads to different patterns of signs. Distinguishing between these conditions is an important step in the diagnostic process, as it can influence the urgency and type of treatment required.
Causes of Spinal Compression
The pressure on the conus medullaris that defines lumbar myelopathy can originate from several sources, often grouped into degenerative conditions and other external causes. Degenerative changes from aging are frequent culprits. Common causes include:
- Spinal stenosis: A gradual narrowing of the spinal canal that can crowd the space available for the spinal cord and nerve roots.
- Herniated disc: The bulging or rupture of an intervertebral disc, causing its inner material to press on the conus medullaris. Those at the T12-L1 or L1-L2 level are most likely to cause this condition.
- Bone spurs (osteophytes): Bony growths that develop on the vertebrae and contribute to the narrowing of the spinal canal.
- Traumatic injuries: Fractures of the vertebrae from an accident or fall can cause bone fragments to enter the spinal canal.
- Spinal tumors: Cancerous or noncancerous growths can exert pressure on the delicate cord tissue.
- Infections: A spinal epidural abscess can cause inflammation and swelling, leading to compression.
- Rheumatoid arthritis: This condition can also lead to changes that compress the spinal cord.
Identifying the Symptoms
The symptoms of lumbar myelopathy stem from the disruption of nerve signals in the conus medullaris. Patients may experience lower back pain that radiates into one or both legs. Sensory disturbances are also common, manifesting as numbness, tingling, or a “pins-and-needles” sensation in the legs and feet.
Motor function is often affected, leading to weakness in the leg muscles. This can make activities like walking, climbing stairs, or rising from a chair difficult. Many individuals report problems with balance and coordination, resulting in an unsteady gait. The compression can also alter normal reflexes in the lower extremities.
Red Flag Symptoms
Certain symptoms are “red flags” because they indicate severe compression that may require immediate medical intervention to prevent permanent damage. One is bowel or bladder dysfunction, which can present as urinary retention, incontinence, or loss of bowel control. Another warning sign is “saddle anesthesia,” a loss of sensation in the areas that would touch a saddle—the groin, buttocks, and inner thighs. The sudden onset of these symptoms with back pain and leg weakness constitutes a medical emergency.
The Diagnostic Process
Diagnosing lumbar myelopathy begins with a medical history and physical examination. A physician will ask about the nature of the symptoms, their onset, and any history of back problems. The physical exam is followed by a detailed neurological assessment to evaluate muscle strength, sensation, and reflexes in the legs.
While the physical exam provides important clues, imaging studies are necessary to confirm the diagnosis and identify the cause of the compression. Magnetic Resonance Imaging (MRI) is the preferred method. An MRI uses magnetic fields and radio waves to create detailed images of soft tissues, including the spinal cord and nerve roots, allowing doctors to visualize compression.
In some cases, other imaging tests may be used. A Computed Tomography (CT) scan is better for visualizing bone structures and can identify fractures or bone spurs. X-rays may be ordered to assess the spine’s alignment and stability. Occasionally, an electromyogram (EMG) might be performed to assess the degree of nerve damage.
Approaches to Treatment
The approach to treating lumbar myelopathy depends on the underlying cause and the severity of the symptoms. The primary goal is to alleviate pressure on the spinal cord, which can halt symptom progression and allow for neurological recovery. Treatments are categorized as non-surgical or surgical.
Non-surgical management is reserved for milder cases and focuses on controlling symptoms. This may include physical therapy to improve strength, balance, and mobility. Medications such as non-steroidal anti-inflammatory drugs (NSAIDs) may be prescribed to reduce discomfort. Corticosteroid injections can be administered to reduce swelling, though this is a temporary measure.
When compression is significant or symptoms are progressing, surgery is recommended. The objective is decompression—the physical removal of whatever is pressing on the conus medullaris. Common procedures include a laminectomy to create more space in the spinal canal or a discectomy to remove the compressing part of a herniated disc. A spinal fusion may be performed to stabilize the vertebrae.