The human spine consists of stacked bones (vertebrae) separated by intervertebral discs. These discs function as shock absorbers, providing flexibility and support. A disc has a tough outer layer (annulus fibrosus) encasing a soft, jelly-like center (nucleus pulposus). A disc herniation occurs when the nucleus pulposus pushes out through a tear in the outer ring, displacing material beyond its boundaries. While a 13mm measurement appears significant, size alone does not fully determine the severity of symptoms or the necessary treatment plan.
Contextualizing the 13mm Measurement
Medical professionals classify the size of a herniated disc to understand its physical extent. In the lower back, where this injury is most common, a herniation under 5.0 millimeters is considered small. Moderate herniations generally fall within the 5.0 to 10.0-millimeter range. A 13-millimeter herniation is definitively classified as a large or significant herniation.
This 13mm measurement represents a substantial displacement of disc material beyond the vertebral boundary. For context, this is a considerable amount of material inside the confined space of the spinal canal. A large herniation, especially one exceeding 10 millimeters, is considered severe in terms of physical size. This size can potentially occupy a significant portion of the spinal canal, which houses sensitive nerves.
What Determines Severity Beyond Size
The severity of a patient’s condition depends on the effect the disc size has on surrounding structures, not the size alone. A large, 13mm herniation may cause few symptoms if it does not press directly on a nerve root or the spinal cord. Conversely, a smaller herniation can cause intense pain if it impinges directly upon a sensitive nerve. The primary driver of pain and functional loss is the degree of nerve root or spinal cord compression (impingement).
The anatomical location of the herniation is also a major factor in determining its impact. A central herniation projects straight back into the middle of the spinal canal, potentially compressing the cauda equina (the bundle of nerves resembling a horse’s tail). A paracentral or lateral herniation pushes out to the side, more likely compressing a single nerve root as it exits the spine. Compression causes both mechanical irritation from pressure and chemical irritation from inflammatory substances released by the disc material.
Typical Symptoms of Significant Disc Compression
When a significant herniated disc, such as 13mm, causes nerve root compression, it results in radiculopathy. In the lower back, this is commonly called sciatica, characterized by sharp or burning pain that radiates from the buttocks down the leg and sometimes into the foot. The pain often worsens with movements like coughing, sneezing, or prolonged sitting, which temporarily increase pressure within the spinal column.
Patients may also experience neurological deficits, including numbness, tingling, or a pins-and-needles sensation in the affected limb. Compression can also lead to muscle weakness in the foot or leg, potentially causing difficulty walking or lifting the foot. In rare instances, a large central herniation can compress the entire cauda equina nerve bundle, which is a medical emergency. This causes progressive loss of sensation in the saddle area (buttocks, genitals, inner thighs), along with new-onset bladder or bowel dysfunction.
Treatment Approaches for a 13mm Herniation
Initial management for most herniated discs, even large ones like 13mm, begins with conservative, non-surgical methods. This involves relative rest followed by physical therapy to strengthen core muscles and improve mobility. Non-steroidal anti-inflammatory drugs (NSAIDs) are used to manage pain and reduce inflammation.
If severe symptoms persist, a physician may recommend an epidural steroid injection. This procedure involves injecting anti-inflammatory medication directly around the compressed nerve root to reduce swelling and alleviate pain. Many large herniations show significant size reduction or fully resolve over time with conservative treatment, often within six months.
Surgery is reserved for cases where conservative treatments fail after about six weeks, or if the patient experiences progressive neurological worsening. Cauda equina syndrome, marked by severe weakness or bowel/bladder issues, requires urgent surgical intervention. The most common procedure for a lumbar herniation is a microdiscectomy, where a small portion of the disc material is removed to decompress the trapped nerve root. This procedure is effective at relieving leg pain caused by nerve pressure and results in a more rapid return to function.