Lateral recess stenosis describes a condition where a specific passage within the spinal canal narrows, potentially compressing the nerve roots that travel through it. This narrowing can lead to various symptoms, affecting a person’s comfort and mobility. Understanding its causes involves examining the spine’s structure and how various factors lead to changes over time.
The Spinal Lateral Recess Explained
The human spine is a column of stacked bones called vertebrae, which provide support and protect the spinal cord. Between each vertebra are intervertebral discs that act as shock absorbers and allow for movement. The vertebrae align to form the spinal canal, a central tunnel encasing the spinal cord and its branching nerve roots.
Individual nerve roots exit through small openings called neural foramina. The lateral recess is a specific area within the spinal canal, located just before the nerve roots pass through these foramina. This passageway, sometimes referred to as the subarticular recess, is where the nerve root descends before exiting the main spinal canal.
The lateral recess is bounded by several spinal structures, including a part of the vertebra called the pedicle, the intervertebral disc, and the facet joints. Any encroachment into this limited space can compress the nerve root, leading to symptoms associated with lateral recess stenosis. The space in the lateral recess is particularly vulnerable to narrowing due to its confined nature.
Degenerative Processes in the Spine
The most common causes of lateral recess stenosis are age-related degenerative changes that occur in the spine. These processes involve gradual wear and tear on spinal structures over many years, reducing the available space for nerve roots.
Intervertebral Disc Degeneration
Intervertebral discs naturally lose hydration and elasticity over time. This process, known as disc degeneration, can lead to the discs flattening and bulging outward. A bulging disc can protrude into the lateral recess, encroaching upon the space where nerve roots travel. The reduction in disc height further contributes to spinal instability, placing additional stress on surrounding structures.
Ligamentum Flavum Hypertrophy
The ligamentum flavum is a ligament that runs along the back of the spinal canal, connecting the vertebrae. With age, this ligament can thicken and become less elastic, a process called hypertrophy. When it thickens, it can buckle inward into the spinal canal and into the lateral recess, reducing the space available for the nerve roots. This thickening is a significant contributor to spinal canal narrowing.
Facet Joint Enlargement (Osteoarthritis)
Facet joints are small joints located at the back of each vertebra, providing stability and allowing for spinal movement. Facet joints can develop osteoarthritis, a condition characterized by the breakdown of cartilage. As cartilage wears away, the body may respond by forming new bone growth called bone spurs, or osteophytes. These enlarged facet joints and bone spurs can protrude into the lateral recess, compressing the nerve roots.
Disc Herniation and Spondylolisthesis
Beyond general degenerative processes, specific conditions can significantly narrow the lateral recess, leading to nerve compression. These mechanisms often involve more pronounced structural changes within the spinal column.
Disc Herniation
While disc bulging contributes to narrowing, a disc herniation involves the inner, gel-like material of an intervertebral disc protruding or rupturing through its outer fibrous ring. This extruded disc material can directly press on nerve roots as they pass through or near the lateral recess. A herniated disc can cause acute compression, leading to symptoms like pain and weakness. The material can also migrate, affecting nerve roots at different levels.
Spondylolisthesis
Spondylolisthesis describes a condition where one vertebra slips forward over the vertebra below it. This misalignment can occur due to degeneration or other factors, creating instability in the spine. When a vertebra shifts out of its normal position, it can significantly reduce the overall space within the spinal canal and narrow the lateral recess. The slippage can lead to compression of nerve roots, causing symptoms related to the reduced space.
Contributing Factors and Susceptibility
Several factors do not directly cause lateral recess stenosis but can increase an individual’s likelihood of developing the condition or accelerate the degenerative changes that lead to it. These elements often work in combination with the primary degenerative processes.
Age is the most significant factor, as spinal structures naturally undergo wear and tear over a lifetime. Degenerative spinal changes are observed in a high percentage of people over 50, with prevalence increasing with age. The cumulative effect of years of stress on the spine makes older individuals more susceptible to conditions like lateral recess stenosis.
Genetic predisposition plays a role in susceptibility to spinal stenosis. Some individuals may inherit a naturally narrower spinal canal, making them more prone to nerve compression even with minor degenerative changes.
Certain occupations and lifestyle choices can contribute to spinal degeneration. Jobs involving repetitive stress, heavy lifting, or prolonged awkward postures can place excessive strain on the spine over time. This chronic mechanical stress can accelerate the degenerative processes in the discs, ligaments, and facet joints, increasing the risk of developing lateral recess stenosis.
Previous spinal injuries or surgeries can also alter spinal mechanics and potentially lead to accelerated degenerative changes. Trauma to the spine can result in changes that narrow the lateral recess, while surgical interventions might modify spinal alignment or stability, affecting long-term spinal health.
Obesity adds mechanical stress to the spine, particularly in the lower back. Increased body weight can accelerate the degeneration of intervertebral discs and contribute to conditions like spinal stenosis. Studies show a correlation between higher body mass index (BMI) and an increased risk of disc degeneration and spinal stenosis.