Cervical spinal stenosis (CSS) is defined by the narrowing of the spinal canal within the neck vertebrae. This narrowing can compress sensitive structures, specifically the spinal cord and the nerve roots exiting the spine. Magnetic Resonance Imaging (MRI) is the primary tool used by physicians and radiologists to diagnose and assess this condition because it provides a detailed view of the soft tissues that are often the source of compression.
Interpreting the Cervical Spine MRI
The MRI scan produces detailed cross-sectional images of the neck, allowing visualization of the bony vertebrae, the intervertebral discs, and the delicate neural structures. The spinal cord sits protected within the central spinal canal, surrounded by cerebrospinal fluid (CSF). The CSF appears bright white on a specific type of MRI sequence called the T2-weighted image, which is an important indicator of the space available for the spinal cord.
Stenosis is visualized as a reduction in the space available for the spinal cord and nerves. Narrowing in the central spinal canal is termed central canal stenosis. Narrowing affecting the small openings where nerve roots exit is called foraminal stenosis. Severe central canal stenosis is the most concerning finding because it directly impacts the spinal cord. Severity is determined by how much the canal is narrowed and whether the spinal cord itself is being affected.
Specific Measurements That Indicate Severe Stenosis
The diagnosis of severe cervical stenosis relies on both quantitative measurements and qualitative signs of spinal cord compromise. A central canal diameter of less than 10 millimeters suggests stenosis, while a measurement below 7 millimeters indicates severe or critical narrowing. The “space available for the cord,” calculated by subtracting the spinal cord’s diameter from the canal’s diameter, is another measurement used to gauge potential compression risk.
Qualitative signs on the MRI are often more telling for a severe diagnosis than the measurements alone. One of the most significant indicators is the effacement of the cerebrospinal fluid (CSF) surrounding the spinal cord. In a severe case, the bright white CSF signal is completely obliterated at the level of compression, indicating the spinal cord is directly touching the surrounding bone or disc material.
The most serious qualitative sign is a T2 signal change within the spinal cord itself, appearing as a focal bright spot. This bright signal, known as myelomalacia, suggests internal injury, edema, or gliosis in the cord tissue due to chronic, forceful compression. Radiologists may use grading scales to standardize the severity, such as classifying stenosis by the degree of cord deformity and the presence of this internal signal change. Another method, the Torg-Pavlov ratio, divides the spinal canal diameter by the vertebral body diameter on an X-ray, where a ratio less than 0.8 suggests significant stenosis.
Linking Severe Imaging Findings to Physical Symptoms
The severe compression seen on the MRI directly correlates with the type and extent of neurological symptoms a patient experiences. Severe central canal stenosis, particularly with the presence of T2 signal changes, is highly associated with a clinical condition called Cervical Myelopathy. Myelopathy is dysfunction of the spinal cord itself and represents a more urgent clinical condition.
Symptoms of myelopathy are often subtle at first but progress to affect global function. These include clumsiness in the hands, difficulty with fine motor tasks like buttoning a shirt, and a loss of manual dexterity. Patients may also experience gait disturbance, unsteadiness, trouble with balance, or frequent falls.
The compression can also affect the exiting nerve roots, a condition known as Cervical Radiculopathy, which typically causes pain, weakness, or numbness that travels down one arm in a specific pattern. While radiculopathy involves the nerve root, severe central stenosis affects the entire spinal cord, potentially leading to symptoms in both the upper and lower extremities and sometimes even bowel or bladder changes.
Treatment Pathways Following a Severe Diagnosis
A diagnosis of severe, symptomatic cervical spinal stenosis, especially when associated with myelopathy or a T2 signal change on MRI, typically changes the treatment approach. Conservative management, which includes physical therapy, anti-inflammatory medications, and epidural steroid injections, is often the first step for milder cases or for radiculopathy alone. However, for severe central stenosis causing progressive myelopathy, conservative measures are generally less effective at halting disease progression, and surgical intervention is frequently recommended.
The goal of surgery is to decompress the spinal cord by physically removing the structures causing the severe narrowing. Common surgical procedures include laminectomy, which removes a portion of the bone at the back of the vertebra, or laminoplasty, which creates more space by hinging and repositioning the bone. In some cases, the surgeon may also perform a fusion to stabilize the spine following decompression. Consulting with a specialist, such as a neurosurgeon or orthopedic spine surgeon, is necessary to determine the most appropriate and tailored surgical plan based on the specific levels of stenosis and the severity of the cord compression visualized on the MRI.