A spinal cord cyst is a fluid-filled sac that develops within or adjacent to the delicate structures of the spinal column. These lesions contain fluid, most commonly cerebrospinal fluid (CSF), which normally surrounds and cushions the brain and spinal cord. The severity of the condition varies significantly, ranging from completely asymptomatic findings to progressive disorders causing neurological deficits. The cyst’s location and size determine its potential impact on the body’s central communication pathway.
Defining Spinal Cord Cysts and Major Types
Spinal cysts are classified based on their anatomical position relative to the spinal cord tissue. The two primary categories are intramedullary and extramedullary, indicating whether the cyst is inside or outside the spinal cord.
Intramedullary cysts form directly within the spinal cord tissue. The most common type is a syrinx, which defines the disorder syringomyelia. A syrinx is an elongated, fluid-filled cavity, typically in the cervical or thoracic spine, that expands the central canal and compresses surrounding nerve fibers.
Extramedullary cysts develop outside the spinal cord but within the spinal canal. This category includes several distinct types. Arachnoid cysts are thin-walled, CSF-filled sacs that form from the arachnoid membrane, often located on the surface of the spinal cord. Perineural cysts, often called Tarlov cysts, are dilations of the nerve root sheath, frequently found in the sacral region.
Recognizing Common Symptoms
Symptoms arise when the expanding fluid sac exerts pressure on the spinal cord or nerve roots. Due to the slow growth of many cysts, symptoms often develop gradually, sometimes over many years, and can be intermittent or progressive.
A common initial complaint is chronic, localized pain in the back, neck, or shoulders, which may radiate down the arms or legs. Sensory changes are a frequent manifestation, often presenting as numbness, tingling, or a burning sensation (paresthesia).
A specific sign related to intramedullary cysts is the loss of sensitivity to pain and temperature while the sense of touch remains preserved. As the cyst enlarges, motor function is affected, leading to progressive muscle weakness, stiffness, and loss of reflexes in the limbs. In severe cases, patients may experience difficulty with balance, changes in bowel or bladder function, or sexual dysfunction, which signifies a serious level of neurological impairment.
Understanding Causes and Diagnostic Imaging
The formation of a spinal cord cyst stems from underlying conditions, categorized as either congenital or acquired. Congenital causes are present from birth, such as a Chiari malformation, where brain tissue extends into the spinal canal and disrupts the normal flow of CSF.
Acquired cysts result from an event later in life, commonly following spinal cord trauma or injury. Other acquired causes include inflammatory conditions like meningitis, which can cause scarring (arachnoiditis) that impedes CSF flow, or the presence of a spinal tumor that creates an obstruction.
Diagnostic Imaging
To accurately diagnose and characterize a cyst, a physician relies on specialized imaging techniques. Magnetic Resonance Imaging (MRI) is the definitive method because it provides detailed, high-resolution visualization of soft tissues. MRI clearly shows the fluid-filled cyst, its size, and its exact relationship to the spinal cord and surrounding nerves. If a standard MRI is inconclusive, a CT myelogram may be used, which involves injecting a contrast dye into the spinal fluid space.
Treatment Approaches and Long-Term Management
The decision to treat a spinal cord cyst depends on whether it is causing symptoms or showing signs of progressive growth. For cysts that are small, stable, and not causing neurological problems, a strategy of watchful waiting is recommended. This involves regular clinical check-ups and follow-up MRIs to monitor the cyst’s size and the patient’s neurological status.
When a cyst is symptomatic or rapidly expanding, surgical intervention is necessary to relieve pressure and prevent irreversible nerve damage. One approach involves draining the cyst fluid, either through fenestration (creating a window in the cyst wall) or by installing a shunt. A shunt diverts the fluid to another body cavity, such as the abdomen.
If the cyst is secondary to an underlying cause like a Chiari malformation, the primary surgery focuses on decompressing the space at the base of the skull to restore CSF flow. Restoring flow can often cause the syrinx to shrink. Following treatment, long-term management includes a personalized rehabilitation plan, such as physical therapy, to help regain muscle strength and function lost due to nerve compression.