Syringohydromyelia is a rare disorder characterized by the formation of a fluid-filled cavity, or syrinx, within the spinal cord. This abnormal fluid collection typically expands over time, placing pressure on surrounding nerve fibers and disrupting communication between the brain and the body. This pressure leads to a progressive decline in neurological function, resulting in chronic pain, weakness, and loss of sensation. The condition can affect individuals of any age, though symptoms most often present in young adults (ages 20 to 40).
Understanding the Spinal Cord Cavity
The term “syringohydromyelia” describes the fluid-filled cavity within the spinal cord, combining two concepts. The spinal cord contains a tiny, central channel known as the central canal. Hydromyelia refers specifically to the abnormal dilation or widening of this central canal, where the cavity is lined by cells called ependyma.
A syrinx is a cystic cavity that forms within the spinal cord tissue itself, often developing from the central canal but dissecting into the surrounding white matter. This cavity is typically filled with cerebrospinal fluid (CSF), the clear liquid that normally surrounds the brain and spinal cord. Because the two conditions often coexist, the combined term “syringohydromyelia” is used, though “syringomyelia” is the most common clinical term.
The syrinx cavity most frequently forms in the cervical (neck) region of the spine, extending downward into the thoracic cord. As the syrinx expands, it exerts pressure on the nerve pathways running through the spinal cord. This pressure damages the nerve fibers responsible for transmitting sensory and motor signals.
The resulting nerve damage causes the neurological deficits experienced by the patient. The location and size of the cavity directly determine the specific symptoms and their severity, with larger or higher-cervical syrinxes causing more widespread effects.
Primary Causes of the Condition
Syringohydromyelia develops when the normal circulation of cerebrospinal fluid (CSF) around the brain and spinal cord is obstructed, causing fluid to accumulate and create an expanding cavity. The most common underlying cause for this obstruction is a Chiari I Malformation, a structural defect present from birth.
Chiari I Malformation involves the cerebellar tonsils extending down through the foramen magnum (the opening at the base of the skull) and into the spinal canal. This descent crowds the area and blocks the natural flow of CSF between the brain and the spinal cord. This obstruction is thought to create pressure differences, forcing CSF into the central canal and initiating syrinx formation.
While Chiari Malformation is the most frequent trigger, the condition can also arise from acquired causes. Trauma to the spine, such as a severe accident, can lead to scarring and obstruction of the CSF pathway, sometimes causing a syrinx to form months or years later. This delayed-onset presentation is termed post-traumatic syringomyelia.
Spinal tumors are another potential cause, as a tumor growing within the spinal cord tissue can interfere with fluid dynamics or secrete fluid directly, leading to cavity formation. Arachnoiditis, the inflammation and scarring of the arachnoid membrane covering the spinal cord, can also block the flow of CSF, resulting in syrinx development.
Recognizing the Physical Symptoms
The progression of syringohydromyelia symptoms is often gradual, developing over months or years, depending on the cavity’s location and size. A hallmark sensory symptom is dissociated sensory loss, where the patient loses the ability to feel pain and temperature, but the sense of touch, vibration, and position is preserved. This occurs because the syrinx typically begins in the center of the spinal cord, damaging the nerve fibers that cross there to carry pain and temperature signals.
This sensory loss frequently manifests in a “cape-like” or “suspended” distribution, affecting the shoulders, upper back, and arms, which corresponds to the location of the most common cervical syrinxes. Because patients cannot feel heat or sharp objects in these areas, they may sustain burns or injuries without realizing it, which can lead to chronic skin ulcerations on the hands.
Motor symptoms are common, typically beginning with muscle weakness and atrophy in the hands and arms, as the syrinx expands to damage the nerve cells controlling these muscles. Patients may notice difficulty with fine motor tasks, leading to hand deformities like the “claw hand” in advanced cases. Muscle stiffness, or spasticity, may also occur in the legs, making walking and mobility difficult.
Chronic pain is a significant complaint, often described as a deep, aching, or burning sensation in the neck, shoulders, and extremities. This neuropathic pain is caused by the direct damage to the spinal cord’s sensory pathways. In cases where the syrinx extends upward into the brainstem, a condition called syringobulbia, patients may experience additional symptoms such as dizziness, facial numbness, or swallowing difficulties.
Diagnosis and Management Strategies
The definitive diagnosis of syringohydromyelia relies on advanced medical imaging, with Magnetic Resonance Imaging (MRI) being the standard of care. MRI provides detailed images of the spinal cord and brain, allowing physicians to visualize the fluid-filled syrinx cavity and determine its size and location. MRI is also essential for identifying the underlying cause, such as a Chiari I Malformation or a spinal cord tumor, which guides the treatment plan.
For patients who are asymptomatic or whose symptoms are stable and mild, the initial management strategy often involves careful observation and periodic follow-up MRI scans. The goal of this monitoring is to track whether the syrinx is growing or if the patient’s neurological function is deteriorating. If symptoms are progressive or severe, surgical intervention is generally recommended to relieve pressure on the spinal cord.
The specific surgical approach depends on the cause of the syrinx. If the condition is caused by a Chiari I Malformation, the primary treatment is posterior fossa decompression. This procedure involves removing a small section of bone at the back of the skull and sometimes the upper vertebrae to create more space for the cerebellum and restore the normal flow of CSF around the brainstem and spinal cord.
If the syrinx is caused by a tumor or other mass, the obstruction is surgically removed, often allowing the syrinx to drain and resolve naturally. If addressing the underlying cause is not feasible or has failed, a shunting procedure may be performed. This involves inserting a thin, flexible tube (a shunt) to drain the fluid from the syrinx cavity into another body area, such as the abdomen, where it is safely absorbed.
Beyond addressing the underlying cause, management focuses on symptom relief. Medications are used to manage chronic neuropathic pain, and physical therapy is recommended to maintain muscle strength and function. While surgery aims to halt the progression of neurological damage, it may not completely reverse symptoms resulting from long-standing spinal cord compression. Regular follow-up and long-term care are necessary, as the syrinx can sometimes recur.