Syringomyelia is a chronic neurological condition characterized by the formation of a fluid-filled cavity, known as a syrinx, within the spinal cord tissue. This syrinx is essentially an accumulation of cerebrospinal fluid (CSF) that expands over time, causing pressure and damage to surrounding nerve fibers. When this cavity forms specifically within the brainstem, the condition is termed syringobulbia. Both conditions involve the central nervous system, and the progressive enlargement of the syrinx compresses delicate structures, leading to various neurological deficits.
The Formation and Causes of Syringes
The underlying mechanism in both syringomyelia and syringobulbia is the disruption of the normal flow dynamics of cerebrospinal fluid (CSF). CSF is the liquid that surrounds and cushions the brain and spinal cord. When CSF circulation is blocked, the fluid is forced into the spinal cord’s central canal, leading to syrinx formation and expansion. The most common cause associated with this disruption is a Chiari Type I malformation, a structural defect present from birth.
A Chiari Type I malformation occurs when the cerebellar tonsils extend downward through the foramen magnum (the opening at the base of the skull) and into the spinal canal. This herniation obstructs the pathway for CSF to flow, creating pressure differences that drive fluid into the cord tissue. This type of syringomyelia is often referred to as communicating syringomyelia, with symptoms typically manifesting between the ages of 25 and 40.
Syringes can also develop from acquired causes, sometimes called non-communicating syringomyelia. Post-traumatic syringomyelia is a common acquired form that can develop months or years after a spinal cord injury. The initial trauma often leads to the formation of scar tissue, which then blocks the CSF flow and initiates syrinx formation.
Other conditions that create obstructions or inflammation around the spinal cord can also lead to the development of a syrinx. These causes include spinal cord tumors, such as hemangioblastomas and ependymomas, as well as arachnoiditis, which is inflammation and scarring of the protective membranes. If the cause remains unknown, the condition is classified as idiopathic syringomyelia.
Clinical Manifestations Based on Location
Symptoms depend on the syrinx’s size, location, and extent, which determines the damaged nerve pathways. In syringomyelia (spinal cord), sensory loss often occurs due to damage to the spinothalamic tract, which carries pain and temperature signals. This results in the inability to feel heat, cold, or pain, frequently in the hands, arms, and upper chest, sometimes called a “shawl-like” distribution.
Expansion of the syrinx affects motor neurons in the spinal cord’s anterior horn, causing progressive muscle weakness and atrophy, often starting in the hands and forearms. Patients may also experience chronic pain, stiffness in the back and limbs, and loss of reflexes. Further extension can impact nerves controlling the bladder and bowel.
Syringobulbia occurs when the syrinx extends into the brainstem, which controls many involuntary functions and processes sensory information from the face and head. Damage in this region often involves the cranial nerves. Manifestations include difficulty swallowing (dysphagia) and changes in voice (dysphonia or hoarseness).
Motor and sensory control of the face may be affected, potentially leading to facial numbness or weakness. Other symptoms arise from the syrinx compressing localized nerve nuclei and tracts within the brainstem.
Syringobulbia Symptoms
Nystagmus (involuntary and rapid movement of the eyeballs)
Vertigo
Unsteady gait
Tinnitus (ringing in the ears)
Diagnostic Procedures and Tools
Diagnosis begins with a comprehensive medical history review and a detailed neurological examination. The physician assesses motor function, reflexes, and sensory capabilities, looking for specific patterns of weakness and sensory loss suggestive of a syrinx. The neurological exam helps to localize the potential area of damage within the central nervous system.
Magnetic Resonance Imaging (MRI) is the definitive tool for confirming the presence of a syrinx. MRI provides detailed images of the spinal cord and brain, allowing visualization of the syrinx, measurement of its size, and determination of its full extent. MRI can also identify the underlying cause, such as a Chiari malformation or a spinal cord tumor.
A specialized technique called Cine phase-contrast MRI may be used for further insight. This dynamic imaging method observes the movement of cerebrospinal fluid around the spinal cord and within the syrinx, providing information valuable for surgical planning. If a tumor is suspected, gadolinium-enhanced MRI images are obtained to differentiate the syrinx from solid tissue or scar material.
Management and Treatment Options
Treatment aims to halt syrinx progression, alleviate symptoms, and prevent further neurological deterioration. For asymptomatic or mildly symptomatic patients, a conservative approach of watchful waiting is adopted. This involves regular neurological examinations and periodic MRI scans to monitor the syrinx’s size and progression over time.
If symptoms are severe or rapidly worsening, surgical intervention is recommended to restore the normal flow of cerebrospinal fluid. For cases associated with a Chiari Type I malformation, the most common procedure is a posterior fossa decompression. This involves removing small pieces of bone at the back of the skull and upper vertebrae to create more space around the brainstem and upper spinal cord, relieving the CSF obstruction.
If the syrinx is caused by a tumor or scar tissue, the surgical focus is removing that specific blockage. If decompression fails or an underlying cause cannot be addressed, a direct drainage procedure may be performed. This involves placing a shunt (a thin tube) into the syrinx cavity to drain the fluid to another body cavity, such as the abdomen, where it is absorbed.
Pain management is an important component of long-term care, as chronic pain is a frequent and disabling symptom. Medications such as gabapentin or pregabalin may be used to target neuropathic pain. Physical therapy is also recommended to help maintain muscle strength, mobility, and function. Patients are advised to avoid heavy lifting or straining, which can temporarily increase pressure and potentially expand the syrinx.