Syringomyelia (Spinal Cord Cyst - Syrinx)
Syringomyelia is a chronic, progressive condition characterized by a fluid-filled cystic cavity (a syrinx) within the spinal cord. Its most common cause is Chiari malformation. Its hallmark is dissociated sensory loss, in which pain and temperature sensation are lost; treatment targets the underlying cause.
Last updated: 2026-06-07
Definition
Syringomyelia is a chronic, progressive condition defined by the development of a fluid-filled cystic cavity within the spinal cord. 'Syrinx' refers to this tube-shaped cavity, which can form either by widening of the central canal in the middle of the cord or by a new cavity within the spinal cord tissue. The cavity may enlarge over time, pressing on cord tissue and causing neurological symptoms. It is most common in the neck (cervical) and mid-back (thoracic) regions; when it extends into the brainstem it is called syringobulbia.
Causes and Risk Factors
The most common cause is Chiari malformation, in which disruption of cerebrospinal fluid (CSF) circulation at the foramen magnum triggers cyst formation within the cord. Other causes include post-traumatic syringomyelia developing after spinal cord injury, inflammation of the spinal coverings (arachnoiditis), intramedullary tumors, and spinal canal narrowing. In a proportion of cases no underlying cause is found (idiopathic). Whatever the origin, the shared mechanism is that disturbed CSF circulation leads to fluid accumulation within the spinal cord.
Symptoms
The most characteristic finding is dissociated sensory loss: pain and temperature sensation are lost while touch and vibration are preserved. With a cervical syrinx this loss has a 'cape-like' distribution over the shoulders and arms; the patient may unknowingly sustain burns and cuts. This may be accompanied by weakness in the arms and wasting of the hand muscles, neuropathic (burning) pain, stiffness in the legs, and difficulty walking. When it extends into the brainstem, swallowing difficulty and hoarseness can occur, and in children progressive scoliosis may be seen.
Diagnosis
The gold standard for diagnosis is MRI of the spinal cord; on T2-weighted images the syrinx appears as a bright (hyperintense), fluid-signal cystic cavity with widening of the cord. The cavity may extend from a few vertebral levels to the entire cord. To identify the underlying cause, cranial MRI is used to look for Chiari malformation, and the whole spine is assessed for tumor, trauma, or arachnoiditis. Contrast enhancement raises the possibility of tumor or infection. The differential diagnosis includes intramedullary tumor, multiple sclerosis, and motor neuron disease.
Treatment
Treatment targets the underlying cause; the goals are to halt cyst enlargement and restore CSF circulation. For Chiari-related syringomyelia, posterior fossa decompression is performed, and the syrinx usually regresses without needing to be drained separately. In post-traumatic or refractory cases, a thin catheter may be placed between the syrinx and the subarachnoid space (syringo-subarachnoid shunt), with release of adhesions (arachnoidolysis). When an intramedullary tumor is the cause, removing the tumor usually allows the syrinx to regress. For asymptomatic, stable cysts, close follow-up and symptom-directed care (medications for neuropathic pain, physical therapy) may be preferred.
Prognosis
The natural course varies with the cause and the rate of cyst growth; most cases progress slowly and some remain stable. After surgery, the syrinx shrinks or disappears (usually over months) in a substantial proportion of cases and neurological symptoms stabilize; pain responds best, while motor and sensory deficits improve less and dissociated sensory loss may be permanent. Early diagnosis and treatment are important to prevent permanent damage. Repeat surgery may be needed for reasons such as shunt blockage; outcomes are individual and none can be guaranteed.
References
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:1405-1411.
- Winn HR, ed. Youmans Neurological Surgery. 6th ed. Saunders; 2011.
- Oldfield EH, et al. Pathophysiology of syringomyelia associated with Chiari I malformation. J Neurosurg. 1994.
This article is for general information and does not replace a medical examination. Diagnosis and treatment decisions are individual.