Syringomyelia is a condition in which an abnormal fluid-filled cavity, or syrinx, develops within the central canal of the spinal cord. The syrinx is a result of disrupted CSF drainage from the central canal, commonly caused by a Chiari malformation or previous trauma to the cervical or thoracic spine. In select cases, the syrinx may occur in the brainstem, and is then referred to as syringobulbia. The syrinx initially compresses and permanently damages crossing fibers of the spinothalamic tract. Further expansion may affect other tracts of the spinal cord. Symptoms include dissociated sensory loss, presenting as a cape-like distribution of decreased sensitivity to pain and temperature, and flaccid atrophic paralysis in the upper extremities. MRI is the diagnostic modality of choice. Treatment depends on clinical features and associated findings. Symptomatic treatment commonly suffices in stable courses of disease, while patients with progressive neurological deterioration require surgical decompression.
- Arnold-chiari malformation, especially type I (most common cause) 
- Posttraumatic SCI (3–4% of patients with SCI develop symptomatic syringomyelia)
- Postinflammatory: transverse myelitis, arachnoiditis
- Postinfectious (meningitis)
- Intramedullar tumors: ependymoma, hemangioblastoma
- Other congenital malformations: tethered spinal cord syndrome
- Obstructed central canal of spinal cord (usually in the cervical spine, the thoracic or lumbar spine are less commonly affected); → impaired CSF drainage → formation of a dilated fluid-filled cavity in central spinal cord (syrinx) → compression of the anterior white commissure and damage (with reactive gliosis) to crossing neural fibers (from the second-order neurons) of the lateral spinothalamic tract first (which affect pain and temperature) → bilateral dissociated sensory loss and dysesthetic pain
- Expansion of the syrinx may damage: 
- Lower motor neurons in the at segment level → initially bilateral weakness → eventual bilateral flaccid paresis and muscle atrophy
- Upper motor neurons in the medial part of the → unilateral or bilateral spastic paresis below the level of the syrinx
- Descending hypothalamic fibers in T1 to T4 cord segments → Horner syndrome
- Posterior column (advanced disease) → loss of position sense and vibration sense in the feet 
- Medulla →
- Hydromyelia: an abnormal widening of the central canal of the spinal cord in which CSF collects, despite there being a connection to the 4th ventricle of the brain
- Often asymptomatic and/or slowly progressing (similar to )
- Cape-like distribution (neck, shoulders, arms)
- Spastic paraparesis of the lower limbs may occur.
- Autonomic disturbances: anhidrosis, disturbances in bladder and colon function, erectile dysfunction ,
- Respiratory insufficiency
- Other: painless ulcers of the hands, s, thoracic scoliosis
- Syringobulbia: a neurological disorder characterized by syringomyelia affecting the brainstem
- Hemiparaplegic syndrome ()
- See “.”
The differential diagnoses listed here are not exhaustive.
Conservative therapy is usually sufficient, but definitive surgical treatment is recommended for patients with progressive neurological symptoms.
- Removal of the tumor (if present)
- Decompression by drainage of CSF fluid from the cavity