Epidemiology
Etiology
- Arnold-chiari malformation, especially type I (most common cause)
- Posttraumatic spinal cord injury (3–4% of patients with SCI develop symptomatic syringomyelia)
- Symptoms of syringomyelia may only develop months to years after the injury. The injury typically affects the cervical spine (e.g., following a motor vehicle accident).
Pathophysiology
- 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 anterior horns at segment level → initially bilateral weakness → eventual bilateral flaccid paresis and muscle atrophy
- Muscle atrophy typically begins in the hands and progresses to the arms and shoulders.
- Upper motor neurons in the medial part of the lateral corticospinal tract → unilateral or bilateral spastic paresis below the level of the syrinx
- Descending hypothalamic fibers in T1 to T4 cord segments → Horner syndrome
- Lower motor neurons in the anterior horns at segment level → initially bilateral weakness → eventual bilateral flaccid paresis and muscle atrophy
Tip
Syringomyelia is an abnormal fluid-filled dilation of the central canal of the spinal cord occurring as a result of impaired CSF flow.
Clinical features
- Often asymptomatic and/or slowly progressing (similar to central cord syndrome)
- Cape-like distribution (neck, shoulders, arms)
- The sensation deficit may be exacerbated with raised intramedullary pressure due to coughing, sneezing, or raised intra-abdominal pressure (e.g., straining because of constipation).
- Dissociated sensory loss
- The loss of sensation of pain and temperature, while the sensation of light touch, vibration, and position remain intact.
- Dysthetic pain
- Muscle atrophy, fasciculations, and areflexia (patients may present with a claw hand deformity)
- Syringobulbia: a neurological disorder characterized by syringomyelia affecting the brainstem
- Tongue atrophy
- Loss of pain and temperature sensation in trigeminal nerve
- Nystagmus
- Dysphagia
- Palatal and pharyngeal weakness