Syringomyelia
Overview
Syringomyelia is a condition characterised by the formation of a fluid-filled cavity (syrinx) within the spinal cord. It is a major complication of arnold-chiari-malformation type II, occurring in 40–80% of adults with CM-II. However, syringomyelia can also arise from other causes including Chiari type I, spinal cord trauma, intramedullary tumours, and idiopathic causes.
Clinical Features
Sensory
- Dissociated sensory loss: loss of pain and temperature sensation with preserved touch/vibration/proprioception, reflecting damage to decussating spinothalamic fibres crossing the central canal
- “Cape” distribution: sensory loss over the shoulders and upper arms, expanding as the syrinx enlarges
- Dysesthetic burning pain (central neuropathic pain)
Motor
- Segmental weakness: hand amyotrophy (thenar, hypothenar, interossei wasting) — classic “bishop’s hand” or “claw hand”
- Spastic paraparesis/tetraparesis as the syrinx compresses descending corticospinal tracts
- Upper motor neuron signs below the level of the lesion (hyperreflexia, Babinski sign)
Autonomic
- Worsening neurogenic bladder/bowel (already compromised by underlying myelomeningocele in CM-II)
- Horner’s syndrome if syrinx involves the lateral horn at C8–T2 (intermediolateral cell column)
Relationship to CM-II
In CM-II, the syrinx is driven by altered CSF dynamics at the foramen magnum — the crowded posterior fossa creates a pressure gradient that draws CSF into the central canal. Decompressive surgery (posterior fossa decompression with duraplasty) can collapse the syrinx by restoring normal CSF flow. Untreated syringomyelia in CM-II patients is a major driver of progressive neurological deterioration in adulthood.
Diagnosis
- MRI (T2-weighted) is the diagnostic gold standard — shows the syrinx as a hyperintense CSF-filled cavity
- Whole-spine imaging is essential (multiple or holocord syrinx is possible)
- Cine phase-contrast MRI can assess CSF flow dynamics at the foramen magnum
Treatment
- Posterior fossa decompression for Chiari-associated syringomyelia
- Syrinx shunting (syringo-subarachnoid or syringo-peritoneal) for refractory cases
- Tethered cord release if concomitant tethering contributes
- Untethering alone may stabilise or improve syrinx in some CM-II patients
- Surveillance: annual neurological exam + MRI every 2–5 years (sooner if symptomatic progression)
References
- DeepSeek chat summary (2026). Clinical Summary: Arnold–Chiari Type II Malformation in Adults. 1