Syringomyelia

Syringomyelia is a fluid-filled cavity, or syrinx, within the spinal cord. It develops when normal cerebrospinal fluid (CSF) movement is disturbed. A blockage at the craniocervical junction can redirect pressure into the cord, much like a narrowed drain forcing fluid into the surrounding wall rather than allowing it to pass freely. As the cavity enlarges, it stretches and damages spinal cord tissue and the nerve fibres that cross through it. The most common association is Chiari I malformation, in which part of the cerebellar tonsils extends downward through the foramen magnum and interferes with CSF flow. Other causes include previous spinal cord trauma, a spinal cord tumour, arachnoiditis or scar tissue, and cases in which no cause is identified. The cause matters because treatment must restore flow or remove the obstruction when one is present; draining the cavity alone does not correct every underlying problem. The location of early damage explains the characteristic examination pattern. Crossing spinothalamic fibres near the centre of the cord carry pain and temperature information, so they are often injured before the dorsal-column pathways that carry...