What is syringomyelia?

Syringomyelia is a disorder in which a fluid-filled cyst (called a syrinx) forms within the spinal cord. Over time, the syrinx can get bigger and can damage the spinal cord and compress and injure the nerve fibers that carry information to the brain and from the brain to the rest of the body

The syrinx may represent dilation of the central canal or a separate cavity within the spinal parenchyma and is usually located within the cervical or thoracic spine Syringomyelia is most associated with Chiari type 1 malformation but may also occur with spinal cord inflammation, infection, neoplasms, or trauma. 

Patients frequently have loss of pain/temperature sensation in the dermatomes corresponding to the site of spinal involvement (eg, "cape" distribution). This is due to disturbance of the crossing spinothalamic tracts (STTs) in the anterior white commissure.

In contrast, vibratory/proprioceptive sensation is typically intact due to preservation of the dorsal columns (ie, dissociated sensory loss).

Continued syrinx enlargement can encroach on the central aspect of the lateral corticospinal tracts (LCTs) (in which the upper extremity fibers are somatotopically arranged more centrally) and/or the anterior horn gray matter. This produces weakness that disproportionately affects the upper extremities compared with the lower extremities



https://www.webmd.com/brain/what-is-syringomyelia

https://www.neurosurgery.columbia.edu/patient-care/conditions/syringomyelia