A syrinx is a fluid-filled cavity that develops in the spinal cord (called syringomyelia), in the brain stem (called syringobulbia), or in both.
Syrinxes are rare. In about half of the people who have a syrinx, it is present at birth, and then for poorly understood reasons, it enlarges during the teen or young adult years. Often, children who have a syrinx at birth also have other structural abnormalities of the brain, spinal cord, or junction between the skull and spine. Usually, syrinxes that develop later in life are due to injuries or tumors. About 30% of tumors that originate in the spinal cord eventually produce a syrinx.
Syrinxes that grow in the spinal cord press on it from within. They tend to first affect nerve fibers that carry information about pain and temperature from the body to the brain. Later, they affect fibers that carry signals from the brain to stimulate muscle movement. Syrinxes can occur anywhere along the length of the spinal cord. But they often begin in the neck and may extend downward to affect the entire cord. Syrinxes that extend into or begin in the lower part of the brain stem may compress pathways of the spinal cord and cranial nerves (which lead directly from the brain to other parts of the head and neck).
Symptoms usually begin subtly between adolescence and about age 45.
Syrinxes in the neck often make people less sensitive to pain and temperature, particularly in the arms, upper back, lower neck, and hands. Thus, cuts and burns on the arms and hands are common. People may not recognize this decreased sensitivity for years. As a syrinx expands and lengthens, it can cause weakness and wasting (atrophy) of muscles, usually beginning in the hands. Later, the syrinx causes weakness and spasms in the legs. Symptoms may be more severe on one side of the body.
Syrinxes in the brain stem can cause vertigo, nystagmus (rapid movement of the eyes in one direction followed by a slower drift back to the original position), loss of sensation in the face (on one or both sides), loss of taste, difficulty speaking, hoarseness, and difficulty swallowing. Muscles of the tongue may weaken and waste away.
Doctors may suspect a syrinx in a young child or teenager who has typical symptoms.
Magnetic resonance imaging (MRI) of the entire spinal cord and brain is done after paramagnetic contrast agent, such as gadolinium, is injected. Gadolinium outlines the syrinx (and tumor if present), helping doctors identify it.
A neurosurgeon may make a hole in a syrinx to drain it and prevent it from expanding, but surgery does not always correct the problem. Even if the syrinx is drained, the nervous system may already be damaged irreversibly. Symptoms may not be relieved, or the syrinx may recur.
Disorders that contributed to or caused the syrinx (such as structural abnormalities or spinal tumors) are corrected when possible.
Last full review/revision March 2013 by Michael Rubin, MDCM