Syringomyelia is a disorder in which a cyst, called a syrinx, forms around the central canal of the spinal cord. This usually expands in all directions and destroys the centre of the cord, and may expand into adjacent areas such as the ventral horns and lateral columns.

The damage caused by the syrinx gives rise to pain, weakness, and stiffness in the back, shoulders, arms, or legs.

Other symptoms may include headaches and a loss of the ability to feel extremes of hot or cold, especially in the hands.

In most cases, the disorder is related to a congenital abnormality called a Chiari I malformation which occurs in the brain during foetal development.

The condition usually progresses very slowly, possibly over many years.

Syringomyelia may be precipitated by trauma, infection, bleeding or neoplasia. Symptoms may appear months or years after the trigger, and give rise to pain, weakness, and sensory impairment originating at the site of trauma.

Sudden exacerbations can occur and are thought to be caused by rupture of the syrinx because of raised venous pressure, as seen in sneezing or violent coughing.

Pain and temperature sensation are lost due to spinothalamic tract damage.

One side may be affected more than the other. Classically, the sensation loss is experienced in a shawl-like distribution over the arms, shoulders and upper body.

Patients may experience severe chronic pain, abnormal sensations and loss of sensation particularly in the hands in the case of a cervical syrinx.

Classically, syringomyelia spares the dorsal column/medial lemniscus of the spinal cord, leaving pressure, vibration, touch and proprioception intact in the upper extremities.

Light touch, vibration and position senses in the feet are affected as the syrinx enlarges into the dorsal columns.

Motor features

These begin to occur when the syrinx extends and damages the motoneurones of the ventral horn, causing a lower motoneurone lesion at that site, e.g. in the cervical cord. Muscle wasting and weakness usually begins in the hands and then affects the forearms and shoulders. Tendon reflexes may be lost as a result of loss of motoneurones.

Some patients experience paralysis or paresis below the syrinx temporarily or permanently, as a result of damage to the pyramidal (corticospinal) tract.

Respiratory - intercostal -muscles may be involved, and if the syrinx affects C4,5 the phrenic nerve may be involved causing paralysis of the diaphragm.

Autonomic features

A syrinx may also disrupt the autonomic nervous system, leading to abnormal body temperature or sweating, bowel, bladder or sexual functions.

This MRI of the neck shows the presence of a syrinx.