Syringomyelia is a disorder in which a cyst, called a syrinx, forms around the central canal of the spinal cord.
The cyst usually destroys the centre of the cord, and may expand into adjacent areas such as the ventral horns and lateral columns.
Each patient experiences a different combination of symptoms. 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.
Pain and temperature sensation are lost due to damage to the anterolateral system and spinothalamic tract.
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.
The motor consequences of the syrinx 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.