One or more cavities (syrinx) are present within the spinal cord. Frequent association with Arnold-Chiari Malformation is reported. Characteristic pain and sensory disturbances are seen.
Prevalence is 2 to 8/100,000 in general population.
Familial cases described. It has also been reported after traumatic injury (acquired disorder).
Congenital syringomyelia is divided into two forms. The embryonic form is an abnormal dilatation of the central canal of the spinal cord and a gap in the posterior vertebral arches, hence an open neural tube defect. The fetal form has an intact vertebral column and is a closed neural tube defect. Secondary syringomyelia is characterized by cavitations and gliosis of the spinal cord (usually cervical or thoracic), the medulla, or both. An obstacle to cerebrospinal fluid circulation in the fourth ventricle toward the subarachnoid space has been suggested to explain the syndrome. It seems similar to a craniocervical junction malformation such as Chiari Type I and the Arnold-Chiari, which is associated in 84% of cases (intramedullary tumors and hydrocephalus have been also observed). The cavity often expands during adolescence or the young adult years.
Clinical (back pain; headaches; stiffness or weakness of shoulders, arms, or legs; loss of the ability to feel extremes of hot or cold). Radiography, CT scan, and particularly MRI make diagnosis.
Onset most commonly occurs between the ages of 25 and 40 years, but it can be earlier. First sign is usually paresthesias in the upper limbs; then loss of pain and temperature sensation in a characteristic distribution, usually “suspended,” involving arms and trunk but not legs (because of lesion to the posterior horns and the fascicle of Lissauer sensory fibers). The progression is very slow. Other clinical features can be observed that involve neurological function: autonomic pathways such as Horner Syndrome, skin trophic changes, neurogenic bladder, reduced or absent reflex in arms, and bilateral Babinski signs. Spastic paraparesis can occur. Scoliosis is frequent. Treatment is either with surgery in order to arrest or slow progression of syrinx, if minor neurological signs only analgesia is the principle treatment.
Precautions before anesthesia
Evaluate neurological function with a precise clinical examination. Locate intramedullary cysts (MRI).
Careful positioning is needed, particularly in the case of an association with Arnold-Chiari Malformation. Perimedullar anesthesia should be avoided and is contraindicated at the level of the cyst because of the size diminution of epidural space but have been described. Somatosensory evoked potential monitoring can be difficult in a case of scoliosis surgery. Avoid increases of intracranial pressure during anesthesia.