Electrophysiological Evaluation of Syringomyelia

Since magnetic resonance imaging is able to detect small syrinx cavities in patients, it is important to be able to determine the presence and degree of deficits caused by the syrinx. Whether or not to proceed with surgery can be a difficult decision. The authors sought to determine what electrophysiological testing could be used to better evaluate the degree of neurological deficits in syringomyelia. The authors studied 37 patients with known syringomyelia, and 28 healthy controls.

Symptoms among the study subjects included protopathic pain, hypesthesia, spinal ataxia, paresis, headaches, autonomic dysfunction, secondary scoliosis, and swallowing difficulties. Pain and change in sensation are first recognized with syrinx. Neurological deficits are usually slower in onset.

Somatosensory evoked potential (SSEP) and motor evoked potential (MEP) recordings were done on all subjects. This testing monitors nerve fiber integrity of the corticospinal tract. The authors also evaluated silent period testing which evaluates integrity of the spinothalamic tract fibers. The spinothalamic tract fibers lie closer to the inside of the neural tube. This is the area where syringomyelia are found.

The silent period is evaluated by measuring the electrical activity of slow conducting larger nerve fibers after repeated cutaneous stimulation of small sensory fibers. Early onset, as well as long duration of the silent period was considered to be a physiological change seen in the population of patients with syringomyelia.

The authors concluded that silent periods were more sensitive than SSEPs and MEPs in detecting abnormalities in the spine due to syringomyelia. This could be helpful in making the decision for surgery.