Syringomyelia refers to a cavitation of the cord characteristically originating in the central canal. The condition is frequently of congenital origin, however, it may result from defects in the vasculature, neoplasms, trauma, etc. Degeneration often occurs in the central canal of the cervical cord and progresses peripherally in an irregular fashion. Generally, the cavitation first affects the crossing spinothalamic fibers in the anterior white commissure producing segmental loss of pain and temperature sensation. As the cavitation extends it may involve varied structures depending on the direction of the expansion. It may expand to involve the anterior horn with segmental signs of lower motor neuron disease; if the intermediolateral cell column is involved there may localized autonomic effects. When syrinx proceeds dorsally it may affect the posterior white columns leading to loss of discriminatory touch and proprioception below the level of the cavity.
A Sample Case: A 30 year old man noticed a weakness of his right hand which was progressing and causing him problems serious enough to seek medical attention.
On examination he demonstrated bilateral weakness, atrophy, and fasciculations of the intrinsic muscles of his hands and shoulders. Upper motor neuron syndrome signs, i.e., weakness, hypertonia, hyperreflexia, positive Babinski, were evident in both lower extremities. Dermatomes C-2 through T-6 demonstrated bilateral loss of pain and temperature sensation. There was bilateral impairment of position and vibratory sense below the hips.
MRI investigation showed a central cavitation at C-2 through T-7 which expanded symmetrically in all directions. It involved the anterior white commissure (spinothalamic fibers) and included portions of the posterior white columns, lateral white funiculus, and anterior gray horns.
Weakness in the right hand was the major complaint but the neurologic exam demonstrated weakness, atrophy and fasciculation indicative of lower motor neuron disease, i.e., anterior horn cells, in both hands.
Though the patient had not noticed loss of pain sensation in his hands the loss could be demonstrated upon testing; apparently there was enough sparing of the crossing fibers of the spinothalamic tracts to make the effect less noticeable.
Though the patient did not complain of weakness of the lower extremity, there were upper motor neuron syndrome symptoms, e.g., hyperreflexia and Babinski sign, indicating some involvement of the lateral white funiculus containing the lateral corticospinal and lateral reticulospinal tracts.
The unrecognized loss of vibratory sensation from the lower extremity indicates some impact on the fasciculus gracilis.