Effects of surgery on the sensory deficits of syringomyelia and predictors of outcome: a long term prospective study.

OBJECTIVE To quantify the effects of surgery on the thermal deficits of syringomyelia and assess the predictors for such effects. METHODS The subjects were 16 consecutive patients (12 men, 4 women; mean (SD) duration of sensory symptoms, 5.1 (4.5) years) presenting with the typical symptoms of syringomyelia related to Chiari I malformation or trauma, and requiring surgical treatment. They were evaluated before surgery, then at six months and two years. Sensory evaluation included determination of the extent of thermal deficits and quantitative assessment of thermal, mechanical, vibration detection, and pain thresholds. Neuropathic pain intensity was evaluated on visual analogue scales. Magnetic resonance imaging was done before and after surgery to measure syrinx dimensions. RESULTS The magnitude and extent of thermal deficits improved in a subgroup of patients and this was best predicted by the duration of sensory symptoms: patients operated on less than two years after the onset of their symptoms tended to improve, while those operated on later were stabilised or deteriorated slightly. The effect of surgery on thermal deficits was correlated with the duration of sensory symptoms. Surgery also affected vibration deficits in patients with the Chiari malformation, neuropathic pain on effort, and syrinx dimensions. CONCLUSIONS The duration of sensory deficits is the best predictive factor of the efficacy of surgery for the thermal symptoms of syringomyelia. Early surgery is required if these deficits are to be minimised.