Sensitivity disorders and neuropathic pain related to syringomyelia. A prospective study

The present prospective study aimed to perform quantitative sensory testing (QST) in patients with painful or painless syringomyelia before and after surgical treatment of their syrinx (at 3 and 9 months). Eighteen consecutiv e patients with cervical or dorso-lumbar syringomyelia completed the study and 9 underwent surgery. Twelve patients had central neuropathic pain (of w hom 6 were followed up). Spontaneous pain and brush-evoked allodynia were a ssessed. Von Frey hairs, vibrameter and a thermotest device were wed to det ermine the mechanical; vibratory-, thermal-detection thresholds, and the me chanical and thermal pain thresholds. Results showed evidence of deficits i n temperature and pain sensibility in 17 cases, often associated with defic its in vibration and touch sensitivity (11 cases). Magnetic resonance scan, including axial images, demonstrated good correlation between paramedian e xtension of the syrinx and the laterality of thermal deficits. Somatosensor y evoked potentials (11 patients) were abnormal in 9 cases at level, and sh owed good correlation with deficits in vibration. The magnitude of the ther mal and tactile deficit was similar between areas of spontaneous pain and a djacent non painful areas. Surgery induced a significant decrease of tactil e deficits, and to a lesser extent, of thermal deficits. Effects on neuropa thic pain were positive in 3 patients (total disappearance of pain) and neg ligeable or negative in 3 patients, despite collapse of the syrinx (in 2 ca ses). These results confirm that QST are useful in clinical practice to qua ntify the clinical results of surgery in patients with syringomyelia, and a llow some hypotheses about the mechanisms of neuropathic pain in these pati ents.