Assessment of spinal somatosensory systems with diffusion tensor imaging in syringomyelia.

OBJECTIVE: We tested the use of diffusion tensor imaging with three-dimensional fiber tracking (DTI-FT) for the assessment of spinal sensory tract lesions. We systematically examined the relationships between tract lesions quantified with DTI-FT, and somatosensory dysfunction assessed with quantitative sensory testing (QST) and laser evoked potentials (LEP), in patients with syringomyelia. METHODS: We studied 28 patients with cervical syringomyelia and thermosensory impairment of the hands, and 19 healthy volunteers. We performed a DTI-FT of the spinal cord focusing on the upper segment (C3-C4) of the syrinx. Three-dimensional DTI-FT parameters (i.e. fractional anisotropy (FA) and apparent diffusion coefficient (ADC)) of the full, anterior and posterior spinal cord were individually compared to QST (i.e. thermal detection thresholds) and LEP (i.e. amplitude, latency and spinothalamic tract (STT) conduction time) of the hands. RESULTS: Patients had a significantly lower FA, but not ADC, than healthy subjects. Mean FA of the full section of the spinal cord was related both to sensory deficits (i.e. increase of warm (rho = -0.63, p<0.010) and cold thresholds (rho = -0.72;p< 0.001 of the hands) and to changes in LEP parameters, in particular STT conduction time (rho = -0.75;p<0.010). Correlations between FA and the clinical and electrophysiological measurements were higher in the anterior area (where the STT is confined) than in the posterior area of the spinal cord. CONCLUSIONS: These data indicate that diffusion tensor imaging with 3D-fiber tracking is a new imaging method which is suitable for the objective and quantitative anatomical assessment of spinal somatosensory system dysfunction.