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

OBJECTIVE The use of diffusion tensor imaging with three-dimensional fibre tracking (DTI-FT) was tested for the assessment of spinal sensory tract lesions. The relationships between tract lesions quantified with DTI-FT were systematically examined, and somatosensory dysfunction was assessed with quantitative sensory testing (QST) and laser-evoked potentials (LEP), in patients with syringomyelia. METHODS 28 patients with cervical syringomyelia and thermosensory impairment of the hands, and 19 healthy volunteers, were studied. A DTI-FT of the spinal cord was performed, focusing on the upper segment (C3-C4) of the syrinx. Three-dimensional DTI-FT parameters (fractional anisotropy (FA) and apparent diffusion coefficient (ADC)) of the full, anterior and posterior spinal cord were individually compared with QST (thermal detection thresholds) and LEP (amplitude, latency and spinothalamic tract (STT) conduction time) of the hands. RESULTS Patients had a significantly lower FA, but not ADC, than healthy subjects. The mean FA of the full section of the spinal cord was correlated both to sensory deficits (ie, increase in 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 measures were higher in the anterior area (where the spinothalamic tracts are located) than in the posterior area of the spinal cord. CONCLUSIONS The data indicate that diffusion tensor imaging with 3D-fibre tracking is a new imaging method suitable for the objective and quantitative anatomical assessment of spinal somatosensory system dysfunction.