gms | German Medical Science

Objective: Diffusion-weighted imaging (DTI) based tractography is used regularly in the planning of neurosurgical treatment of brain tumors. In contrast, the validity of DTI in spinal cord disorders is still controversial due to technical challenges. In the present study, DTI parameters were correlated to electrophysiological findings before and after microsurgical resection of intramedullary neoplasms of the human cervical spinal cord.

Method: Four patients (1 female, age 38±11 [mean±SD] years) scheduled for surgical treatment of intramedullary tumors of the upper cervical spinal cord were enrolled in this study. Patients underwent MR and electrophysiological examinations before and after surgery. A transverse-oriented single-shot electrocardiogram (ECG) triggered echo-planar imaging (EPI) sequence with monopolar spin-echo diffusion preparation was applied for highly resolved DTI of the spinal cord at 3 Tesla. Mean diffusivity (MD) and fractional anisotropy (FA) were analyzed. Total (TMCT) and peripheral motor conduction time (PMCT) were evaluated by motor-evoked potentials to the abductor digiti minimi (H-MEP) and tibialis anterior (F-MEP) muscles after transcranial magnetic stimulation (TMS) and electrical nerve root stimulation (ENRS), respectively. Total (TACT) and peripheral afferent conduction time (PACT) was determined by sensory-evoked potentials of the medial (H-SEP) and tibial nerve (F-SEP) derived on spinal and cortical level.

Results: FA values showed negative correlation with the TMCT to the foot and hand as well as with the TACT of the H-SEP. There was an invert relation between MD values and the TMCT to the foot and hand and the TACT of the H-SEP. There was no significant correlation between the peripheral conduction times (PMCT/PACT) with DTI metrics. Cortical amplitudes of H-MEPs, H-SEP and F-SEP showed a positive correlation to FA, but negative correlation with MD metrics. Noteably, F-MEP amplitudes after TMS showed an unexpected invert relation to DTI parameter indicating spinal hyperexcitability in patients with cervical spinal cord tumours. Spinal amplitudes of motor and afferent evoked-potential did not show any association to DTI metrics.

Conclusions: There is a good correlation of DTI metric in intramedullary neoplasms of the human cervical spine with electrophysiological parameter. Our findings validate the results of DTI-based tractography and show the feasibility of this technique in the neurosurgical treatment of intramedullary tumors of the upper cervical spine.