Application of neurite orientation dispersion and density imaging or diffusion tensor imaging to quantify the severity of cervical spondylotic myelopathy and assess postoperative neurological recovery

Publication date: Available online 12 July 2017
Source:The Spine Journal
Author(s): Genki Okita, Tetsuro Ohba, Tomohiro Takamura, Shigeto Ebata, Ryo Ueda, Hiroshi Onishi, Hirotaka Haro, Masaaki Hori
Background Context.Surgical outcome and the severity of cervical spondylotic myelopathy (CSM) are unpredictable and cannot be estimated by conventional anatomical MRI. The utility of diffusion tensor imaging (DTI) to quantify the severity of CSM and assess postoperative neurological recovery has been investigated. However, whether conventional DTI should be applied in a clinical setting remains controversial. Neurite orientation dispersion and density imaging (NODDI) is a recently introduced model-based diffusion-weighted MRI technique that quantifies specific microstructural features related directly to neuronal morphology. However, there are as yet few clinical applications of NODDI reported. Indeed, there are no reports to indicate NODDI is useful for diagnosing CSM.Study Design.Retrospective cohort study using consecutive patients.Purpose.To evaluate the utility of NODDI and conventional DTI for detecting changes in spinal cord microstructure. In particular, to quantify the preoperative severity of CSM and assess postoperative neurological recovery from this myelopathy.Patient Sample.We included 27 consecutive patients with a nontraumatic cervical lesion from CSM who underwent laminoplasty at a single institution between April 2012 and April 2015. Patients underwent MRI before and approximately 2 weeks after surgery.Outcome Measures.In addition to conventional DTI metrics, we evaluated intracellular volume fraction (ICVF) and orientation dispersion index (ODI), which are metrics derived from NODDI. The 10-s grip and release test and the Japanese Orthopedic Association scoring system were used before and one year after surgery to assess neurological outcome.Methods.NODDI and conventional DTI values were measured at the C2-C3 intervertebral level (control value) and the most compressed levels (C3-C7 intervertebral levels) were measured. The changes of these values pre- and postoperative were demonstrated. Correlations between NODDI and conventional DTI values and clinical outcome were determined.Results.Preoperative fractional anisotropy was significantly correlated with the severity of neural damage, but not with postoperative neurological recovery. No significant correlation could be found between preoperative ICVF, ODI, apparent diffusion coefficient, and the severity of preoperative neurological dysfunction. Preoperative ICVF was most strongly correlated with the severity of neurological dysfunction and postoperative neurological recovery.Conclusion.Conventional DTI may be applied clinically to assess the severity of myelopathy. NODDI may be more valuable than conventional DTI to predict outcome following surgery in patients with CSM.



http://ift.tt/2sTGjxf