Hisanori Mihara*, Yasunori Tatara, Takanori Niimura and Yohei Ito
Background: About half a century ago, Crandall classified the pathology of cervical myelopathy into five types. Several further classification systems were subsequently proposed. However, many patients do not fit into any of the types described in these classification systems.
Methods: This study included 315 consecutive patients who were diagnosed with cervical myelopathy, underwent surgical treatment, and were followed up for at least two years. In each case, the motor and sensory functions of each extremity were evaluated utilizing the Grip and Release Test (GRT), the Triangle Step Test (TST), and the sensory score. Then, spinal cord cross-sections were assessed for damage, and the cases were classified into the following five types: Type I (anterior lesion), which involved dysfunction of a unilateral upper extremity; Type II (central lesion), which involved dysfunction of the bilateral upper extremities; Type III (posterior lesion), which involved lower extremity dysfunction with deep sensory disturbance; Type IV (hemilateral lesion), which involved unilateral palsy; and Type V (transverse lesion), which involved the spreading of neurological symptoms to all extremities. Comparisons of pre- and postoperative neurological status were performed among the five types.
Findings: All but two patients were successfully classified into the five types. The mean age at surgery was higher in Types III and V. As for the preoperative severity of myelopathy, the patients’ motor and sensory function scores decreased from Type I to Type V. Types I (67.0%) and II (65.6%) demonstrated significantly greater postoperative neurological improvement than Types III (42.5%) and V (50.8%), according to the Japanese Orthopaedic Association score recovery rate.
Conclusion: Based on our classification system, Types I and II of cervical myelopathy, in which the cord damage was mainly located in the grey matter, exhibited greater postoperative neurological improvement than other types involving long tract symptoms.