New Classification of Spinal Lipoma : Its Clinical Importance and Future Perspective

Abstract

  Herein, we describe the details of the new classification of spinal lipomas based on the embryonic stage, placing special emphasis on its clinical importance and future perspectives.

  This new classification system classifies spinal lipomas into four types. Type 1 spinal lipomas develop during primary neurulation, and are typically diagnosed during infancy. Magnetic resonance imaging (MRI) generally shows a linear fusion line, and radical resection is feasible. Type 2 spinal lipomas involve junctional neurulations, and the border between the spinal cord and the lipoma is obscure and irregular. Myelodysplasia of the conus medullaris is commonly observed, and radical resection is not indicated. Type 3 spinal lipomas develop during the early phase of secondary neurulation. These present with no dorsal dural or soft tissue defects, while associated skin stigmata are either subtle or absent. Diagnosis can be delayed because of the lack of skin stigmata. Myelodysplasia of the conus medullaris is commonly observed and radical resection is not indicated. Type 4 spinal lipomas develop in the late phase of secondary neurulation and often present as filum lipomas associated with tiny lumbosacral dimples. Surgery for these lesions is straightforward.

  The clinical importance of the new classification system can be summarized as follows :

  1) Spinal lipomas were systematically classified based on the embryonic stage.

  2) Spinal lipomas develop not only during primary neurulation, but also during the junctional and secondary neurulation periods, as a continuous spectrum of embryonic development.

  3) Each type of spinal lipoma correlates well with clinical features, and the selection of the surgical procedure can be indicated by the lipoma type.

  This new classification is expected to open the door for future research. The natural history of spinal lipomas and their long-term prognosis can be more clearly revealed using the different types of spinal lipoma here. In addition, folic acid can be useful in reducing the prevalence of type 1 spinal lipomas as they develop during primary neurulation, similar to myelomeningocele.

  This new classification of spinal lipomas is theoretically and clinically practical. Further clinical research on spinal lipomas is expected based on this new classification system.