Reconsidering the tectorial membrane: a morphological study

Background: Published descriptions of the tectorial membrane have been inconsistent. Descriptions vary from a simple ligamentous band extending between the axis and occiput to a more complex layered structure composed of bands of fibers. The purpose of this study was to examine and document the macrostructure of the tectorial membrane. Materials and Methods: The tectorial membrane was examined by fine dissection in 11 formalin-fixed human adult cadavers. Detailed descriptions of the macrostructure and attachments were recorded. Results: Each tectorial membrane examined consisted of two distinct layers. The superficial layer was composed variably of three or four bands. Its fibers extend caudally over multiple spinal levels, becoming continuous with the posterior longitudinal ligament. The deeper layer routinely consisted of three bands, each being firmly adherent to the posterior aspect of the body of the second cervical vertebra. Attachments of fibers from both layers extended beyond the foramen magnum to create a semicircular attachment onto the base of the skull. Conclusions: The tectorial membrane has a more complex structure than has been described to date in standard anatomical texts. The existence of a layered and banded composition may have implications for understanding its function and for the clinical assessment of this structure.