Surgical Decisions for Cervical Spondylotic Myelopathy
Originally authored by: Sait Naderi, M.D., Edward C. Benzel, M.D., and Nevan G. Baldwin, M.D
Department of Neurosurgery, Marmara University, School of Medicine, Istanbul, Turkey; and Division of Neurosurgery, University of New Mexico, School of Medicine, Albuquerque, New Mexico
INTRODUCTION
Cervical spondylotic myelopathy can produce a variety of clinical signs and symptoms secondary to neural compromise and biomechanical involvement of the spine. The surgical treatment of cervical spondylotic myelopathy remains a controversial issue after many years of study, evolution, and refinement. Several ventral, dorsal, or combined approaches have been defined. The complications associated with ventral approaches and the concerns about kyphosis following dorsal approaches led to the development of a variety of laminoplasty procedures. This paper reviews the biomechanical basis of cervical spondylotic myelopathy and its effect on choosing the appropriate surgical approach.
Cervical spondylotic myelopathy (CSM) occurs secondary to cervical spondylosis and is characterized by degeneration of the cervical intervertebral discs, with subsequent changes in the bones and soft tissues. Cervical spondylotic myelopathy often has an accelerated pattern of progression,[44] and results in three clinical manifestations: 1) myelopathy; 2) radiculopathy; and 3) myeloradiculopathy. The rational for this categorization scheme is based on the differing clinical manifestations (that is, myelopathy vs. radiculopathy) and surgical approaches (that is, decompression of the spinal cord vs. decompression of the nerve root) associated with each. Many surgical approaches have been proposed for patients with CSM; however, there are no standard methods for determining which is preferable. These approaches include: 1) laminectomy, with or without fusion; 2) laminoplasty; 3) medial (central) corpectomy with grafting, with or without fusion; and 4) ventral discectomy.
These multiple surgical options raise many questions regarding the decision-making process. The following pages address these questions by outlining the surgical component of the decision-making process.
Coronal Bowstring Effect
It has been suggested that the spinal cord can also be tethered in the coronal plane.[8,39] This coronal plane tethering (coronal bowstring effect) is secondary to the ventral tethering of the spinal cord by the nerve roots or dentate ligaments (Fig. 5 upper left). A laminectomy is often ineffective in relieving spinal cord distortion when this occurs (Fig. 5 upper right). A ventral decompressive procedure or a laminectomy plus dentate ligament section (DLS) (Fig. 5 lower) may alternatively relieve the spinal cord distortion in this type
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