Friday, August 2, 2019
Cervical cord compression in adult thoracolumbar deformity patients
Lumbar and cervical degeneration frequently coexist as the pathophysiology and predisposing factors leading to degenerative changes in the different regions of the spine are likely similar. Patients undergoing major thoracolumbar deformity surgery are theoretically at increased risk of cervical spinal cord injury if they have cervical stenosis due to the long duration of these cases in which the neck may be positioned in extension and during which hypotension is common. Dr. Shimizu and the spine surgeons at Columbia were aware of the common concurrence of thoracolumbar deformity and cervical degeneration and began ordering pre-operative cervical MRIs on all adult patients undergoing major thoracolumbar deformity surgery (> 5 levels). They rated each level in the cervical spine using the Cord Compression index, which provides a 0-3 grading system. They classified patients with Grade 2 (loss of CSF around cord) and Grade 3 (clear cord compression) compression as having significant cord compression. Their cohort include 121 patients (82% female, average age 55, range 23-82), the majority (56%) of whom were diagnosed with adult idiopathic scoliosis. The group had relatively severe coronal deformity (average main thoracic curve 40 degrees, thoracolumbar or lumbar curve 45 degrees) with more mild sagittal imbalance (PI-LL mismatch 8.5 degrees, SVA 46 mm). They found that 41 (34%) patients had significant cervical cord compression. Of these 41 patients, 35 were asymptomatic with no or subtle exam findings, and 6 were clearly myelopathic. As a result of the surveillance for cervical pathology, four patients underwent cervical surgery prior to their thoracolumbar deformity procedure. Multivariate regression demonstrated that age, BMI, and increasing PI-LL mismatch were risk factors for cervical cord compression. In fact, 8/14 of patients in their 70s and 2/2 patients in their 80s had significant cervical cord compression.
This is a well-designed study that documents the relatively high prevalence of cervical cord compression in patients undergoing adult deformity surgery. Given the common pathophysiology leading to both cervical and thoracolumbar disease, the results are not surprising. The authors' definition of significant cord compression likely included many patients with effacement of the CSF without actual cord compression, and 32/41 had the more mild, Grade 2 findings. This does beg the question of what to do with a non-myelopathic patient planning to undergo major deformity surgery who is found to have significant cervical cord compression. Given that cervical surgery is generally not indicated for this patient if they were to present without thoracolumbar deformity, it seems most appropriate to proceed with the deformity operation using appropriate neuromonitoring techniques to ensure that positioning does not cause a problem with the cervical spinal cord. While the authors state that they obtain cervical MRIs on all of their thoracolumbar deformity patients undergoing surgery, this likely changes management rarely. The 4 patients who underwent cervical surgery prior to thoracolumbar deformity surgery were all myelopathic on clinical exam, suggesting that a thorough cervical history and physical in all thoracolumbar deformity patients might be a better, more cost-effective screening tool than an MRI on all deformity patients. This paper is a good reminder to evaluate the cervical spine in all patients with significant thoracolumbar disease.
Please read Dr. Shimizu's article in the August 1 issue. Does this motivate you to obtain cervical MRIs in your adult deformity patients? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor