Rudolph D Schrot (Department of Neurological Surgery, University of California Davis, Sacramento, USA) and others report in the Journal of Neurosurgery: Spine that patients with cervical spondylolysis at higher levels have significantly greater preoperative headache pain than patients with the condition at lower levels. However, they state that there were no significant differences between patients with spondylolysis at higher levels and those with the condition at lower levels in the amount of postoperative headache relief—indicating that headache relief is not associated with the level of operation.
Schrot et al state that headache is commonly associated with lower cervical spondylolysis, and that anterior neck surgery is associated with a significant reduction in headache pain. However, they add that the mechanism for headache at these lower levels is unknown. “The trigeminocervical nucleus could theoretically extend further down in the cervical spinal cord than expected from anatomical studies. Therefore, the lower cervical roots may project to the trigeminocervical nucleus. Alternatively, kinesthetic impairment in the lower cervical spine could cause headache directly through the structures innervated by C1–3,” Schrot et al comment.
If spinal-mediated headache is a referred pain phenomenon, according to the investigators, then operations on more rostral intervertebral discs might result in greater pain relief. They add: “Alternatively, if kinesthetic improvements after cervical spine surgery bring about headache relief, then cervical arthroplasty might result in greater symptomatic benefit for headaches.” The aim of their study therefore was to compare headache relief in patients undergoing artificial disc replacement vs. those undergoing fusion, and also to compare the amount of headache relief of patients who were operated on at different levels.
Using data from the investigational device exemption (IDE) study of the Mobi-C (LDR) cervical disc replacement device, Schrot et al reviewed the outcomes of 260 patients (all with preoperative headache) who underwent single-level discectomy and arthroplasty (69%) with the Mobi-C or who underwent single-level anterior discectomy and fusion (ACDF). The authors report: “[Patients with affected areas at] higher levels (levels more proximal to the head) were associated with significantly greater preoperative pain. There was no difference, however, in degree of postoperative pain relief as a function of surgical level.”
They also found that the arthroplasty group had a 0.19 lower postoperative headache pain score than the fusion group, but this difference was not significant (p=0.07). The authors state these results indicate that spinal kinesthetics are “less likely” to be important in mediating headache relief because if they were, Schrot et al claim, cervical disc replacement would have been associated with a greater benefit compared with fusion—they add: “Alternative mechanisms for headache relief in cervical spondylosis must be sought.”
Further commenting on the study, author Kee Kim (chief, Spinal Neurosurgery, Department of Neurological Surgery, University of California, Davis, School of Medicine, Sacramento, USA) said: “Given that abnormal flow or blockage of spinal fluid can cause headaches, I believe the headache relief after anterior or posterior cervical decompression may be in part due to restoration of normal spinal fluid circulation. Regardless, I would like to stress that headache alone should not be the indication for operating on those patients.”