THE EDITORIAL DEBATE: PROS AND CONS
|Year : 2016 | Volume
| Issue : 1 | Page : 19--22
Multilevel cervical myelopathy due to cervical spondylosis/ossification of posterior longitudinal ligament—A complex problem
Department of Neurosurgery, Madurai Medical College, Madurai, Tamil Nadu, India
Department of Neurosurgery, Madurai Medical College, Madurai, Tamil Nadu
|How to cite this article:|
Muthukumar N. Multilevel cervical myelopathy due to cervical spondylosis/ossification of posterior longitudinal ligament—A complex problem.Neurol India 2016;64:19-22
|How to cite this URL:|
Muthukumar N. Multilevel cervical myelopathy due to cervical spondylosis/ossification of posterior longitudinal ligament—A complex problem. Neurol India [serial online] 2016 [cited 2021 Oct 22 ];64:19-22
Available from: https://www.neurologyindia.com/text.asp?2016/64/1/19/173634
Cervical myelopathy due to multilevel cervical spondylosis (CSM) and/or ossification of the posterior longitudinal ligament (OPLL) is a commonly encountered clinical problem. CSM is the most common cause of acquired neurological disability in those over 50 years of age. The natural course of the disease without treatment is generally poor. However, with appropriate surgical treatment, the neurological deficits can be reversed or at least stabilized and steps can be taken to ensure that the surgical treatment remains cost-effective. Despite the widespread prevalence of cervical myelopathy, the choice of the appropriate surgical approach remains a matter of debate. It is unfortunate that despite the plethora of professional societies devoted to the care of spine, no definite guidelines have been provided to the practicing spine surgeons about the choice of approach for multilevel cervical myelopathy and, till date, the choice of approach depends to a large extent on the surgeon's preference. It is evident that this approach is manifestly wrong and a patient-specific and pathoanatomy-based approach is more reasonable.
In this issue of Neurology India, Gupta and Rajshekar have reported their experience with a three-level corpectomy for multilevel cervical myelopathy due to CSM/OPLL. The authors should be congratulated for their meticulous analysis and a good follow-up (mean follow-up of 5 years). As with any good study, this study raises as many questions as it answers. There are many take-home messages from this article as well as certain limitations, both of which should be addressed.
It is important to note that only 60% of the patients treated by Gupta and Rajshekhar had radiological follow up, and when the authors mentioned that they had a 90% fusion rate, this fusion rate applies to only 20 of the 33 patients treated. Graft-related complications were rare in this series and whether such excellent results with multilevel un-instrumented fusions can be replicated by other surgeons remains to be seen. As the authors themselves note in their discussion, in the literature, long segment fusions are associated with a higher incidence of graft-related complications.
Only four of the 33 patients had postoperative dysphagia despite having undergone a 3-level corpectomy. The incidence of postoperative dysphagia after anterior cervical spine surgery has been reported to vary between 5% and 69%. Another study has shown that the incidence of postoperative dysphagia is often underreported by surgeons in medical charts. In the present study by Gupta and Rajshekhar, two of the four patients with dysphagia had an increase in the prevertebral soft tissue shadow which resolved with the use of steroids. This raises two important questions: (1) Does the postoperative prevertebral soft tissue size correlate with the incidence and severity of dysphagia? and (2) can steroids be used routinely in patients undergoing anterior cervical procedures to minimize the incidence of postoperative dysphagia? Interesting findings are reported in the literature with regard to the above queries. Intuitively, an increased thickness of the prevertebral soft tissues should be associated with an increased incidence and severity of dysphagia. However, a recent study by Kepler et al., has shown that even though an increase in swelling of the prevertebral soft tissue is common after anterior cervical spine surgery, the width of the prevertebral soft tissue swelling did not correlate with postoperative dysphagia. It was also interesting to note that the soft tissue swelling often persists for 6 weeks by which time the symptoms of dysphagia have resolved to a great extent. This is another evidence, though counter-intuitive, to show that the degree of postoperative prevertebral soft tissue swelling does not correlate with the occurrence of dysphagia. Should we use steroids as a matter of routine in patients undergoing anterior cervical spine surgery to decrease the incidence of postoperative dysphagia? A recent prospective randomized study by Jeyamohan et al., has shown that the use of steroids significantly decreases the severity of dysphagia, airway difficulties, and the need for reintubation. However, graft fusion was delayed in the steroid-treated group. Therefore, short-term use of steroids in patients with moderate and severe dysphagia in the postoperative period appears to be a reasonable option with the caveat that bony fusion is more likely to be delayed. While using steroids for postoperative dysphagia, caution should also be exercised in situ ations where the patient is either suffering from diabetes mellitus or is a smoker. These patients are more likely to have a higher risk of nonunion.
Postoperative C5 Radiculopathy
Two of the 33 patients developed postoperative C5 radiculopathy. This is similar to the rates reported in the literature., Interestingly, both patients reported by Gupta and Rajshekhar improved during their stay in the hospital itself. This is contrary to my personal experience where improvement takes several weeks and is often incomplete (unpublished data). Similar to my personal experience, less than satisfactory outcomes were reported by Odate et al. In their study, 23 of 32 patients had residual weakness. In the index study, there was no mention about the presence of intramedullary signal changes in this group of patients as there have been suggestions that signal changes suggestive of anterior horn involvement might be the reason for the persistent postoperative C5 palsy. Another factor that should be discussed in the context of C5 palsy is the width of decompression. In the index study discussed, the width of the corpectomy was 16 mm. In an interesting study, Odate et al., have shown that when the corpectomy width is more than 15 mm, there is a statistically significant increase in the postoperative C5 palsy. They also pointed out that an asymmetric decompression was another risk factor with the chance of C5 palsy being more on the side of wider decompression. Future studies should analyze if restricting the width of the decompression to 15 mm will decrease the incidence of postoperative C5 palsy.
Intraoperative Cerebrospinal Fluid Leak
In the present study, the incidence of cerebrospinal fluid (CSF) leak was 15.2%. This is higher than the incidence of 6.3% seen following a corpectomy and uninstrumented fusion that was reported earlier by the same group for patients with OPLL. An analysis of their earlier publication  provides the explanation for this apparent discrepancy. In their previous study of 144 patients with OPLL who underwent a similar procedure, the rate of CSF leak was around 5% for 1- and 2-level corpectomies whereas it was 16.7% for 3-level corpectomies. In the present series with both OPLL and CSM patients, there is an overall incidence of 15.2%. This indicates that irrespective of the nature of the underlying pathology, whether it is OPLL or CSM, 3-level corpectomies are associated with higher rates of intra-operative CSF leaks. Even though all their patients improved without complications such as meningitis, this fact should be borne in mind by the surgeons and should be addressed during preoperative counselling of the patients. Since 57% of this study group harbored an OPLL, it might be interesting to know what percentage of these OPLL patients had a double-layer sign indicative of dural ossification, as this is certainly associated with a higher risk of dural laceration and intra-operative CSF leak. In my practice, a CT scan is routinely used in patients with OPLL irrespective of the thickness of the OPLL and both the presence/absence of dural ossification and the canal occupancy ratio have a bearing on the choice of approach (anterior versus posterior).
The functional outcomes reported by Gupta and Rajshekhar are in line with what has already been reported in the literature. However, the use of modified Japanese Orthopedic Association (mJOA) score along with Nurick's grading would have enhanced the overall value of this study as an Indian modification of the JOA score has been published. Certainly, Nurick's grade is much easier to apply in routine clinical practice. However, one of the limitations of Nurick's scoring system is that it is heavily weighted towards lower extremity functions with very little allowance for upper extremity and sphincteric functions. Interestingly, a previous study from the same institution advocated the use of both Nurick's scale and mJOA scale.
It is rare to find studies on cervical myelopathy with an average follow-up of more than 5 years such as the index study. Gupta and Rajshekhar had the unique opportunity to follow these patients for such long durations. Therefore, this study could have been embellished if they had addressed certain important issues such as the incidence of adjacent segment disease in their patients following the 3-level corpectomy. In a previous study from the same institution which analyzed 1- and 2-level corpectomy, the incidence of adjacent segment disease was 75% during a short-term follow-up of 17.5 months. It might be interesting to know the rates of adjacent segment disease in 3-level corpectomies with an average follow-up of 5 years. Theoretically, multilevel anterior cervical corpectomies should be associated with slightly higher incidence of vocal cord paresis. Surprisingly, there is no mention of vocal cord paresis in this series. In their earlier publications from the same institution, the role of intramedullary signal changes in cervical myelopathy was discussed elaborately., This is another factor that could have been analyzed in the context of the 3-level corpectomy performed in the study.
Is the Anterior Approach Superior to the Posterior Approach in Diseases of 3- or More Levels?
Even though the index study discussed does not per se compare anterior versus posterior approaches for cervical myelopathy, it might be pertinent to discuss this. Several recent studies have shown that there is no clear advantage of anterior or posterior approach over one another in the treatment of 3- or multi-level disease., A recent review by Lawrence et al., showed that improvements in JOA scores were similar with both the approaches, canal diameter increase was larger with the use of the posterior approach, the incidence of postoperative C5 palsy was similar with both the approaches, the dysphagia rates were lower with posterior surgery, and infection rates were lower with anterior surgery. One study by Liu et al., separately compared the outcomes of anterior and posterior approaches for CSM and OPLL. In this study, Liu et al., found that at the early stages after operation, the anterior approaches had better clinical outcomes but showed more complications than the posterior approaches for both CSM and OPLL. However, during the later stages of follow-up, there was no difference in outcome between the anterior and posterior approaches for patients with CSM and OPLL with canal occupancy of <60% whereas for OPLL patients with canal occupancy of >60%, anterior approaches have a better outcome. A recent AOSpine North America study of 264 CSM patients found that when patient and disease factors are well-matched, anterior and posterior approaches have equal efficacy in the treatment of patients with CSM.
Properly designed randomized control trials with long-term follow-up, which take into account all the patient-specific and pathoanatomical factors and co-morbidities, can answer this perplexing question of whether to adopt an anterior or a posterior approach for a multilevel disease. However, will such a study ever be conducted?
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