Cervical spondylotic myelopathy has been reported as the most common cause of spinal cord dysfunction in individuals older than age fifty-five, although the rate of occurrence is blurred by the difficulty of making a precise and timely diagnosis. The symptoms that patients present with can be inconsistent and show high variability from patient to patient1-4.
Magnetic resonance imaging (MRI) has been a beneficial tool for evaluating anteroposterior sagittal diameter, the compression ratio, and the canal-occupying ratio5,6. According to numerous biomechanical and cadaveric studies, cervical flexion results in tension forces on the spinal cord and can cause ventral spinal cord compression against osteophytes and discs. In neck extension, the cervical cord shortens, and there is an increase in the cross-sectional area of the anteroposterior diameter of the spinal cord. In addition, the space available to the spinal cord is reduced as the ligamentum flavum folds inward7,8.
We report three cases of progressive myelopathy. The first patient had undergone a previous multilevel cervical laminectomy. Although an initial MRI with the neck in the neutral position showed no spinal cord compression, the patient subsequently underwent dynamic MRI with the neck in extension, which revealed flattening of the spinal cord by soft tissues buckling into the laminectomy defect. The second patient had undergone a previous cervical laminectomy and arthrodesis with lateral mass internal fixation. He presented with progressive myelopathy and exhibited cord flattening on extension MRI, similar to that seen in the first patient. The third patient presented with myelopathic symptoms, had undergone a prior multilevel laminectomy, and had been followed for a syrinx; a cervical MRI with the neck in extension revealed severe stenosis. All three patients were informed that data concerning their cases would be submitted for publication, and they all provided consent.
Case 1. A fifty-eight-year-old man presented following a rear-end motor vehicle collision with new symptoms of neck pain and myelopathy. The patient had undergone a previous C3-C6 laminectomy at an outside institution more than ten years prior to this presentation. Following the initial surgery, he had had a full recovery and had been completely asymptomatic prior to this accident. A cervical MRI with the neck in the neutral position (Fig. 1-A) revealed a patent central spinal canal; however, there was evidence of myelomalacia with increased intensity of the signal within the spinal cord at the C4 and C5 levels on the T2-weighted MRI sequences. The patient had sensory changes as well as bilateral 4/5 intrinsic weakness in finger abduction and thumb abduction. He was experiencing loss of dexterity, increased neck pain, and loss of balance (particularly while the neck was extended), consistent with cervical myelopathy. The cervical MRI scan was repeated with the neck in extension (Fig. 1-B). The patient had severe stenosis and complete obliteration of the normal cerebrospinal fluid signal on the extension MRI. The severe stenosis extended from C3 to C4 through the C5 to C6 levels, secondary to severe infolding of the posterior muscles and soft tissues into the spinal canal during extension.
The patient underwent a posterior instrumented arthrodesis from C3 to T2, with removal of scar tissue from the dorsal aspect of the dura and placement of cross-links. The cross-links were utilized to form a protective barrier over the dura to prevent infolding of soft tissues. One and one-half years after surgery, anteroposterior and lateral view radiographs of the cervical spine showed the instrumentation in a satisfactory position, with no lucency surrounding the instrumentation. The patient is still being followed regularly for residual myelopathic symptoms; however, these have not progressed since the last surgery.
Case 2. A fifty-six-year-old man presented to our clinic with increasing neck pain, bilateral arm pain, and right shoulder pain. The patient noted progressive pain, loss of balance, and limb ataxia over a period of five months, all exacerbated by neck extension. The deep tendon reflex in the left biceps was hyperreflexic. Motor strength was 5 of 5 in the bilateral upper extremities, and he had a negative Hoffmann sign. He had a history of myelopathy that had been first diagnosed after rolling a vehicle two years earlier. Two months later, he had undergone a cervical laminectomy from C3 to C6, with lateral mass internal fixation and fusion from C3 to C7. At that time, the patient had no abnormal symptoms of pain, but he did have some residual neurological symptoms following the surgery. These symptoms had remained stable until the patient presented to us with increasing pain and progression of cervical myelopathic symptoms two years postoperatively. He underwent a cervical MRI scan with the neck in the neutral position (Fig. 2-A). This scan showed no signs of cord compression, but increased spinal cord signal and worsened spinal cord myelomalacia were evident when compared with the initial MRI that had been performed two years earlier. Because of the patient’s history and exacerbation of symptoms with neck extension, an MRI with the neck in extension was obtained (Fig. 2-B); it revealed severe cervical stenosis at C5-C6. The spinal canal was free of central canal stenosis in both the neutral and flexed positions. In contrast, extension compressed the anteroposterior diameter of the cord to a severely flattened 5 mm. Despite the prior fusion, the soft tissues in the back of the neck appeared to be pushed into the spinal canal by the occiput. This suggested the possibility of trauma to the spinal cord with normal repetitive extension motion. Revision surgery was discussed and is being considered, but has not yet been performed.
Case 3. A fifty-eight-year-old man, who had undergone a previous posterior cervical laminectomy from C3 to C7 more than ten years ago presented to our clinic with loss of dexterity, chronic cervical pain, and pain in the left arm that followed a C7-C8 radicular pattern. Initially after the first surgery, the pain in the neck and left arm had resolved, but it had returned one year postoperatively. He subsequently transferred his care and continued with routine monitoring and physical examinations every six to twelve months. Over the past two years, he has had a progressive mild loss of dexterity and increased clumsiness. At the most recent follow-up, he had a positive Hoffmann sign in both upper extremities and mild hyperreflexia in the biceps bilaterally. He had a negative Spurling test. He demonstrated 4/5 intrinsic hand-muscle weakness bilaterally.
The patient underwent a cervical MRI scan with the neck in the neutral position (Fig. 3-A), followed by an MRI with the neck in extension (Fig. 3-B). The MRI in the neutral position revealed a syrinx from C4 to C7, but no substantial stenosis. Review of prior scans showed that the syrinx was chronic and unchanged. The cervical MRI with the neck in extension revealed severe cervical stenosis from C5 to C6. The patient will be returning to discuss additional treatment options.
To our knowledge, this case series is the first documentation of use of a dynamic cervical MRI scan to reveal severe stenosis in patients that have undergone prior posterior cervical laminectomy. MRI scans are routinely completed with the neck in a neutral position. Our cases document the marked differences seen between MRIs with the neck in a neutral position compared with those with the neck in extension. The former technique revealed minimal or no stenosis, while the latter revealed severe central stenosis with cord compression. Therefore, a dynamic MRI scan with the neck in extension should be considered when a patient who has previously undergone a laminectomy or a laminectomy with fusion presents with either new or progressive myelopathic symptoms.
Dynamic MRI studies are not obtained on a routine basis. They are time-consuming and add to the cost of the evaluation. In addition, some patients with neck pain are unable to tolerate the extremes of motion. Our three patients were placed on a wedge (approximately 5-in high) in order to flex the head; then, the same wedge was placed under the shoulders to extend the neck. The image quality may have been somewhat degraded because the patient was placed farther from the coil; however, the images were adequate to discern gross compression of the cord.
In conclusion, we highlight the importance of dynamic MRI imaging of the cervical spine in patients who have had a prior cervical laminectomy and have persistent or new-onset myelopathy. Because the osseous roof of the posterior portion of the spine has been resected, soft tissues may compress the exposed cord, as seen in our three cases. Our results suggest that when postlaminectomy patients present with progressive myelopathy despite normal alignment, an MRI with the neck in extension may provide additional diagnostic information for the evaluation of cervical myelopathy. Furthermore, these cases highlight a potential negative aspect of laminectomy, with or without fusion, as a treatment for myelopathy. We recognize that each of these cases presented somewhat differently and that this is a very limited sample size; however, we are not attempting to answer why this occurs, but simply share our experiences and illuminate another type of diagnostic study that may help others make a diagnosis in difficult cases. Additional studies into the mechanism of compression following cervical laminectomy, as well as studies that determine whether similar compression occurs in more patients, are needed.
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Disclosure: One or more of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of an aspect of this work. In addition, one or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.