Cervical Spondylotic Myelopathy (CSM): Nothing is easy!

CSM_1Although CSM is a frequent cause of myelopathy, its natural history is not clear, the clinical and radiological diagnosis might be particularly difficult and approaches to treatments are not standardized nor based on evidence medicine.
CSM is a degenerative condition of the cervical spine (spondylosis, disk herniation, spur formation, degenerative changes of facet joints, longitudinal ligaments and ligamentum flavum) leading to narrowing of the spinal canal (AP diameter < 13 mm), and to myelopathy and radiculopathy.
First symptoms are chronic suboccipital and cervical pain and decreased neck mobility but patients come generally to medical examination when they manifest weakness and paresthesia of arms and gait difficulties. In typical cases, the neurologist appreciates, together with reduced cervical motility, the presence of radicular signs of the superior limbs and corticospinal signs of the inferior limbs.
It should be never forgotten that false-positive and false-negative MRI results occur frequently in patients with radiculopathy and that therefore clinical findings about root involvement are fundamental when evaluating for surgery. Furthermore and not rarely patients have tandem spinal stenosis (simultaneous cervical and lumbar stenosis). Thus, complete neurological examination is determinant.
MRI examination is needed for diagnosis as the MRI images might show both spinal canal stenosis and signs of myelopathy. MRI diffusion tensor imaging (DTI) could be also useful.
However, in doubtful cases it is important to remember that, there is also the contribution of dynamic factors such as the effect of movements of the cervical spine on the spinal cord, and of vascular factors (spinal artery deformation and compression with resulting spine ischemia and hypoxia). Thus, it would be also important, for therapeutic decisions, to include, besides structural factors, the presence of cervical spine instability. Flexion-extension Rx views may detect cervical instability. Even when the diagnosis of CSM is done, but the disease is mild, it is not clear what it is the correct time for surgery as the deterioration rate remains unknown (deterioration is probably rare) and there are no radiological features able to predict the outcome (except probably for large and extended MRI T2 medullary hyperintensities). However, when radiological and clinical features are both significant but the patient is too invalidated by the condition, it would be probably too late for surgery. However, the main goal of surgery should be to avoid the progression of the disease and, therefore, there should be objective signs of myelopathy with clnical, MRI and evoked potentials tests.
Somatosensory and motor evoked potential could be useful to find signs of medullary involvement in doubtful cases.
Important elements to favor surgery are age < 75, the clinical severity and speed of progression of neurological symptoms and signs. Clinical severity is better evaluated with the aid of the modified Japanese Orthopedic Association (mJOA) scoring system. Surgical intervention is considered for score > 12 or >16. A favorable outcome (confirming that surgery was the best option) would be do demonstrate, after surgery, the improvement of evoked potential in comparison to the condition before surgery.
Surgical approach could be extremely varied depending of the site(s) of stenosis and associated degenerative lesions of disks and articulations. There would not be substantial differences of outcome between anterior and posterior approaches. Anterior approaches include: discectomy without or with bone graft, cervical instrumentation. Posterior approaches include decompressive laminectomy and foraminotomy, hemilaminectomy and laminoplasty.
Perioperative and delayed complications (among which, dysphagia, infections and other medical problems but also worsening of myelopathy) are not rare, especially in older patients. The use of combined anterior-posterior procedures show the higher risks of complications. Pre-surgery evaluation should include also neurologists and internal medicine specialists.
Probably most cases of mild or moderate CSM will not deteriorate or require surgery if the patient follow a strict conservative treatment consisting of cervical exercises with physical therapists, postural learning with occupational therapists, using collar in case of pain exacerbation, avoiding risky activities, avoiding cervical manipulations and prolonged flexion of the neck. However, for these patients, the neurological survey should be accurate and timed.

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