Cervical Spondylotic Myelopathy
Cervical Spondylotic Myelopathy or CSM is a condition in which the spinal cord is compressed or pinched in the neck or the cervical spine due to the aging process. The cervical spondylotic myelopathy happens due to the degeneration or wear and tear of the cervical spine due to their aging process. This can happen at one or multiple levels.
Patients with congenital stenosis of their cervical spine may be predisposed to this condition. These patients have a smaller diameter of the spinal canal since birth. The immediate effects of CSM may be precipitated by a subtle trauma overlying cervical stenosis and aging process. As opposed to cervical radiculopathy in which the patient has tingling, numbness or weakness of a specific nerve root presenting in the upper extremity, CSM can present with involvement of either one or to all four extremities in the form of sensory deficit and weakness with or without the involvement of gait, bowel or bladder with tingling and numbness all over the body or presenting with electric shock-like sensations going down the body. These patients may even present with inability to ambulate without aid or support. Subtle findings may be an imbalance or subclinical retention of urine.
Causes of Cervical Spondylotic Myelopathy:
CSM is essentially caused due to the aging process leading to wear and tear of the cervical spine. The presentation may be more profound or early in patients with congenital cervical stenosis. The wear and tear lead to degeneration of the disc space with protrusion of the disc towards the spinal cord. At the same time, the degeneration will lead to thickening of the ligament of the back of the spine cord called the ligamentum flavum which also contributes to the compression or squeezing of the spinal cord in the neck. This compression of the cord can cause a direct effect over the spinal cord as well as have an indirect effect by decreasing the blood supply to the nerves.
Presentation Signs And Symptoms of Cervical Spondylotic Myelopathy:
The patients with Cervical Spondylotic Myelopathy patients may or may not have neck pain. They may present with varied signs and symptoms involving either extremities, bowel or bladder function, or gait abnormalities. These patients may also have a loss of dexterity of their hands or an imbalance of their posture. On examination by a physician, these patients may elicit inability to walk in a straight line, numbness in specific dermatomes, increased tone of the muscles either upper or lower extremities or spasticity, weakness of specific muscle groups specially hand grip and presentation of electric shock-like sensation or deep flexion of the neck which is also known as the L’hermitte sign. These patients can present with specific presentations like Central cord syndrome, Brown Sequard Syndrome, Anterior Cord Syndrome, partial or complete spinal cord injury, etc.
Diagnosis of Cervical Spondylotic Myelopathy:
After a thorough history and physical examination, an initial X rays may help us know about the degenerative changes in the cervical spine as well as look for evidence of fracture, subluxation, or dislocations. Patients will usually require advanced imaging to confirm the diagnosis as well as to know the pathology and exact level or levels involved. Magnetic Resonance Imaging (MRI) helps to look at the soft tissue, disc, ligaments, etc. and is the investigation of choice in these patients. Computed Tomography (CT Scan) is helpful in understanding the bony anatomy of the spine and may also be needed. In patients who are not able to undergo MRI (presence of a pacemaker, aneurysmal clips, etc.) may need to undergo myelography. Electromyography and urinary bladder studies may be helpful in milder or subtle patients to understand the severity of disease and to help decide the best course of treatment for the patient.
Treatment Options of Cervical Spondylotic Myelopathy:
The patients with mild and early presentations can be treated conservatively and followed closely for the development of any worsening of the symptoms. These patients can be followed by a spine surgeon or a neurologist. Some medications can be helpful in the symptoms. At the same time, physical therapy can also help in strengthening muscles, balance as well as keeping the neck movement at an optimum level. The course of CSM is that of gradual deterioration in most patients but there are patients who can stay stable for a long time. These patients may have sudden rapid deterioration in presence of subtle trauma or even without that. The patients with severe CSM present with weakness, involvement of hand dexterity, involvement of gait, bowel, bladder, spasticity or increased tone of muscles, and usually need surgical treatment in the form of decompression of the cervical spine. The decompression of the cervical spine can be performed from the front or the back depending on the location of the stenosis and the configuration of the neck. The patients would usually require to undergo fusion surgery along with decompression to take care of the instability of the spine following the decompression surgery.
Anterior Cervical Discectomy / Corpectomy and Fusion
Patients who have compression from the front and have a kyphotic (forward hunching) posture of the neck may require surgery from the front. Surgery usually involves discectomy as one or multiple levels or removal of the whole body of the cervical vertebrae (corpectomy) with its disc. Preoperative or operative instability of the cervical spine will require insertion of cage/graft and fixation of the cervical spine with plate.
The image shows the plate used for anterior cervical decompression and fusion surgery. The plate is fixed on the vertebrae from the front and a cage filled with bone graft is inserted in the space of intervertebral disc. The fusion provides stability to the segment and alleviates the symptoms of cervical spondylitic myelopathy from the accompanied decompression.
Posterior Cervical Decompression and fusion
The patient who has profound compression from the back and have a good lordotic posture may need decompression from the back. This decompression usually involve removal of the posterior part of the cervical vertebrae called the lamina along with insertion of screws and fixation of rods to allow fusion to prevent future complications of laminectomy as well as take care of instability. Occasionally patients may require both front and back surgery.
Occasionally, these patients may be good candidate for non-fusion surgery in the form of laminoplasty. In this surgery, the posterior part of the cervical vertebrae called the lamina are cut on one side and hinged on the other side after weakening it, to crank open the space for the spinal cord. The open portion is fixed with small plates at multiple levels. These patients are shown to retain good range of motion as compared to patients who undergo fusion surgery.
Prognosis of Cervical Spondylotic Myelopathy:
The patients with mild involvement can be treat it conservatively (without surgery) but need regular follow up and constant supervision under the care of a spine surgeon. These patients may have a stable period with slow and gradual deterioration. Occasionally patients may do very well with conservative treatment. Patients who do not show progressions and are treated early in the process have fair to good prognosis. They usually recover near to the complete functions as well as become symptom free. The patients who presents with severe symptoms or rapid deterioration have poorer prognosis and may not be able to recover full functions and may have residual weakness, spasticity, involvement of gait, bowel or bladder and hand dexterity. It may take months and years to recover and rehabilitate for CSM.
Risks of Cervical Spondylotic Myelopathy Surgery:
The patients who undergo surgery for CSM have usual risks of orthopedic surgery which include infection, bleeding, failure of implants, need for repeat surgery. There is a risk of breakdown of adjacent segments with need for extension of the fusion by another surgery. The patients also have risks for injury to the nerves or spinal cord leading to temporary or permanent deterioration of functions, inability to recover completely and regain full functions. Surgery of cervical spine also carries a risk of deterioration of neurological status which may also lead to involvement of respiratory functions needing treatment in the form of intubation and ICU support and even death. As with any spine surgery, the patients are also at risk of blindness, stroke, cardiac events, paralysis or death. The patient can also have secondary complications to their impaired neurological status like bed sores, lung problems like atelectasis and pneumonia, blood clots or deep vein thrombosis, pulmonary embolism, urosepsis and even death.