Don't Rely on Signs of Cord Compression to Make the Diagnosis
Cervical myelopathy doesn't always present with obvious signs and symptoms. Sometimes people have this condition and don't even know it. Cervical myelopathy is a degenerative condition that occurs with aging. Adults affected most often are 50 years old and older. The term myelopathy refers to any problem that affects the spinal cord, but especially compression of the spinal cord. Cervical tells us the area affected is the cervical spine (neck region).
There are several reasons why cord compression develops. Sometimes the posterior longitudinal ligament (PLL) along the back of the spine thickens and hardens. Without its normal flexibility, it can buckle and put pressure on the cord. Bone spurs, disc herniation, and spondylolysis can also apply pressure to the spinal cord. Spondylolysis refers to a defect (usually a fracture) in the par interarticularis, a supportive column of bone in the vertebra.
The diagnosis of cervical myelopathy is a clinical diagnosis. That means in order to make the diagnosis, the physician relies on the patient's history, specific tests performed during the physical exam, and the results of advanced imaging studies. There isn't a blood test or other simple way to identify this condition.
Patients with cervical myelopathy can experience a wide range of signs and symptoms. There can be difficulty walking, using the hands, bowel and bladder function, or even wasting of the muscles of the hands. When the muscles are affected, motor function, coordination, and muscle mass can change. Sometimes there is also a loss of normal sensation with numbness and tingling of the fingers and toes. In addition, there can be debilitating pain.
In this study, those clinical tests are the focus. The authors wanted to see how often those tests are positive in people with and without apparent cervical myelopathy. The main clinical tests used to look for cervical myelopathy include the Hoffman sign, inverted brachioradialis reflex, clonus, and Babinski. These are called provocative tests because the examiner applies some type of stimulus to the patient to evoke an abnormal response.
The Hoffmann sign is done by quickly snapping or flicking the patient's middle fingernail. A positive sign occurs if the tip of the thumb bends in response to this flicking. An inverted brachioradialis test is positive if, when the brachioradialis muscle is tapped with a reflex hammer, the fingers flex and the expected reflex is weak or absent.
Clonus is a rhythmic beating of the foot and ankle when the ankle is quickly and forcefully moved into a flexed position. The Babinski sign (when positive) is seen as an extension of the big toe (rather than flexion) and a fanning open of the other toes when the pointed end of the reflex hammer is used along the bottom of the foot from heel to toes.
The test results of two groups of patients were compared. The first group (the cervical myelopathy group) had a history of symptoms, positive MRI for cord compression, was treated with surgery to take pressure off the cord, and improved after surgery. Improvement in signs and symptoms after surgery is an important confirmation that the diagnosis of cervical myelopathy was correct. The second group (control group) had neck pain that went down the arm but no symptoms of myelopathy. Their imaging tests were negative for cord compression.
After performing the four provocative tests to patients in both groups, the authors compared the results and reported their findings. Patients who had visible cord compression on MRI studies were also more likely to have positive provocative tests. But they found that overall, these signs were not very sensitive in detecting myelopathy. Almost one-fourth of the group with cervical myelopathy who improved after surgery had no positive signs of cord compression.
The Hoffman sign was the most sensitive but still not very high (59 per cent). The inverted brachioradialis test had 51 per cent sensitivity. Babinski and clonus were very low in sensitivity (13 per cent). The more sensitive a test is, the more likely it is an indication of a true positive test. However, when the tests were positive, it was a good indicator that cord compression was present.
The authors conclude by saying that you can't rely on signs of myelopathy to make the diagnosis. On the other hand, the lack of positive signs doesn't rule out the condition either. When the tests are positive, it's a pretty good indication that cord compression exists. The one group of patients that may not present like others is those who have diabetes.
Signs of myelopathy in adults with diabetes are very low. The reason for this is probably the decreased transmission of nerve impulses resulting in slower (not faster) reflexes. That's because diabetes affects the peripheral nerves most often.
In general, the appearance of these four signs is not necessarily an indication of how severe the cord compression is since it was possible to have severe compression without myelopathic signs. On the other hand, the more damage was present in patient's spinal cords, the more likely it was that they would have positive provocative signs.
Since the treatment of cervical myelopathy is often surgery, the decision to operate should be based on not just the presence of these clinical signs, but also the results of advanced imaging. Surgery may be needed even when provocative signs are negative because the MRI shows damage to the spinal cord.
John M. Rhee, MD, et al. Prevalence of Physical Signs in Cervical Myelopathy. In Spine. April 20, 2009. Vol. 34. No. 9. Pp. 890-895.
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