By way of background, the spinal cord in the neck is connected to the nerves of the arms through pairs of spinal nerves. These spinal nerves, also known as roots or “radicles,” transmit incoming messages (electrical impulses) from the arms’ nerves concerning sensations of touch, pain, heat and cold on various patches of skin. Additionally, the cervical roots convey outgoing messages (also electrical impulses) through the arms’ nerves to their muscles, causing them to contract.
So when a cervical root is pinched, the pinch can cause not just pain, but--by blocking incoming and outgoing nerve impulses--it can also produce numbness of patches of skin, weakness of muscles, or both. The syndrome caused by the pinch in the neck is called cervical radiculopathy. The suffix “-pathy” means damage or impairment, so radiculopathy means damage or impairment of a radicle (root).
There are four pairs of cervical roots connecting the spinal cord to the arms’ nerves and they are named for the segment of spinal cord to which they are attached--C5, C6, C7 and C8, with the “C” designating cervical. While a pinch of any of these roots typically produces searing, deep pain in the shoulder which preoccupies the unfortunate person who has it, the shoulder pain is the least identifying or diagnostic component of the person’s symptoms.
The pain often shoots into the arm on the affected side, and certain movements of head and neck can worsen or reproduce this pain. While the arm component of the pain is less intense than that felt in the shoulder, its location is often the key to figuring out which root is pinched. Moreover, the pattern of numbness or weakness also varies according to which root is pinched. These patterns are almost identical from person to person and are as follows:
C5 impairment can send pain over the top of the shoulder in the first fourth of the arm which is also where numbness occurs, when present. When there is weakness, it involves the ability to elevate the arm sideways to the level of the shoulder or above. There are no good (rubber-hammer-type) reflexes the doctor can use to test this root.
C6 impairment can send pain as far as the thumb which is also where numbness occurs, when present. When there is weakness, it involves the ability to bend the elbow. The doctor can additionally test for C6 impairment with the biceps-reflex which involves striking a tendon in the crook of the elbow.
C7 impairment can send pain as far as the middle fingers which is also where numbness occurs, when present. When there is weakness, it involves the ability to straighten the elbow. The doctor can additionally test for C7 impairment with the triceps-reflex which involves striking a tendon on the back of the elbow.
C8 impairment can send pain as far as the little finger which is also where numbness occurs, when present. When there is weakness, it involves certain hand-movements, including the ability to join the tips of the thumb and the little finger and also to spread the fingers sideways. There are no good reflexes the doctor can use to test this root.
Having identified the typical syndromes, the next step is to understand what caused the pinch in the first place. It is typically one of two things--a herniated (“slipped”) disk or a bony spur. Younger adults are more likely to have a herniated disk and older adults are more likely to have a bony spur. Disks are soft structures sandwiched between each pair of spinal column bones (vertebral bodies). Their ordinarily tough outer membranes can weaken and allow extrusion of inner disk material--somewhat like toothpaste squeezed out of a tube--into the side-canals through which the spinal roots must pass. This traps and compresses them. Bony spurs, in contrast, are not soft at all. Instead, they are hard ridges of excess bone located on the edges of the back-bones. They are produced by arthritic degeneration. They, too, can trap and compress the spinal roots where they exit the spine.
How is cervical radiculopathy diagnosed? As described, the patient’s history and examination are often very informative and specific. When the pattern of nerve-impairment is ambiguous, tests of nerve and muscle electricity--called nerve conduction studies and electromyography--can help localize the impairment. These electrical tests can also detect impairments in the nerves of the arms which might mimic cervical radiculopathy, but require different medical management.
Until the 1980s myelograms made the best pictures of the pinches occurring in the spine. To perform a myelogram a doctor started with a lumbar puncture (also known as a spinal tap) in the patient’s lower back and injected x-ray dye into the watery space within the membrane covering the spinal cord and its roots. The patient was then tilted so that the dye ran into the corresponding space in the neck. Standard x-ray pictures showed the column of dye together with any indentations of the column caused by a herniated disk or bony spur.
Magnetic resonance imaging (MRI) was developed in the 1980s and created similar pictures but without having to do a spinal tap or dye infusion. Computed tomographic (CT) scans, developed in the 1970s, are generally the least useful of the spinal imaging techniques, except when an immediately preceding myelogram has been performed, in which case they can be strikingly helpful. Each of these these imaging tests has its strengths and weaknesses--none of them is always the best--so testing must be tailored to each case.
And how about treatment of this condition? Well, that’s a story deserving its own essay. Stay tuned.
(C) 2005 by Gary Cordingley
