Neck Pain: Part 1: Narrowing the Differential
Richard L. Aptaker, DOTHE PHYSICIAN AND SPORTSMEDICINE - VOL 24 - NO. 10 - OCTOBER 96
This is the first of two articles on neck pain. The second article, on treatment, will appear in a subsequent issue.
In Brief: Neck pain or related upper-limb pain can be very disabling for active patients young and old. The broad differential includes such conditions as strain, sprain, disk injury, radiculopathy, carpal tunnel syndrome, ulnar neuropathy, and degenerative shoulder disease. A diagnosis can often be made solely based on history and physical exam findings. It is essential to determine whether the pain is localized or radiating. Localized neck pain generally points to muscle strains, ligament sprains, and degenerative facet or disk processes. Pain that radiates into the upper limbs frequently stems from nerve involvement. Unless significant trauma has occurred, diagnostic images are not warranted unless they are likely to change treatment.
The typical active person takes neck movements for granted until pain limits activity. Health clubs and physical therapy facilities are filled with people striving to develop great strength and flexibility in their upper and lower limbs, as well as in the abdomen. Even the low back has machines dedicated to increasing its strength. The neck, though, is frequently neglected when it comes to preventing and rehabilitating injuries.
Yet the cervical spine is one of the key links in the kinetic chain of physical motion. It controls head movement and, therefore, a person's ability to direct his or her organs of sensation. When bone, muscles, or nerves of the neck region are damaged, activities ranging from sedentary to record-setting are disrupted.
The primary care physician, therefore, must have a rational approach to diagnosing patients' common neck and associated upper-limb syndromes so that appropriate treatment can be initiated. The reader is referred elsewhere (1-4) for information on traumatic spine or cord injuries, burners or stingers, transient paresis, or the criteria for recommending participation in contact or collision sports.
Taking a Detailed History
Most clinically significant conditions involving the neck and upper limbs are diagnosed after a careful history and physical exam, except in cases of significant trauma, which require imaging studies to exclude a fracture or instability. The history starts with the patient's age and the duration, frequency, and other characteristics of symptoms. This helps formulate the early differential diagnosis.
For example, a 24-year-old female tennis player experiences neck pain the day after a long practice, which included hitting serves and overheads. She likely has an acute cervical muscle strain and/or minor ligament sprain, with probable facet joint irritation from the repetitive cervical extension. On the other hand, a 60-year-old swimmer who has had years of neck pain that is worse a few hours after swimming probably has a degenerative condition.
Pain duration and frequency. Muscle strains usually resolve within a few days to a couple of weeks, ligament sprains may take up to a couple of months, and disk injuries or herniations with radiculopathy can take 3 to 6 months for full recovery. Chronic pain beyond 6 months is likely associated with a degenerative process, be it in the disk, bone, or ligament, or from subtle mechanical instability caused by faulty posture or biomechanics.
Pain that increases with activity or within a few hours after activity, but settles down with rest or a change in position, is commonly referred to as mechanical pain. Pain that persists or worsens despite rest and treatment, pain that persists around the clock, or pain that worsens at night raises suspicion for a metabolic or neoplastic condition or for psychosocial factors that prolong recovery. It's important, therefore, to inquire about recent fevers, weight loss, or history of carcinoma; the resulting information might suggest the expeditious use of appropriate lab tests and imaging. Questions about recent personal stresses, worker's compensation, or third-party liability cases may also provide useful information.
Location. It is essential to determine whether the pain is localized or radiating; therefore, knowledge of the anatomic region is essential (see "C-Spine Anatomy," below). Localized pain generally points to muscle strains, ligament sprains, and facet or disk (degenerative) processes, although these structures commonly radiate pain to the periscapular or upper trapezius area as well (5,6). Pain that radiates into the upper limbs frequently stems from nerve involvement, although myofascial pain radiation patterns occur occasionally.
Upper cervical nerve injuries are relatively rare and refer dysesthetic pain to the head (C-1, C-2), the neck (C-3), and the upper trapezius region (C-4). The C-5 nerve transmits pain to the shoulder and lateral arm, and occasionally the radial forearm. The C-6 nerve pattern is very similar but invariably includes the radial forearm and thumb, and occasionally the index finger. The C-7 nerve refers pain to the posterior arm, dorsal (occasionally ventral) forearm, and the index and middle fingers. The C-8 nerve classically radiates pain to the medial arm, ulnar forearm, and the ring and little fingers.
Additionally, evidence indicates that the lower cervical nerve roots, disks, spinal longitudinal ligaments (5), and facet joints (6) refer pain to the scapular region. Along with myofascial pain trigger points or biomechanically induced muscle strains, these structures are the common origins of scapular and periscapular pain.
Other differential diagnostic considerations for referred pain include thoracic outlet syndrome and ulnar neuropathy, in which pain refers to the medial arm, forearm, and ring and little fingers, similar to a C-8 radiculopathy. Thoracic outlet syndrome typically will involve more proximal pain as well, such as in the axilla or scapula. Carpal tunnel syndrome characteristically causes dysesthesias in the thumb and first two fingers, and sometimes pain up the arm as high as the neck, thereby mimicking a C-6 or C-7 radiculopathy. Shoulder degenerative joint disease or acromioclavicular, subacromial, or rotator-cuff pathology may be confused with a C-5 radiculopathy.
Reflex sympathetic dystrophy is frequently associated with fractures or even minor trauma to the upper extremity. Pain from brachial plexus injuries or neuritis radiates to multiple dermatomes and myotomes in the arm and forearm, although patients characteristically have little neck pain. Finally, with the increasing incidence of cumulative trauma disorders related to the workplace, many "weekend warriors" complain of vague symptoms in their neck and upper extremities that they attribute to their sport but that actually result from overuse the other 5 days a week.
Characteristics. The quality or intensity of the pain may give clues to its origin. A muscle, ligament, or disk may give rise to sharp pain acutely, and more of a dull, aching sensation in the subacute or chronic period. Pain of bone and joint origin may refer through the sensory portion of the motor nerves (sclerotome), and is described as a deep or boring pain. Electrical, numbing, tingling, or shooting sensations generally describe neurogenic pain, while throbbing sensations have been attributed to vascular causes.
Clinicians should not be deceived by the overdiagnosed "muscle spasm." Although in an acute injury muscle guarding can occur as a protective mechanism, its long-term presence is usually the sign of a deeper pain generator (disk, bone, nerve root irritation). The "spasm" is the muscle's attempt to stabilize the neck and prevent painful motion.
Aggravating and alleviating factors. Finally, asking about aggravating and alleviating factors can further define the pain generator. Combinations of flexion, extension, or lateral bending with rotation that cause localized neck pain may point to muscle, ligament, discogenic, and/or degenerative bone pain. Pain primarily with neck extension is frequently due to compression of the posterior elements, including the facet joints. If pain radiates into the upper limb, a nerve root is usually involved. In an athlete age 50 or older, foraminal stenosis is common; in the younger athlete a discogenic source is more likely. Relief of symptoms with cervical traction generally points to a discogenic or disk-space-narrowing process.
Recumbency usually alleviates mechanical pain, although nocturnal pain with dysesthesias in the arms or hands raises suspicion for thoracic outlet syndrome, carpal tunnel syndrome, or shoulder impingement. Morning pain and stiffness is seen with osteoarthritis. Pain with overhead activities that radiates into the upper extremities may stem from thoracic outlet syndrome or shoulder impingement. Pain toward the end of the activity or end of the day is associated more with a degenerative process or chronic overuse syndrome. Relief usually comes from rest.
Stepwise Physical Exam
The history often gives a fairly good picture of what is causing the patient's pain. At the very least, some key exclusions help to narrow the differential. Physical examination can eliminate more diagnoses. The exam is divided into several categories: posture, range of motion, palpation, motor strength, muscle stretch reflexes, and special tests. Doing the same basic exam each time will help physicians develop expertise and speed so that they do not miss clinically important diagnoses.
Posture. The patient should have a smooth cervical lordosis with gentle transition into thoracic kyphosis. A "forward" head (ear forward of the acromion) or accentuated cervicothoracic hump creates a constant flexion moment of the head over the spine. Similarly, flexed posturing at the hips from tight hip flexors results in a compensatory increase in the lumbar and cervical lordoses. These postures lead to contractile overuse of the posterior cervical muscles to maintain an upright head. Obesity with rounded shoulders or a hunched posture, as seen with patients who have overdeveloped anterior chest wall muscles, can predispose patients to thoracic outlet syndrome or other chronic strain patterns.
Cervical range of motion. In general, the patient should be able to touch chin to chest with mouth closed (flexion of about 60°), look almost straight up to the ceiling (extension of about 70°), rotate chin to approach the shoulder (rotation of about 80°), and bend the ear toward the shoulder (lateral bending of about 45°). Allowances for aging must be made. Having the patient hold a tongue blade in his or her mouth makes visualizing the angles easier.
The Spurling test (7) (foraminal compression test) is useful to evaluate nerve root irritability (figure 1). If this maneuver causes only local pain, the discomfort is probably related to irritation of the facet or other posterior element, making a nerve-root process less likely.
Although there are no established criteria for telling whether loss of motion is due to pain inhibition or muscle, ligament, or joint restriction, it is valuable to note asymmetrical restrictions, as well as which movements cause pain. This can be useful for prescribing and monitoring a treatment program.
Palpation. The spinous processes and the interspinous ligaments from C-2 through T-1 can be palpated expeditiously during the assessment of flexion and extension. Exquisite bony tenderness may indicate a fracture; interspinous pain may be consistent with a ligament sprain, which is confirmed by pain in the same area during neck flexion.
The facet articulations are approximately a thumb's breadth to either side of the spinous process. Point tenderness here, especially with extension and rotation to the same side, suggests that the patient has facet joint pain.
Finally, the surrounding soft tissues of the neck and shoulder girdle should be palpated. Trigger points of the paraspinal and shoulder girdle regions will refer pain to a more distal area (8). Tender points may indicate a localized muscle strain, in which case contraction of the muscle containing the tender point should cause pain. An area that is tender to palpation but not painful during muscle contraction may represent pain referred from some other area. These patterns can also be identified during range-of-motion testing.
Motor strength. A focused exam of the major muscles (figure 2) is essential in any active patient complaining of neck pain, because patients can have pure motor radiculopathies with few or no extremity symptoms. In an athlete, maximal force must be applied when testing the major muscle groups to detect early weakness. By repetitively loading the patient's resisting muscle with rapid, consecutive impulses, more subtle weakness can be detected. Even if the pressure overpowers the patient, the key is detecting asymmetries in strength or differences from one myotome to the next.
In the 60-year-old swimmer described previously, who may have shoulder muscle weakness from years of rotator cuff pathology, it would be appropriate to overpower the patient's shoulder abduction to ensure it was adequately tested. It would be erroneous, though, to attribute shoulder muscle weakness to a neurologic process if the biceps and brachioradialis reflexes are normal and other non-rotator-cuff muscles innervated by C-5 and C-6 are strong. A brief shoulder exam (see "Other tests," below) will help to make the diagnosis.
Muscle stretch reflexes. Historically, muscle stretch reflexes have been referred to as "deep tendon reflexes," although it is well known that the reflex is initiated by the rapid stretch of muscle fibers (figure 3). Repetitive tapping may show a gradual decline in the reflex response not otherwise seen with a single tap. Absent or decreased reflexes are not necessarily pathologic, especially in athletes who have well-developed muscles. Upper-limb reflexes can often be increased by having the patient perform an isometric contraction such as squeezing the knees together during testing.
Asymmetry between sides should raise suspicion of an abnormality. Occasionally, an inversion response is seen, as when tapping the triceps tendon causes forearm flexion rather than the appropriate forearm extension. This is usually associated with nerve root or spinal cord pathology at the level tested.
Sensation. The sensory exam can usually be eliminated from an otherwise straightforward presentation of neck pain, even if radiculopathy exists. The wide variation of dermatomal innervation and the subjectivity of the test make it less useful than motor or reflex testing. However, if the differential diagnosis of upper-limb dysesthesias includes a peripheral nerve entrapment, then checking for a sensory loss in a peripheral nerve distribution is useful.
Other tests. Numbness or tingling in any combination of the thumb and first three fingers can be associated with carpal tunnel syndrome. The Phalen wrist flexion test (9) is done by full passive flexion of the patient's wrist for 30 to 60 seconds and looking for reproduction or worsening of finger dysesthesias. Tinel's sign (10) is elicited by tapping over the median nerve at the carpal tunnel. Electrical shooting sensations indicate median nerve irritation.
Dysesthesias along the ulnar forearm from the elbow into the fourth and fifth fingers may be associated with ulnar nerve entrapment at the elbow (cubital tunnel syndrome) and must be differentiated from a C-8 radiculopathy. Tinel's sign may be elicited by lightly tapping over the ulnar groove and reproducing distal symptoms. The elbow flexion test (11) is performed by having the patient fully flex the elbow and observing for ulnar nerve distribution symptoms within a few minutes. Diagnosing carpal tunnel syndrome or ulnar neuropathy does not exclude a simultaneous cervical radiculopathy (double crush syndrome) (12).
Thoracic outlet syndrome, although a controversial diagnosis, may cause dysesthesias in the shoulder girdle and ulnar distribution of the forearm and hand. In Adson's test (13), the patient turns his or her head to the involved side, raises the chin, and holds a deep inspiration while the ipsilateral radial pulse is palpated with the arm slightly abducted from the side. The test is positive for thoracic outlet syndrome if the pulse intensity diminishes and the patient's symptoms are reproduced.
Roos' test (14) requires the patient to abduct the shoulders 90°, flex the elbows 90°, and open and close the hands slowly for 3 minutes. Hand pallor, ulnar dysesthesias, and a diminished pulse are considered positive for thoracic outlet syndrome, although the test has also been found to be positive in carpal tunnel syndrome (15). Whether thoracic outlet syndrome is secondary to vascular, neurogenic, or nonspecific causes (16) requires further workup of the patient.
Shoulder problems are often confused with a C-5 or C-6 radiculopathy or with cervical spondylosis. If muscle strength and reflexes are normal, which makes a radiculopathy less likely, the key differentiating feature is pain with neck movement versus shoulder movement.
If the Spurling test and general range-of-motion assessment point away from neck pathology, the next step is to look for shoulder impingement. The patient stands with arms at his or her sides and internally rotates them by pointing the thumbs posteriorly. As the patient actively flexes or abducts the arms overhead, shoulder pain, especially after 90°, is a positive sign. Pain when the patient actively moves the elbow to his or her mouth (the examiner can tell the patient to kiss the elbow) can also be associated with impingement.
Immediate resolution of symptoms after a subacromial injection of 5 to 10 mL of 1% lidocaine hydrochloride is consistent with subacromial pathology (17). A negative test (no improvement), however, does not rule out acromioclavicular or glenohumeral disorders, and further investigation may be warranted.
When Diagnostic Testing Is Warranted
The physician must decide whether a diagnostic test will change treatment. If not, the test is not necessary at that time. If a patient does not progress as expected, however, diagnostic testing is indicated because the intervention strategy may need to change.
X-ray. Plain radiographs of the cervical spine should be done immediately after significant athletic trauma from a direct blow to the neck or head. The basic evaluation includes anteroposterior (AP), lateral, right and left oblique, and AP odontoid views. If these are normal but the patient's neck may be unstable, lateral flexion and extension views can help evaluate ligament stability. An equivocal bony abnormality or persistent pain out of proportion to the clinical scenario may warrant a computed tomography scan.
In most other painful conditions, including mild radiculopathy (motor strength 4/5 or greater), radiographs can be delayed until after a trial of conservative treatment. However, if at 4 to 6 weeks no significant improvement is apparent, the basic plain radiographic evaluation should be done to evaluate for anatomic structures or abnormalities that may be delaying healing. These may include severely narrowed disk spaces, foraminal outlet narrowing, a degenerative facet joint, and other spondylotic changes.
MRI. Magnetic resonance imaging (MRI) is useful to evaluate for a mechanical compression that may be causing radiculopathy. MRI, however, shows only anatomy and gives no information about the physiologic process that may be causing pain. Correlating the images with the history and physical examination, therefore, establishes whether MRI pathology is clinically relevant.
In mild radiculopathy, MRI is not initially needed because most patients improve with conservative care. If, however, the patient's weakness progresses, pain is intractable, or 6 to 8 weeks of therapy bring no improvement, an MRI is useful to identify the anatomic lesion. Because asymptomatic patients may have cervical MRI abnormalities (18), the radiologist should be told a specific condition to look for to avoid a false-positive study. A nonspecific order, such as "r/o neck pathology," rarely provides useful information for a patient who has neck pain.
EMG and nerve conduction. Needle electromyography (EMG), though more popular before the MRI era to help localize the level of nerve root injury, is still useful in evaluating the physiologic state of nerves and muscles in a patient who has upper-limb weakness and is not improving with therapy. EMG can help indicate whether an injured nerve is stable or actively denervating, or whether reinnervation has occurred. It can also help distinguish between nerve root lesions and brachial plexopathy. EMG abnormalities, though, may not be seen for up to 21 days after onset of injury or symptoms, making it less useful in early stages.
Nerve conduction studies are still the test of choice to document or rule out upper-limb nerve entrapments that may confound the diagnosis of radiculopathy. Again, EMG and nerve conduction studies should be used to confirm the clinical assessment when it will help to prescribe, or change, a given course of treatment.
Hands-On Clinical Sleuthing
Because a working diagnosis can often be made after the history and physical, these two aspects of clinical assessment must not only be focused but also diligently carried out in patients who have neck pain. For example, ruling out neuromotor weakness in cases of radiculopathy is paramount and does not require imaging or electrodiagnostic testing. Diagnostic imaging, however, is required for traumatic injuries or when the results are likely to alter treatment decisions.
Dr Aptaker is the chief of the Department of Physical Medicine, the director of the Spine Clinic, and a staff physician at the Sports Medicine Clinic at Kaiser Permanente Medical Center in San Francisco. He is a member of the Physiatric Association of Spine, Sports, & Occupational Medicine and the American Osteopathic Academy of Sports Medicine. Address correspondence to Richard L. Aptaker, DO, Kaiser Permanente Medical Center, 1635 Divisadero St, Suite 300, San Francisco, CA 94115.