ARM PAIN
ARM PAIN: Excerpt from Differential Diagnosis in Primary Care
An anatomic breakdown of the arm into its components is the key
to a sound differential diagnosis in arm pain. Pain may be referred from
more proximal portions of the extremity such as the shoulder (e.g.,
bursitis) or brachial plexus (e.g., cervical rib), so these areas must also
be examined.
Beginning with the skin and subcutaneous tissue, one recalls
herpes zoster, cellulitis, contusions, and a variety of dermatologic
conditions that should be obvious. Weber–Christian disease, which usually
affects the thighs, is more obscure. Rheumatoid and rheumatic nodules may
occur on the skin and are, of course, painful. Beneath the skin the
muscles, fascia, and bursae are frequent sites of inflammation and
trauma. Contusions, rupture of the ligaments, and bursitis (particularly
tennis elbow) are common acute traumatic conditions (bursitis, however, is
more likely the result of chronic strain). Inflammatory lesions of the
muscles include epidemic myalgia, trichinosis, nonarticular rheumatism, and
dermatomyositis. Muscle cramping from hypocalcemia or other electrolyte
disturbances must be considered in the differential diagnosis of arm pain.
The superficial and deep veins are the site of thrombophlebitis and
hemorrhage, both prominent causes of arm pain. The arteries may be
involved by emboli (from auricular fibrillation, myocardial infarction, and
SBE), thrombosis (especially in Buerger disease and blood dyscrasias such as
sickle cell anemia), and vasculitis (periarteritis nodosa is one example).
Acute trauma to the artery may cause pain. When one moves centrally along
the arterial pathways, additional causes of pain come to mind. For example,
dissecting aneurysms or acute subclavian steal syndrome may cause severe
pain down the arm, but pain is referred to the arm from a myocardial infarct
as well. When superficial or deep infections of the arm spread to the
lymphatics, lymphangitis may develop and cause arm pain.
The nerves may be a source of pain, both centrally and locally.
Buerger disease, cellulitis, and osteomyelitis may involve the nerve
locally. Neuromas may cause focal pain in the distribution of the involved
peripheral nerve. Carpal tunnel syndrome, which may be caused by rheumatoid
arthritis, amyloidosis, acromegaly, hypothyroidism, or multiple myeloma, may
compress the median nerve (and occasionally the ulnar nerve) to cause pain
in the hand and even up the arm. Moving up the nerve pathways, another
frequent spot for nerve compression is the brachial plexus. Pancoast tumors,
cervical ribs, and the scalenus anticus syndrome may be the cause of arm
pain originating from the plexus.
The cervical nerve roots may be compressed by diseases of the spine
and spinal cord. A herniated disc, cervical spondylosis, metastatic
carcinoma, tuberculosis of the spine, multiple myeloma, and cord tumors
(e.g., meningiomas, neurofibromas, and ependymomas) are the most notable.
Syringomyelia and tabes dorsalis are other sources of arm pain that
originate in the spinal cord. As one moves up the cord to the
brainstem, one recalls the thalamic syndrome (usually caused by occlusion
of the thalamogeniculate artery) as a cause of pain in the arm.
The bone and joints are deeper in the arm. They prompt the
diagnosis of osteomyelitis, primary and metastatic bone tumors, and diseases
of the joints such as osteoarthritis, rheumatoid arthritis, gout, gonococcal
arthritis, and Reiter syndrome. A more extensive discussion of joint
disorders can be found on page 282.
Systemic diseases that cause arm pain from peripheral nerve involvement
include diabetes mellitus (with ischemic neuropathy), periarteritis nodosa,
and macroglobulinemia. Sickle cell anemia may also cause an ischemic
neuropathy.
Approach to the Diagnosis
The association of other symptoms and signs found on a good history and
physical examination is most important in pinpointing the diagnosis. Thus,
arm pain with tenderness and limitation of motion at the elbow suggests
tennis elbow, gout, or rheumatoid arthritis. Arm pain with loss of sensation
in the distribution of the median nerve suggests carpal tunnel syndrome.
Injection of lidocaine into bursa or trigger points may be diagnostic.
The laboratory workup should include x-rays of the involved area and of the
cervical spine, especially if there is a radicular distribution of the pain.
If there are focal neurologic signs, a neurologist should be consulted
before ordering an MRI: A cervical rib will not be missed in this way. An
ECG and myocardial enzymes may be necessary to exclude a myocardial infarct,
and an exercise tolerance test will help to exclude coronary insufficiency.
Arteriogram, phlebogram, lymphangiogram, electromyogram with nerve
conduction studies, myelogram, and nerve blocks will be necessary in
specific cases.
Other Useful Tests
-
Stellate ganglion block (Reflex sympathetic dystrophy)
-
Dermatomal somatosensory evoked potentials (DSEPs) (neuropathy,
radiculopathy, demyelinating disease)
-
Arthritis panel
-
Chest x-ray (Pancoast tumor)
-
MRI of shoulder (torn rotator cuff)
Pictures
Book Source Details
- Book Title: Differential Diagnosis in Primary Care
- Author(s): R. Douglas Collins MD, FACP
- Year of Publication: 2007
- Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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