Neuroscience Group of NE Wisconsin

Setting the Standard for Comprehensive, Compassionate Brain, Spine and Pain Care

"There's a great deal of awareness when it comes to carpal tunnel syndrome. Just about everyone knows the classic symptoms," states Gizell R. Larson, M.D. of The Neuroscience Group of Northeast Wisconsin, "But sometimes, the same symptoms associated with carpal tunnel can be indications of other, and in some cases, more serious medical problems."

On their way to the muscles, they innervate, peripheral nerve trunks pass by fibrous bands, go around bony structures, become sandwiched within and between muscle bellies, and often lie close to the skin surface. For all of these reasons they are liable to focal injury.

Focal nerve injuries occur due to compression, entrapment, crush, sketch, and transection.

Entrapment neuropathy refers to chronic distortion or angulation of the nerve by an internal source, such as a fibrous band or a constricting tunnel. Predisposing factors include abnormal fibrous bands, hypertrophied muscles, and congenitally narrowed tunnels. Examples include media neuropathy at or distal to the wrist (carpal tunnel syndrome, CTS).

CTS can occur in one or both hands and can occur at any age, however, work-related CTS is more common in people between the ages of 20-50 and non-work-related CTS is most common in people over age 50. Regardless of age, CTS is more prevalent in women than in men. Onset of CTS is gradual, however, it can lead to permanent nerve and muscle damage without timely diagnosis and treatment.

"Carpal tunnel syndrome may actually be a preliminary sign of other conditions such as generalized peripheral neuropathy. It is not always easy to pinpoint exactly where the nerve entrapment is taking place," Larson states, "While the symptoms may all point to nerve entrapment at the wrist, the actual entrapment may, in fact be proximal to the carpal tunnel. In many cases, electrodiagnosis is the only way to accurately determine the location of the nerve entrapment."

ABSTRACT:
Carpal Tunnel Syndrome

Often the same symptoms associated with Carpal Tunnel Syndrome (CTS) can be indications of other, sometimes more serious medical problems. The key is to determine the exact location of the nerve entrapment - whether or not it is the carpal tunnel.

Proper diagnosis of CTS may be aided by the use of practice parameters established by The Quality Standards Subcommittee of the American Academy of Neurology (AAN). "The most important issue with diagnosis and the use of diagnostic testing is to really have a clear picture of what questions are to be answered by the tests," cautions Neurologist Gizell R. Larson, M.D. The diagnostic practice parameters are included in this article.

Treatment of CTS depends upon the diagnosis as to whether there has been axonal degeneration of the nerve to the muscle. The sooner the diagnosis and treatment to the nerve is started, the greater the chance for full patient recovery.

"The single most important factor in diagnosis of CTS is excluding other causes of the same symptoms," Larson states.

The electrodiagnostic examination is an extension of the clinical examination. It is performed primarily to diagnose, or exclude, lesions of the peripheral neuromuscular system. The electrodiagnostic examination should be viewed as an independent assessment of the patient, performed not only to confirm the clinical diagnosis, if it is correct, but equally to provide an alternative explanation for the patient's symptoms and signs, if the clinical diagnosis is erroneous.

The Quality Standards Subcommittee of the American Academy of Neurology (AAN) has developed practice parameters to assist physicians in the diagnosis of CTS. These parameters follow:

"Carpal tunnel syndrome may actually be a preliminary sign of other conditions... "

I. HISTORY
A. The likelihood of CTS increases with the number of standard symptoms and provocative factors above.
1. Dull, aching discomfort in the hand, forearm or upper arm
2. Paresthesias in the hand
3. Weakness or clumsiness of the hand
4. Dry skin, swelling, or color changes in the hand
5. Occurrence of any of these symptoms in the median distribution

B. Provocative factor
1. Sleep
2. Sustained hand and/or arm positions
3. Repetitive actions of the hand or wrist

C. Mitigating factors
1. Changes in hand posture
2. Shaking in the hand

II. PHYSICAL EXAMINATION
A. May be normal
B. Symptoms elicited by tapping or direct pressure over the median nerve at the wrist (Tinel's sign), or with forced flexion or extension of the wrist (Phalen's sign)
C. Sensory loss in the median nerve distribution
D. Weakness or atrophy in the thenar muscles
E. Dry skin on the digits I-III

III. DIFFERENTIAL DIAGNOSIS
A. Cervical radiculopathy (especially C-7)
B. Brachial plexopathy (especially upper trunk)
C. Proximal median neuropathy (especially at the pronator teres muscle)
D. Peripheral neuropathy
E. Vascular or neurogenic thoracic outlet syndrome
F. Central disorders such as multiple sclerosis and cerebral infarction; spinal cord lesions, and pituitary lesions

IV. CONFIRMATORY STUDIES
If the diagnosis is uncertain with only a few of the clinical features present, confirmatory testing or therapeutic trial is needed, and may include:

A. Electromyography (EMG) and nerve conduction studies (NCS), which can confirm a median neuropathy at the wrist, but are not able to exclude the diagnosis of CTS. EMG/NCS can help define the severity of damage.

B. Therapeutic trials with one of the non-invasive treatment methods

V. FURTHER DIAGNOSTIC TESTING
A. Indications for further testing include:
1. Exclusion or confirmation of associated disease
2. Exclusion or confirmation of alternative diagnoses

B. Contraindications - none

C. Imaging (radiography or magnetic) - local structural disease
1. Wrist - for previous fractures, local deformity, primary bone or joint disease, evidence of local tumor
2. Cervical spine - for cervical radiculopathy
3. Chest - for brachial plexopathy or thoracic outlet syndrome

D. Endocrine, hematologic or serologic test for pregnancy or systemic disorders such as diabetes, hypothyroidism, acromegaly and gout

E. Neuropathy evaluation - protein electrophoresis, tissue biopsy for amyloid, spinal fluid examination, assessment for connective tissue disorders

F. Electrophysiologic testing - EMG/NCS testing for diffuse disorders

G. The benefits of the following diagnostic techniques have yet to be fully established:
1. Carpal tunnel pressure measurements
2. Sensory quantitation, including vibrometry
3. MRI quantitation of the carpal tunnel
4. Ultrasound of the carpal tunnel
5. Current perception threshold
(Copyright, 1992, American Academy of Neurology)

"One of the most important elements to establish by EMG is whether there has been axonal degeneration of the nerve to the muscle. Nerve conduction studies reveal the type, location and severity of nerve entrapment as well as the presence or absence of any generalized neuropathy." Larson states, "The sooner we can diagnose and treat the nerve, the less chance for degeneration of the nerve --and the greater the chance for the patient to have a complete recovery."

"Probably the single most important factor in diagnosis of CTS is excluding other causes of the same symptoms"

Treatment of CTS should be pursued if the symptoms interfere with a patient's ability to perform daily activities.

Non-invasive measures are the first treatment unless the patient is exhibiting progressing motor or severe sensory deficit or axonal degeneration. Non-invasive treatments include:

When non-invasive treatments are not effective, or when patients exhibit progressing motor or severe sensory deficit or axonal degeneration, invasive treatment is indicated. Invasive treatments include:

"Probably the single most important factor in diagnosis of CTS is excluding other causes of the same symptoms," Larson states, "Although CTS is indeed the most common cause, a differential diagnosis as listed above, should be considered. A directed history and neurologic examination can reveal the hereditary and systemic factors that predispose patients to nerve entrapment and suggest alternate diagnoses."