Entrapment neuropathy results from interference with the normal path of the nerve. Basically, the nerve gets squeezed due to a lack of space and the bony and muscular path where the nerve lies. One of the most common entrapment areas is the carpal tunnel. There are many factors that can narrow this canal. Several things outside of the canal such as tumors, trauma, spurs, and even disc herniations can cause pressure on the nerve resulting in such symptoms as pain and numbness and tingling. Certain systemic conditions such as rheumatoid arthritis and diabetes can also affect the nerve's ability to move and glide in its tract.
Chronic pressure on the nerve can damage its structure and blood flow. It is important to remove the pressure from the nerve before permanent damage occurs. Conservative treatment such as tissue mobilization, splinting, nerve mobilization/manipulation and other therapy modalities are effective with early detection. Steroid injections may be necessary to reduce inflammation and pain. Surgical intervention may be necessary in nonresponsive and chronic cases and cases with tumors or spurs compressing the nerve.
There are 3 key nerves in the upper extremity that may experience entrapment syndromes. The radial nerve, ulnar nerve and median nerve. The median nerve is the most commonly entrapped nerve in the upper extremity (carpal tunnel) with radial nerve and ulnar nerve entrapments following. The symptoms experiences are based on the location of the entrapment (anywhere from the neck to the wrist) and the type of nerve entrapped. Motor nerves affect muscles and will typically result in weakness when trapped. Sensory nerves on the other hand will typical result in decreased sensation or numbness and tingling. Thoracic outlet syndrome is another area which involves the neurovascular bundle (nerves, blood vessels) and is another topic outside this discussion.
Accurate diagnosis to locate the entrapment location is important. Standard orthopedic and neurological examination may help identify common entrapment conditions. When no apparent cause is obvious or the case is non-responsive, it may be necessary to perform advanced diagnostic testing to identify the entrapment point. Ultrasound and electrodiagnostics are frequently used. MRI is generally less useful but may be necessary in the case of tumors. Laboratory work may be necessary to rule out systemic conditions like rheumatoid arthritis, hypothyroidism and some cancers. In general, it is important to identify the source in the course of the nerve which may range from the neck to the wrist. Location drives the treatment options available.
Dr. Riggs has recently completed an article accepted for publication on non-carpal tunnel median nerve entrapments and is working on a subsequent articles on ulnar and radial nerve entrapments and lower extremity entrapments.