Entrapment neuropathies are very common in people with diabetes, occurring in one in every three patients. These neuropathies result from squeezing of individual nerves as they pass through bony or ligamentous areas that do not allow expansion so the nerve is trapped if there is swelling for any reason. The entrapment neuropathies can produce symptoms similar to the mononeuropathies described in a previous post but they differ in several ways:
* Onset of mononeuropathies is sudden while entrapment neuropathies have a gradual onset.
* Mononeuropathies are self-limited, usually resolving over six weeks while entrapment neuropathies persist unless the nerve is released by surgery.
* Mononeuropathies are painful from the start while entrapment neuropathies gradually get more and more painful.
The entrapment neuropathies include
* Carpal tunnel syndrome: produces reduced sensation in the fingers and weakness touching the thumb to the fifth finger. The median nerve is trapped at the wrist.
* Ulnar entrapment: produces reduced sensation in part of the fourth finger and the entire fifth finger as well as the hand between the fifth finger and the wrist. The ulnar nerve is trapped at the elbow.
* Radial nerve entrapment: produces loss of sensation in the back of the hand and “wrist drop” from weakness of the muscles that straighten up the wrist. The radial nerve is trapped at the elbow.
* Common peroneal entrapment: produces loss of sensation in the side of the leg and top of the foot and “drop foot” from weakness of the muscles that pull up the foot. The common peroneal nerve is trapped as it passes the head of the fibula, one of the two bones that begin at the knee joint and end at the ankle.
* Tarsal tunnel syndrome: produces loss of sensation on both sides of the foot and wasting of the muscles of the foot resulting in decreased toe movement. It is like the carpal tunnel syndrome in the foot and results from trapping of the tibial nerve between two of the small foot bones.
* Lateral femoral cutaneous nerve entrapment: produces loss of sensation on the outside of the thigh but no muscle weakness. It results from trapping of that nerve at the groin.
The entrapment neuropathies respond to rest, splints, drugs that promote water loss, injections of steroids and surgery if necessary. The important thing is not to confuse them with mononeuropathies