Trapped nerves

Nerve entrapment causes pain, weakness in the muscles served by the affected nerve (paralysis, or palsy - a term now rarely used) and numbness or tingling (called paraesthesiae) - or all three. The resulting disability depends on the nerve that's trapped, and the length of time of the disability depends on the degree of damage to the nerve. From the top down the most common trapped nerves are the cervical nerves, in the neck, where they may be subject to pressure due to degenerative discs or vertebrae affected by osteoarthrosis - a condition called cervical spondylosis. There may be pain in the arm or shoulder, numbness and tingling in the hands and weakness of movement and clumsiness affecting the fingers. In severe cases where the spinal canal is narrowed there may also be difficulties with walking. While minor degrees of cervical spondylosis may respond to manipulation or physiotherapy, any sign that the spinal cord is being compressed requires the opinion of a neurosurgeon.

In the arm there are three nerves: the radial nerve which opens the fist and which supplies sensation to the back of the thumb, which can be affected by pressure in the upper arm; the ulnar nerve which supplies some of the muscles of the hand and sensation along its inner border, which is commonly compressed as it comes round the elbow and may result in a claw hand deformity with flexion of the last two fingers, and the median nerve which also supplies some of the muscles in the hand and sensation to the thumb and the first two fingers, and which is commonly trapped as it passes through the tunnel called the carpal tunnel at the front of the wrist (see carpal tunnel syndrome in the wrist and hand section under bones and joints).

Discs bulging between the vertebrae of the lower back, so-called slipped discs, can press on nerve roots of the sciatic nerve which is responsible for sensation and movement in the leg and foot. The pressure causes sciatica with pain and numbness and tingling down the back of the leg. Some foot movements may be weak. One of the branches of the sciatic nerve, called the common peroneal nerve, passes around the outside of the knee, and it may be damaged during periods of prolonged squatting. This causes an inability to lift up the toes, producing foot drop (called strawberry picker’s foot, because people picking strawberries commonly damage this nerve).

 
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