Brachialgia is the medical term for pain produced by a trapped nerve in the neck leading to pain radiating down the arm. Like sciatica, it can be of sudden onset and extremely severe or of gradual onset and with symptoms that are more prolonged. The cause of the trapped nerve in the neck that produces the brachialgia is either a disc prolapse or more longstanding degenerate changes producing compression on the cervical nerve root. Because the cause of the brachialgia is a trapped nerve, there are other symptoms that can be associated with the arm pain. Most typically, these symptoms are of paraesthesia (pins and needles) in the arm and these symptoms may be very localised, for example exclusively into the thumb. The distribution of both the pain and the paraesthesia does depend to a certain extent on which of the nerve roots is pressed upon in the cervical spine.
Like paraesthesia, the other not uncommon sensory disturbance that a patient with brachialgia describes is overt numbness in the arm. Again, this does not tend to be global but rather in a specific distribution that is related to which of the cervical nerve roots is compressed. Rarely, the severity of the nerve root entrapment in the cervical spine is so marked that in addition to producing pain and/or sensory disturbance, the motor (power) function of the arm is affected. This is rare but in such cases the sufferer may notice reduced power in the arm and, like the sensory disturbances described above, this is commonly very localised. For example, the sufferer may notice weakness of their triceps muscle such that they are unable to extend their elbow, an action required when pushing things away or doing such physical activities as press-ups.