brachial plexopathy
Meaning of brachial plexopathy: The pattern of what is weak and what is numb points to where along the nerve network the trouble actually sits.
Definition of brachial plexopathy
Brachial plexopathy is damage to the brachial plexus, the dense network of nerves that leaves the lower neck, passes beneath the collarbone and divides into the nerves of the arm. Injury there causes weakness, numbness, tingling or pain covering the territory of the affected part of the network rather than that of one named nerve. Causes range from stretching injury to tumor and radiation.
Why does the pattern of weakness matter?
Because it locates the damage. Nerve roots leaving the neck merge and redistribute inside the brachial plexus before emerging as the named nerves of the arm, so fibers from one root finish up spread across several nerves. Damage high in the network, near the neck, affects the shoulder and upper arm and leaves the hand working. Damage low in the network affects the hand and forearm and spares the shoulder. Damage to one nerve further down produces a much smaller and sharply bounded loss. Mapping which muscles are weak and which patches of skin are numb tells an examiner roughly where along the network the problem sits, before any scan is ordered.
What causes it?
| Cause | Typical picture |
|---|---|
| Stretch injury | A fall driving the head and shoulder apart, as in motorcycle crashes |
| Birth related | A shoulder caught during delivery; the upper network usually affected |
| Tumor growing into it | Steadily worsening pain first, then loss in the hand and forearm |
| Radiation given earlier | Painless numbness and weakness creeping on long afterward |
| Inflammatory attack | Sudden severe shoulder pain, then weakness as the pain fades |
The inflammatory form catches people out because the pain arrives first and settles before the weakness is noticed, so the two are not connected at the time.
How are tumor and radiation damage told apart?
They can look alike and they occur in the same people, so the distinction gets made repeatedly. Pain that leads and grows, loss concentrated in the lower network, and a drooping eyelid with a small pupil on the same side all point toward a tumor pressing on or invading the nerves. Numbness and weakness that arrive slowly and painlessly, long after radiation reached the area, point toward scarring from the treatment. Electrical testing helps, since rippling spontaneous muscle activity called myokymia is characteristic of radiation injury and rare with tumor. Imaging settles most of the rest. The general word for damage to any such nerve network is plexopathy.
Also known as
Used in a sentence
Brachial plexopathy was suspected from the pattern of weakness in the hand and forearm.
Good to know
Pain that leads the picture, with a drooping eyelid and small pupil, favors tumor involving the lower part of the network, while painless weakness appearing long after treatment, with myokymia on electrical testing, favors radiation injury.
Word origin
Where “brachial plexopathy” comes from
Brachial comes from the Latin brachium, meaning arm. Plexus is Latin for a braid or interweaving, and the ending -pathy comes from the Greek pathos, meaning suffering or disease.