Plexus disorders

[Becky]

The networks of interwoven nerve fibers from different spinal nerves (plexuses) may be damaged by injury, tumors, pockets of blood (hematomas), or autoimmune reactions.

Pain, weakness, and loss of sensation occur in all or part of an arm or a leg.
Electromyography and nerve conduction studies help doctors locate the damage, and magnetic resonance imaging or computed tomography helps identify the cause.
Sometimes treating the disorder causing the problem improves nerve function.

(See also Overview of the Peripheral Nervous System.)
A plexus is like an electrical junction box, which distributes wires to different parts of a house. In a plexus, nerve fibers from different spinal nerves (which connect the spinal cord to the rest of the body) are sorted. The fibers are recombined so that all fibers going to a specific body part are put together in one nerve. Damage to nerves in the major plexuses causes problems in the arms or legs that these nerves supply.
The major plexuses are the

Brachial plexus, which is located in the neck and shoulders and which distributes nerves throughout the arms
Lumbosacral plexus, which distributes nerves to the pelvis and legs

The lumbosacral plexus includes the

Lumbar plexus, located in the lower back
Sacral plexus, located in the pelvis