After a high-energy accident — often a motorcycle crash — an arm that no longer responds: you can't lift the shoulder, bend the elbow, or move the hand. Sometimes intense pain, like electric shocks. Then the diagnosis: a brachial plexus injury.
It is one of the most serious injuries of the upper limb, but also one where early specialized care makes the greatest difference. This article explains what the brachial plexus is, what an injury causes, and why, here more than anywhere else, every month counts.
The brachial plexus: the arm's "electrical panel"
The brachial plexus is a network of nerves that arises from the spinal cord at the neck, from five nerve roots, then branches like a tree to form the major nerves of the upper limb. It carries every command from the brain to the muscles of the arm, and all the sensory information from the hand back to the brain.
A picture to understand it
The brachial plexus is like the electrical panel that distributes power to an entire floor: depending on where the circuit is cut, a different part of the limb "goes dark." An injury high in the plexus mainly deprives the shoulder and elbow; an injury low in the plexus mainly deprives the hand. A complete injury paralyzes the whole arm. This logic of levels explains the wide variety of presentations.
This network organization also explains why the plexus connects all the nerves covered elsewhere on this site: it is the common source of the median, ulnar, and radial nerves. See the carpal tunnel article.
What an injury causes, according to its level
A plexus injury is not limited to weakness: it often combines loss of strength, loss of sensation, and frequently neuropathic pain — burning, electric shocks — sometimes intense and long-lasting. The presentation depends on the level involved:
High injury (upper roots)
The shoulder no longer lifts and the elbow no longer bends, but the hand may still work.
Low injury (lower roots)
The hand, wrist, and fingers are affected — pinch, fine grip — while the shoulder and elbow are more spared.
Complete injury
The entire upper limb is paralyzed, with widespread loss of sensation and often significant pain.
Not all injuries are the same: the distinction that changes the prognosis
This is a crucial point, and often misunderstood. Behind the word "palsy" lie injuries of very different severity, with prognoses ranging from spontaneous recovery to no recovery at all without surgery.
From most reversible to most severe
The nerve is stunned, but intact: simply concussed, it can recover on its own within a few weeks to a few months. This is the most favorable form.
The nerve is torn but remains in relative continuity: spontaneous recovery is incomplete or impossible, and surgical repair is often necessary.
The root is torn from the spinal cord (avulsion): this is the most severe injury. Spontaneous recovery is then impossible, and only a complex surgical strategy can restore function.
Distinguishing these situations is the whole purpose of the work-up: it separates an injury that can be monitored from one that must be operated on without too much delay. Certain signs — very intense pain, a particular finding on examination of the eye and eyelid (Claude Bernard-Horner syndrome) — point to a severe injury, close to the spinal cord.
The decisive factor: time
Here is the most important message in the whole article, and the one that justifies a prompt specialized consultation.
Why every month counts
When a nerve is repaired, it must grow back from the repair site to the muscle, very slowly — on the order of one millimeter per day, a theoretical figure. But a muscle deprived of its nerve for too long deteriorates irreversibly: after a certain time, even a repaired nerve no longer finds a muscle able to respond.
In practice, beyond about 6 to 12 months, the chances of recovery after repair drop sharply. This is why a severe injury must be assessed early and operated on within the right window — neither too early, when spontaneous recovery is possible, nor too late, when there is nothing left to reinnervate.
This time factor is what most sets plexus care apart from the other conditions on this site: elsewhere, waiting is often reasonable; here, waiting without specialized advice can lose chances for good. Early advice does not necessarily commit you to immediate surgery — it makes it possible to set up the right monitoring and not miss any surgical window.
The work-up
The work-up combines several complementary approaches, because none is sufficient on its own:
Repeated over time, it precisely maps the affected muscles and the areas of sensory loss, and looks for warning signs of a severe injury. Repeating it shows whether recovery is beginning.
It visualizes the nerves and looks for tears and signs of root avulsion. Advanced imaging techniques now improve the detection of avulsions.
Combined with MRI by the few radiologists familiar with plexus injuries, it makes the assessment more sensitive.
3D reconstruction (AVATAR software) helps refine the type of anatomical injury by "traveling" virtually inside the patient.
It measures the electrical activity of the nerves and muscles, locates the injury, and assesses any regrowth. It is not informative right away — some findings appear only after a few weeks.
Reconstructive surgery
Brachial plexus surgery is a highly specialized, microsurgical procedure whose goal is not to "restore the nerve as it was" but to recover useful functions — being able to bend the elbow, stabilize the shoulder, regain a grip. The aim is not perfect recovery, but the best possible function.
Depending on the injury, several techniques are combined:
Freeing the nerve when it is compressed by scar tissue but still in continuity.
A tear is bridged with a fragment of nerve taken from elsewhere, serving as a "bridge" for regrowth.
The key technique for root avulsions: a still-functioning donor nerve is connected to the nerve to be reactivated — restoring, for example, elbow flexion.
Muscle or tendon transfers, at a later stage, to complete the recovery.
The choice depends on the type and level of injury, the time elapsed, age, and which functions to restore first. It is a tailored strategy, built for each patient. See the expertise page on brachial plexus surgery.
Obstetric palsy in the newborn
There is a particular form that occurs at birth: obstetric brachial plexus palsy, caused by traction on the baby's shoulder during a difficult delivery. It most often affects the upper plexus, causing involvement of the shoulder and elbow.
Reassuring news, and a note of caution
Most babies recover on their own within the first few months. But some children retain a deficit, and forms that show no sign of recovery in the first months call for early specialized advice, because here too there is a window for possible surgery.
The message is the same as in adults: monitor closely, and do not let the moment pass when surgery could help.
Root avulsions are rare in the newborn.
Borrowed from adult surgery: nerve transfers work very well in babies.
Mosaic recovery and co-contractions, which defy all the rules of nerve mapping.
A baby is not a miniature adult, and the surgical strategies are different.
Living with it, and rehabilitation
Whether or not there is surgery, rehabilitation is essential and lengthy. It keeps the joints supple while the muscle waits for its nerve, prevents deformities, and supports the return of movement. Occupational therapy helps preserve independence and adapt everyday tasks.
Neuropathic pain must be treated early and specifically: it is part of the condition and must not be neglected. Recovery, for its part, is long — many months, often more than a year — and calls for patience and sustained support.
The legal side of compensation for personal injury should be considered early, with specialized lawyers.
The overall picture
This table sums up the article: the type of injury determines whether surgery is needed, and time determines whether it is still possible.
Follow-up after surgery
As every case is unique, see our knowledge center for cases put in context and explained.
Frequently asked questions
Glossary
A network of nerves, arising from the spinal cord at the neck, that controls the entire upper limb.
The origin of a nerve as it leaves the spinal cord; tearing it out is the most severe injury.
Tearing of a root out of the spinal cord: no spontaneous recovery is possible.
Pain arising from the nerve injury itself — burning, electric shocks — to be treated early.
A fragment of nerve used as a bridge to reconnect two torn nerve ends.
Connecting a functioning donor nerve to a paralyzed nerve to give it a new source of control.
A set of eye and eyelid signs suggesting a severe injury, close to the spinal cord.
References
Management of Adult Brachial Plexus Injuries. J Hand Surg. 2021 — beyond 6 months, a marked decline in regenerative potential and fibrosis of denervated muscles; Horner syndrome and deafferentation pain point to a preganglionic injury
Impact of Surgery Timing on Outcomes After Nerve Transfers. Plast Reconstr Surg Glob Open. 2025 — operating too early (< 3 months) is pointless if spontaneous reinnervation is possible, but beyond 12 months the risk is irreversible damage to the motor endplate
Surgical outcomes following nerve transfers in upper brachial plexus injuries. Indian J Plast Surg. 2009 — nerve transfers are the main option for root avulsions
Diffusion Tensor Imaging for Diagnosing Root Avulsions in Traumatic Adult Brachial Plexus Injuries. 2020 — conventional MRI has modest accuracy for avulsions; diffusion imaging improves their detection
Brachial plexus birth palsy: injury and rehabilitation. 2017 — high rate of spontaneous recovery (66-92%); monitoring and rehabilitation as first-line management
Neonatal brachial plexus palsy natural history (reviews 2017-2025) — about 80% of complete C5-T1 injuries retain a deficit at 18 months; surgery is considered when there is no active elbow flexion by 4-6 months
Peripheral nerve regeneration (~1 mm/day) — the physiological basis for the repair window and the timeline for muscle reinnervation
Long-term functional outcomes of nerve transfers by restored function
Reviewed and approved by Dr Frédéric Teboul, hand, brachial plexus, and peripheral nerve surgeon, member of the Académie Nationale de Chirurgie.
Last updated: 20 August 2026
Disclaimer. This article is for information only. It does not replace a medical consultation. Upper-limb palsy after trauma is a situation where early specialized advice is decisive: seek care without delay.
Author of this publication
Every piece of content is signed by its author and reviewed before publication.
Author
Dr Frédéric Teboul
Brachial plexus and peripheral nerve surgeon