Nerve Injuries After Accidents – Causes and Effects

Our nerves function much like electrical cables: they transmit information between the brain, spinal cord, and different parts of the body. To protect these delicate nerve fibers (axons), they are surrounded by a strong outer sheath, similar to the insulation of a cable.

Cartoon-style neuron in knight armor with helmet and shield, showing a friendly and confident expression. — A strong neuron in knight armor demonstrates the protective function of the myelin sheath against external influences.

In everyday life, this sheath provides reliable protection. However, under significant stress — such as during accidents, falls, or crushing injuries — functional impairments or damage can occur, commonly referred to as nerve injuries after accidents.

Illustration of a yellow nerve cell hitting the ground upside down, symbolizing nerve damage after an accident. — Most nerves remain unharmed in accidents, but sometimes they can be affected.

Types of Nerve Injuries

When nerve function is impaired, various nerve injury symptoms may occur – including tingling, numbness, pain, or muscle weakness. We distinguish between two main types of nerve injuries:

Primary nerve injury: Occurs directly at the time of the accident.
Secondary nerve injury: Develops later during the healing process, for example due to scar formation.

Cartoon-style illustration of a yellow nerve cell with a sad face and a plaster on its head, symbolizing nerve damage. — When nerve function is impaired, tingling, numbness, pain, or weakness may occur.

Primary Nerve Injuries: Immediate Consequences After an Accident

These injuries happen directly at the moment of trauma. Depending on the type of accident, several forms can occur.
These immediate injuries are a common form of nerve damage after trauma and can affect both the nerve sheath and the inner fibers.

Cartoon-style illustration of a yellow nerve cell with a stone falling on its head, symbolizing primary nerve injuries after accidents. — Strong external forces can sometimes lead to nerve damage.

Nerve transection

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This video clip shows the complete transection of a nerve by a sharp object. Both the nerve sheath and the axons are damaged in the process. Due to the nerve’s slight resting tension, the two ends retract from each other. As a result, nerve conduction is completely interrupted.

Cause: Sharp objects such as knives, glass shards, or metal edges.
Consequence: The nerve is completely or partially severed. The ends pull apart, similar to a snapped cable. Signal transmission is interrupted, which can result in paralysis, sensory disturbances, or pain.

Nerve compression

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This video shows how a nerve is squeezed by pressure from the outside. The nerve stays whole on the outside, but depending on how strong the pressure is, it can be damaged inside. This may affect how well it sends signals.

Cause: Strong pressure, for example from a bone fracture or trapped limbs.
Example: A fracture of the upper arm bone can compress the radial nerve in the upper arm canal, often resulting in the characteristic “wrist drop.”
Consequence: The outer sheath remains intact, but the transmission of nerve impulses is impaired.

Nerve rupture

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The nerve sheath protects the inner nerve fibers from tensile forces. If external traction exceeds the tensile strength of the sheath, the internal fibers may become damaged. Depending on the force, the outer sheath may appear intact, while the conducting structures inside are severely impaired.

Cause: Strong traction forces, such as from a dislocated shoulder or motorcycle accident.
Examples:
- A shoulder dislocation can affect the axillary nerve, which may limit shoulder mobility.
- A knee dislocation poses a risk to the peroneal nerve, potentially impairing foot lifting.
Consequence: The nerve may appear intact on the outside, but the internal fibers can be damaged and lose conductivity.

Other Causes of Nerve Damage

Not only mechanical forces can damage nerves. Heat, cold, electric shock, or chemical substances can also affect these sensitive structures.

Cartoon-style illustration of a nerve cell with heat damage on the left arm, frostbite on the right arm, and acid burns on the feet. — Cold, heat, chemicals, or electricity can also affect the nerves and cause damage.

Secondary Nerve Injuries After Accidents: Delayed Effects After an Accident

Not all nerve injuries after accidents appear immediately; some develop gradually over time. These delayed effects are known as secondary nerve injuries.

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This video clip shows a nerve surrounded by scar tissue. As the scar contracts, the nerve structure within it may become compressed.
Just before entering the scar, the nerve often shows a swelling — likely due to congestion — which can be visualized using imaging techniques.

Scar formation

Cause: Soft tissue injuries that lead to scar formation during the healing process.
Problem: Over time, scar tissue can contract. Nerves embedded in scar tissue may come under increasing pressure.
Consequence: Symptoms such as numbness, tingling, or muscle weakness may appear weeks or even months after the injury.
Often, patients initially notice no symptoms. Only over time, as scar tissue hardens, do abnormal sensations develop that should be medically evaluated.

Scar tissue can gradually constrict nerves and affect their function over weeks or months.

Diagnostic Options

If metal implants (such as screws or plates) make MRI scans difficult, high-resolution nerve ultrasound is a helpful alternative. This method allows for precise visualization of nerves, even near metal.

Metal implants can sometimes contribute to nerve irritation — nerve ultrasound helps visualize the structures despite the metal.

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Disclaimer: This video is for informational purposes only. It does not replace medical advice or examination.

This video clip shows a nerve ultrasound examination in a patient with a humeral fracture. The radial nerve is highlighted in yellow.
The patient underwent surgical fixation with a plate and screws. After the procedure, he developed a wrist drop.
Ultrasound revealed that the radial nerve — which runs directly along the mid-humerus — was injured by one of the screws.
The screw had been inserted from the side opposite the nerve, and its protruding tip lifted the nerve away from the bone.
Although nerve continuity was preserved, function was lost due to compression by the screw.

Conclusion: Early Assessment Can Improve Treatment Options

Regardless of whether symptoms occur immediately after an accident or appear later, early evaluation of potential nerve injuries after accidents is strongly recommended.
Modern diagnostic techniques — including nerve conduction studies, electromyography (EMG), high-resolution nerve ultrasound, and MR neurography — make it possible to detect nerve changes at an early stage.

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Disclaimer: The information provided on this page is for general informational purposes only and does not constitute medical advice. It is not a substitute for personal consultation, examination, or treatment by a physician or other qualified healthcare professional. No guarantees of healing or cure are made. While we strive for accuracy and completeness, we cannot guarantee that all content is up to date or free from errors, and we accept no liability for any inaccuracies.