3 Types of Nerve Injury: Symptoms, Causes & Treatment

Nerve injuries can develop due to various factors, including physical trauma and medical diseases. The following are some of the most common causes of nerve injuries:

Traumatic Causes

Nerve injuries can occur due to traumatic incidents, like accidents or falls, where the nerves get damaged due to sudden impact or excessive pressure. These injuries disrupt the normal communication between the brain and the body. It affects various sensations and functions. Below are the traumatic causes of nerve injuries:

1. Mechanical Injury: Physical trauma, such as fractures, dislocations, and crush injuries that directly impact nerves.

2. Penetrating Injuries: Sharp items like knives or glass shards can penetrate tissues and harm nerves.

3. Stretch Injuries: During accidents or injuries, nerves can be stretched beyond their natural range, causing injury.

4. Compression: Prolonged nerve compression, such as carpal tunnel syndrome, can result in harm.

Latrogenic Causes

Latrogenic nerve injuries stem from medical procedures or treatments where nerves might inadvertently get harmed. These unintended injuries can disrupt nerve function, impacting sensations and bodily functions. Below are the iatrogenic causes of nerve injuries:

1. Surgical Interventions: Nerve injuries can occur during surgical interventions, particularly those involving nerves or adjacent structures.

2. Medical Injections: Inadvertent nerve injury can result from injections, including nerve blocks or vaccinations.

3. Medical Equipment: Catheters or needles can cause nerve injury when inserted or removed.

Disease-Related Factors

Disease-related nerve injuries arise from certain health conditions affected by the nerves, such as diabetes, autoimmune disorders, or infections. 

These underlying diseases can harm the nerves, disrupting communication between the brain and the body. It causes various symptoms and impairments. Below are the disease-related causes of nerve injuries:

1. Inflammatory conditions: Autoimmune illnesses can cause nerve inflammation (e.g., Guillain-Barré syndrome).

2. Infectious Diseases: Some illnesses, such as leprosy and herpes zoster, can directly impact nerves.

3. Metabolic Disorders: Diabetes and other metabolic disorders can cause nerve damage over time (diabetic neuropathy).

4. Tumours: These can compress or invade nerves, resulting in harm.

Toxic Sources

Toxic nerve injuries occur when exposure to harmful substances, like certain chemicals or drugs, damages the nerves in the body. These toxins can interfere with the normal functioning of nerves, causing a range of sensations and functions to be compromised. These include:

1. Chemical Exposure: Certain chemicals or toxins, such as lead, can cause nerve damage.

2. Alcohol and Drug Misuse: Neuropathy can be caused by long-term alcohol or drug misuse.

Entrapment and Compression

Anatomical pressure points or tight areas in the body can compress or entrap nerves, resulting in nerve damage (e.g., carpal tunnel syndrome).

Nerve injuries are divided into many groups based on various characteristics, including the size and severity of the lesion. The Sunderland and Seddon classifications are two of the most regularly used categorisation methods for describing nerve damage. 

Seddon's Classification

Seddon's Classification, often known as the Seddon Classification of Nerve Injuries, is a system for categorising peripheral nerve injuries. Sir Herbert Sheddon developed it. This classification divides nerve injuries into three main categories:

1. Neurapraxia (Type I): This is the mildest form of nerve injury. Neurapraxia is a momentary lack of nerve function caused by nerve compression or stretching. The nerve is unharmed, and no structural damage has occurred. Recovery is typically quick and complete.
2. Axonotmesis (Type II): Axonotmesis involves nerve fibre (axon) injury but with varying degrees of damage to the surrounding connective tissue. Seddon categorised this category further into:
3. Axonotmesis with Myelin Damage: In this subtype, the myelin sheath around the nerve fibres is damaged, which can delay nerve transmission. Nerve regeneration is possible, but recovery may be slow.
4. Axonotmesis without Myelin Damage: In this subtype, the myelin sheath is not damaged, but the nerve fibres are harmed. Recovery is still possible but may be slower than axonotmesis with myelin injury.
5. Neurotmesis (Type III): Neurotmesis is the most severe type of nerve injury. It involves full nerve fibre destruction and injury to the surrounding connective tissue.

Sunderland's Classification

The Sunderland Classification is a system for categorising nerve injuries based on severity. Dr Thomas J. Sunderland, a British neurosurgeon, developed it. This classification divides nerve injuries into five main categories:

1. First Degree: Nerves are stretched but not torn. Recovery is usually complete and spontaneous.

2. Second Degree: Some nerve fibres are damaged, causing a loss of function. However, recovery is still likely with time.

3. Third Degree: Here, the nerve fibres are partially torn. Recovery might occur, but it could be incomplete and take longer.

4. Fourth Degree: Nerve fibres are completely severed, requiring surgical repair for potential recovery.

5. Fifth Degree: The nerve is completely severed and cannot be repaired, necessitating alternative treatments or accommodations.

Accurate diagnosis is crucial for determining the nerve injury's location, type, and severity, guiding treatment decisions. Here are the key steps and methods involved in diagnosing nerve injuries:

Clinical Evaluation

1. Patient History: Taking a full medical history, including information regarding the development of symptoms and any medical problems, is the first step in diagnosis.

2. Physical Examination: It checks muscle strength, sensitivity, reflexes, and any apparent symptoms of nerve injury. This includes muscle atrophy or weakening.

Imaging

1. Nerve Conduction Studies (NCS): NCS is a technique that examines the speed and strength of electrical signals as they pass along nerves. It can aid in identifying nerve damage, the magnitude of the injury, and the location of the injury.

2. Electromyography (EMG): EMG measures muscular electrical activity and can help detect whether muscle weakness is caused by nerve injury.

3. Ultrasound Imaging: This can assist in discovering structural abnormalities or nerve compression by seeing nerves and surrounding tissues.

4. MRI Scans: They can provide detailed images of soft tissues such as nerves. They are very helpful in diagnosing nerve compression, tumours, and lesions.

5. Computed Tomography (CT) Myelography: CT myelography injects contrast dye into the spinal fluid to see the spinal cord and nerve roots. 

Laboratory Examinations

Blood tests may be performed to rule out any underlying medical diseases that may be causing or contributing to nerve damage. This includes diabetes, vitamin deficiencies, or autoimmune disorders.

Specialised Examinations

1. QST (Quantitative Sensory Testing): QST assesses a patient's capacity to detect numerous sensory cues such as touch, temperature, and vibration. It can aid in the detection of sensory nerve problems.

2. Skin Biopsy: A skin biopsy may be conducted to examine nerve fibre density in the skin in situations of tiny fibre neuropathy or some rare nerve illnesses.

Electrodiagnostic

1. Somatosensory Evoked Potentials (SSEPs) and Visual Evoked Potentials (VEPs): These tests assess the nervous system's electrical reactions to certain sensory stimuli. They can aid in the diagnosis of disorders affecting the nerve system's sensory pathways.

The treatment of nerve injuries depends on the type, severity, and location of the injury, as well as the underlying cause. Here are some common approaches to the treatment of nerve injuries:

1. Observation and Rest: Mild nerve injuries might heal on their own with rest and time.

2. Physical Therapy: Special exercises can help maintain muscle strength and flexibility during nerve recovery.

3. Medications: Pain relievers and anti-inflammatory drugs can manage discomfort during healing.

4. Nerve Decompression: Relieving the pressure can aid recovery if nerves are compressed.

5. Electrical Stimulation: Techniques like TENS (Transcutaneous Electrical Nerve Stimulation) can alleviate pain and aid healing.

6. Bracing or Splinting: Supportive devices can protect and immobilize the affected area.

7. Surgery: Severely damaged nerves might need surgical repair or grafting.

Preventing nerve injuries involves taking precautions and changing one's lifestyle to limit the chance of trauma, compression, and other variables that might cause nerve injury. Here are precautions to take to lessen the risk of nerve injury:

1. Implement safety practices in the workplace and leisure settings to limit the chance of accidents, falls, and collisions.

2. When participating in high-risk activities, wear adequate protection gear such as helmets, padding, and safety harnesses.

3. Promote responsible conduct, such as safe driving and avoiding risky activities that can result in traumatic injuries.

4. Exercise regularly to improve general health and lower the risk of nerve-related disorders.

5. Smoking can decrease circulation and contribute to nerve injury; quitting is advisable.

Understanding the types of nerve injuries and their potential treatments is essential for medical specialists and those affected by them. Remember that preventing nerve injuries is generally more beneficial and less challenging than treating them after they occur.

Please contact HexaHealth to learn more about this issue or have any other medical concerns. HexaHealth is one of the best patient care and service platforms in India. So, why wait? Schedule your consultation today!

Suggested Reads

1. Vagus Nerve Stimulation

2. Optic Nerve Disorder