What are dermatomes and how do they relate to spinal nerves. How can dermatome knowledge aid in diagnosing nerve-related conditions. What are the key dermatomes associated with L2 and L3 spinal nerves.

The Fundamentals of Dermatomes: Mapping Skin to Spinal Nerves

Dermatomes play a crucial role in our nervous system, serving as a bridge between our skin and the brain. These distinct areas of skin are innervated by specific spinal nerves, creating a systematic map of sensory information across the body. Understanding dermatomes is essential for healthcare professionals, as it aids in diagnosing and treating various neurological conditions.

How exactly are dermatomes defined? A dermatome is a region of skin that receives sensory input from a single spinal nerve. This intricate network covers the entire body, from the scalp to the toes, with each dermatome corresponding to a specific spinal nerve root.

The Spinal Nerve Classification System

To fully grasp the concept of dermatomes, it’s important to understand how spinal nerves are classified. There are 31 pairs of spinal nerves, divided into five groups based on their exit points from the spine:

• Cervical nerves (C1-C8): Exiting from the neck region
• Thoracic nerves (T1-T12): Exiting from the torso region
• Lumbar nerves (L1-L5): Exiting from the lower back region
• Sacral nerves (S1-S5): Exiting from the base of the spine
• Coccygeal nerve pair: Exiting from the tailbone (coccyx)

Interestingly, 30 out of these 31 pairs have corresponding dermatomes. The exception is the C1 spinal nerve, which doesn’t have an associated dermatome.

Exploring the L2 and L3 Dermatomes: Key Areas and Functions

The L2 and L3 dermatomes are particularly significant in the lumbar region, playing crucial roles in sensory perception and motor function of the lower body. But what specific areas do these dermatomes cover?

L2 Dermatome

The L2 dermatome encompasses the following areas:

• Lower back
• Hips
• Tops of the inner thighs

L3 Dermatome

The L3 dermatome covers:

• Lower back
• Inner thighs
• Inner legs just below the knees

Understanding these specific areas is crucial for healthcare professionals when diagnosing and treating conditions affecting the lumbar region.

Clinical Significance: How Dermatome Knowledge Aids in Diagnosis

Dermatome knowledge is invaluable in clinical settings, serving as a diagnostic tool for various neurological conditions. When symptoms occur within a specific dermatome, it can indicate damage or disruption to the corresponding nerve root. This information helps healthcare providers pinpoint the source of the problem and develop targeted treatment plans.

Common Conditions Affecting Dermatomes

Several medical conditions can impact spinal nerves and their associated dermatomes. Some of the most prevalent include:

1. Shingles (Herpes Zoster)
2. Pinched nerves
3. Traumatic injuries

By identifying the affected dermatome, healthcare professionals can more accurately diagnose these conditions and provide appropriate treatment.

Shingles: A Prime Example of Dermatome Involvement

Shingles, also known as herpes zoster, provides an excellent illustration of how dermatome knowledge aids in diagnosis and treatment. This viral infection, caused by the reactivation of the varicella-zoster virus, typically manifests along a single dermatome.

In adults, shingles often appears on the trunk, following one of the thoracic dermatomes. The characteristic rash is usually preceded by pain, itching, or tingling in the affected area. Other symptoms may include:

• Headache
• Sensitivity to bright light
• General malaise

In cases where a person has a weakened immune system, the shingles rash may spread across three or more dermatomes, a condition known as disseminated zoster.

Pinched Nerves: Locating the Source of Discomfort

Pinched nerves occur when a nerve root becomes compressed by surrounding structures such as bones, discs, tendons, or ligaments. While this compression can happen anywhere along the spine, it’s most common in the lumbar region.

How do dermatomes help in diagnosing pinched nerves? When a nerve is pinched, it can cause pain, tingling, or numbness in its corresponding dermatome. By identifying the affected dermatome, healthcare providers can trace the symptoms back to the specific nerve root causing the issue. This information is crucial for accurate diagnosis and developing an effective treatment plan.

Traumatic Injuries: Assessing Nerve Damage

Traumatic injuries to nerves can result from accidents or surgical procedures. In these cases, understanding dermatomes becomes particularly important. The severity and location of symptoms within specific dermatomes can help doctors determine the extent and precise location of nerve damage.

For instance, if a patient experiences numbness or tingling in the area covered by the L2 dermatome following a lower back injury, it may indicate damage to the L2 nerve root. This information guides further diagnostic tests and informs treatment decisions.

Beyond L2 and L3: A Comprehensive Look at Other Key Dermatomes

While our focus has been on the L2 and L3 dermatomes, it’s important to understand the broader picture. Let’s explore some other significant dermatomes and their corresponding areas:

Cervical Dermatomes

• C2: Base of the skull, behind the ear
• C3: Back of the head and upper neck
• C4: Lower neck and upper shoulders
• C5: Upper shoulders and collarbones
• C6: Upper forearms, thumbs, and index fingers
• C7: Upper back, backs of the arms, and middle fingers
• C8: Upper back, inner arms, ring and pinky fingers

Thoracic Dermatomes

• T1: Upper chest, back, and upper forearm
• T2-T4: Upper chest and back
• T5-T7: Mid-chest and back
• T8-T9: Upper abdomen and mid-back
• T10: Midline of the abdomen and mid-back
• T11-T12: Lower abdomen and mid-back

Remaining Lumbar Dermatomes

• L1: Groin, upper hips, and lower back
• L4: Backs of the knees, inner sections of the lower legs, and heels
• L5: Tops of the feet and fronts of the lower legs

Sacral Dermatomes

• S1: Lower back, buttocks, backs of the legs, and outer toes
• S2: Buttocks, genitals, backs of the legs, and heels
• S3: Buttocks and genitals
• S4-S5: Buttocks

The coccygeal nerves have a corresponding dermatome located on the buttocks, specifically in the area directly surrounding the tailbone or coccyx.

Practical Applications of Dermatome Knowledge in Healthcare

Understanding dermatomes has numerous practical applications in healthcare settings. Let’s explore some of the ways this knowledge is utilized:

Diagnostic Tool

As we’ve discussed, dermatome knowledge serves as a valuable diagnostic tool. When patients present with sensory symptoms like pain, numbness, or tingling, healthcare providers can use dermatome maps to identify the potentially affected nerve root. This helps narrow down the list of possible conditions and guides further diagnostic testing.

Surgical Planning

In neurosurgery and orthopedic surgery, dermatome knowledge is crucial for planning procedures involving the spine or peripheral nerves. Surgeons use this information to minimize the risk of nerve damage and to anticipate potential post-operative sensory changes.

Pain Management

For pain specialists, understanding dermatomes is essential in administering nerve blocks or other localized treatments. By targeting specific dermatomes, they can provide more precise and effective pain relief.

Rehabilitation

Physical therapists and occupational therapists use dermatome knowledge to assess sensory function and track progress in patients recovering from nerve injuries or neurological conditions. This information helps them design and adjust treatment plans for optimal recovery.

Patient Education

Healthcare providers can use dermatome maps to explain to patients the connection between their symptoms and specific nerve roots. This visual aid can help patients better understand their condition and the rationale behind certain treatments or diagnostic tests.

Challenges and Limitations in Dermatome Mapping

While dermatome knowledge is incredibly useful, it’s important to acknowledge that there are some challenges and limitations to consider:

Individual Variations

Dermatome maps represent a general pattern, but there can be slight variations from person to person. The precise boundaries of dermatomes may differ slightly among individuals.

Overlap

Dermatomes are not entirely discrete; there is often some overlap between adjacent dermatomes. This means that a single area of skin might receive sensory input from more than one spinal nerve.

Complex Conditions

Some neurological conditions can affect multiple nerve roots or produce symptoms that don’t neatly align with dermatome patterns. In these cases, dermatome knowledge alone may not be sufficient for diagnosis.

Dynamic Nature

The nervous system has some capacity for adaptation and reorganization. Following injury or in certain conditions, the sensory distribution might change over time.

Despite these limitations, dermatome knowledge remains a valuable tool in clinical practice when used in conjunction with other diagnostic methods and a comprehensive understanding of neuroanatomy.

Future Directions: Advancing Our Understanding of Dermatomes

As medical science continues to advance, our understanding of dermatomes and their clinical applications is likely to evolve. Some areas of ongoing research and potential future developments include:

Advanced Imaging Techniques

Improved neuroimaging technologies may allow for more precise mapping of individual dermatomes and their variations. This could lead to more personalized diagnostic and treatment approaches.

Neuroplasticity Studies

Further research into neuroplasticity may provide insights into how dermatomes can change over time, particularly in response to injury or disease. This could have implications for rehabilitation strategies.

Integration with Other Systems

Exploring the relationships between dermatomes and other bodily systems, such as the musculoskeletal or lymphatic systems, may lead to more holistic approaches to diagnosis and treatment.

Technological Applications

The development of advanced sensors or wearable devices that can map and monitor dermatome-specific sensations could revolutionize diagnostic processes and long-term patient monitoring.

Therapeutic Targeting

As our understanding of dermatomes becomes more nuanced, it may lead to more targeted therapies, such as precise nerve stimulation techniques or localized drug delivery systems.

These potential advancements underscore the ongoing importance of dermatome knowledge in medical science and clinical practice. As research progresses, we can expect even more sophisticated applications of this fundamental concept in neurology and related fields.

Dermatomes: Definition, chart, and diagram

Dermatomes are areas of skin that send signals to the brain through the spinal nerves. The dermatome system covers the entire body from the hands and fingers to the feet and toes.

The part of a nerve that exits the spinal cord is called the nerve root. Damage to a nerve root can trigger symptoms in the nerve’s corresponding dermatome.

Below, we show the locations of the dermatomes throughout the body. We also describe health conditions that can damage the spinal nerves and affect their dermatomes.

Share on PinterestVarious health problems damage the spinal nerves and affect the surrounding skin.

A dermatome is an area of skin that sends information to the brain via a single spinal nerve.

Spinal nerves exit the spine in pairs. There are 31 pairs in total, and 30 of these have corresponding dermatomes.

The exception is the C1 spinal nerve, which does not have a corresponding dermatome.

The spinal nerves are classified into five groups, according to the region of the spine from which they exit.

The five groups and their points of exit from the spine are:

1. Cervical nerves: These exit the neck region and are labeled C1–C8.
2. Thoracic nerves: These exit the torso region and are labeled T1–T12.
3. Lumbar nerves: These exit the lower back region and are labeled L1–L5.
4. Sacral nerves: These exit the base of the spine and are labeled S1–S5.
5. A coccygeal nerve pair: These exit the tailbone, or coccyx.

Each dermatome shares the label of its corresponding spinal nerve.

Some dermatomes overlap to a certain extent, and the precise layout of the dermatomes can vary slightly from one person to the next.

Below, we list the locations of the dermatomes that correspond to the spinal nerves in each group.

Cervical nerves and their dermatomes

• C2: the base of the skull, behind the ear
• C3: the back of the head and the upper neck
• C4: the lower neck and upper shoulders
• C5: the upper shoulders and the two collarbones
• C6: the upper forearms and the thumbs and index fingers
• C7: the upper back, backs of the arms, and middle fingers
• C8: the upper back, inner arms, and ring and pinky fingers

Thoracic nerves and their dermatomes

• T1: the upper chest and back and upper forearm
• T2, T3, and T4: the upper chest and back
• T5, T6, and T7: the mid-chest and back
• T8 and T9: the upper abdomen and mid-back
• T10: the midline of the abdomen and the mid-back
• T11 and T12: the lower abdomen and mid-back

Lumbar nerves and their dermatomes

• L1: the groin, upper hips, and lower back
• L2: the lower back, hips, and tops of the inner thighs
• L3: the lower back, inner thighs, and inner legs just below the knees
• L4: the backs of the knees, inner sections of the lower legs, and the heels
• L5: the tops of the feet and the fronts of the lower legs

Sacral nerves and their dermatomes

• S1: the lower back, buttocks, backs of the legs, and outer toes
• S2: the buttocks, genitals, backs of the legs, and heels
• S3: the buttocks and genitals
• S4 and S5: the buttocks

The coccygeal nerves and their dermatome

The dermatome corresponding with the coccygeal nerves is located on the buttocks, in the area directly around the tailbone, or coccyx.

Symptoms that occur within a dermatome sometimes indicate damage or disruption to the dermatome’s corresponding nerve. The location of these symptoms can, therefore, help doctors diagnose certain underlying medical conditions.

Some conditions that can affect the nerves and their corresponding dermatomes are:

Shingles

Shingles, or herpes zoster, is a viral infection caused by the reactivation of the varicella-zoster virus. This is the same virus that causes chickenpox.

After the body recovers from chickenpox, the virus can lie dormant and eventually reactivate as shingles.

In adults, shingles typically causes a rash to form on the trunk, along one of the thoracic dermatomes. The rash may be preceded by pain, itching, or tingling in the area.

Some other symptoms of shingles can include:

• a headache
• sensitivity to bright light
• a general feeling of being unwell

A person with a weakened immune system may develop a more widespread shingles rash that covers three or more dermatomes. Doctors refer to this as disseminated zoster.

Pinched nerves

A pinched nerve occurs when a nerve root has become compressed by a bone, disc, tendon, or ligament. This compression can occur anywhere along the spine, but it usually occurs in the lower, or lumbar, region.

A pinched nerve can cause pain, tingling, or numbness in its corresponding dermatome. As such, the location of the symptoms can help a doctor identify the affected nerve.

The doctor then diagnoses and treats the underlying cause of the pinched nerve and recommends ways to relieve the symptoms.

Traumatic injury

A traumatic injury to the nerves may result from an accident or surgery.

The severity of symptoms can help doctors determine the extent of the nerve injury.

Dermatomes are areas of skin, each of which is connected to a single spinal nerve. Together, these areas create a surface map of the body.

Dysfunction or damage to a spinal nerve can trigger symptoms in the corresponding dermatome. Nerves damage or dysfunction may result from infection, compression, or traumatic injury.

Doctors can sometimes use the severity of symptoms in a dermatome to determine the extent and location of nerve damage. They then work to diagnose and treat the underlying cause of the damage.

All About the L3-L4 Spinal Segment

The L3-L4 spinal motion segment, positioned in the middle of the lumbar spine, plays an important role in supporting the weight of the torso and protecting the cauda equina (nerves that descend from the spinal cord). While the L3-L4 motion segment is less likely to be injured compared to its lower counterparts, it may be subject to degeneration, trauma, and disc-related problems.

Learn how the lumbar spinal discs function and how lower back conditions can cause back pain and/or radiating pain. Watch Now

This article highlights the anatomy of the L3-L4 motion segment, the potential problems that may occur in this region, and the treatment options.

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Anatomy of the L3-L4 Spinal Motion Segment

The L3-L4 motion segment includes the following structures:

The L3-L4 motion segment provides a bony enclosure to protect the cauda equina and other delicate structures.

See Lumbar Spine Anatomy and Pain

In This Article:

• All About the L3-L4 Spinal Segment

• L3-L4 Treatment

• Lumbar Spine Anatomy Video

Potential Problems at L3-L4

Potential problems that may occur at the L3-L4 motion segment are:

• Osteoarthritis. The L3-L4 facets are typically subject to recurrent rotational strain, which may cause osteoarthritis to develop in these joints, resulting in facet joint pain.

  ¹
  Cramer GD. The Lumbar Region. In: Clinical Anatomy of the Spine, Spinal Cord, and Ans. Elsevier; 2014:246-311. doi:10.1016/b978-0-323-07954-9.00007-4

  See Facet Joint Disorders and Back Pain

• Degenerative spondylolisthesis. Age-related changes in the facet joints may result in the forward slippage of the L3 vertebra over L4.

  ¹
  Cramer GD. The Lumbar Region. In: Clinical Anatomy of the Spine, Spinal Cord, and Ans. Elsevier; 2014:246-311. doi:10.1016/b978-0-323-07954-9.00007-4

  See Degenerative Spondylolisthesis

• Disc problems. The L3-L4 disc may degenerate or herniate due to age-related changes or from trauma.

  See Lumbar Herniated Disc: What You Should Know

When subject to acute trauma, the L3-L4 motion segment may rarely undergo facet joint dislocation, fracture, and/or damage to the cauda equina. Rarely, tumors and infections may affect the L3-L4 motion segment.

The L3-L4 motion segment may cause muscle pain, discogenic pain, radicular (nerve root) pain, and/or radiculopathy (neurologic deficit) that typically affects the lower back and/or the legs.

When the L3 spinal nerve is involved, the following symptoms may occur:

• Sharp pain, typically felt as a shooting and/or burning feeling that may occur in the thigh and/or inner part of the leg.

  ³
  Dulebohn SC, Ngnitewe Massa R, Mesfin FB. Disc Herniation. [Updated 2019 Aug 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441822/

• Numbness in the thigh and/or inner part of the leg.

  ³
  Dulebohn SC, Ngnitewe Massa R, Mesfin FB. Disc Herniation. [Updated 2019 Aug 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441822/

• Weakness while moving the thigh and/or knee in different directions.

  ³
  Dulebohn SC, Ngnitewe Massa R, Mesfin FB. Disc Herniation. [Updated 2019 Aug 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441822/

• Abnormal sensations, such as a feeling of pins-and-needles and/or tingling.

These symptoms are typically experienced in one leg. Rarely, both legs may be affected together.

Read more about Lumbar Radiculopathy

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An injury to the cauda equina is called cauda equina syndrome. This syndrome is characterized by weakness, numbness, tingling, and /or paralysis in both legs. There may also be a reduction or complete loss of bowel and/or bladder control. Immediate medical attention is crucial in this condition to preserve leg function.

See Cauda Equina Syndrome

Nonsurgical treatments are often tried first to treat the conditions originating from L3-L4, except for cauda equina syndrome, which must have urgent surgical consultation. In rare cases, surgery may be considered.

See Non-Surgical Treatments for Lower Back Pain

Dr. Andrew Cole has 30 years of experience specializing in spine and joint pain management. Dr. Cole has held numerous medical appointments throughout his career, and recently served as the Executive Director of Rehabilitation & Performance Medicine Enterprise for Swedish Health Services and as Medical Director of Ambulatory Musculoskeletal Services for Swedish Medical Group.

• 1
  Cramer GD. The Lumbar Region. In: Clinical Anatomy of the Spine, Spinal Cord, and Ans. Elsevier; 2014:246-311. doi:10.1016/b978-0-323-07954-9.00007-4
• 2
  Wilke H-J, Volkheimer D. Basic Biomechanics of the Lumbar Spine. In: Biomechanics of the Spine. Elsevier; 2018:51-67. doi:10.1016/b978-0-12-812851-0.00004-5
• 3
  Dulebohn SC, Ngnitewe Massa R, Mesfin FB. Disc Herniation. [Updated 2019 Aug 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441822/

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• Lumbar Spine Anatomy and Pain

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Classification of the level and severity of spinal cord injury

Medical rehabilitation

Until the early 1990s, there was no single generally accepted classification of the level and severity of spinal cord injury. Doctors often used different definitions of the level of injury, complete and incomplete injuries. This article provides a classification developed by the American Spinal Injury Association (ASIA).

The spinal cord is located inside the spinal canal. Segmental levels of the spinal cord are determined by the anterior and posterior spinal roots, which connect to the spinal nerves near the intervertebral foramina. There are 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1-3 coccygeal segments of the spinal cord (Figure 1) . The upper cervical segments are located at the level of the bodies of the cervical vertebrae corresponding to their serial number. The lower cervical and upper thoracic segments are one vertebra higher than the corresponding vertebral bodies. In the middle thoracic region, this difference is equal to two vertebrae, in the lower thoracic region, to three vertebrae. The lumbar segments are located at the level of the bodies of the tenth and eleventh thoracic vertebrae, the sacral and coccygeal segments correspond to the levels of the twelfth thoracic and first lumbar vertebrae. The lower border of the spinal cord tapering in the form of a cone is located at the level of the second lumbar vertebra. Below this level is the terminal filament, which is the remnant of the final section of the embryonic spinal cord and is surrounded by the roots of the spinal nerves and the membranes of the spinal cord. The roots of the spinal nerves at this level form the so-called cauda equina.

Figure 1. Spine and segmentation of the spinal cord

Sensory and motor levels

A dermatome is a skin area innervated by a certain segment of the spinal cord. Figures 2 and 3 show dermatomes and key points for their definition, as well as muscle groups recommended for testing by the American Spinal Injury Association. After injury, dermatomes may expand or contract due to spinal cord plasticity. The complete form that ASIA recommends filling out when examining a patient with a spinal cord injury is available in English in pdf format (Adobe Acrobat Reader required to view).

Figure 2. Areas of sensitive innervation

C2-C4. C2-dermatome includes the skin of the occiput and upper neck. C3 – lower neck and collarbone. C4 – subclavian region.
C5-T1. These dermatomes are located on the arms. C5 – outer surface of the arm at and above the elbow. C6 – radial (from the side of the thumb) part of the forearm and hand. C7 – middle finger, C8 – lateral part of the hand, T1 – inner side of the forearm.
T2-T12. Thoracic dermatomes are located in the axillary and thoracic region. T3-T12 cover chest and back to hips. The nipples are located in the middle of T4. T10 is located near the navel. T12 ends just above the thigh.
L1-L5. Dermatomes located in the area of ​​the hip joints and groin are innervated by the L1 segment of the spinal cord. L2 and L3 cover the front of the thighs and knees. L4 and L5 – medial (inner) and lateral (outer) parts of the legs.
S1-S5. S1 is located on the heel and calf. S2 – back of the thighs and popliteal fossa. S3 – medial buttocks and S4-S5 – perineum. S5 – anal area.

Figure 3. Key muscle groups

Ten muscle groups reflect the motor innervation of the cervical and lumbosacral sections of the spinal cord. The ASIA system does not test the abdominal muscles (i.e., T2-11), since at the thoracic level it is much easier to locate the affected segment of the spinal cord along the corresponding dermatome. Some other muscles (such as the popliteal) are also excluded, since the segments that innervate them are already represented by other muscles.
Muscles of the hand. C5 innervates the flexors of the forearm (biceps), C6 the extensors of the wrist, C7 the extensors of the forearm (triceps), C8 the flexors of the fingers, and T1 the abductor (adductor) of the little finger.
Leg muscles. Innervated by the lumbar segments of the spinal cord. L2 innervates the hip flexors (m. psoas), L3 – knee extensors (m. quadriceps), L4 – dorsal foot flexors (m. tibialis anterior), L5 – thumb extensors (m. extensor hallucis longus), S1 – plantar flexors of the foot (m. gastrocnemius).
The anal sphincter is innervated by S4-S5. It is very important in the neurological examination of patients with spinal cord injury. If voluntary contraction of the anal sphincter is possible, the spinal cord injury is considered incomplete, regardless of any other evidence. It is important to note that testing certain muscle groups according to the ASIA classification simplifies the real situation, since almost every muscle receives innervation from two or more segments of the spinal cord.

Levels of spinal cord injury

Doctors use two different definitions of the level of spinal cord injury. Based on the same neurological examination, neuropathologists and rehabilitation specialists can determine a different level of injury. Neuropathologists usually determine the level of damage by the first segment of the spinal cord in which dysfunction is detected. At the same time, physical therapy and rehabilitation doctors determine the level of damage in the lowest segment with preserved function. Thus, if a patient has normal sensitivity at the C3 level and none with C4, the rehabilitator will say that the sensory level is C3, and the neuropathologist or neurosurgeon will call the damage level C4. Most traumatologists and orthopedists determine the level of damage by the level of damage to the spine.
ASIA recommends determining the level of damage by the lowest segment with preserved function.

Complete or partial damage

In the clinic, spinal cord injury is usually described as complete or incomplete. A complete injury is one in which there is no motor or sensory function below the site of injury. However, this definition is not always applicable. The following three examples illustrate the shortcomings and ambiguities of the traditional definition. The ASIA committee considered these issues when developing the spinal cord injury classification in 1992 year.

• Partially protected areas. Often, some segments of the spinal cord below the injury site retain a partial function, although in the other underlying segments, both motor and sensory function are absent. This is a fairly common occurrence. Many patients have areas of partial preservation. What kind of damage in this case – complete or incomplete, and at what level?
• Lateral preservation. A function can be partially saved on one side, but not on the other, or be there on another level. For example, if a patient has no sensitivity with C4 on the right and with T1 on the left, is this damage complete or incomplete, and at what level?
• Restore function. An initially missing function below the fault can then be restored. Does this mean that the spinal cord injury was complete and became incomplete? This is not a trivial matter, because if, for example, a clinical trial is being conducted in which only patients with complete spinal cord injury participate, it is necessary to stipulate the timing of the assessment of the status.

Most clinicians consider damage complete if there is a level of the spinal cord below which no function is detected. The Committee of the American Spinal Injury Association decided to take this criterion to its logical limit: the injury is considered complete if there is no motor and sensory function in the anal and perineal regions, which are innervated by the sacral (S4-S5) spinal cord.
The decision to make the absence of function at the S4-S5 level the criterion for complete damage not only removed the issue of zones of partial and lateral function preservation, but also solved the problem of restoration of function. As it turned out, only in a small number of patients in whom neurological functions at the level of S4-S5 were absent, they are restored spontaneously. The ASIA classification separately indicates the motor and sensory levels on each side and the zones of partial preservation, as this simplifies the criterion for assessing the completeness of the damage.
Finally, the question itself: complete damage or incomplete, can be debatable. The absence of motor and sensory function below the injury site does not necessarily mean the absence of axons that cross the injury site. Animal studies and clinical data indicate that the function that is absent below the site of injury can be restored to some extent by restoring the blood supply to the spinal cord (in the case of arteriovenous malformation caused by ischemia), decompression (if there is chronic compression – compression of the spinal cord) or drug therapy, for example, 4-aminopyridine. Assessing spinal cord injury as complete, one should not deprive a person of hope for recovery.

Classification of severity of spinal cord injury

Physicians have long used the clinical neurological deficit score, developed at Stokes Manville before World War II and introduced by Frankel in the 1970s. On this scale, patients were divided into five categories: no function (A), only sensory function (B), some sensory and motor function preserved (C), useful motor function (D), and normal (E).

ASIA Injury Severity Scale

A=Complete: No motor or sensory function in the sacral segments S4-S5
B=Incomplete: Sensation preserved but no motor function in segments below the neurological level, including S4-S5.
C=Incomplete: Motor function below the neurological level is preserved, but more than half of the key muscles are below
neurological level have a strength of less than 3 points.
D=Incomplete: Below neurological level of motor function is preserved, and at least half of the key muscles below the neurological level have a strength of 3 or more.
E=Normal: motor and sensory functions are normal.

Clinical syndromes

Central
Brown-Sekara
Front pillars
Brain cone
Pony tail

The ASIA Spinal Cord Injury Severity Scale is based on the Frankel scale, but differs from it in a number of important ways.
First, the absence of any function below the level of damage was replaced in category A with the absence of motor and sensory function in the sacral segments S4-S5. This definition is clear and unambiguous.
Category B ASIA is essentially identical to Frankel B, but adds a requirement for retained sensory function in S4-S5. It should be noted that the defining moment in categories A and B on the ASIA scale is the preservation of motor and sensory function in S4-S5.
ASIA also added a quantitative measure for categories C and D. The Frankel scale required clinicians to rate the functional fitness of the lower extremities. This not only introduced a subjective element into the classification, but also ignored the assessment of hand function in patients with cervical spinal cord injury. To circumvent this problem, ASIA specifies that category C includes patients with more than half of the key (recommended for testing) muscles retaining strength less than 3 points. Otherwise, the patient is assigned to category D.
Category E is interesting in that it includes patients with spinal cord injury without any neurological deficit, at least detectable on neurological examination. The ASIA Motor and Sensory Scale does not take into account the presence of spasticity, pain, muscle weakness, and some forms of dysesthesia that may result from spinal cord injury. Such patients should be assigned to category E.
ASIA has also classified incomplete spinal cord injury into five types.
Central syndrome (with greater damage to the gray matter of the spinal cord – hemorrhages, necrosis): unequal severity of motor disorders in the upper and lower extremities, a varied degree of sensitivity impairment.
Brown-Sequard syndrome – damage to one half of the spinal cord: impaired motor functions and proprioceptive sensitivity on the side of the lesion and loss of pain and temperature sensitivity on the other side.
Syndrome of the anterior pillars: impaired motor functions of both pain and temperature sensitivity while maintaining proprioceptive sensitivity (damage affects the lateral corticospinal and corticothalamic tracts, the posterior columns remain intact).
Syndromes of the conus medullary and cauda equina are observed when there is damage in the region of the cone of the spinal cord and cauda equina. In this case, the spinal nerves are injured, which is manifested by flaccid paralysis of the lower extremities, anesthesia of the sciatic zone, impaired bowel and bladder functions.

Conclusion

There is no unity in terminology related to the level and severity of spinal cord injury. The American Spinal Injury Association has attempted to standardize the terms used to describe spinal cord injury.