Cervical Spine (Neck)
Neck Anatomy and Disorders
Neck anatomy is a well-engineered structure of bones, nerves, muscles, ligaments and tendons. The cervical spine (neck) is delicate - housing the spinal cord that sends messages from the brain to control all aspects of the body - while also remarkably flexible, allowing movement in all directions, and strong.
The neck begins at the base of the skull and through a series of seven vertebral segments connects to the thoracic spine (the upper back).
With its complex and intricate construct, and the many stresses and force that can be placed on it through a trauma or even just daily activities, the cervical spine is at risk for developing a number of painful conditions, such as:
- Cervical degenerative disc disease
- Cervical herniated disc
- Cervical stenosis
- Simple muscle strain resulting in a painful or stiff neck.
The cervical spine maintains several crucial roles, including:
- Housing and protecting the spinal cord. A bundle of nerves that extends from the brain and runs through the cervical spine and thoracic spine (upper and middle back) prior to ending just before the lumbar spine (lower back), the spinal cord relays messages from the brain to the rest of the body.
- Supporting the head and its movement. The cervical spine literally shoulders a big load, as the head weighs on average between 10 and 13 pounds. In addition to supporting the head, the cervical spine allows for the head's flexibility, including rotational, flexion/extension and lateral bending motions.
- Facilitating flow of blood to the brain. Vertebral openings (vertebral foramen) in the cervical spine provide a passageway for vertebral arteries to pass and ensure proper blood flow to the brain. These openings are present only in the vertebrae of the cervical spine.
The cervical vertebrae play a key role in maintaining these functions in the neck.
The cervical spine is comprised of seven vertebrae - C1, C2, C3, C4, C5, C6, C7 (often noted as C1-C7) - that begin at the base of the skull and extend down to the thoracic spine. The cervical vertebrae are composed of cylindrical bones (vertebral bodies) that lie in front of the spinal cord, and work with the muscles, joints, ligaments and tendons to provide support, structure and stabilization to the neck.
The first cervical vertebra is unique in that it is a ring that rotates around the second vertebral body (the odontoid). The cervical vertebrae closest to the skull are the smallest. All of the cervical vertebrae are smaller than the vertebrae in the thoracic spine (upper back) and the lumbar spine (lower back).
Stacked on top of each other with a cervical disc in between them, the cervical vertebrae provide strength and structure to the cervical spine and support the head.
The cervical vertebrae also provide for structure and control of certain types of movement in the neck (with the movement described in terms of the two vertebral bodies that are connected), including:
- Rotation (moving the head from side to side). Most rotation of the neck takes place in the first two segments of the cervical spine, specifically the atlas (C1) and the axis (C2).
- Flexion (moving the head forward) and extension (moving the head backward). Most flexion and extension movements in the neck are controlled by the C5-C6 and C6-C7 segments of the spine. Unlike the first two cervical vertebrae, the remaining five cervical vertebrae, C3 through C7, are constructed more similarly to the rest of the spine, with three joints making up each vertebral segment (a disc in the front and two facets joints in the back).
For the most part, the cervical vertebrae are extremely durable and resistant to injury. Most neck pain relating to the cervical vertebrae is the result of wear and tear, not an injury.
If a cervical vertebra is fractured by trauma, such as in a car accident, a fall, a diving accident that jars the head, or any other significant cervical injury, the spinal cord can be damaged, possibly resulting in not only cervical pain but different types of impaired functioning depending on which cervical vertebra has been injured.
For example, a cervical injury to:
- C1, C2 or C3 (one of the first three cervical vertebrae) may result in functional loss of the diaphragm and necessitate the use of a ventilator to aid in breathing
- C4 (the fourth cervical vertebra, etc) may prompt loss of functional control of the shoulders and biceps
- C5 may result in complete functional loss at the wrists and hands in addition to partial loss of the shoulders and biceps
- C6 may result in complete loss of hand function and limited use of the wrist
- C7 may result in decreased skillful use in the hands and fingers, and limited use of the arms.
A full review of cervical fractures is beyond the scope of this article.
It should be noted that trauma to cervical vertebrae occurs less often than cervical pain and other symptoms resulting from changes that occur with aging, such as the development of bone spurs and cervical osteoarthritis.
A bone spur (medically known as an osteophyte) describes an enlargement of the facet joints, the small stabilizing joints that are located between and behind the adjacent cervical vertebrae. Bone spurs are smooth structures that can grow on the bones and tend to occur in adults over 60 years of age. Patients with cervical bone spurs may or may not have symptoms, which could include neck pain and/or referred pain and weakness in the arms and the legs. For example, patients with cervical bone spurs may experience dull neck pain that occurs when standing. In some instances, the pain may be referred to the shoulders or prompt headaches.
However, it must be emphasized that the presence of bone spurs in and of themselves does not necessarily mean this is what is generating a patient's pain. Most bones spurs are simply radiographic findings indicating a patient has degeneration in the neck.
Bone spurs may form as the result of cervical osteoarthritis, a condition marked by degeneration and breakdown of the cartilage between the facet joints in the cervical spine. With cervical osteoarthritis (also known as cervical arthritis), different symptoms may occur, such as pain that:
- Refers to the shoulder or between the shoulder blades
- Feels worse at certain times of the day (early in the morning, late at night)
- Calms with rest.
There are six cervical discs and 23 total discs in the entire spinal column. Each cervical disc rests between the cervical vertebrae, acts as a shock absorber in the cervical spine and allows the neck to handle much stress.
Composed of collagen and ligaments, the cervical discs also hold the cervical vertebrae together and allow for flexibility and different movements of the neck.
Each cervical disc is made up of a tough exterior (annulus fibrosus) and a soft, jelly interior (nucleus pulposus), with the circular, outer core comprised of collagen fibers that surround the inner core and distribute pressure and force on the structure. The nucleus pulposus is a loose, fibrous network suspended in mucoprotein gel that is sealed by the annulus fibrosus and needs to be well-hydrated in order to maintain its strength and softness, and serve as the major carrier of the body's axial load.
With age, the cervical discs lose water, stiffen and become less flexible in adjusting to compression. Such degenerative changes may result in the inner core of the cervical disc extruding through the outer core and coming in contact with the spinal nerve root (what is known as a herniated cervical disc).
In other instances, the cervical disc may degenerate as a result of direct trauma or gradual changes. With no blood supply and very few nerve endings, the cervical discs cannot repair themselves.
Cervical Symptoms from Degenerative Disc Disease
Cervical degenerative disc disease refers to when a cervical disc is the actual source of pain in the neck, possibly from twisting or falling on the neck but more likely from day-to-day wear and tear on the cervical spine.
Cervical symptoms related to a degenerative cervical disc may include a stiff neck and/or numbness, tingling and weakness in the neck, arms and shoulders as a result of a cervical nerve that has been irritated or pinched by the degeneration. Such cervical symptoms may persist for several months and fluctuate in terms of intensity.
Patients with a degenerative cervical disc will typically begin with non-surgical treatments (NSAIDs, exercise, chiropractic, physical therapy, etc.) to seek cervical pain relief; however, if such treatment proves ineffective, a cervical spine surgery that removes the disc or fuses the spine may be necessary.
While not as common as degenerative disc disease in the lumbar spine (lower back), cervical disc disease nevertheless is a relatively common source of neck pain.
In addition to the seven cervical vertebrae, cervical anatomy features eight cervical nerves (C1-C8) that branch off of the spinal cord and control different types of bodily and sensory activities.
Each cervical nerve is named based on the lower cervical vertebra that it runs between. As an example, the nerve root that runs between the second cervical vertebra and the third cervical vertebra in the neck is described as the C3 nerve.
Branching off from the nerves in the spinal cord, the cervical nerves are responsible for relaying messages and ensuring functioning to different body parts. More specifically:
- C1 and C2 (the first two cervical nerves) control the head.
- C3 and C4 help control the diaphragm (the sheet of muscle that stretches to the bottom of the rib cage and plays an important role in breathing and respiration).
- C5 controls upper body muscles like the Deltoids (which form the rounded contours of the shoulders) and the Biceps (which allow flexion of the elbow and rotation of the forearm).
- C6 controls the wrist extensors (muscles like the extensor carpi radialis longus, extensor carpi radialis brevis and extensor carpi ulnaris that control wrist extension and hyperextension) and also provides some innervation to the biceps.
- C7 controls the Triceps (the large muscle on the back of the arm that allows for straightening of the elbow).
- C8 controls the hands.
When any of the highly sensitive cervical nerves are irritated (possibly from a herniated cervical disc or cervical stenosis), neck pain and other symptoms may ensue, with functioning possibly affected in different ways.
A herniated cervical disc occurs when a nerve root is irritated and/or pinched as a result of a cervical disc's inner core extruding through the outer core and coming in contact with the nerve root. Depending on the location of the cervical disc herniation and which cervical nerve is affected (most often C6, C7; sometimes C5, C8), various cervical symptoms may occur.
For example, when the following cervical nerve is compressed as a result of a herniated disc, patient symptoms may include:
- C5 - shoulder pain, deltoid weakness, small amount of shoulder numbness, and/or diminished biceps reflex
- C6 - weakness in the biceps and wrist extensors, radiating arm pain/numbness in the thumb, and/or diminished brachioradialis reflex (mid-forearm)
- C7 - radiating arm pain/numbness to the middle finger and/or a diminished triceps reflex· C8 - hand dysfunction, pain/numbness on the outside of the hand and/or impaired reflexes in the hand.
If standard non-surgical treatments (exercise, NSAIDs, etc.) do not provide relief in a 6-12 week period for symptoms from a cervical disc herniation, a surgery that removes the pressure on the irritated nerve and creates more room for it to heal and function may be recommended.
Cervical Symptoms from Cervical Stenosis
Cervical stenosis refers to when the spinal cord in the neck is compressed, potentially resulting in no symptoms at all or rather noticeable symptoms including:
- Radicular arm pain
- A heavy feeling in the legs
- An inability to walk at a brisk pace
- Fine motor skill deterioration
- Intermittent shooting pain in the arms and legs
- Pain that is made worse with certain positions (called cervical foraminal stenosis) such as when holding the neck in extension.
Spinal cord compression that results in dysfunction is described as cervical stenosis with myelopathy.
Over time, degenerative changes to the cervical vertebrae, discs and joints may have significant effects on the spinal cord, which runs from the brain through the cervical spine and thoracic spine before branching off to other parts of the body.
Cervical stenosis is one such degenerative condition that may affect the spinal cord and lead to compromised coordination of the extremities. When diagnosing cervical stenosis, doctors must determine whether progressive dysfunction (myelopathy) is present as a result of the spinal cord compression.
While extremely rare, progressive cases of cervical stenosis with myelopathy may result in weakness and paralysis, thus making accurate diagnosis and treatment especially important.
Symptoms of Spinal Cord Compression and Dysfunction
It's important to know that in many cases cervical stenosis is asymptomatic, meaning that the spinal cord is compressed but the patient is not experiencing any of the common symptoms. In these cases, the patient may simply be monitored to ensure that the spinal cord continues to function normally and that myelopathy (i.e. spinal cord dysfunction) does not develop as a result of the compression.
In other situations, cervical stenosis with myelopathy may present itself in symptoms that include a heavy feeling in the arms and legs, cervical pain that is referred to the arm, shooting pains in the arms and legs, and/or difficulty walking and performing activities involving fine motor skills (handwriting, buttoning a shirt, etc.).
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