Accurate Education – Neck Pain

Neck pain may originate from pathology within the neck (primary) or neck pain may be referred from other parts of the body (secondary). The focus of this section is on primary neck pain. In primary neck pain, pain  can arise from the supportive structures of the cervical skeleton including muscles and their ligament attachments, the facet (or zygapophyseal) joints, the fibrous capsule (annulus fibrosus) of the intervertebral discs or from nerve structures. The nerve structures most commonly involved are the spinal nerve roots exiting the spinal cord bilaterally at each cervical vertebral level, but predominantly the lower neck, nerves C-4 through C-8.

The spinal cord itself is insensitive to pain but the membranes covering the cord, the arachnoid and dura, have nerve endings and registers pain. When the spinal cord in the neck is compressed by a herniated disc, enlarged facet joint and/or bone spur, complaints may include lack of coordination, clumsiness in gait or use of the upper extremities, and alterations in bowel and bladder control (incontinence or retention).

Neck Pain Based on Anatomic Source

Neck Pain: Myofascial

When evaluating neck pain based on anatomic source, the most common source is myofascial, pain arising from muscle and fascia, the tough membrane surrounding muscle and other tissues in the body. Muscle pain develops as a result of trauma, either abruptly such as in a whiplash injury or gradually, associated with other spinal injury when muscles tighten up to reduce movement of injured tissues, as may occur with a ruptured disc or chronic facet arthritis.

A very underappreciated atraumatic cause of myofascial pain in the neck and shoulders is that which evolves slowly as a result of prolonged muscle tension related to stress. When muscles remain in prolonged contraction, perceived as being tense or tight, muscle fibers develop painful areas called trigger points (RrP). As TrPs evolve over time they begin as points of muscle tenderness noted only upon palpation or stretching of the muscle, developing into a source of spontaneous pain, requiring neither palpation nor stretching. TrPs further evolve into sources of referred pain in which the pain is perceived in patterns distributed beyond the source location.

TrPs are most commonly found in the neck and shoulders with referral patterns responsible for headaches, facial pain and pain extending down the arms or into the uppar back and shoulders.  Myofascial and TrP pain can be constant or intermittent and can be quite severe, to the point of requiring opioids for relief. In fact, TrPs and their referral patterns can mimic the pain associated with herniated discs and facet pain, leading to aggressive treatment modalities including surgery and interventional procedures, including epidural steroid injections and nerve blocks to obtain relief. Unfortunately, neither surgery nor these interventional procedures will be effective for TrP pain and can actually make TrP pain worse.

For more information regading myofascial pain, trigger points and their treatment:

See Myofascial Pain

See Trigger Point Therapy

Neck Pain: Neurogenic (Nerve Root)

Neck pain generated from spinal nerve roots is a result of compression or chemical irritation. Compression of a nerve root can occur with disc bulging or herniation, enlargement of facet joints adjacent to the nerve root, bone spurs or a combination of any or all three. Chemical irritation of nerve roots can occur when discs are injured and leak contents that are inflammatory, especially when herniated discs extrude highly irritating components of the nucleus pulposis, or central core of the disc. Bone spurs can result from trauma or degenerative processes related to chronic use and repetitive overuse.

Neurogenic pain from affected nerve roots is typically described as burning, electric, tingling and sometimes sharp or stabbing. The location and distribution of nerve root pain varies based on the nerve root involved in patterns called dermatomes. A dermatome is “an area of the skin supplied by nerves from a single spinal root” Dermatomes have been carefully mapped  to demonstrate “typical” anatomic distributions but, unfortunately, there is a great deal of individual variation that render these maps unreliable.

Disc protrusions and herniations are common sources of nerve root compression and irritation. A posterior lateral disc protrusion results in compression of the nerve whose number corresponds to that of the lower vertebral body. For instance, a disc protrusion at the C5-6 interspace involves the 6th nerve root. The most common location for a disc protrusion is C5-6, followed closely by C6-7, and then by C4-5. Protrusions at C2-3 and C7-T1 can occur but are rare.

Spinal nerve roots exit the spinal cord through windows (neural foramen) at each level of the cervical spine. In the normal cervical spine, the cervical nerve root occupies about one third of the neural foramen. Degenerative changes of the spine, hypertrophy (enlargement) of ligaments, and intervertebral disc protrusions decrease the available space of the nerve. When the patient extends his/her neck, the neural foramen decrease
s in size, which accentuates nerve root compression. If neck extension is not painful, it is unlikely that the pain is caused by nerve root compression in the neural foramen.

Radicular Pain

Compression or irritation of the C-6 nerve root typically results in a “radicular” pattern of pain, extending down the arm and to the hand, thumb and index finger. With the C-7 nerve root the radicular  pattern of pain typically extends down the arm and to the hand and middle finger while similarlly the C-8 nerve root involves the 5th finger. Although disc protrusions at C3-4 are not common, when they occur and the fourth nerve root is compressed, the pain distribution is to the superior aspect of the shoulder rather than into the arm, forearm, or hand.

Neck Pain: Facet

The facet joints in the neck providing movement forward (flexion), backward (extension), leaning side to side (abduction) and rotation can be sources of pain, typically as a result of arthritis or trauma.

Neck Pain: Discs

Pain arising from damaged discs can arise from the disc itself or from nerve roots that are either compressed by the disc or irritated by inflammatory chemicals released from the damaged disc. The fibrous capsule (annulus) of intervertebral discs contains pain receptors that register pain when discs are damaged or disrupted (discogenic pain). Discogenic pain has pain referral patterns that are typical for each cervical disc. While individual variations are common, knowing usual pain referral patterns can help correlate findings on MRIs with a person’s percieved pain to accurately define a source. Referral patterns from disrupted discs can be unilateral or bilateral.

The following discogenic pain referral patterns have been identified:

Arm-Abduction Sign

The arm-abduction sign, when pain is relieved by resting hand on head, is usually positive in cervical nerve root compression. Theoretically, tension on the nerve is decreased by arm abduction. This may be the only position of comfort for patients with large lateral disc herniations.

Hoffmann’s sign

Hof fmann sign is used to predict cervical spinal cord compression. Hoffmann’s sign, elicited by flicking the distal phalanx of the long finger. A negative response is no motion of the thumb. A positive response is flexion of the thumb at the interphalangeal joint. The sensitivity of the Hoffmann sign relative to cord compression was 58%, specificity 78%, positive predictive value 62%, negative predictive value 75%.

Sensation

Strength

Different muscles are innervated by specific spinal nerves and the presence of weakness allows identification of an affected nerve. The amount of weakness indicates the degree of damage to the motor component of the nerve. In nerve root compression, it is not uncommon to discover weakness that the patient may not be aware of.

Reflexes

In most patients with neck pain, an absent or depressed deep-tendon reflex is the result of nerve root compression. When the reflexes are hyperactive, the lesion is centrally located either in the spinal cord or brain involving the pyramidal system. While the intensity of deep-tendon reflexes is variable between normal individuals; however, asymmetry in reflex response usually indicates pathology.

Age correlates with the source of chronic LBP. Specifically, lumbar intervertebral disc cases were found to be significantly younger (average age 43.7 years) than cases of facet joint pain cases (59.8 years ) and SI pain cases (62.3 years).

There are multiple arguments in favor of, or against, the diagnostic accuracy of controlled local anesthetic blocks, but controlled local anesthetic blocks continue to be the best available tool to identify intervertebral discs, facet, or sacroiliac joint(s) as the source of low back pain. Unfortunately, these procedures are invasive, expensive, painful and often difficult to interpret, and therefore they may not be suitable for routine clinical use as a primary diagnostic modality. This leaves clinical assessment as the only process in many cases.