Pinch nerve in neck pain in arm
The cervical spine (neck) is made up of seven vertebrae. C-1 articulates with the occiput of the skull above and with C-2 below.
The atlanto-occipital joint primarily allows flexion and extension, while the atlantoaxial articulation primarily provides rotation. Vertebrae C-3 through C-7 as an interdependent group allow for varying degrees of flexion, extension, lateral bending, and rotation. Flexion centers on C-5 and C-6 and extension on C-6 and C-7, which is why degenerative changes and spine injuries most commonly occur at these levels.
Intervertebral disks are found from C2-3 and below and are subjected to significant deformation during flexion and extension. Disk degeneration may be painful in its own right, while herniation can lead to compression of the nerve root (radiculopathy) or spinal cord (myelopathy). The term “radiculopathy” refers to a pinched nerve.
Eight pairs of cervical spinal nerves exit bilaterally through the intervertebral foramina. Each spinal nerve is named for the vertebra above which it exits; for example, the C-6 nerve exits above the C-6 vertebra. Therefore, a herniated disk or significant foraminal narrowing at the C5-6 level will most commonly involve the C-6 nerve. The exception is the C-8 spinal nerve, which exits between the C-7 and T-1 vertebrae.
The posterior aspect of the cervical vertebral articulation contains the facet joints, which are true synovial joints, while a bony lip off the lateral margin of the upper vertebral body forms the uncovertebral joint with the vertebra below. Both joints are subject to degenerative changes that may produce pain with cervical extension combined with lateral bending and rotation. Hypertrophy of these joints may affect the surrounding anatomic structures, including the spinal cord, nerve roots, and exiting spinal nerves, as well as the vertebral artery and the sympathetic rami.
The muscles of the neck are divided into four major compartments: anterior (flexion), posterior (extension), and the lateral groups (lateral bending). The posterior muscles are the strongest group and most likely to be the source of pain in conditions resulting from poor posture, in which these muscles are chronically contracting to hold the head upright. The weaker anterior and lateral muscles are involved more in whiplash type injuries in which they stretch suddenly.
The most common type of injury is muscle strain. Muscle strains usually resolve within a few days to a couple of weeks, ligament sprains may take up to a couple of months, and disk injuries or herniations with radiculopathy can take 3 to 6 months for full recovery. Chronic pain beyond 6 months is likely associated with a degenerative process, be it in the disk, bone, or ligament, or from subtle mechanical instability caused by faulty posture or biomechanics.
Pain that increases with activity or within a few hours after activity, but settles down with rest or a change in position, is commonly referred to as mechanical pain. Pain that persists or worsens despite rest and treatment, pain that persists around the clock, or pain that worsens at night raises suspicion for a metabolic or neoplastic condition or for psychosocial factors that prolong recovery.
It is important to determine whether the pain is localized or radiating; therefore, knowledge of the anatomic region is essential. Localized pain generally points to muscle strains, ligament sprains, and facet or disk (degenerative) processes, although these structures commonly radiate pain to the scapula or upper trapezius area as well. Pain that radiates into the upper limbs frequently stems from nerve involvement, although myofascial pain radiation patterns occur occasionally.
Upper cervical nerve injuries are relatively rare and refer dysesthetic pain to the head (C-1, C-2), the neck (C-3), and the upper trapezius region (C-4). The C-5 nerve transmits pain to the shoulder and lateral arm, and occasionally the radial forearm. The C-6 nerve pattern is very similar but invariably includes the radial forearm and thumb, and occasionally the index finger. The C-7 nerve refers pain to the posterior arm, dorsal (occasionally ventral) forearm, and the index and middle fingers. The C-8 nerve classically radiates pain to the medial arm, ulnar forearm, and the ring and little fingers.
Other differential diagnostic considerations for referred pain include thoracic outlet syndrome and ulnar neuropathy, in which pain refers to the medial arm, forearm, and ring and little fingers, similar to a C-8 radiculopathy. Thoracic outlet syndrome typically will involve more proximal pain as well, such as in the axilla or scapula. Carpal tunnel syndrome characteristically causes dysesthesias in the thumb and first two fingers, and sometimes pain up the arm as high as the neck, thereby mimicking a C-6 or C-7 radiculopathy. Shoulder degenerative joint disease or acromioclavicular, subacromial, or rotator-cuff pathology may be confused with a C-5 radiculopathy.
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