Structural causes of radiculopathy include any process that causes mechanical compression of nerve roots, such as herniated discs (most common in the cervical or lumbar spine), degenerative disease of the spine (e.g., spondylosis), or tumor.
Nonstructural causes of radiculopathy include diabetic radiculopathy, which likely occurs due to infarction of a nerve root (most commonly affecting the thoracic or lumbar nerve roots), or Herpes zoster, which causes radiculopathy due to viral-mediated inflammation of a nerve root.
Cervical nerve roots exit the cord to enter their foramen at the disc space above their respective vertebra, where they are vulnerable to compression from disc herniation or foraminal stenosis. For example, the C7 nerve root exits the cord at the C6-C7 disc space level (i.e., above C7) and is susceptible to compression from this disc or by foraminal stenosis at this level.
Lumbar nerve roots exit the cord to enter their foramen below their respective vertebra. For example, the L5 nerve root exits the cord at the L5-S1 disc space level (i.e., below L5). The root actually exits above the disc, however, so a herniated disc will affect the next root that is descending within the spinal canal to exit at the next foramen. In other words, a herniated disc at the L5-S1 disc level will most likely affect the S1 root, but foraminal stenosis at the L5-S1 intervertebral foramen level will affect the exiting L5 root.
Radiculopathic pain is characterized by sharp, shooting discomfort, which may include paresthesias or dysesthesias, radiating proximally to distally in the distribution of the affected nerve root. There may or may not be associated neck or back pain.
Cervical radiculopathies typically begin in the lateral neck/trapezius region, and lumbar radiculopathies typically begin in the buttock/hip region; both radiate downward within the distribution of the affected
nerve root. Tables 47-1 and 47-2 summarize the clinical features of cervical and lumbar radiculopathies.
TABLE 47-1 Clues to the Localization of Cervical Radiculopathy
Cervical
Root
Level
Probable
Site of
Herniated
Disc
Distribution of Pain
and Paresthesiasa
Easily Testable
Muscles That May
Be Affectedb
Reflex That
May Be
Diminishedc
C5
C4-C5
Scapula, deltoid, upper arm
Deltoid, biceps
Biceps
C6
C5-C6d
Biceps region, lateral forearm, dorsal thumb and second finger
Biceps, brachioradialis, extensor carpi radialis (wrist extension)
Biceps
C7
C6-C7d
Triceps region, dorsal forearm to dorsal third (and possibly also second and fourth) finger(s)
Triceps, extensor digitorum communis (finger extension)
Triceps
C8
C7-T1
Medial (inner) forearm to fifth and fourth fingers
Interossei, finger flexors
Triceps
T1e
T1-T2
Axilla to medial (inner) upper arm
Interossei, abductor pollicis brevis (thumb abduction), abductor digiti minimi (little finger abduction)
None
a All of the cervical radiculopathies can begin in lateral neck/trapezius/shoulder region before radiating into arm.
b See Chapter 25, Examination of Upper Extremity Muscle Strength, for details on testing these muscles.
c See Chapter 37, Examination of the Muscle Stretch Reflexes, for details on testing these reflexes.
d These are the most common sites for cervical disc herniation.
e T1 root lesions are uncommon and are more likely to occur due to lesions other than disc herniation, including other spinal lesions or apical chest lesions (i.e., Pancoast tumor, in which there usually is also ipsilateral Horner’s syndrome).Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
