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nerve root

One of the 2 bundles or nerve fibers emerging from the spinal cord (dorsal & ventral roots). They join to form a single spinal nerve after relay in the dorsal root ganglia. Cranial nerve 5 is similarly formed from 2 roots. Nerve roots innervating muscles C1-C2 sternocleidomastoid C2-C4 trapezius C3-C5 diaphragm C5-C6 supraspinatus, infraspinatus, deltoid, biceps, brachialis, brachioradialis, supination of forearm C5-C7 serratus C6-C7 triceps, radial deviation of wrist C6-C8 extensors of wrist & metacarpophalangeal joints, pronation of forearm C7-C8 wrist flexors, ulnar deviation of wrist, flexor & abductor pollicis brevis C8 thumb opposition, interossei, lumbricals T1-T12 innervate the trunk (thorax & abdominal walls.) L2-L3 iliopsoas, hip flexions L2-L4 quadriceps, thigh adductors L4 deep tendon reflex at knee tests L4 L4-L5 tibialis anterior (walking on heels tests function) L4,L5 gluteus medius L5 extensor hallicus longus, great toe dorsiflexion L5-S1 peroneus longus, peroneus brevis L5-S1 gluteus maximus L5,S1-S2 biceps femoris, soleus, gastrocnemius S1 walking on toes tests function S1-S2 short plantar S2-S3 smooth muscles of urinary bladder S3-S5 perineal muscles Sensory findings of nerve root involvement* C3 (C2-C3) pain into the back of neck to the pinnae of the ear & the angle of the jaw C4 (C3-C4) pain into the back of neck to the levator scapulae to the anterior chest C5 (C4-C5) pain into the side of the neck to the superior lateral shoulder; numbness over the deltoid C6 (C5-C6) pain to the lateral aspects of the arm & forearm & into the thumb & index finger with numbness of the thumb & dorsum of hand C7 (C6-C7) pain into the midforearm to middle & ring fingers C8 (C7-C8) pain into the medial aspect of the forearm into the ring & small fingers with numbness of the ulnar border & small finger L4 (L3-L4) pain in sacroiliac joint, hip, posterolateral thigh, anterior aspect of leg, L4 dermatome L5 (L4-L5) pain in sacroiliac joint, hip, L5 dermatome (includes great toe) S1 (L5-S1) pain in lateral aspect of leg & foot, S1 dermatome (includes lateral toes) * Nerve root & (disc level) Motor findings of nerve root involvement* C3 (C2-C3) no reflex changes C4 (C3-C4) no reflex changes C5 (C4-C5) deltoid muscle atrophy & weakness of shoulder abduction C6 (C5-C6) weak biceps & brachioradialis muscles; decreased biceps & brachioradialis tendon reflexes C7 (C6-C7) triceps muscle weakness with decreased triceps muscle reflex C8 (C7-T1) triceps muscle weakness with weakness of intrinsic muscles of hand * Nerve root & (disc level)

Related

peripheral nerve radiculopathy

General

nervous system structure

References

  1. B. Ourmazdi, M.D. Synopsis of Neurology & Examination, B & B Books, Saratoga, CA, 1998
  2. Principles of Ambulatory Medicine, 4th edition, Barker et al (eds), Williams & Wilkins, Baltimore, 1995, pg 864, 879
  3. Stedman's Medical Dictionary 27th ed, Williams & Wilkins, Baltimore, 1999