nerve root
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Introduction
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)
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)