8.2. Clinical Presentations of C1–C4 Lesions
Trauma to the Greater Occipital Nerve C2
- Innervates the skin of the posterior scalp
- The lesser occipital nerve (C2):
- Associated with flexion extension or rotary injury of the neck (motor vehicle accidents, falls, athletic injuries)
- Very frequently associated with upper trunk (C5–C6) brachial plexus traction injury
- Injury to C2 sensory fibers; pain, paraesthesias in the greater and lesser occipital nerve distribution of the mastoid, lateral, and posterior head as well as the occiput
- Severe C2 irritation:
- Pain projected to brow and behind the eyes
- Frequent trigger of unilateral migraine headache
- The great auricular nerve (C2–C3):
- Paraesthesias and pain in the lower cheek, lower pinna of the external ear (overlaps auriculotemporal nerve of the Vth)
- Irritation of this nerve causes:
- Neurogenic inflammation and vasodilation of the pinna; probable genesis of the red ear syndrome
- C-fibers release substance P (also interacts with mast cells to release histamine) and calcitonin gene related peptide. The former causing endothelial plasma leakage and the latter vasodilatation of the affected vessels.
- Transverse colli (C2–C3) pain in the anterior neck
- Pain in the anterior and upper neck
- Supraclavicular nerves
- Pain in the supraclavicular fossa and clavicle
Injury of the Motor Roots of the Cervical Plexus (Ansa Hypoglossi)
- Dysfunction of ventral roots of C2:
- Weakness of the infrahyoid muscle group and middle scalene:
- Decreased anterior and lateral head flexion
- Decreased function of the sternocleidomastoid:
- Rotation of the head to contralateral side
- Weakness of the trapezius muscle with decreased shoulder elevation
- Phrenic nerve:
- C3–C5 (primary root is C4)
- Paralysis of affected diaphragm:
- Spinal accessory component (C2) involvement weakens the lateral cuff of the diaphragm
- Unilateral weakness: dyspnea with exertion but not at rest
- Rarely involved with traction injury but not infrequently damaged with scalenectomy and neurolysis (lies adjacent to the middle scalene muscle)
- Anatomic variant is innervation of the phrenic nerve by the subclavian nerve
- Paradoxical elevation of the affected diaphragm with inspiration
- Middle scalene and levator scapulae muscles:
- Weakness of lateral neck flexion
- Decreased rotation of the scapula
- Branches to the accessory nerve
- Supply the sternocleidomastoid (C2)
- Trapezius (C3–C4)
Trauma to the Motor Roots of the Cervical Plexus
- Most often branches rather than the entire plexus are injured
- Penetrating wounds
- Surgical procedures:
- Carotid endarterectomy
- Scalenectomy with neurolysis
- Biopsy of lymph nodes
- Penetrating wounds
- Damage to the phrenic nerve:
- Mediastinal processes greater than direct damage
- Spinal cord injury (C3–C4 level)
- Parsonage–Turner syndrome (C5–C6 primarily)
- Neuralgia amyotrophica (any root)
- Compressed by aortic aneurysm
- Mediastinal lymph nodes
- Neck or chest surgical procedures
- HZ (Herpes Zoster)
- Critical illness neuropathy (diaphragm frequently involved)
- Hypophosphatemia (diaphragmatic involvement)
- Tuberculosis
- Sarcoid
- AIDP
- Motor neuron disease
- Diabetes mellitus
- CMT2C
- Liver transplant (clamped with inferior vena cava)
- Indwelling central venous catheter or its placement
Specific Nerve Damage (Procedures or Processes)
- Greater auricular nerve
- Face lift or parotid surgery
- Greater occipital nerve:
- Entrapped by the semispinalis and trapezius muscle
- Neurofibroma
- Direct trauma
- Lesser occipital nerve
- Lacerations
- Surgical procedures of the posterior triangle of the neck
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