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🌱 來自: Huppert’s Notes
Peripheral Nervous System🚧 施工中
Peripheral Nervous System
Includes nerves and ganglia outside the brain and spinal cord.
Spinal roots
• Description: Includes the motor and sensory nerve roots that exit the spinal cord proper and enter into the spinal foramina
• Lesion: Main features of radiculopathy at each level:
- Cervical cord: C5–6 – loss of biceps power and reflexes; C7 – loss of triceps, wrist/finger extension power; C8 – impaired wrist/finger flexion
- Thoracic cord: Localize using site of back pain and sensory level; T4 – nipples, T10 – umbilicus; lesion causes paralysis with leg weakness, disturbances of bowel/bladder function
- Lumbar cord: L2–4 – paralysis of flexion/adduction of thigh, leg extension at knee, absent patellar reflex; L5–S1 – paralysis of extension of thigh, leg flexion at knee, movements of ankle/foot, absent ankle jerk (S1)
- Sacral cord/conus medullaris: S3–5 – bilateral saddle anesthesia, urinary retention/lax anal tone; S2–4 – absent bulbocavernosus reflex; S4–5 – absent anal reflex
- Cauda equina: Low back and radicular pain, asymmetric leg weakness and sensory loss, variable areflexia of the lower extremities
Peripheral nerves
• Lesion: Mid or distal limb pain, weakness (with LMN signs) or sensory abnormalities following the nerve distribution, “stocking or glove” distribution, loss of reflexes
Neuromuscular junction
• Lesion: Proximal weakness, diplopia, possible bulbar weakness (dysarthria, dysphagia, facial weakness) that may get worse with use (aka fatiguability); sensation is spared
Muscle
• Lesion: Bilateral proximal or distal weakness (typically proximal weakness is more than distal weakness); sensation is spared
Cranial nerves
• Description: See Table 12.1
TABLE 12.1 • Cranial Nerves and their Functions
• Cranial nerve reflexes: Automatic response to a stimulus that does not require conscious thought
- Pupillary light reflex (direct and consensual pupil constriction to light): II → III
- Corneal reflex (touch cornea → blink): V → VII
- Jaw jerk (tap chin with reflex hammer → jaw protrudes forward): V3 (sensory) → V3 (motor, masseter)
- Vestibulo-ocular reflex (turn head laterally, eyes remain fixated on target): VIII → III, VI
- Gag reflex (touch posterior pharynx → gag): IX → X
- Cough reflex (advanced suction tube through endotracheal tube and suction deep in trachea → cough): X (sensory) → X (motor)