Cervical plexus injury vs Lumbar plexus injury
How to tell Cervical plexus injury and Lumbar plexus injury apart when a board question makes them look alike.
Cervical plexus (C1 to C4): phrenic nerve and diaphragm; lumbar plexus (L1 to L4): femoral and obturator nerves of the thigh.
Side by side
Cervical plexus includes C1-C4 contributions and phrenic nerve C3-C5 for diaphragm function, plus cutaneous neck sensation.
Lumbar plexus includes femoral and obturator nerves, affecting hip flexion, knee extension, thigh sensation, and hip adduction.
Cervical plexus includes C1-C4 contributions and phrenic nerve C3-C5 for diaphragm function, plus cutaneous neck sensation.
Lumbar plexus includes femoral and obturator nerves, affecting hip flexion, knee extension, thigh sensation, and hip adduction.
The trap
Plexus injuries are common after trauma, surgery, or compressive lesions, so the pattern of weakness and sensory loss localizes the level. Cervical plexus injury is the high-yield phrenic nerve story (hiccups, hemidiaphragm paralysis, dyspnea). Lumbar plexus injury (often from psoas hematoma in anticoagulated patients, retroperitoneal hemorrhage, surgical retractor injury, or diabetic amyotrophy) presents with thigh and groin pain plus quadriceps weakness with falls. Brachial plexus injury is a separate entity (Erb-Duchenne C5-C6 vs Klumpke C8-T1).
The repair move
Before naming the answer, force the stem through the separator: Cervical plexus is neck/diaphragm C3-C5; lumbar plexus is femoral/obturator leg function.
Try a free question
CoreA 35-year-old man undergoes a thyroidectomy and develops unilateral diaphragmatic paralysis (right hemidiaphragm elevated on chest X-ray) with mild dyspnea. The phrenic nerve is at risk during such surgery. Which spinal cord segments contribute to the phrenic nerve?
Show answer and explanation
Answer: A. C3, C4, C5. Phrenic nerve arises from cervical plexus (C3, C4, C5; 'C3, C4, C5 keep the diaphragm alive'). It runs anterior to the anterior scalene muscle, descends in the neck and thorax, and innervates the diaphragm motor and sensory. Phrenic nerve injury during thyroid, neck, or cardiothoracic surgery, central line placement, or trauma can cause diaphragmatic paralysis with elevated hemidiaphragm and dyspnea.
Why the other choices are tempting
- B. T1-T4 sympathetic outflow includes pupil dilation, cardiac acceleration; not phrenic.
- C. T5-T9 contributes to thoracoabdominal innervation but not the diaphragm.
- D. L1-L4 forms the lumbar plexus (femoral, obturator nerves) for lower extremity.
- E. S2-S4 is sacral plexus contributing to pelvic floor and parts of lower extremity.
Flashcards
Tap a card to flip it.
What clue supports Cervical plexus injury?
Choose Cervical plexus injury when the stem gives this pattern: Cervical plexus includes C1-C4 contributions and phrenic nerve C3-C5 for diaphragm function, plus cutaneous neck sensation.
What clue supports Lumbar plexus injury?
Choose Lumbar plexus injury when the stem gives this contrasting pattern: Lumbar plexus includes femoral and obturator nerves, affecting hip flexion, knee extension, thigh sensation, and hip adduction.
Quick answers
What is the fastest way to tell Cervical plexus injury from Lumbar plexus injury?
Cervical plexus (C1 to C4): phrenic nerve and diaphragm; lumbar plexus (L1 to L4): femoral and obturator nerves of the thigh.
What is the key clue for Cervical plexus injury?
Cervical plexus includes C1-C4 contributions and phrenic nerve C3-C5 for diaphragm function, plus cutaneous neck sensation.
What is the key clue for Lumbar plexus injury?
Lumbar plexus includes femoral and obturator nerves, affecting hip flexion, knee extension, thigh sensation, and hip adduction.
What is the common trap with Cervical plexus injury vs Lumbar plexus injury?
Plexus injuries are common after trauma, surgery, or compressive lesions, so the pattern of weakness and sensory loss localizes the level. Cervical plexus injury is the high-yield phrenic nerve story (hiccups, hemidiaphragm paralysis, dyspnea). Lumbar plexus injury (often from psoas hematoma in anticoagulated patients, retroperitoneal hemorrhage, surgical retractor injury, or diabetic amyotrophy) presents with thigh and groin pain plus quadriceps weakness with falls. Brachial plexus injury is a separate entity (Erb-Duchenne C5-C6 vs Klumpke C8-T1).