MMT Nerve Innervation and Muscle Function 2 — Questions and Answers
Question 1: Weakness of the tibialis anterior during MMT dorsiflexion testing most directly implicates which nerve root?
- L3
- L4 (Correct answer)
- L5
- S1
Correct answer: L4
The tibialis anterior is innervated by the deep peroneal nerve at L4-L5, with L4 being the dominant root level identified during MMT.
Question 2: The serratus anterior, tested by scapular protraction in MMT, is innervated by which nerve?
- Thoracodorsal nerve
- Long thoracic nerve (Correct answer)
- Medial pectoral nerve
- Suprascapular nerve
Correct answer: Long thoracic nerve
The long thoracic nerve (C5-C7) innervates the serratus anterior; injury causes medial scapular winging observed during MMT.
Question 3: During MMT, weakness of elbow extension most directly implicates which nerve at which root level?
- Musculocutaneous nerve C5-C6
- Median nerve C6-C7
- Radial nerve C7-C8 (Correct answer)
- Ulnar nerve C8-T1
Correct answer: Radial nerve C7-C8
Elbow extension (triceps brachii) is innervated by the radial nerve at C7-C8, with C7 being the key root level tested.
Question 4: The gluteus maximus, the primary muscle for hip extension MMT, is innervated by which nerve?
- Superior gluteal nerve
- Inferior gluteal nerve (Correct answer)
- Sciatic nerve
- Pudendal nerve
Correct answer: Inferior gluteal nerve
The gluteus maximus is innervated by the inferior gluteal nerve (L5-S2), making it the nerve tested during hip extension MMT.
Question 5: In MMT, weakness of extensor hallucis longus (great toe extension) is a classic indicator of which nerve root dysfunction?
- L4
- L5 (Correct answer)
- S1
- S2
Correct answer: L5
The extensor hallucis longus is innervated by the deep peroneal nerve at L5, making great toe extension weakness a hallmark L5 nerve root sign.
Question 6: Which nerve root level is primarily tested when assessing shoulder abduction strength during MMT?
- C3-C4
- C5-C6 (Correct answer)
- C6-C7
- C7-C8
Correct answer: C5-C6
Shoulder abduction via the deltoid is innervated at C5-C6 via the axillary nerve, making this the key root level tested during MMT.
Question 7: Hip adduction weakness during MMT most likely indicates involvement of which nerve?
- Superior gluteal nerve
- Femoral nerve
- Obturator nerve (Correct answer)
- Sciatic nerve
Correct answer: Obturator nerve
Hip adduction is performed by the adductor group innervated by the obturator nerve (L2-L4), so adduction weakness implicates this nerve.
MMT Nerve Innervation and Muscle Function 2
Weakness of the tibialis anterior during MMT dorsiflexion testing most directly implicates which nerve root?