Describe the lumbosacral plexus.
"The lumbosacral plexus are a network of nerves arising from the ventral rami of L1–L5, S1-S4 nerve roots. The nerves of lumbar plexus emerge from within the psoas major muscle and they are described in relation to this muscle. There are certain nerves that arise only from the lumbar plexus, others only from the sacral plexus, and some receive a contribution from both. The lumbosacral trunk (L4 and L5) joins the network of the sacral ventral rami (S1–S4) to form the lumbosacral plexus.
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Describe the nerves arising from the lumbar plexus and their innervation.
Describe the nerves arising from the lumbosacral plexus and their innervation.
Describe the nerves arising purely from the sacral plexus.
What are the terminal branches of the sciatic nerve?
"The terminal branches of the sciatic nerve are the tibial nerve and the common peroneal nerve.
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Describe the clinical deficit following injury to the sciatic nerve.
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- Paralysis of hamstring muscles (semitendinosus, semimembranosus and biceps femoris) and all muscles of leg and foot supplied by nerve.
- Loss of all movement below the knee joint with foot drop.
- All sensation is lost below the knee except that supplied by the saphenous nerve (branch of femoral), i.e., over medial malleolus and medial border of foot to great toe.
What is the root value of the tibial nerve.
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The root value of the tibial nerve is L4, 5, S1, 2, 3.
Note: the Tibial nerve is the largest terminal branch of the sciatic nerve.
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Name the muscles innervated by the tibial nerve?
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The muscles innervated by the tibial nerve are as follows:
- Soleus.
- Tibialis posterior.
- Flexor hallucis longus.
- Flexor digitorum longus.
- Plantaris.
- Popliteus.
- Gastrocnemius.
- All the muscles of the sole of the foot (via the medial and lateral plantar nerves).
Note: the sensory distribution of the tibial nerve is the sole of the foot.
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"What is the root value of the common peroneal nerve? "
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The root value of the common peroneal nerve is L4, L5, S1,S2.
Note: the common peroneal nerve is the smaller terminal branch of the sciatic nerve.
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Name the muscle and the nerve root tested during the ankle reflex.
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The ankle reflex tests:
- Gastrocnemius : S1 (via sciatic nerve-tibial branch)
Note: The knee jerk tests the quadriceps: L3, L4 (via femoral nerve)
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How would you clinically test the L5 nerve root.
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- Sensory : Test the cutaneous sensation over the dorsum of the foot 1st – 4th web spaces (the 1st webspace is supplied by the deep peroneal nerve and the 2nd- 4th webspaces by the superficial peroneal nerve).
- Motor : Test the function of extensor hallucis longus