Sacral Plexus Lecture Notes

Overview

• Previously discussed cervical, brachial, and lumbar plexuses.
• Sacral plexus originates from:
  • L4, L5 down to S1, S2, S3, S4, S5, and Coccygeal 1.
• Key nerve: Sciatic nerve, significant clinical correlations.

Nerve Branches and Functions

1. Superior Gluteal Nerve

• Origin: L4, L5, S1
• Function: Supplies gluteus medius and minimus (hip abductors).

2. Inferior Gluteal Nerve

• Origin: L5, S1, S2
• Function: Supplies gluteus maximus (hip extension and lateral rotation).

3. Nerve to Obturator Internus

• Origin: L5, S1, S2 (anterior division)
• Function: Supplies obturator internus and superior gemellus (hip lateral rotation).

4. Posterior Cutaneous Nerve of Thigh

• Origin: S1, S2, S3 (posterior division)
• Function: Sensory supply to:
  • Inferior buttocks
  • Posterior thigh
  • Popliteal region
  • Skin around calf and heel

5. Sciatic Nerve

• Origin: L4, L5, S1, S2, S3
• Function: Main nerve of the lower limb, divides into:
  • Tibial Nerve (anterior division):l4-s3
    - Motor: Hamstrings(long head of biceps femoris,semi tendanous,semi membraneous),adductor magnus,poplitoeus,planteris,tibialis posterior,flexor digitiform longus, flexor holicus longus,triceps surae(gastrocenimus,soleus)
    - , calf muscles, intrinsic foot muscles
  • - Sensory/cutaneous: Posterior leg, sole of foot
  • Common Fibular Nerve/peroneal nerve (posterior division):l4-s3
    - Motor: Short head of biceps femoris, ankle evertors(fibular breviis/longus),extensor halluis longus,extensor digitiform longus,tibialis anterior
    - Sensory: Lateral leg

6. Nerve to Piriformis

• Origin: S1, S2 (posterior division)
• Function: Supplies piriformis muscle (hip lateral rotation).

7. Pudendal Nerve

• Origin: S2, S3, S4
• Function:
  • Motor: External anal and urethral sphincters
  • Sensory: Perineum (male and female specific regions),genitals

8. Coccygeal Plexus

• Origin: S4, S5, Coccygeal 1
• Function: Sensory supply to the coccygeal region.skin

Clinical Correlations

• Sciatica:
  • Often caused by herniated discs.
  • Compression of the sciatic nerve leads to pain and dysfunction.
  • Symptoms: Sharp pain, numbness, and tingling down the posterior and lateral leg.
  • Treatments: Rest, NSAIDs, physical therapy, or surgery.

Important Concepts

Hilton’s Law

• Nerve supplying a muscle that crosses a joint will also supply the skin over that joint.

Summary

• Sacral plexus is key for motor and sensory innervation of the lower limb.
• Understanding its branches helps diagnose and manage lower limb pathologies effectively.