Are the cluneal nerves derived from the ventral or dorsal rami of the spinal nerves?

The Cluneal Nerves: Anatomical Origin from Dorsal Rami

The cluneal nerves are derived from the dorsal rami of spinal nerves, not the ventral rami. 1, 2, 3

Anatomical Classification of Cluneal Nerves

The cluneal nerves can be divided into three groups based on their origin and distribution:

1. Superior Cluneal Nerves

   • Originate from the dorsal rami of primarily upper lumbar spinal nerves (L1-L3)
   • Recent anatomical studies show contributions from:
     • L1 (75% of specimens)
     • L2 (90% of specimens)
     • L3 (95% of specimens)
     • L4 (45% of specimens)
     • L5 (10% of specimens) 2
   • Cross the iliac crest to innervate the skin and subcutaneous tissue of the upper gluteal region 4

2. Middle Cluneal Nerves

   • Arise from the dorsal rami of sacral nerves S1-S4
   • Most commonly formed by:
     • S1-S2 (48% of specimens)
     • S1-S4 (20% of specimens)
     • S2-S4 (20% of specimens)
     • Other combinations less common 1
   • Pierce the gluteus maximus muscle to supply the gluteal skin 1

3. Inferior Cluneal Nerves

   • Derived from branches of the posterior femoral cutaneous nerve
   • The posterior femoral cutaneous nerve itself arises from the sacral plexus (ventral rami)
   • Can be divided into lateral and medial components based on their course relative to the ischial tuberosity 5

Anatomical Significance and Clinical Implications

• The cluneal nerves follow the general pattern of spinal nerves, where:

  • Dorsal rami supply the posterior (extensor) compartments
  • Ventral rami supply the anterior (flexor) compartments

• This anatomical arrangement is important because:

  • Entrapment of superior cluneal nerves can cause low back pain that may be confused with lumbar disk disease 2
  • Knowledge of cluneal nerve anatomy is crucial during posterior iliac crest harvest procedures to avoid nerve injury 3
  • Ultrasound-guided nerve blocks of superior cluneal nerves may be useful for pain management after hip surgery 4

Distinguishing Features from Plexus Nerves

It's important to note that unlike the cluneal nerves, the major nerve plexuses (brachial and lumbosacral) are formed from ventral rami:

• The brachial plexus is formed from the ventral rami of C5-T1 spinal nerves 6, 7
• The lumbosacral plexus is formed from the ventral rami of L1-L5 with contributions from T12 and S1-S4 6

This anatomical distinction helps explain why cluneal nerve pathology presents differently from plexopathy, which affects multiple peripheral nerve distributions derived from ventral rami 6.