Suboccipital Triangle

trigonum suboccipitale

The suboccipital triangle is a small muscular space in the posterior craniovertebral junction, bounded by three muscles: rectus capitis posterior major (medial side), obliquus capitis superior (superolateral side), and obliquus capitis inferior (inferior side). The floor is the posterior atlanto-occipital membrane and the posterior arch of the atlas. The vertebral artery (V3 segment) lies in the vertebral groove on the posterior arch of C1 and then passes through the posterior atlanto-occipital membrane to enter the foramen magnum, running through the floor of the triangle.

Region: Neck

Clinical Relevance

Clinical Notes

The suboccipital triangle is the primary surgical anatomy for posterior craniovertebral junction approaches and suboccipital decompression. The V3 vertebral artery in the triangle is the critical vascular structure: it emerges from the C1 transverse foramen, curves posteromedially in the vertebral groove on C1, and pierces the posterior atlanto-occipital membrane to ascend into the cranium. During suboccipital decompression (for Chiari malformation), the posterior arch of C1 is removed and the overlying posterior atlanto-occipital membrane and suboccipital triangle muscles are elevated carefully to preserve the V3 vertebral artery.

Pathology

Common Injuries & Conditions

Vertebral Artery Injury in Suboccipital Triangle Dissection

The V3 segment of the vertebral artery running in the vertebral groove on the posterior C1 arch and piercing the posterior atlanto-occipital membrane is at risk during suboccipital craniotomy and C1 posterior arch resection; inadvertent vascular injury produces vertebral artery haemorrhage requiring immediate vascular control and may necessitate endovascular embolisation.