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Superior Nuchal Line

linea nuchalis superior

The superior nuchal line is a curved bony ridge running horizontally across the external surface of the occipital bone from the external occipital protuberance (inion) to the mastoid process on each side. It marks the attachment of the trapezius, sternocleidomastoid, and splenius capitis muscles to the skull. Below it, the inferior nuchal line provides attachment for the suboccipital muscles. Between the two lines is the attachment zone of the semispinalis capitis.

Region: Head & Skull

Clinical Relevance

Clinical Notes

The superior nuchal line is the key landmark for the horizontal skin incision in posterior fossa craniotomy (the classic hockey-stick incision follows the inferior nuchal line). In occipital condyle fracture and craniovertebral junction surgery, the posterior musculature attached to the superior nuchal line is reflected to expose the suboccipital bone. Suboccipital triangle dissection follows the superior nuchal line laterally. In forensic anthropology, the superior nuchal line prominence (nuchal crest) is used in sex determination of skulls.

Pathology

Common Injuries & Conditions

Muscle Attachment Avulsion at Superior Nuchal Line

High-energy cervical hyperflexion or direct occipital trauma may avulse the trapezius or SCM from the superior nuchal line, producing occipital tenderness and swelling at the muscle origin; imaging distinguishes muscular avulsion from occipital bone fracture extending to the nuchal line.