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Suboccipital Muscles: Stepwise Dissection

Surgical Correlation

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A, The right trapezius and sternocleidomastoid have been preserved. The left trapezius and sternocleidomastoid have been reflected along with the galea aponeurotica to expose the underlying semispinalis capitis, splenius capitis, and levator scapulae. B, The right sternocleidomastoid and trapezius have been reflected to expose the splenius capitis. The left splenius capitis has been removed to expose the underlying semispinalis and longissimus capitis. C, The right splenius capitis has been removed to expose the semispinalis and longissimus capitis. The left semi-spinalis and longissimus capitis have been removed to expose the suboccipital triangle formed by the superior oblique, which passes from the C1 transverse process to the occipital bone, the inferior oblique, which extends from the transverse process of C1 to the spinous process of C2, and the rectus capitis posterior major, which extends from the occipital bone below the inferior nuchal line to the spinous process of C2. The vertebral artery courses in the depths of the suboccipital triangle as it passes behind the superior facet of C1 and across the upper edge of the posterior atlantal arch. D, Both semispinalis capitis muscles have been reflected laterally to expose the suboccipital triangles bilaterally. E, The muscles forming the left suboccipital triangle have been removed. The vertebral artery ascends slightly lateral from the transverse process of C2 to reach the transverse process of C1 and turns medially behind the superior facet of C1 to reach the upper surface of the posterior arch of C1. The C2 ganglion is located between the posterior arch of C1 and the lamina of C2. The dorsal ramus of C2 produces a medial branch that forms the majority of the greater occipital nerve. F, The muscles forming both suboccipital triangles have been removed. The rectus capitis posterior minor, which extends from the posterior arch of C1 to the occipital bone below the inferior nuchal line, has been preserved. The vertebral arteries cross the posterior arch of the atlas and penetrate the posterior atlanto-occipital membrane to reach the dura. (Images courtesy of AL Rhoton, Jr.)

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