Suboccipital Exposure Detaching the Trapezius and Splenius Capitis Muscle. Following detachment the muscle is reflected inferomedially to expose the longissimus capitis muscle, the deep lamina of deep cervical fascia and the occipital artery. The longissimus capitis muscle is attached to the posterior edge of mastoid process, deeply to the splenius capitis and sternocleidomastoid muscles. (Image courtesy of E de Oliveira)