Bilateral and asymmetric anatomical variation extending between the trapezius and sternocleidomastoid muscles
The trapezius and sternocleidomastoid muscles are often the target of anatomical variations,
including supernumerary insertion heads. Here we present a case report of a peculiar bilateral
and asymmetric anatomical variation not yet reported in the region of the posterior cervical
triangle. During the dissection routine for the preparation of didactic pieces for the exposure of
the musculature of the nape region, we observed in a corpse of male, black and middle age,
spindle-shaped muscle bundles with approximately 8 cm in length, extending transversely in
the nuchal region in latero-anterior direction, from the upper third of the trapezius muscle to
the upper third of the sternocleidomastoid muscle. This anatomical curiosity reminds us of the
common embryonic origin of these two key neck muscles.
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