An Anatomical Variation of the Lesser Occipital Nerve in the "Carefree part" of the Posterior Triangle.

The occurrence of the lesser occipital nerve (LON) at an anomalous location in the "carefree part" within the posterior triangle has been seldom reported in the literature. We are reporting a rare case of location of the LON in the "carefree part" of the posterior triangle, in a 55-year-old formalin embalmed male cadaver. LON, after emerging from the posterior margin of the sternomastoid muscle (SM), ran obliquely towards the trapezius muscle. Here, it hooked around the unusual separated muscle fasciculus of the trapezius, 7.5 cm below the superior nuchal line. Further, LON gave contributions to spinal accessory nerve (SAN); one deep into the SM and another one in the posterior triangle. The knowledge on the unusual location and course of the LON and its contribution to the SAN is significantly important while an anaesthetic blockade is being performed for the management of a cervicogenic headache and a super selective radical neck dissection.