ObjectivesThe incisivus labii superioris muscle, which originates from the floor of the incisive fossa of the maxilla, has previously been described, it is not well understood. The purpose of this study was to investigate the incisivus labii superioris muscle with detailed dissection.MethodsTwenty-six halves from thirteen fresh frozen cadaveric Caucasian heads were used in this study. First, the incisivus labii superioris muscle was dissected to reveal its origin and insertion, and its relationship to other mimetic muscles. Secondly, the distance from the midline to the innermost part of the bony attachment of the muscle was measured. The literature describing the incisivus labii superioris muscle was reviewed.ResultsThe incisivus labii superioris muscle consisted of two parts, inferior and superior. The former merged into the orbicularis oris and the latter into the nasalis. The mean distance from the midline to the innermost part of the bony attachment of the incisivus labii superioris muscle was 4.8 ± 1.7 mm on the right side and 4.9 ±1.7 mm on the left.ConclusionsThe results of the present study suggest that the inferior part of the incisivus labii superioris should be considered as an accessory muscle of the orbicularis oris complex, and the superior part is the nasalis muscle.

Extramedullary tumors composed of myeloblasts or monoblasts can present in various locations. Patients with a history of acute myeloid leukemia (AML) can present with neuropathic pain and no evidence of relapse of their leukemia. Neuroleukemiosis is a form of extramedullary tumor present in the peripheral nervous systems (PNS) of leukemia patients. We report two AML patients who were in remission and later presented with neurological symptoms due to neuroleukemiosis with negative bone marrow biopsies.

Injury to the nerves of the lumbar plexus can result in significant disability. Therefore, the clinician should be knowledgeable of both the normal and variant anatomy of these branches. We report what we believe to be the first description of the accessory obturator nerve providing a branch to the psoas major muscle. Such a variant innervation to the psoas major muscle should be kept in mind by those who examine patients or operate near the lumbar plexus.