Sphenomandibularis

Abstract: In order to achieve a better functional and clinical knowledge of a masticatory muscle called the sphenomandibularis that is suspected to be responsible for headaches by compressing the maxillary nerve, bilateral dissections of the infratemporal fossa were performed on ten human cadavers and completed by histological and radiological studies of the same areas. Both macroscopic and microscopic observations obvi- ously showed that the so-called sphenomandibularis muscle corresponds to the deep portion of the tempo- ralis muscle, since there is no epimysial septum between these two structures, which previously have been de- scribed as being completely independent from each other. In spite of the close topographic relationship be- tween the deep belly of the temporalis and the lateral pterygoid muscle, as well as their similar innervation pattern, the sphenomandibularis in fact has to be con- sidered functionally as an original but non-isolated positional fascicle of the temporalis muscle itself. Our observations, correlated with MR images, suggest in- deed that the deep belly of the temporalis muscle is of functional importance in the masticatory movements, but is not involved by its neurovascular vicinity in the genesis of specific headaches. Its surgical release, how- ever, should be discussed in the case of a temporal myoplasty.

Abstract: Temporalis is an important muscle of mastication In recent years, there has been controversy about its detailed anatomy, and claims have been made about the existence of a variant muscle, sphenomandibularis The present case report describes an anomalous muscle within the infratemporal fossa distinct from both temporalis and sphenomandibularis Functionally the muscle could pull the buccinator laterally as the jaw closes Clin Anat 19:648–650, 2006 © 2006 Wiley-Liss, Inc

Abstract: Purpose The common chimpanzee ( Pan troglodytes ) is the primate that is phylogenetically most closely related to humans ( Homo sapiens ). In order to shed light on the anatomy and function of the temporalis muscle in the chimpanzee, we have analyzed the expression patterns of the mRNA transcripts of the myosin heavy chain (MyHC) isoforms in different parts of the muscle. Basic procedures We dissected the superficial, deep and sphenomandibularis portions of the temporalis muscle in five adult P. troglodytes and quantified the expression of the mRNA transcripts of the MyHC isoforms in each portion using real-time quantitative polymerase chain reaction. Main findings We observed significant differences in the patterns of expression of the mRNA transcripts of the MyHC-IIM isoform between the sphenomandibularis portion and the anterior superficial temporalis (33.6% vs 47.0%; P = 0.032) and between the sphenomandibularis portion and the anterior deep temporalis (33.6% vs 43.0; P = 0.016). We also observed non-significant differences between the patterns of expression in the anterior and posterior superficial temporalis. Principal conclusions The differential expression patterns of the mRNA transcripts of the MyHC isoforms in the temporalis muscle in P. troglodytes may be related to the functional differences that have been observed in electromyographic studies in other species of primates. Our findings can be applicable to the fields of comparative anatomy, evolutionary anatomy, and anthropology.

Abstract: In order to achieve a better functional and clinical knowledge of a masticatory muscle called the sphenomandibularis that is suspected to be responsible for headaches by compressing the maxillary nerve, bilateral dissections of the infratemporal fossa were performed on ten human cadavers and completed by histological and radiological studies of the same areas Both macroscopic and microscopic observations obviously showed that the so-called sphenomandibularis muscle corresponds to the deep portion of the temporalis muscle, since there is no epimysial septum between these two structures, which previously have been described as being completely independent from each other In spite of the close topographic relationship between the deep belly of the temporalis and the lateral pterygoid muscle, as well as their similar innervation pattern, the sphenomandibularis in fact has to be considered functionally as an original but non-isolated positional fascicle of the temporalis muscle itself Our observations, correlated with MR images, suggest indeed that the deep belly of the temporalis muscle is of functional importance in the masticatory movements, but is not involved by its neurovascular vicinity in the genesis of specific headaches Its surgical release, however, should be discussed in the case of a temporal myoplasty