petrotympanic fissure
The petrotympanic fissure, also known as the Glaserian (or glaserian) fissure, is a small fissure in the temporal bone that connects the mandibular (glenoid) fossa and the tympanic cavity. It is a medial continuation of the tympanosquamosal suture that runs between the superior borders of the tympanic and petrous parts of the temporal bone.
Terminology
Some authors apply the label of petrotympanic fissure to what appears to be the fissure between the squamous and tympanic parts of the temporal bone , but that structure would more correctly be labeled the tympanosquamous (squamotympanic) fissure. Other depictions point to a cleft emanating anteromedially from the mandibular fossa toward the greater wing of sphenoid , but that structure is more accurately labeled the petrosquamous fissure.
Some authors describe the glaserian fissure as the medial extension of the petrotympanic fissure , but most sources consider these synonymous.
Gross anatomy
The fissure contains
- chorda tympani
- anterior ligament of malleus , which overlaps with the discomallear ligament (connecting the articular disc and capsule of the temporomandibular joint and the malleus in the tympanic cavity)
- anterior tympanic artery, a branch of internal maxillary artery
The fissure is composed of two canals :
- external canal: larger, lateral, containing anterior ligament of malleus and anterior tympanic artery
- internal canal: smaller, medial, containing chorda tympani; also known as canal of Huguier, anterior canaliculus for chorda tympani, anterior tympanic aperture, or iter chordae anterius
Boundaries
The anterior/superior wall of the fissure (the petrous part) is a coronally oriented inferior projection of the tegmen tympani , sometimes known as the crista tegmentalis .
The posterior/inferior wall of the fissure (the tympanic part) is the anterior tympanic spine, which is the anterior part of the incomplete tympanic ring .
Radiographic features
CT
The fissure is well profiled on sagittal views as an upward convex tunnel-shaped osseous channel extending from the posteromedial aspect of the temporomandibular joint to the epitympanum .
History and etymology
The structure is named after Swiss anatomist Johann Heinrich Glaser (1629-1675), who did not actually describe this fissure but rather described the split part of the tympanic ring that connects the tympanic cavity with the external auditory canal . The fissure was probably first described by Joseph Guichard Duverney (1648-1730) around the same time, in the late 1600s, and then eponymically misassociated by others with Glaser in the mid-1700s . The eponym was popular enough that it became used as an adjective without capitalization (glaserian), similar to eustachian or fallopian . The term "petrotympanic fissure" was not used until Jakob Henle (1809-1885) named it in 1855 .
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