Middle Cranial Fossa Approach: The Incudomalleolar Joint as a Reliable Landmark

Abstract

Introduction The middle cranial fossa approach is performed by fewer neurotologists owing to a reduced number of indications. Consistent landmarks are mandatory to guide the surgeon in a narrow field. Objectives We have evaluated the incus and malleus head and the incudomalleal joint (IMJ) as a key landmark for identifying the superior semicircular canal (SSC) and to get oriented along the floor of the middle cranial fossa. Methods A combination of 20 temporal bone dissections and CT imaging were utilized to test and describe these landmarks. Results The blue line of the SSC is consistently identified along the prolongation of a virtual line through the IMJ and the angulation toward the root of zygoma. The mean distance from the zygoma toward the IMJ ranged from 1.60 to 1.90cm. Once the IMJ was identified, the blue line of the SSC was consistently found along the virtual line through the IMJ within 5 to 9mm. Conclusions The IMJ is a safe and consistent anatomical marker in the surgical approach to the middle cranial fossa floor. Opening the tegmen 1.5 to 2cm medial to the root of the zygoma and identifying the joint allows to trace a virtual line toward the SSC within 5 to 9mm. Knowledge of the close relationship between the direction of the IMJ and the superior canal can be used in all transtemporal approaches, thus orienting the surgeon in a rather narrow field with limited retraction of the dura and brain.

Asociación entre dehiscencia del canal semicircular superior y dehiscencia del tegmen tympani. Revisión narrativa cronológica

“…Hashmiy cols. realizaron un estudio en 20 cadáveres utilizando articulación/ unión incudomaleolar como punto de referencia en las imágenes de TC preoperatorias para identificar la dehiscencia del canal de cara a un enfoque quirúrgico a través de fosa craneal media cuando coexistían ambas dehiscencias, concluyendo que es el marcador anatómico seguro 28 . Heywoody cols.…”

Anatomical Analysis of the Eustachian Tube in the Temporal Bone Through the Middle Fossa Window

“…• Showing the depth measurements of ZR (posterior origin of the zygomatic arc) and external auditory canal using the external approach (13-15) • The incudomalleolar joint (16) • The lesser petrosal nerve, which can be exposed before GSPN during the elevation of the dura mater on the middle fossa floor (17) • FS as an internal landmark (18) • The head of the malleus (14,19) Considering the complex anatomy of the middle fossa, one of the most vital structures is the horizontal petrous segment of ICA. Tewari et al ( 20) delineated the mean distance from ZR to the carotid canal as 3.28 cm in their radiological study, which analyzed 500 CT scans.…”