Groove For The Lesser Petrosal Nerve Of The Temporal Bone, Anatomy

Description

Lesser petrosal nerve groove on the petrous part of the temporal bone is highlighted as a narrow sulcus on the superior (anterior) surface of the petrous pyramid, positioned lateral to the greater petrosal canal and its hiatus. The furrow tracks anteromedially from the region of the petrous ridge toward the foramen ovale area of the sphenoid, maintaining a shallow course across the middle cranial fossa floor. Nearby landmarks that logically frame this relationship include the greater petrosal nerve pathway emerging from the facial canal at the hiatus, and the adjacent bony relief of the petrous apex and tegmen tympani. Small, easy to miss. Clinically, this groove matters because it marks the intracranial segment of the parasympathetic pathway from the glossopharyngeal nerve (via the tympanic plexus and lesser petrosal nerve) toward the otic ganglion, with downstream secretomotor fibers reaching the parotid gland through the auriculotemporal nerve. Skull base procedures that traverse the middle cranial fossa, including approaches near the petrous apex or along the petrous ridge, can place this structure at risk, and bony identification can be more reliable than trying to follow the nerve itself. The fixed perspective emphasizes how close the lesser petrosal groove sits to the greater petrosal canal, a common point of confusion when teaching petrous temporal bone surface anatomy. Use this illustration in head and neck anatomy labs, dental and otolaryngology teaching on parasympathetic innervation of the parotid gland, and surgical atlas figures covering middle cranial fossa landmarks, foramen ovale relationships, and petrous temporal bone orientation. It also supports radiology and anatomy correlation discussions when reviewing skull base CT, where shallow sulci and canals on the petrous surface help confirm laterality and surgical corridors. Anatomical accuracy verified by SciePro's Medical Advisory Board.