Petrous

Petrous is an adjective meaning stone-like or rock-hard. In medical and anatomical usage, it most often refers to the petrous part of the temporal bone, known as the pars petrosa. The term derives from Latin petrosus, meaning rocky or stony, and is used to describe the dense, compact portion of the temporal bone that forms part of the base of the skull.

Anatomy and structure: The petrous part of the temporal bone is a pyramid-shaped, osseous region that houses key components of the inner ear and surrounding nerves. It encloses the bony labyrinth, which contains the cochlea and vestibular apparatus essential for hearing and balance. The internal acoustic meatus, through which cranial nerves VII and VIII pass, traverses the petrous portion and a canal for the facial nerve runs within it. The petrous apex is the narrow, medial projection at the inferior aspect of this region. The bone is among the densest in the human body, contributing to protection of delicate inner-ear structures and adjacent neural pathways.

Clinical relevance: The petrous temporal bone is a critical landmark in radiology and skull-base surgery. Fractures of the petrous bone can cause complications such as CSF leakage, hearing loss, vestibular dysfunction, and facial nerve palsy. Imaging with CT and MRI focuses on detailing the petrous region to assess fracture patterns, tumor involvement, or congenital abnormalities. Surgical procedures involving the inner ear, inner-ear reach, or cranial nerves often require careful consideration of the petrous bone’s anatomy.

Other notes: Beyond anatomy, petrous in general English describes something stone-like, from the same Latin root, but in medical terminology it is chiefly used to denote the pars petrosa of the temporal bone.