What is the petrous bone?
The petrous bone, pars petrosa, is one of three bones that make up the temporal bone. The other two bones are the pars tympanica and the pars squamosa. For the most part, the petrous bone projects into the interior of the bony skull (exception: mastoid process).
The pars petrosa owes its name to the fact that the bone is as hard as a rock in places – it is the hardest bone in the human skull. It is divided into several sections: an anterior side (facies anterior), a posterior side (facies posterior), and a lower side (facies inferior), as well as a tip (apex) and the mastoid process. The latter is clearly palpable as an elevation behind the ear. It contains numerous small periosteum-lined air chambers that have a direct connection to the tympanic cavity.
What is the function of the petrous bone?
Where is the temporal bone located?
The petrous bone lies as a three-sided pyramid between the sphenoid bone (Os sphenoidale) and the occipital bone (Os occipitale). Toward its tip. On the front surface of the petrous bone is the roof of the tympanic cavity.
What problems can the petrous bone cause?
A basal skull fracture in the area of the petrous bone (otobasal fracture) can be recognized by bleeding on the mastoid process, the auricle, and sometimes the posterior pharyngeal wall.
A longitudinal fracture of the petrous bone results in a tear at the edge of the tympanic membrane. In contrast, in a transverse fracture of the petrous bone, the eardrum remains uninjured, but blood flows into the pharynx. In addition, there is gaze deviation to the side with the fracture, paralysis of the facial nerve, and failure of the inner ear (with inner ear deafness, rotational vertigo, and nystagmus). If the pyramidal tip is injured, the cranial nerves V and VI are often damaged as well.
Due to the close proximity of the mastoid process and the middle ear, middle ear infections often lead to inflammation of this bone (mastoiditis).
As a rare but dangerous complication of otitis media, suppuration of the petrous pyramid may develop.
In chronic suppurative otitis media, epithelial tissue from the external auditory canal can grow into the middle ear and the bone in the area of the tympanic cavity and petrous bone can be destroyed. Doctors refer to this as a cholesteatoma.
