Temporal bone

The Temporal bone is a bone and belongs to the human skull. It is located at the base of the skull and belongs to the temporal bone (os temporale). The inner ear with its equilibrium organ and cochlea is in its pyramid-like basic shape. The temporal bone fracture and the Gradenigo syndrome are of particular clinical importance for the temporal bone.

What is the petrous bone?

The temporal bone is a part of the human skull. It belongs to the temporal bone (os temporale) and lies at the base of the skull. Because of its pyramid-like shape, it is also called Rock pyramid known. The inner ear, which surrounds the organ of equilibrium and the cochlea, is surrounded by the petrous bone.

A special feature of the petrous bone is its bone structure: It forms a so-called braided bone, in English also "woven bone" (literally: "woven bone"). Normally, this type of bone tissue is only found in bones that are not yet fully developed: During embryonic development, the bones are formed from woven bones to form the skeleton of the skeleton. However, collagen fibers running in parallel reinforce it in other bones and thus turn the braided bone into a lamellar bone. In the case of the temporal bone, however, it is different - even in adults it consists of the original network. As a result, it is less stable than other bones and can break more easily.

Anatomy & structure

The anatomical terms used to describe the petrous bone are based on its rough geometric shape, which resembles a three-sided pyramid. The tip of the petrous bone (apex) lies in the skull bone between the occiput (occipital bone) and the sphenoid bone (sphenoid bone). The base of the petrous bone cannot be clearly delimited from other parts of the bone, but in adults it merges smoothly into the pars squamose and the pars mastoidea; both parts also belong to the temporal bone.

According to the pyramid analogy, medicine also speaks of surfaces or faces and angles or anguli in order to make more precise statements about the temporal bone. This is particularly important when describing fractions precisely. In its entirety, the petrous bone belongs to the temporal bone (os temporale). The canal of the eustachian tube (canalis musculotubaris) is one of three main entrances in the temporal bone and connects it to the middle ear. Nerves can reach the pyramidal structure through the porus acousticus internus and the foramen stylomastoideum.

Function & tasks

As a bone, the temporal bone generally has protective and stabilizing functions. In its special case, it protects the organ of equilibrium and the cochlea that is surrounded by it. These two structures make up the inner ear. The organ of equilibrium consists of semicircular canals that contain fluid and are covered with hair cells. In connection with loose, bone-like solids that lie in the organ of equilibrium, these sensory cells can determine whether a person is standing upright or occupying a different position in space - depending on the direction in which the fine extensions of the hair cells bend.

This type of sensory cell occurs not only in the organ of equilibrium, but also in the cochlea or cochlea. It contains auditory cells that are sensitive to the pressure of sound waves and are therefore responsible for the perception of sounds. The pitch is coded by the location of the stimulation: low frequencies consist of long sound waves that cannot penetrate far into the cochlea, while the highest audible tones with their very short sound waves penetrate the innermost part of the cochlea. This phenomenon is based on the physical properties of the sound waves as well as the anatomy of the cochlea, which spirals and narrows inward.

Diseases

If too much pressure is applied to the petrous bone, the bone can break. The petrous bone fracture often occurs together with other skull fractures and can be accompanied by other clinical pictures. In traumatic brain injury, the brain is also involved; Doctors determine the severity on the basis of three levels, the lowest being the concussion.

It often runs without long-term consequences, whereas the severe traumatic brain injury or the contusion of the brain is accompanied by long unconsciousness immediately after the trauma (at least 60 minutes) and in many cases causes permanent lesions. A petrous bone fracture can also be present in multiple trauma with many body areas involved. The petrous bone is more prone to fractures than other bones because it is a braided bone that is not stabilized by additional collagen lamellae. Burst fractures are therefore particularly common in petrous bone fractures.

Another clinical picture that specifically affects the petrous bone is Gradenigo syndrome or pyramidal apex syndrome. The name of the clinical picture goes back to the Italian physician Giuseppe Conte Gradenigo, who introduced the syndrome to the specialist literature in 1904. Doctors understand it to be an inflammatory complication that can follow an acute otitis media. Purulent discharge from the inflammation is typical. People with Gradenigo syndrome often experience pain behind the eyes, face pain, and double vision due to paralysis of the eye muscles.

Symptoms are due to damage to the cranial nerves involved: acute otitis media migrates to the skull, either spreads to the cranial nerves or causes the tissue to swell (i.e., develop edema), which in turn affects the cranial nerves. The nerves that affect Gradenigo syndrome are the trigeminal nerve, the abducens nerve, and / or the occulomotor nerve.