The infection may spread from the ear to the mastoid bone of the skull, which is the bony bump off the base of the skull, located just behind the ears slightly above the level of the earlobe.
The patient wears headphones when air conduction is tested and a vibrating earpiece behind the ear next to the mastoid bone or along the forehead when bone conduction is tested.
During the procedure, the surgeon makes an incision behind the ear and opens the mastoid bone (the ridge on the skull behind the ear) leading into the middle ear.
Mastoiditis-An inflammation of the bone behind the ear (the mastoid bone) caused by an infection spreading from the middle ear to the cavity in the mastoid bone.
The following are the characters of the second sub-family, Heteromyinae: Incisors narrow; mastoid appearing largely on the top of the skull; eyes and ears moderate or large; hind-limbs and tail elongated.
They have long hind limbs, large eyes and ears; and in correlation with the latter an enlarged auditory bulla to the skull, which is hollow and divided into a tympanic and a mastoid portion.
In the highly specialized mastoid region of the skull, the North American Oligocene Protoptychus approaches to Dipopodomys, while the contemporary Gymnoptychus and Entoptychus likewise appear referable to the Geomyidae.
X P11,1x, premaxilla; Mx, maxilla; Ma, malar; Fr, frontal; L, lachrymal; Pa, parietal; Na, nasal; Sq, squamosal; Ty, tympanic; ExO, exoccipital; AS, alisphenoid; OS, orbito-sphenoid; Per, mastoid bulla.
The cleido-mastoid generally arises from the basi-occipital, and the pectoralis major is connected with the latissimus dorsi.
The first of these, or Geomyinae, is characterized as follows: Incisors broad; mastoid not appearing on the top of the skull; eyes small; ears rudimentary; limbs short, subequal.