90 APPLIED ANATOMY. 



The antrum is a little larger than the attic. The two cavities are continuous 

 through the aditus. The roof of the antrum is level with the roof of the attic and its 

 floor is about level with the top of the membrane. It is thus seen to be directly 

 above and posterior to it. 



Mastoid Cells. The mastoid cells are continuous with the antrum and 

 permeate the mastoid process down to its tip. The cells come so close to the surface 

 that suppuration within them often bursts through and discharges behind the ear. 

 The upper, inner, and lower portions of the bone are also sometimes perforated, which 

 will be referred to later. 



Middle-ear Disease. Suppuration from middle-ear disease is caused by an 

 infective inflammation travelling up the Eustachian tube from the pharynx and nasal 

 cavities. It may pass to the attic above and thence to the mastoid antrum and 

 mastoid cells. Pus usually finds an exit by perforating the tympanic membrane and 

 discharging through the external auditory meatus. As already stated, it may pass 

 down the Eustachian tube to be blown out of the anterior nares. It has been known 

 to pass down the canal for the tensor tympani muscle, and form a retropharyngeal 

 abscess. As the pus reaches the pharynx behind the prevertebral fascia, it may 

 extend laterally and appear externally behind the sternomastoid muscle. Having 

 thus reached the base of the skull, the infection may involve the meninges and brain 

 through the crevices in the bone. It is rare for it to perforate the bone below and 



FIG. 105. Teuotoiny of the tensor tympani tendon 

 and separation of the incus from the stapes. 



Modified from Georges Laurens. 



FIG. 106. Removal of the incus by means of Ludwig's 

 hook. 



anteriorly, and thus implicate the jugular vein and internal carotid artery. It may 

 eat into the posterior wall and involve the facial nerve, which is covered by only a 

 thin shell of bone, and produce facial paralysis, attack the internal ear through the 

 fenestra ovalis and rotunda and pass through the internal meatus to the brain. If it 

 extends upward and involves the attic and antrum, it may perforate the roof, or 

 tegmen, and form a subdural abscess in the back part of the middle cerebral fossa, 

 whence it travels a distance of about a centimetre to the lateral sinus, causing a 

 thrombus to form, or it may produce an abscess of the temporosphenoidal lobe of 

 the brain. The antrum and mastoid cells being continuous, the posterior and inner 

 walls may be perforated, the pus thereby reaching the posterior cerebral fossa, 

 again involving the lateral sinus, or producing a cerebellar abscess. If it perforates 

 the mastoid process on its inner wall at the groove for the digastric muscle, the pus 

 gains access to the back of the neck, forming what is known as BczolcC s abscess. 



Operations on the Middle Ear. The operations on the middle ear, besides 

 those involving the membrane, are done either for the removal of the remains of the 

 membrane and ossicles, or else to clear out the antrum and mastoid cells and even, 

 if necessary, examine the lateral sinus and jugular vein and explore the brain. They 

 are done for suppurative affections, which may be either chronic, producing local 

 symptoms, or acute, producing in addition constitutional disturbances and even 

 general infection. Caries of the bones is a prominent condition in suppurative cases 



