_Nerve-involvement._ | _Nerve-involvement._ | _Nerve-involvement._ Olfactory. | Fifth (second and | Seventh. Optic. | third divisions). | Eighth. Third. | Sixth. | Ninth. Fourth. | Seventh. | Tenth. Fifth (first | Eighth. | Eleventh. division). | | Twelfth (?). Sixth. | | ----------------------+----------------------+---------------------- FRACTURE OF THE MASTOID PORTION OF THE TEMPORAL BONE Fractures limited to this region are of rare occurrence. Our knowledge of the condition is obtained from the researches of Lèon Boullet, who first described the fracture in 1876, reporting at the same time 26 cases. The fracture usually results from sharp blows delivered along the posterior border of the mastoid process, the force acting obliquely from above downwards and forwards. More rarely, the process is detached as the result of a blow delivered immediately above the ear, that organ sharing in the displacement. In either case the detachment is usually of an incomplete nature, mainly on account of the muscular and pericranial attachments in the region involved. According to Boullet, the following symptoms result:-- =Surgical emphysema and pneumatocele.= Air escapes from the mastoid cells and antrum into the overlying tissues, either spreading widely through the subaponeurotic space of the scalp and cellular tissues of the neck (surgical emphysema), or remaining localized and forming a tumour of inconsiderable size (pneumatocele). In either case palpation reveals that peculiar crepitation which is pathognomonic of tumours of this nature. =Bleeding from the ear.= Hæmorrhage takes place into the middle ear, and, as the tympanic membrane is usually lacerated, the blood escapes from the external ear. In the event of the tympanic membrane being uninjured, the blood may escape along the Eustachian tube into the naso-pharynx. Boullet also pointed out that certain complications may be associated with the mastoid lesion. These are as follows:-- _Immediate._ _Remote._ Wound of the lateral sinus. Deafness. Laceration of dura and brain. Otitis media. Injury to the aqueductus Fallopii Caries and necrosis of the and paralysis of the petrous bone. seventh nerve.