Pathology of the Head and Neck

Ear and Temporal Bone Chapter 8 255Maternal rubella is an important factor in the genesisof congenital sensorineural hearing loss. The virus is anRNA one. In two cases the temporal bones showed inflammatorycollections at the upper end near the junctionwith Reissner’s membrane and adherent to it [29].The organ of Corti was mainly normal.In herpes zoster auris (Ramsay Hunt syndrome), thevirus (the DNA herpes varicella virus) enters the inner earalong the seventh and eighth cranial nerves, presumablyfrom nerve ganglia where it lies dormant until the immunologicalstatus of the patient deteriorates. In histopathologicalstudies previously described there were extensiveinflammatory changes mainly in those two cranialnerves serving in the transmission of the virus. Varicellazoster has also been detected in the cytoplasm and nucleiof inflammatory cells of the middle ear in two cases ofthe Ramsay-Hunt syndrome by an immunofluorescencemethod [30]. Herpes varicella-zoster viral (VZV) DNAhas been identified, using the polymerase chain reaction,in archival celloidin-embedded temporal bone sectionsfrom two patients who clinically had Ramsay-Hunt syndrome(herpes zoster oticus) [119].A condition possibly due to viral infection in the innerear is that of Bell’s palsy, which is manifested clinicallyas a peripheral facial paralysis. The suggestion hasbeen made, with some virological support, that this conditionis the result of infection with herpes simplex virus,type 1. There have been a very small number of reportsof temporal bone studies from patients with Bell’spalsy. In two cases of Bell’s palsy I studied, serial sectionsof the temporal bones both showed the followinghistological findings. In the genu region there appearedto be constriction of the facial nerve by inflammatorytissue, which formed a sheath around it and encroachedon its interior. The adjacent bone showed foci of resorptionwith abundant osteoclasts (Fig. 8.20). The geniculateganglion was infiltrated by lymphocytes. In someplaces the affected facial nerve appeared severely oedematousand nerve cells were shrunken and showed aneosinophilic cytoplasm. The descending part of the facialnerve presented swelling and vacuolation of myelinsheaths with some loss of axis cylinders. These findingsare compatible with geniculate ganglionitis. In one ofthese cases, herpes simplex viral type 1 was demonstratedin archival paraffin-embedded sections of the affectedgeniculate ganglion by carrying out PCR followed byelectrophoresis on agarose gel [14].Pe t ro s i t i s : bacterial infections of the inner ear may involveboth the petrous bone itself and the labyrinthinestructures within it. Bacterial infection of the petrousbone is frequently derived by extension from middle earinfection. There are four possible routes by which infectionmay extend from the middle ear into the petrousbone [68]:1. Via air cells. Mastoid air cells frequently extend inthe temporal bone as far as the apical region. It isFig. 8.20. Interface between geniculate ganglion and adjacentbone in a case of Bell’s palsy, showing numerous osteoclasts withHowship’s lacunae. Reproduced from Michaels and Hellquist [68]possible, therefore, that infection to the petrous apexmay extend from the middle ear by the medium ofinfection of air cells;2. As direct spread of the inflammatory process by bonenecrosis (osteitis);3. By extension through the bone marrow of the petrousbone (osteomyelitis);4. Along vessels and nerves.In addition to inflammatory infiltration the pathologicalprocess of petrositis comprises three main changesin the bone tissue, all of which may be seen simultaneously:(a) bone necrosis, (b) bone erosion, (c) new boneformation. Petrositis is of great importance because involvementof the labyrinth, nerves, artery, veins, meningesand cerebral tissue embedded in and surroundingthe petrous bone may each cause serious symptoms, andperhaps death.Extension to the labyrinth may lead to labyrinthitiswith destruction of the organs of hearing and balance.Important nerves may be damaged. The facial nerveis at risk early on. Involvement of the trigeminal ganglionand the sixth cranial nerve lead to “Gradenigo’ssyndrome”. Extension to the jugular foramen region bythe inflammatory process may cause palsy of the ninth,tenth and eleventh cranial nerves (“jugular foramensyndrome”).The wall of the internal carotid artery may becomeinflamed and this may lead to thrombosis of the vesselwith possible cerebral complications. Similarly, thelateral sinus may become thrombosed and this and/orextension of the thrombus to the superior sagittal sinusmay be associated with the somewhat arcane syndromeof otitic hydrocephalus. Spread of the infectionto the immediately adjacent cranial structures will leadto meningitis and cerebral abscess.Labyrinthitis: the source of labyrinthitis is, in manyinstances, otitis media, as with petrositis. Infection may