Histopathological changes in the foetal and infantile inner ear caused by maternal rubella

Incidence evaluation of snhl in high risk neonates

OBJECTIVE

to evaluate hearing in high-risk neonates to find the incidence of congenital and early acquired sensory-neural hearing loss.

STUDY DESIGN AND SETTING

The study was designed as a consecutive cases, hospital based study in a tertiary care hospital.

PATIENTS

The subjects were 70 normal born neonates and 70 high-risk neonates. The 70 neonates with various high risks included in the study had family history of deafness, prematurity, IUGR, asphyxia, perinatal infections, hyperbilirubinemia, neonatal sepsis, meningitis, ototoxicity and fetal malformations.

INTERVENTIONS

The study was conducted over a period of two years from Sep 2000 to Aug 2002. BERA using Octavus neuro-otological computer and a main unit BERA module with integrated pre-amplifier was performed within first 28 days of life and at 6 months follow up.

RESULTS

44 out of 140 neonates showed abnormalities on initial BERA testing. 28 ears out of 67 ears (44 neonates) had losses confirmed at repeat BERA. Wave V was considered to determine the threshold of hearing and was found to be consistently present in neonates and also the wave . Hyperbilirubinemia (18 cases) and prematurity (29 cases) were the most commonly observed. The cases of Hyperbilirubinemia showed raised thresholds, absolute latencies and Wave 1 abnormalities (suggesting affection of eighth nerve). In the cases of Prematurity, 8 ears showed raised threshold at follow up. Asphyxia was found in 5 cases and is known to affect the auditory nerve. Family history of deafness found in 3 cases showed X-linked inheritance in one case and autosomal recessive inheritance in the others. Perinatal Rubella was observed in two cases, which showed hearing loss. Congenital malformations were seen in 7 cases (Waardenberg, Downs, Hydrocephalus and T-O Fistula). Neonatal Sepsis was observed in 3 cases and is known to affect the eighth nerve. IUGR was observed in 3 cases, two had normal hearing while one had no waveforms.

CONCLUSION

BERA should be used as a screening tool to test the auditory function in all high-risk neonates.

Effect of upper respiratory infection on hearing in the ferret model

In an effort to develop an adult animal model for acquired viral-induced hearing loss, three groups of mature ferrets were inoculated intranasally with respiratory viruses (influenza A/Port Chalmers, influenza B/Mass, and parainfluenza I), which have been implicated as causative agents in idiopathic sudden hearing loss (ISHL). All ferrets challenged with influenza A/Port Chalmers (A/PC) exhibited clinical signs of infection, but neither of the other two groups exhibited such signs. Conductive and/or sensorineural hearing losses were demonstrated in eight of 15 ferrets challenged with influenza A/PC and four of 10 ferrets in the group challenged with influenza B/Mass by brainstem auditory-evoked responses (BAERs) and acoustic immittance. None of the four ferrets infected with parainfluenza I demonstrated auditory dysfunction. When auditory changes were observed, nasal washes were performed, and tissues of the middle and inner ears were collected for viral assay and morphologic examination. All ferrets demonstrating auditory changes were shown to be infected by isolation of virus from nasal tissues. Virus was isolated from eustachian tube tissue in six of the eight ferrets infected with influenza A/PC, which also demonstrated altered BAERs and one of the four infected with influenza B/Mass, which also had auditory changes. Virus was isolated from the middle ear of two ferrets infected with influenza A/PC and from the inner ear of another two ferrets from the same group. These data suggest that influenza A/PC has a greater effect on auditory function in the ferret model than either influenza B/Mass or parainfluenza I and that the ferret may be an appropriate adult model to examine the etiologic role of viral upper respiratory tract infections in some acquired hearing impairments.

Middle and inner ear changes in congenital rubella

Temporal bone changes in a 14-month-old female infant with congenital rubella are described. The inner ears showed cochleo-saccular degeneration, with more severe involvement of the right side. Perivascular round cell infiltration was demonstrated in the base of the cochlea, stria vascularis, and superior ampullary cribriform region, consistent with viral infection. Whether the latter was related to the rubella or the the patient's terminal viral infection is undetermined. Predominant involvement of the cochlea saccule may have been related o their blood supply from the vestibulo-cochlear artery, which is a more direct continuation of the labyrinthine artery than are the other branches. Middle ear changes consisted of a fetal type of stapes, a small area of malleus head fixation on one side, and absence of the medial component of the posterior incudal ligament, with a joint-like attachment between the short process of the incus and the medial wall of the fossa incudis. This may be an abnormality, or it might represent a variation of normal development.

The occurrence of the Tullio phenomenon in congenitally deaf children

One hundred and fifty deaf children between 5 and 16 years old of the 'Rudolf Mees' Institute were investigated in search of the Tullio phenomenon with nystagmus as a criterion. Seventy-six out of those 300 ears were positive. A functioning (calorically excitable) pars superior of the labyrinth was a 'conditio sine qua non' for this reflex. We may assume that deaf ears which show a positive Tullio phenomenon have a labyrinthine pathology of the Mondini-Alexander type and that this symptom is a pathologic one.

Viral disease of the labyrinth. I. Review of the literature and discussion of the role of cytomegalovirus in congenital deafness

Review of the literature concerning the histopathology of viral induced deafness indicates two general patterns of viral infection of the inner ear: 1) An endolymphatic labyrinthitis secondary to viremia via the stria vascularis is described in rubella, mumps, rubeola, and cytomegalovirus. 2) A perilymphatic infection secondary to meningeal, perineural, or endoneural spread is seen in varicella-zoster. Pathologic changes of degeneration and atrophy are due to inflammation and seem to be constant no matter if the infection is prenatal or postnatal. Two published reports of prenatal and perinatal cytomegalovirus infection show endolymphatic labyrinthitis similar to that casued by the other viruses. Subsequent clinical studies indicate the presence of hearing loss in mildly symptomatic and/or asymptomatic children with cytomegalovirus infections. Cytomegalovirus infection may prove to be the most significant cause of congenital and/or viral induced deafness in the future as the number of children infected with rubella, rubeola, and mumps decreases due to the use of appropriate vaccines.