The Inner Ear and Diseases of the Bony Labyrinth

Chapter 633 The Inner Ear and Diseases of the Bony Labyrinth



Joseph Haddad, Jr.



Genetic factors can affect the anatomy and function of the inner ear. Infectious agents, including viruses, bacteria, and protozoa, also can cause abnormal function, most commonly as sequelae of congenital infection or bacterial meningitis. Other acquired diseases of the labyrinthine capsule include otosclerosis, osteopetrosis, Langerhans’ cell histiocytosis, fibrous dysplasia, and other types of bony dysplasia. All of these can cause both conductive and sensorineural hearing loss as well as vestibular dysfunction. Use of currently available vaccines reduces the risk for bacterial meningitis and the associated sensorineural hearing loss.



Viruses


The most common cause of childhood sensorineural hearing loss (SNHL) is congenital cytomegalovirus (CMV) infection (Chapter 247). The strongest predictor of delayed hearing loss appears to be the presence of symptoms at birth; prolonged viral shedding may also be a risk factor. In one large study, children who passed initial audiologic examinations but who had CMV-related symptoms at birth were ~6 times more likely to develop hearing loss than those who were asymptomatic. Stabilization or perhaps reversal of the hearing loss may be possible by using ganciclovir in very young infants with congenital CMV infection.


Other viral causes of SNHL include congenital rubella as well as acquired mumps, rubella, rubeola (measles), and fifth disease, caused by parvovirus B19. Many other viruses also occasionally are associated with SNHL. In as many as 50% of cases, hearing loss, which usually is bilateral and often is asymmetric, progresses and worsens over weeks to years.


Before an effective vaccine was introduced, rubella was responsible for as many as 60% of cases of childhood SNHL. Vaccination in developed countries has reduced the rate of rubella by >97%. Similarly, measles and mumps are now uncommon causes of SNHL in the USA because of successful vaccination programs.


Herpes simplex encephalitis can also be associated with SNHL, which is more common in children with congenital herpesvirus infection. Acyclovir and other antiviral agents can help the hearing loss and other central nervous system manifestations (Chapter 237).



Toxoplasmosis


Toxoplasma gondii is a protozoan that can cause congenital SNHL. In the USA, about 3,000 children are born each yr with congenital toxoplasmosis, and approximately 25% of untreated patients have SNHL. If maternal infection is documented during the fetal period, medical therapy may be able to prevent some of the clinical manifestations, including SNHL of the offspring (Chapter 282).



Bacterial Meningitis


Since the Haemophilus influenzae type b vaccine was introduced, Streptococcus pneumoniae (Chapter 175) and Neisseria meningitides (Chapter 184) have become the leading causes of bacterial meningitis in children in the USA. Hearing loss occurs more commonly with S. pneumoniae,

Only gold members can continue reading. Log In or Register to continue

Related posts:

  1. Rumination, Pica, and Elimination (Enuresis, Encopresis) Disorders
  2. Adolescent Pregnancy
  3. Neisseria gonorrhoeae (Gonococcus)
  4. Blastomycosis (Blastomyces dermatitidis)

Stay updated, free articles. Join our Telegram channel
Tags:
Jun 18, 2016 | Posted by in PEDIATRICS | Comments Off on The Inner Ear and Diseases of the Bony Labyrinth

Full access? Get Clinical Tree
Get Clinical Tree app for offline access