Chapter 19 Flashcards
Congenital hearing loss may be due to abnormalities of the hair cells or auditory nerve ganglia
Sensorineural loss
Congenital hearing loss may be due to structural defects in the external ear canal, eardrum, or ear ossicles
Conductive hearing loss
In this syndrome, malformations in the external ear and ear canal and the ear ossicles can all be involved in causing varying degrees of conductive hearing loss.
Treacher Collins syndrome
In this syndrome, hearing loss may be caused by sensorineural and/or conductive abnormalities
Down Syndrome
Enumerate factors causing sensorineural defects
Prenatal infections (rubella, cytomegalovirus, herpes simple)
Prematurity
Maternal diabetes
This factor can cause both types of deafness
Accutane (retinoids)
The most common ear ossicle to be involved in conductive hearing loss
Stapes
The footplate of stapes is derived from?
Neural crest cells and paraxial mesoderm
These cells direct formation of the footplate and of the oval window
Neural crest cells
The most common abnormality usually involving both ears
Stapes fixation (ankylosis)
These defects are common, include minor and severe abnormalities and are significant from the standpoint of the psychological and emotional trauma they may cause and for the fact that they are often associ- ated with other malformations.
External ear defects
External ears are derived from
Neural crest cells
are skin tags and shallow depressions, respectively, anterior to the ear.
Preauricular appendages and pits
arise when invagination of first arch tissues to form the external auditory meatus fails to occur properly.
Pits
occur when misexpression of genes regulating development of the external ears results in duplications of tissue growth and differentiation.
Appendages
