TY  - CHAP
M1  - Book, Section
TI  - Nonsyndromic Sensorineural Hearing Loss
A1  - Shearer, A. Eliot
A1  - Hildebrand, Michael S.
A1  - Smith, Richard J. H.
A2  - Murray, Michael F.
A2  - Babyatsky, Mark W.
A2  - Giovanni, Monica A.
A2  - Alkuraya, Fowzan S.
A2  - Stewart, Douglas R.
Y1  - 2014
N1  - 
T2  - Clinical Genomics: Practical Applications in Adult Patient Care
AB  - Disease  summary:Hearing  loss  (HL)  is  the  most  common  sensory  deficit  in  humans,  occurring  in  1  in  500  births  and  affecting  278  million  people  worldwide.Conductive  HL  (CHL)  is  characterized  by  abnormalities  of  the  external  and/or  middle  ear,  while  sensorineural  hearing  loss  (SNHL)  is  caused  by  malfunction  of  the  inner  ear,  and  mixed  HL  is  a  combination  of  both  CHL  and  SNHL.Nonsyndromic  HL  (NSHL)  is  not  associated  with  any  abnormalities  of  the  external  ear  or  any  other  organs  and  comprises  the  majority  (70%)  of  hereditary  HL  (Fig.  151-1).Hereditary  basis:Most  cases  of  NSHL  have  a  genetic  etiology.NSHL  is  genetically  heterogeneous  with  64  genes  currently  implicated  in  the  disorder  (Table  151-1).Mutations  in  the  gene  encoding  the  gap  junction  protein  connexin  26  (GJB2)  are  the  most  common  genetic  cause  of  NSHL,  occurring  in  an  estimated  25%  of  autosomal  recessive  cases  in  the  US  population.Differential  diagnosis:Environmental  causes  of  hearing  impairment  (acquired  HL)  account  for  approximately  30%  of  NSHL  in  developed  countriesAcquired  HL  in  children  may  be  caused  byPrenatal  infections  from  TORCH  organisms  (Toxoplasmosis,  Rubella,  Cytomegalovirus  [CMV],  and  Herpes)  with  infection  comprising  the  majority  of  environmental  HL  in  childrenPostnatal  infections,  particularly  bacterial  meningitis  caused  by  Neisseriameningitides,  Haemophilus  influenzae,  or  Streptococcus  pneumoniaeAcquired  HL  in  adults  is  most  often  due  to  environmental  noise  exposure,  though  there  is  evidence  for  gene-environment  interactions  in  “age-related”  HL.Syndromic  hearing  impairment  is  characterized  by  hearing  loss  and  abnormal  findings  of  at  least  one  other  organ  system.  There  are  more  than  400  genetic  syndromes  that  include  hearing  impairment  and  only  the  most  common  are  briefly  outlined  here.Autosomal  dominant  syndromic  hearing  impairmentWaardenburg  syndrome:  variable  SNHL,  pigmentary  abnormalities  including  white  forelock,  and  heterochromia  iridisBranchiootorenal  syndrome  (BOR  syndrome):  CHL,  SNHL,  or  mixed  HL,  branchial  cleft  cysts,  malformations  of  the  external  ear,  and  renal  anomaliesStickler  syndrome:  progressive  SNHL,  cleft  palate,  and  spondyloepiphyseal  dysplasia  leading  to  arthritisAutosomal  recessive  syndromic  hearing  impairmentUsher  syndrome  (USH):  the  most  common  cause  of  deaf-blindness  is  characterized  by  congenital  SNHL,  retinitis  pigmentosa,  and  vestibular  dysfunction.  There  are  three  types  of  USH  differentiated  by  hearing  and  vestibular  phenotypes:USH  type  I:  severe-to-profound  SNHL,  vestibular  deficitsUSH  type  II:  mild-to-severe  SNHL,  normal  vestibular  functionUSH  type  III:  progressive  SNHL  and  progressive  loss  of  vestibular  functionPendred  syndrome:  severe-to-profound  SNHL  and  euthyroid  goiter  associated  with  an  abnormality  of  the  bony  labyrinth  on  CT  examination  (Mondini  dysplasia  or  enlarged  vestibular  aqueduct  [EVA])Jervell  and  Lange-Nielsen  syndrome:  congenital  deafness  and  prolongation  of  the  QT  interval  leading  to  syncopal  episodesX-linked  syndromic  impairmentAlport  syndrome:  progressive  SNHL  and  progressive  glomerulonephritis  which  can  lead  to  end-stage  renal  disease  along  with  variable  ophthalmologic  findings  (eg,  anterior  lenticonus)NSHL  is  distinguished  by  a  lack  of  visible  abnormalities  of  the  external  ear  or  other  organ  systems,  however,  it  can  be  associated  with  abnormalities  of  the  middle  and/or  inner  ear  (Table  151-1).  NSHL  is  categorized  by  mode  of  inheritance  and  the  different  gene  loci  are  designated  DFN  (for  DeaFNess)  and  then  given  a  letter  according  to  inheritance  pattern.Autosomal  dominant  NSHL  (DFNA):  generally  progressive  and  moderate  to  severe.  Significant  genotype-phenotype  correlations  exist  (eg,  WFS1,  DFNA6/14,  causes  low-frequency  SNHL).Autosomal  recessive  NSHL  (DFNB):  generally  congenital  severe  to  profound,  with  exceptions  ...
SN  - 
PB  - McGraw-Hill Education
CY  - New York, NY
Y2  - 2024/04/19
UR  - accessbiomedicalscience.mhmedical.com/content.aspx?aid=1102706328
ER  -