Thursday, July 15, 2010

Temperature-induced hearing loss

There are many reasons why people loose hearing. Environmental factors  - especially prolonged loud noise and infection or injury - are among the leading causes in the US (figure on the right). Drugs, and chemical toxins could also play a role. Genes accounts for less than half of causes. Gene-environment interactions are contributing too. 
  • Drug induced - some medications can result in damage to the auditory system with prolonged use. They are called ototoxic. Here are a few drugs that are known to cause hearing loss: aminoglycoside antibiotics (such as streptomycin, neomycin, kanamycin); salicylates in large quantities (aspirin), loop diuretics (lasix, ethacrynic acid); and drugs used in chemotherapy regimens (cisplatin, carboplatin, nitrogen mustard). Genetics may predispose to vulnerability to drugs.
  • Noise-induced hearing loss (NIHL) - this is hearing loss due to exposure to either a sudden, loud noise or exposure to loud noises for a period of time. A dangerous sound is anything that is 85 dB (sound pressure level - SPL) or higher. Genetics may determine vulnerability thresholds to noise.
  • Temperature-induced hearing loss.  Genetics could cause temporary hearing loss caused by a high body temperature. They recover some time after their body temperature has returned to normal.  
It is well known that high fevers cause hearing loss. High fevers account for about 1,200 to 1,800 cases of hearing loss in the US each year. Artificially-induced high body temperature  - for example by a strenuous workout in a 105 degree room - may be the culprit too.
Mutations in the otoferlin (OTOF) gene  - known to cause neurosensory nonsyndromic recessive deafness - have been recently linked to rare temporary hearing loss caused by a high body temperature.
In one of the cases examined, hearing of a young boy in the morning was better than in the afternoon, and temperature measurements showed that his body temperature in the afternoon was generally higher than that in the morning. Hospital examination showed that when his body temperature rose above 36.5°C, the  hearing loss was severe (70-80dB HL) and this symptom could last for a whole day. The boy with the temperature-dependent hearing loss had two variant OTOF genes, each of which is not usually seen in normal-hearing people.
Another study of a family with three children whose hearing was sensitive to temperature also linked their ailments to OTOF gene.

References

Fukushima K, Ramesh A, Srisailapathy CR, et al. (1996). An autosomal recessive nonsyndromic form of sensorineural hearing loss maps to 3p-DFNB6. Genome Res. 5 (3): 305–8. PMID 8593615

Varga, R. (2005). OTOF mutations revealed by genetic analysis of hearing loss families including a potential temperature sensitive auditory neuropathy allele Journal of Medical Genetics, 43 (7), 576-581 DOI: 10.1136/jmg.2005.03861

Wang, D., Wang, Y., Weil, D., Zhao, Y., Rao, S., Zong, L., Ji, Y., Liu, Q., Li, J., Yang, H., Shen, Y., Benedict-Alderfer, C., Zheng, Q., Petit, C., & Wang, Q. (2010). Screening mutations of OTOF gene in Chinese patients with auditory neuropathy, including a familial case of temperature-sensitive auditory neuropathy BMC Medical Genetics, 11 (1) DOI: 10.1186/1471-2350-11-79

Marlin, S., Feldmann, D., Nguyen, Y., Rouillon, I., Loundon, N., Jonard, L., Bonnet, C., Couderc, R., Garabedian, E., & Petit, C. (2010). Temperature-sensitive auditory neuropathy associated with an otoferlin mutation: Deafening fever! Biochemical and Biophysical Research Communications, 394 (3), 737-742 DOI: 10.1016/j.bbrc.2010.03.06

1 comment:

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