Mexico: Hearing treatment immediately following birth



A Mexican research group is developing a protocol to allow for detection of hearing problems at the prenatal stage. Such a technique would open the way to beginning rehabilitation of newborn babies immediately following birth.

The research team behind this initiative comes from the La Laguna Otology Foundation, which is working jointly with the National Autonomous University of Mexico’s Centre for Neural Development, and Cochlear Academy. These entities have joined forces to carry out an international multicentre study for “Uterine Hearing Screening” with the aim of early detection of possible deafness in all foetuses.

The protocol involves carrying out a descriptive study on a censal segment of pregnant women between 20-and-35-years-old who attend participating medical centres between weeks 32 and 36 of their gestation; they will be submitted to an obstetric ultrasound to check whether the baby receives the sound stimulus. Following birth, an otoacoustic emissions test will be carried out on the baby to check the integrity of their external cochlear hair cells.

Detection procedure

“Cochleopalpebral reflex (CR) is considered a reliable auditory response when it is immediate with a latency of 0.5 seconds. In 1984, Lori Ann Kuczwara and colleagues validated a study of 284 foetuses at week 28, provoking CR. They found the system to be good, quick, non-invasive and, above all, an easily-observable response. Falkner pointed out, after 1966, that cochleopalpebral reflex had never been produced in deaf children from an acoustic stimulus,” explained Dr. Marcelino Covarrubias, otological surgeon, chairman of the La Laguna Otology Foundation, and medical director of the Ángeles Torreón Hospital.

Through the use of a foetal echosonogram, the baby’s face is located, and an electroacoustic transducer (patented L1-40) is placed on the mother’s belly “which generates a sound stimulus with an intensity and frequency calculated according to the attenuation resulting from the passing of the sound through the maternal abdomen, and this is able to provoke the cochleopalpebral reflex in the foetus while, at the same time, the change in foetal cardiac frequency is noted, and this is taken as a positive response indicating that the foetus is hearing,” explains Dr. Covarrubias.

Use of the L1-40 transducer allows for the development of an economical, and easy universal cover strategy to complement the efforts now being made in the area of early detection of deafness. The L1-40 transducer is compatible with all makes of ultrasound equipment. The procedure is innocuous and will be useful for optimising and focusing hearing testing on the newborn. These are also required “to help detect cases of auditory neuropathy, which at the moment can escape screening of the newborn through otoacoustic emission testing,” points out Dr. Melissa Correa Flores, a specialist in audiology, otoneurology, and speech-language pathology, subspecialist in applied phoniatrics for special groups, and member of the La Laguna Otology Foundation and the Oír Bien centre in the town of Zapopan.

The protocol being promoted by Mexican researchers is aimed at making the L1-40 transducer known worldwide so that it can be adapted to any ultrasound equipment, enabling all pregnant women to access this diagnostic method during the final three months of pregnancy.

L1-40 transducer
L1-40 transducer.

“We are not trying to replace brainstem auditory evoked potentials; we just hope that this protocol will become the predecessor of those and that patients not generating a positive response will be channeled to a specialist from the moment of birth,” explains Correa.

Advantages over neonatal hearing screening

With the aim of screening the highest possible number of foetuses using this procedure, the study will need to become part of the analyses routinely carried out by practices caring for pregnant mothers. On average in Mexico, a woman will undergo between three and four ultrasound examinations during pregnancy in order to measure the health parameters of the foetus.

Early diagnosis of deafness is currently carried out after birth; it is a fact that a high percentage of cases in Mexico go without evaluation due to a shortage of equipment and trained specialists, or through lack of knowledge of the diagnostic study.

Despite a neonatal hearing screening programme being implemented in 2010 in Mexico, there is still a lack of technological tools for early detection of hearing loss. “Early diagnosis of deafness is currently attempted when children are born, although regrettably the American Academy of Otolaryngology claims that in 2015 around one million of them did not have access to the hearing examination of the newborn, so it is necessary to increase the programme’s coverage and perfect it,” explains Melissa Correa.

“With current studies for the newborn - transient otoacoustic emissions or brainstem auditory evoked potentials - the integrity of external hair cells is all that is checked, and the auditory pathways are not evaluated, so we could be leaving 11% of patients with auditory dys-synchrony without early detection,” assures Dr. Correa. In line with official 2012 data, between 2,000 and 6,000 children Marcelino Covarrubias encabeza el equipo de investigación. are born with hearing loss every year in Mexico and, despite the existence of institutional programmes for screening them, most of them have neither access nor early rehabilitation. “Detection is still at 78.8% after 24 months of age, and this places limits on early language rehabilitation. Ideally, detection is needed before three months of age, and langauge rehab should begin at six months,” underlined the audiology specialist.

Marcelino Covarrubias
Dr. Marcelino Covarrubias.

The prenatal detection protocol has the support of 16 international research centres, which make up a website where researchers who have already practised the test can register their results on completing the study (cochleopalpebral reflex and variation in foetal cardiac frequency) and birth comparisons. “Once we have the test results, we can publish them throughout the gynaecology and obstetrics communities who have ultrasound equipment, and cases detected without a response will be channeled at the moment of birth to begin an expedited hypoacusis check-up,” concluded Dr. Covarrubias. This prenatal hearing detection protocol could give specialists the possibility to carry out correct diagnosis of hearing problems; all that is needed is possession of ultrasonographic equipment and acquisition of the transducer to adapt to the ultrasound machine via the USB port.

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Photos: Dra. Melissa Correa Flores, Audiología Otoneurología Foniatría, K.A.J.