Audiologic Issues in CHARGE Syndrome
James W. Thelin, PhD, CCC-A, and Sarah E. Krivenki
CHARGE is a syndrome that many audiologists have not encountered. It is rare (1 in 15,000 births) and complex. Audiologic evaluation of individuals with CHARGE syndrome can be challenging as a result of characteristics that are unique to this population. However, some of the characteristics seen in individuals with CHARGE can also be seen in other populations, such as those with severe developmental delays, autism spectrum disorders, and auditory neuropathy/dyssynchrony.
"CHARGE" is the acronym created by R. A. Pagon and her coworkers in 1981 (Pagon, Graham, Zozana, & Yong, 1981) to describe six features of a complex genetic disorder. Since 1981, the diagnostic criteria have been revised, and they will continue to be revised. At present, the criteria include more than 20 physical anomalies, deficits in all sensory modalities, and a behavioral phenotype that is unique. At present, diagnosis is based on clinical evaluation of the presence of certain major and minor features (Blake et al., 1998) and/or the presence of microdeletions in the CHD7 gene on chromosome 8 (Vissers et al., 2004). The vast majority of genetic mutations are sporadic rather than familial.
Though there may be deficits in every sensory modality, for educational purposes, CHARGE is considered to be a deaf-blind syndrome. Complete deafness and blindness are very rare. The most common finding is partial loss of hearing and vision. However, the combination of these two sensory deficits almost always results in overall challenges that are much greater than would be expected from the sum of the two. With multiple sensory deficits, the effects are often subtle and may manifest themselves as unique challenges in communication, learning, and behavior.
Within individuals, each of the 20+ possible anomalies may be absent or present (varying in degree of expression from mild to severe). Thelin and Swanson (2006) have given a description of the most important anomalies. As a result of this complexity, each individual may have a unique set of physical disorders, a unique combination of sensory deficits, and a unique pattern of behavior. The challenge to the clinician is to determine how best to interface with that individual, recognizing the individual's specific abilities, to obtain diagnostic information and to provide needed treatment. As a result of very significant sensory deprivation in all modalities, a substantial percentage of individuals with CHARGE do not develop symbolic communication. Some may use gestures to communicate, while others may rely on more primitive forms of expression.
Approximately half of individuals with CHARGE have severe-to-profound hearing loss. Many of these individuals are very difficult to evaluate audiologically. However, the documentation of hearing loss that enables either the fitting of appropriate amplification (i.e. hearing aids or cochlear implants) or a better understanding of the individual's communication needs may result in the development of the primary means for communication and learning. In the most extreme cases, individuals with CHARGE who have virtually no channels of meaningful sensory input may resort to destructive behaviors and self-mutilation as their only means of communication. In some cases, these behaviors have ceased after audiologic intervention that ended the individual's isolation. A more general observation has been that the acquisition of symbolic communication is highly correlated with successful audiologic intervention -regardless of the degree of hearing loss.
Individuals with CHARGE syndrome are typically delayed in development-motorically, intellectually, and physically. Some individuals do not reach puberty until 20 years of age. The most common report from parents is that their child has reached some developmental milestone well beyond the expected age of acquisition and after the parents had lost hope that the milestone would ever be reached. Parents are keenly sensitive to this issue and discount the advice of clinicians who underestimate their child's potential. It is critical for the clinician to recognize this and to proceed and plan as if goals that may seem unattainable may eventually be attained.
Structural Anomalies and Hearing Loss
In CHARGE, nearly every set of structures in the auditory system may be involved.
External ears typically are malformed and have patterns of malformation that are so distinctive that preemptive diagnoses of CHARGE can be made on the basis of unusually shaped, asymmetrical pinnae. The anomalous pinnae rarely cause hearing loss, but they are often so soft and floppy that they may not support a behind-the-ear hearing aid. Ear canals are often stenotic but rarely occluded.
Middle ears typically have ossicular malformations that result in conductive losses that are greatest in the low frequencies but can be present at all frequencies. Average conductive losses as great as 70 dB have been reported with normal tympanograms. Eustachian tube dysfunction is almost universal, with most children requiring several sets of tympanostomy tubes. When the eustachian tube dysfunction is caused by craniofacial anomalies, middle ear fluid and otitis media may persist into adulthood.
Cochleas and vestibular mechanisms often are dysplastic or aplastic. Many different forms of structural anomalies have been reported, including Mondini's dysplasia, which includes dwarf cochleas and incomplete formation of the semicircular canals. The semicircular canals of the vestibular system are often missing. As a result, individuals with CHARGE may have difficulty walking and performing acts that require balance-related skills, but they rarely have any complaints related to dizziness.
Auditory neural structures may be involved as well. The auditory nerve may be reduced in diameter or absent. Recent evidence suggests that the anatomical assessment of the auditory nerve is best accomplished with magnetic resonance images that are supplemented with information obtained by computerized tomography. Radiographic studies have shown instances of dysgenesis or agenesis of the corpus callosum. In cases with relatively normal hearing, evidence of retrocochlear involvement has been documented using auditory evoked response testing.
There is no characteristic hearing loss in CHARGE syndrome. The most common features are asymmetrical mixed losses that are severe-to-profound in degree. Conductive components, which are due to a combination of ossicular anomalies and middle ear effusion, are often asymmetrical and fluctuating in nature; cochlear hearing loss, often due to cochlear malformations, is typically greater in the high frequencies. Three examples of hearing loss in CHARGE are shown below. Hearing results were specified using the audiometric standard in effect when the audiograms were obtained.
Audiogram 1 (58-year-old female)
This audiogram was selected to illustrate asymmetry of hearing loss between the ears, which is common in CHARGE syndrome. In this case, there is asymmetry in both the conductive and cochlear components and in the overall degree of hearing loss in the two ears. Tympanometry was normal in both ears, indicating that the middle ear losses are due to ossicular anomalies.
This is a rare case of familial CHARGE syndrome that includes the woman whose audiogram is shown, her mother, her brother (one of her four siblings), and three of her nine children (Thelin, Mitchell, Hefner, & Davenport, 1986). Among these individuals, auditory anomalies were found for every individual, but hearing levels ranged from normal to profound hearing loss.
Audiogram 2 (21-year-old female)
This audiogram was selected because it illustrates (a) asymmetrical hearing loss and (b) bilateral mixed loss with significant cochlear loss that is difficult to treat. In the right ear, there is a mild conductive loss through 1500 Hz falling to a profound mixed loss in the higher frequencies. In the left ear, there is a severe-to-profound mixed loss. This young woman has chronic middle-ear disease and has had many surgeries in both ears. Middle-ear effusion and drainage into the ear canals are still a persistent problem. The conductive component of her hearing loss is probably due to a combination of ossicular anomalies and effusion.
A unique aspect of this individual's auditory problems is that even though the cochlear sensitivity in the left ear is in the moderate to moderately severe hearing loss range, because of the large conductive loss, the left ear is unaidable. She wears a behind-the-ear hearing aid in the right ear, but when there is effusion, her aided benefit is reduced. Under the best of conditions, she receives most aided benefit at 2000 Hz and below. With the large conductive loss in the right ear, if she is eating or chewing gum, the internally generated noise is so great that she cannot understand a person who is talking to her. As a result of these factors, her hearing problems are resolved only intermittently. She communicates with both spoken and signed language.
Audiogram 3 (12-year-old male)
This audiogram was selected to illustrate the magnitude of conductive loss that can be present in CHARGE syndrome. The tympanograms were shallow but peaked at room pressure-indicating that the conductive loss was not due to eustachian tube dysfunction or middle-ear effusion but rather to ossicular anomalies. Unmasked bone-conduction thresholds were measured only on the right ear but are shown for the left ear with a dotted line.
The solid lines (labeled with an S) indicate the pure-tone thresholds obtained with supra-aural earphones. It is our interpretation that these thresholds were "bone-conduction" thresholds because, at these signal levels, the earphone cushion on the pinna begins to act as a bone vibrator rather than as an acoustic sound source. The average air-bone gap for the five test frequencies was 61 dB in the right ear and 72 dB in the left ear.
It is our opinion that the thresholds with the supra-aural earphones significantly underestimate the true degree of hearing loss and that a better estimate of the air-conduction thresholds is obtained with insert earphones (dashed lines labeled with an I). The insert earphones may be generating bone-conducted stimulation as well, but we suspect because of the coupling in the external auditory canal and the reduced amount of sound power required, the stimulation is likely to be acoustic. We believe that thresholds obtained with the insert earphones more accurately reflect the individual's hearing loss.
The average insert earphone threshold for the right ear was 103 dB HL (average air-bone gap = 77 dB), and for the left ear it was 105 dB HL (average air-bone gap = 79 dB). These are very large conductive components that are difficult to overcome with conventional hearing aids without encountering feedback. This individual's bone-conduction thresholds make him a candidate for bone-conduction amplification or an auditory osseointegrated device.
Factors in Audiologic Assessment and Treatment
Individuals with CHARGE often have physical and sensory disorders, limited communication ability, and behaviors that provide challenges in the assessment of hearing and the treatment of hearing loss. Listed below are factors to consider when providing audiologic services.
A significant percentage of individuals with CHARGE have no symbolic communication. For individuals with limited communication abilities, the presence of an adult who understands the individual's communication system is very helpful. Adapting audiologic procedures is often necessary. For example, the audiologic assessment of a 27-year-old male who was profoundly intellectually challenged and who had very poor vision was possible because this individual would respond to speech stimuli with grunts, head banging, and rapid eye movements. He responded consistently to speech in each ear at 60 dB HL and to bone-conducted speech at 40 dB HL, indicating the presence of a bilateral mixed hearing loss.
Individuals with CHARGE may exhibit tactile defensiveness, attention deficit disorder, autistic-like behaviors, self-stimulatory behaviors, and in extreme cases, self-mutilation. These challenging behaviors are those by which individuals with severe sensory deprivation deal with the world that they encounter. For these individuals, their behavior may be their only mode of communication. The challenge to the audiologist is to work through these behaviors to obtain an assessment of hearing and to develop a method of treatment. In many cases, successful treatment of hearing loss opens up the best channel of communication for the individual. To reach this goal, it is often necessary to conduct the assessment in small steps with specific, limited objectives over a series of patient visits. Patience and perseverance are essential-and are greatly appreciated by parents who typically rate hearing loss as their child's most significant disability.
Mucus and Saliva
Children with CHARGE often have major breathing, swallowing, and feeding problems. Many are fed with a gastrostomy tube. Frequent breaks may be needed in managing the child and keeping him or her comfortable during assessment.
Audiologic assessment under sedation is often a desirable option. However, there are two concerns. First, in some cases, the individuals with CHARGE are medically fragile and have breathing and swallowing difficulties that need to be taken into consideration. Second, some individuals with CHARGE have shown resistance to sedation and do not respond to standard doses of sedatives.
The characteristic ocular anomaly in CHARGE is coloboma. This is evidenced as a keyhole slot at the bottom of the eye that creates a triangular iris as well as a void on the retina and in the optic nerve. This can create holes in the visual field that prevent detection of visual images-especially from above the individual. If visual reinforcement audiometry is used, the individual may turn his or her head at an unusual angle to place the image on a functioning part of the retina.
For many individuals with CHARGE, their combined auditory and visual deficits are so significant that they have only a small area in front of them in which they can communicate optimally. This area has been called the "communication bubble." The size of the bubble varies depending on the individual's hearing and vision, on the presence of background noise, and on lighting (sensitivity to bright light is common). When the individual with CHARGE is unable to walk or move independently to situate himself or herself for optimal communication, the clinician will need to make these accommodations and place the interaction within the communication bubble.
Amplification needs to be fitted as early as possible. Because the pinnae are often very soft and misshapen, they will not support conventional behind-the-ear hearing aids. Due to permanent and long-standing conductive hearing losses, individuals with CHARGE may be candidates for bone-conduction hearing aids or auditory osseointegrated devices such as the "Baha." Cochlear implantation is sometimes an option, but there are often concerns about the reduced diameter of the auditory nerve and stimulation of the facial nerve by the cochlear implant.
Parents of Children with CHARGE
Parents of children with CHARGE have likely seen dozens of health care providers before seeing an audiologist. These parents realize that they must advocate for their child; they often take and file notes on each visit to a professional; and they are keenly aware of who understands their child's problems and who does not. Many have accessed the 250+ page manual titled CHARGE Syndrome: A Manual for Parents from the CHARGE Syndrome Foundation website . The manual is free to parents and professionals alike. The professionals who are most appreciated are those who acknowledge that they have not encountered CHARGE before but are willing to acquire the information. Also, audiologists and speech-language pathologists should understand that parents of children with CHARGE are eternally hopeful about their child's prospects for the future and appreciate the professional who will encourage them even when the challenges are great.
The typical child with CHARGE has had 10 major surgeries before 3 years of age. Once the survival of the child is assured, parents shift their focus to development, communication, and learning. Our data indicate that there is a significant relationship between development of symbolic communication (spoken or signed language) and early intervention (before 3 years of age) by audiologists and speech-language pathologists. As a result, audiologists and speech-language pathologists have a great opportunity to improve the quality of life for individuals with this complex and multifaceted disorder.
About the Authors
James W. Thelin is an audiologist who teaches graduate students and conducts auditory and vestibular research at the University of Tennessee. He has worked with parents of children with CHARGE syndrome and individuals with CHARGE syndrome for 25 years. He is currently the vice president of the CHARGE Syndrome Foundation, Inc.
Sarah E. Krivenki is a doctor of audiology student at the University of Tennessee who is conducting research on the vestibulo-ocular reflex in CHARGE syndrome.
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