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1 Ph.D. in Human Communication Disorders, UNIFESP, Speech Therapist and Audiologist, Professor of the Course on Speech and Language Pathology and Audiology, University of Sagrado Coração and University of São Paulo Bauru/SP.
2 Ph.D. in Human Communication Disorders, UNIFESP, Speech Therapist and Audiologist, Professor of Federal University of São Paulo - UNIFESP/SP.

The present paper is an integral part of the Doctorate Dissertation submitted to Federal University of São Paulo (UNIFESP)-2000.

Address correspondence to: Dionísia C. Lamônica - R. Júlio Maringoni, 8-47 ap.121, Jardim Estoril - Bauru

Tel:(55 14)234.5173 - Fax:(55 14)223.0694 - E-mail:dionelam@uol.com.br

Article submitted on September 10, 2001. Article accepted on September 29, 2001.

INTRODUCTION

There are a number of studies that have reported hearing losses in cerebral palsy patients (Hopikins, Bice and Colton15, 1954; Chance4, 1964; Dinicola and Sazonna8, 1965; Nober20, 1966; Levine18, 1972; Morris19, 1973; Tormakh25, 1975; Cunningham6, 1977; Stewart21, 1978; Vernon26, 1980; Glasscock13, 1985; Haberfellner and Müller14, 1989; Young27, 1989; Edebol-Tysk9, 1989; Cranford, Boose and More5, 1990; Stringher, Meyerhoff and Wright23, 1991; Eicher, Bastshaw10, 1993; Braga3, 1995; Borg2 1997; Uverant24, 1998; Fobe12, 1999 and Lamônica17, 2000).

Hopikins, Bice and Colton (1954)15 showed a study about the incidence of sensorineural hearing loss according to type of cerebral palsy. In the athetoid type, they found 23% of hearing loss, ataxic, 18%, rigid, 14% and spastic cerebral palsy patients, 7%.

Chance (1964)4 observed in a study with cerebral palsy children that about 30% presented some type of hearing problem, from conductive hearing losses to severe sensorineural losses.

Dinicola and Sazonna (1965)8 stated that if hearing skills are compromised in the first year of life, it will bring severe consequence to the child or even prevent him or her from acquiring vocabulary repertoire and learn spontaneously expressive language.

Levine (1972)18 emphasized that approximately 20% of the children with cerebral palsy presented sensorineural hearing loss. He discussed the discrepancy found in studies concerning percentage and severity of hearing disorders or losses. The author considered that the etiological basis of cerebral palsy may the same that causes the hearing loss, making children with cerebral palsy more susceptible to hearing problems.

Morris (1973)19 evaluated 285 school-age children with cerebral palsy. He stated that hearing losses detected in children with spastic cerebral palsy are probably related to diffuse brain damage, whereas hearing losses in athetoid cerebral palsy patients are related to Kernicterus.

Tormakh (1975)25 stated that cephalic movements are very important for directional orientation of sounds, because when the child can not turn the head freely, he can not turn towards the sound source, bringing disadvantages to the receptive process because the child will have difficulties to judge the sound source and perform sensorial integration.

Cunningham (1977)6 assessed 10 children with cerebral palsy and hearing loss. Among them, four had spastic diplegia, three had spastic quadriplegia and three were coreo-athetoid, all of them presenting moderate to severe hearing loss. The author reported that 50% of them presented hearing losses in frequencies above 2000Hz. As to time of diagnosis, it was observed that only 10% of the subjects had been diagnosed with cerebral palsy and hearing loss at the same time, by the age of 2 months; 50% received the diagnosis of hearing loss on average 6 months after the cerebral palsy diagnosis, and in 40% of the cases, the diagnosis of hearing loss was made only 3.5 years after the diagnosis of cerebral palsy.

Hungria (1984)16 wrote that, as to hypoxia, the cochlea is especially sensitive to insufficient oxygen. Dorsal nucleus of acoustic nerve has more vascularization than the ventral nucleus, and that is why it is more susceptible to insufficient oxygenation, which can lead to selective deafness to high sounds. He also stated that in case of temporary anoxia, the ventral nucleus can also be affected, resulting in simultaneous deafness for low sounds and that children who had been especially sick during the neonatal period, despite being term babies, still have the risk to develop significant hearing loss, even if they presented normal responses in the neonatal hearing screening.

Haberfellner and Müller (1989)14 examined hearing of 75 children with cerebral palsy, ranging in age from 5 to 15 years, 26 athetoid and 49 spastic patients. Pure tone audiometry assessed audibility thresholds in frequencies 500 to 4000Hz. Out of the total, 67% presented normal hearing in both ears. The study also correlated risk factors for the occurrence of cerebral palsy and hearing loss, showing factors related to hearing loss, such as prematurity, low weight at birth, hypoxia and hyperbilirrubinemia.

Young (1989)27 presented data from the study with cerebral palsy patients, stating that hearing losses in the pathology can reach 30%. He reported that ¼ of the athetoid patients, 1/5 of the ataxic and 1/10 of the hemiplegic ataxic patients will definitely present sensorineural losses. He also stated that spastic cerebral palsy patients are prone to hear less when experience severe spasm and abnormal reflex activity block their attention and that, if the patient has a pattern of hyper-extension, he will probably be unable to show any motor reaction to sound. Athetoid cerebral palsy patients may also have difficulties during the assessment, because involuntary movements will interfere in the result of the test and such movements will clearly compete with the auditory stimuli presented.

Braga (1995)3 confirmed that sensorineural problems may occur by association of the etiological basis of cerebral palsy, such as in cases of bilirrubin encephalopathy.

Borg (1997)2 studied the influence of perinatal asphyxia, hypoxia and ischemia to provoke hearing losses by conducting a literature review study of the past 20 years. He stated that the exact etiology of a neonatal hearing loss is hard to be detected. He also confirmed that only a small percentage of hearing losses occurs at the time, considering that the brain is more sensitive to reduction of oxygen than the hearing system. He also stated that pre-term babies are more sensitive than term babies and the hearing loss and cerebral palsy may be present in 8% of the cases, under such events.

In order to study the probable occurrence of hearing loss in subjects with cerebral palsy, we defined the objective of the present study, that is, to check the capacity of detecting pure tones of 250 to 8Khz in subjects with cerebral palsy without complaints of hearing and check what kind of affections parents attributed to their children.

MATERIAL AND METHOD

The present study was conducted at the Clinic of Health Education (CEPS) of the University of Sagrado Coração Bauru - São Paulo.

The contact with cerebral palsy patients was made through rehabilitation centers, clinics and schools that offered care to cerebral palsy subjects in the city of Bauru.

For eligibility to the study, subjects with cerebral palsy had to have confirmed diagnosis through neurological and/or physiatrist assessment signed by a physician. We evaluated 67 subjects with cerebral palsy, both genders, 34 males and 33 females, ages ranging from 7 to 16.10 years of chronological age. Subjects were divided into 4 groups:

· Group 1: Quadriplegic spastic cerebral palsy (G1)
· Group 2: Diplegic spastic cerebral palsy (G2)
· Group 3: Hemiplegic spastic cerebral palsy (G3)
· Group 4: Athetoid cerebral palsy (G4)

Before the conduction of the present study, the project was submitted to the Ethics Committee on Research of Federal University of São Paulo, and it was approved by Resolution 196/96.

All subjects and family members were referred to a first interview, previously scheduled, and invited to participate as volunteers in the study. In the first contact we informed them about objectives and all the clinical procedures to which they would be submitted. Next, they were referred to ENT assessment - otoscopy, so as to exclude factors that could interfere in the results of the audiometry. We performed acoustic immitance measures to check middle ear conditions. If there were any middle ear affections, subjects were referred to medical treatment, especially because type A tympanometry curve was a pre-requirement for inclusion in the experimental group.

The family member responsible for the child participated in one anamnesis session, responding to the protocol that contained information about history, motor skills, hearing skills and etiological basis of the pathology presented. None of the family members reported hearing loss suspicion.

Air pure tone thresholds were collected based on Davis and Silverman (1970) criteria. We used 20 dBHL (ANSI, 69) as normal audibility threshold for all tested frequencies.

The subjects demonstrated detection of sound stimuli depending on motor availability, for example, pressing the answering button, raising the hand, vocalizing or blinking strongly. The results were recorded in the appropriate form.

It is important to point out that the patients remained in the adequate posture, depending on their motor disabilities, but we tried to place them in a position so as to inhibit pathological reflex patterns (especially asymmetrical tonus cervical reflex and/or symmetrical tonus cervical reflex, stretching reflex and involuntary head movement), following cerebral palsy patients handling techniques suggested by Bobath and Bobath1 (1984) and described by Finnie11 (1998).

The device used was AZ-7r INTERACOUSTICS, calibrated according to ANSI 3.6/ ISO 389; Audiometer GSI-61 WELCH-ALLYN, phones TDH-50, MX-41AR, bone oscillator RADIOLAR B-71, Microphone ELETRETO for the subject and phone and microphone ELETRETO for the examiner, calibrated according to ANSI 3.6-ISSO 389.

RESULTS

Graph 1 shows the data concerning auditory sensitivity of subjects who participated in the study. We considered occurrence of hearing loss by analyzing the frequencies 0.25 to 8kHz for the right and left ears, when thresholds of at least one frequency were below 20dB.

In Graphs 2 and 3 we can see the median of hearing thresholds of subjects who had more than one frequency below 20dB, considering frequencies of 0.25 to 8kHz for right and left ears.

Table 1 shows the age in months of the subjects who were diagnosed with hearing loss.

Table 2 presented the factors referred by family members as the probable etiology of cerebral palsy in the studied groups. It is important to point out that each family member could list more than one factor if they considered that they had been one of the causes of the problem.

Factors marked with asterisk are those that were considered by the family members as the causal factor and that can also cause hearing loss (Cunningham6, 1977;. Vernon26, 1980; Edebol - Tysk9, 1989; Braga 19953; Eicher, Bastshaw10, 1993; Braga3, 1995; Borg2, 1997; Fobe12, 1999).

In the four studied groups, we noticed similar hearing thresholds for right and left ears (Graph 1). Audibility thresholds for groups 3 (hemiplegic) and 2 (diplegic) were about 20dB at 2000Hz, worsening at 5 to 10dB in high frequencies of 4, 6 and 8kHz, showing descending configuration (Graph 2 for the right ear and Graph 3 for the left ear). The worst hearing thresholds were found for group 1 (quadriplegic) in whom we observed hearing losses of 50dB from low to high frequencies, maintaining a drop of 5 to 10dB from octave interval (Graphs 1 and 2). The minimum age (Table 1) for detection of hearing loss varied from 7 years (95 months) to 16 years (195 months) and was made through the present study. The main causes reported by the families as causing factors of the problems were hypoxia (77%), to remain in the incubator (52%) and prematurity (47%).

DISCUSSION

Generally speaking, considering all evaluated cerebral patients, we detected hearing losses in 51% of them, regardless of type of cerebral palsy. Analyzing the degree of hearing loss, we found losses from mild to moderate in all types of cerebral palsy, and only in the group of quadriplegic we found severe cases. The literature had already described some variability of hearing losses in cerebral palsy patients (Chance4, 1964; Levine18, 1972; Morris19, 1973; Stewart21, 1978; Haberfellner, Müller14, 1989; Young27, 1989; Borg2, 1997; Uverant24, 1998; Fobe12, 1999).

The configuration of the predominant audiometric curve was descending, that is, hearing loss in high sounds. Cunninghan and Holt6 (1977), Tormakh25 (1975); Fobe12, (1999) also reported this trend of descending curves in cerebral palsy subjects.

There are a number of factors that could explain why family members had no complaints about hearing, or in other words, the fact that the hearing losses were left unnoticed. First of all, the motor deficit per se, difficulty to perform voluntary motor acts and involuntary motor patterns may mask family members' perception. In addition, the strategy of family members to facilitate interaction of subjects, taking them to the stimulus sources, speaking in front of them, trying to interpret their communication or speaking for them may have contributed. Thus, families interpreted their children's hearing difficulties, if noticed, as failures caused by the motor deficits provided by the cerebral palsy, leading to late diagnosis of the hearing loss (after 7 years of age) in the assessed subjects. Another extremely important factor in the discussion concerns the etiological factors of the hearing loss. The revised literature (Chance4, 1964, Nober20, 1966; Levine18, 1966; Morris19, 1973; Stewart21, 1978; Vermon26, 1980; Hungria16, 1984: Glasscock13, 1985; Haberfellner, Müller14, 1989; Cranford et al. 19905; Cunningham and Holt6, 1990; Braga3, 1995; Borg2, 1997; Fobe12, 1999) leaves no doubts as to the fact that the risk factors causing cerebral palsy can also cause hearing loss, observing that such an etiology may represent a risk of occurrence of both affections (Lamônica17, 2000).

Considering the importance of early diagnosis, both for cerebral palsy and hearing loss, professionals in the area should pay more attention to this relevant issue and its pertinent clinical interventions, because the hearing deficit added up to cerebral palsy will negatively interfere in the development of linguistic skills and general communication of these subjects.

Conclusion

After the analysis of the results for detection of pure tone of frequencies 250 to 8000Hz in 67 subjects with diagnosis of cerebral palsy with no hearing complaints, we concluded that the majority (51%) had descending hearing loss, whose severity ranged from mild in frequencies up to 4000Hz to severe in high frequencies. The group with the poorest sensitivity was that of quadriplegic spastic cerebral palsy subjects. In addition, motor difficulties presented by subjects were attributed predominantly by family members to the presence of hypoxia at birth and no family member suspected of hearing loss in these subjects.

The study showed the importance of referring to hearing assessment all subjects with cerebral palsy before they are referred to speech rehabilitation, so that hearing thresholds from 250 to 8000Hz may be evaluated, guaranteeing that speech therapy will focus on hearing and language aspects to improve quality of life of the subjects.

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