The speech and language characteristics of children with Prader-Willi syndrome.

Journal of Speech and Hearing Disorders,Volume 55, 300-309, May 1990

THE SPEECH AND LANGUAGE CHARACTERISTICS OF CHILDREN WITH PRADER-WILLI SYNDROME SALLIE A. KLEPPE* Visalia, CA KERRI MISAKI KATAYAMA Sanger Unified School District, Sanger, CA KENNETH G. SHIPLEY California State University, Fresno DAVID R. FOUSHEE Northwest Speech and Hearing Center, Fresno, CA Prader-Willi syndrome was initially identified in 1956. Since then, a majority of the literature pertaining to Prader-Willi has focused on the medical and genetic aspects of the syndrome. There has been limited information available regarding the speech and language abilities of children with Prader-Willi. This study investigated the communicative development of 18 children with the syndrome, ranging in age from 8:8 to 17:1. A number of evaluative procedures were used to evaluate the subjects' spontaneous speech, articulation, and receptive and expressive language abilities, as well as their voice, fluency, oral mechanisms, hearing, and their developmental histories. A variety of communicative deficiencies were found in the children's speech, language, voice, and fluency. KEY WORDS: Prader-Willi syndrome, genetic syndromes, speech disorders, language disorders, mental impairment

30,000 (Zellweger, 1981) births, although it is possible that these figures are lower than the true prevalence. Several factors have hindered establishing precise prevalence estimates. Prader-Willi has been a clinical diagnosis that has not needed to be reported to public health departments (Bray et al., 1983), the diagnosis is rather easy to miss, and this congenital syndrome may not be properly identified for years after birth (Burke, Kousseff, Gleesen, O'Connell, & Devlin, 1987). A slightly higher prevalence of the syndrome (60%) has been reported with boys (Bray et al., 1983). This may, however, be due to the easier detection of hypogenitalism in boys (Hall, 1979; Krywaniuk, 1977). Several years ago, the Prader-Willi Syndrome Association (1980b) suggested that the syndrome seemed to occur somewhat sporadically in the population and that parents of one Prader-Willi child were not necessarily at greater risk of having another child with the disorder. However, several recent studies have reported the presence of the syndrome with two, three, and even four siblings within a family (Burke et al., 1987; Fernandez, Berry, & Mutton, 1987; Ishikawa, Kanayama, & Wada, 1987; Lubinsky et al., 1987). Bray et al. (1983) have indicated that about 1% of siblings may be affected by the syndrome, which would suggest that there may be a higher recurrence risk factor within some families. The precise etiology of the syndrome has not yet been established in all cases. A number of researchers had once hypothesized that a single, localized developmental

Prader-Willi syndrome was initially reported in 1956. The major characteristics of the syndrome include hypotonia during infancy, hypogonadism, a short physical stature, mental retardation, and the onset of obesity during childhood. Several facial features, including micrognathia and strabismus, are also common.' The literature often includes general descriptions of delayed speech and language development. However, as Edmonston (1982) has commented, "The nature and extent of the speech and language disorders [associated with PraderWilli] and their amenability to treatment procedures have not been reported" (p. 241). Prevalence, Etiology, Progression,and General Descriptionsof the Syndrome The prevalence of Prader-Willi is reportedly somewhere between 1:10,000 (Holm, 1981) and 1:25,000*Sallie A. Kleppe has served as speech-language pathologist for the Kings County Superintendent of Schools, Hanford, CA. 'Photographs illustrating some of the outward manifestations of the syndrome can be found in sources such as Burke et al. (1987); Dyken and Miller (1980); Fuhrmann-Rieger, Kohler, and Fuhrmann (1984); Futterweit, Ritch, Teekhasaenee, and Nelson (1986); Golden et al. (1984); Greenswag and Alexander (1988); Ishikawa et al. (1987); Lubinsky et al. (1987); Mattei et al. (1983); Pauli, Meisner, and Szmanda (1983); and Schwartz, Max, Panny, and Cohen (1985). See Zellweger's (1981, p. 57 or 1988, p. 16) descriptions of more than 30 other clinical features associated with the syndrome. © 1990, American Speech-Language-Hearing Association

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KLEPPE ET AL.:

defect in the hypothalamic region could cause many of the characteristics present in Prader-Willi (Hall & Smith, 1972; Hoefnagel, Costello, & Hatoum, 1967; Jancar, 1971; Krywaniuk, 1977; Zellweger & Schneider, 1968). More recent studies of etiology have focused on an abnormality involving chromosome 15 (Donlon, 1988; Ledbetter et al., 1981, 1982). It is now relatively wellestablished that about 50% of patients with Prader-Willi syndrome demonstrate some form of a chromosome 15 abnormality, most frequently a chromosome 15qll deletion or 15q translocution (Butler, Ledbetter, & Mascarello, 1985; Butler & Palmer, 1983; Golden, Hanchett, Breslin, & Steele, 1984; Mattei, Mattei, & Giraud, 1983; Takano et al., 1986). However, it also appears that no one single hypothesis or abnormality explains all of the chromosome 15 findings (Winsor & Welch, 1983). The syndrome can occur in the presence of chromosome 15 abnormalities or under other presently unknown factors in which a chromosomal abnormality is not found (Fernandez et al., 1987; Fryns, 1988). Some authorities (Krywaniuk, 1977; Zellweger, 1979, 1981, 1988) feel the syndrome can be divided into two phases that relate to the progression of symptoms. Zellweger (1979) describes the first as the hypotonic or atonic phase, and the second as the hyperphagic-obese phase. Hypotonic phase. This phase of Prader-Willi syndrome may occur between birth and 18-24 months of age. Prenatally, diminished or absent intrauterine movement may be present (Hoefnagel et al., 1967; Zellweger & Schneider, 1968). Delivery usually occurs at term, although prolonged gestation periods have been noted (Cohen & Gorlin, 1969; Evans, 1964; Hoefnagel et al., 1967; Jancar, 1971; Zellweger & Schneider, 1968). Zellweger (1979) notes that Prader-Willi children in this hypotonic phase are atonic, unresponsive, and somewhat motionless. He also reports the presence of depressed tendon reflexes, as well as impaired sucking and swallowing reflexes. The absent or reduced sucking and swallowing reflexes can result in feeding difficulties that require the use of special feeding devices. In part because of these feeding problems, delayed weight gains are often found during this phase. Hyperphagic-obese phase. At approximately 18-24 months of age, the Prader-Willi child may enter the second phase of symptom progression. The child becomes more alert and begins to show an interest in food. Hyperphagia is considered a primary characteristic of this phase. Most children begin to gain excessive weight at about 18-24 months and, if untreated, will become significantly obese between 3 and 5 years of age (Hall, 1979; Zellweger, 1979). Individuals with the syndrome have often been described as being easy-going and affectionate in their early years, but subtle changes often occur after about 5 years of age. Personality problems including temper tantrums and stubbornness may develop in late adolescence (Neason, 1979; Prader-Willi Syndrome Association, 1980b).

Prader-Willi 301

Developmental Characteristics Hall (1979) feels that delayed motor milestones are a consistent feature of the disorder. Hall and Smith (1972) reported that, on the average, these children sit at 12 months and walk at 30 months. The Prader-Willi Syndrome Association (1980b) also reports that many children with the syndrome have delayed motor skill development and often experience difficulties with balance, large muscle strength, and coordination. Estimates of intelligence with Prader-Willi vary. The Prader-Willi Syndrome Association (1980b) reports that these children's IQs are usually in the 70s but can be below 40 or above 100. Zellweger (1979) has suggested that IQs range from 20 to 90 and are rarely above 90. However, Holm (1981) has reported that more than 40% of children with the disorder may not be intellectually retarded. Despite these somewhat varied estimates, it is generally accepted that intellectual impairment is frequently associated with the disorder. Many authorities on Prader-Willi syndrome (e.g., Hall & Smith, 1972; Munson-Davis, 1988; Prader-Willi Syndrome Association, 1980b; Schultze, 1979) agree that the speech and language abilities of these children are often delayed or depressed. However, much of the research pertaining to the syndrome is medical in nature and there is relatively little specific information regarding the precise communicative skills of these children. Zellweger (1979), a physician, feels that articulation disorders are common to Prader-Willi children and that, in some cases, dysarthria causes their speech to be almost unintelligible. There is also general consensus that the language skills of children with the syndrome are typically below normal. Hall and Smith (1972) state that children with PraderWilli begin talking in short sentences at approximately 42 months of age. However, it has also been reported that some children with the syndrome may begin talking as early as 24 months (Hall & Smith, 1972; Prader-Willi Syndrome Association, 1980b). Branson (1981) studied the speech and language skills of 21 children with the syndrome and reported two primary patterns of articulatory errors. One pattern involved nasal air emissions with fricatives, affricates, and occasionally, plosives. The other pattern included difficulties with syllable-sequencing tasks where place and manner of articulation varied. Additional difficulties reported with some subjects included delayed phonologic development and faulty phonologic learning. Of Branson's 21 subjects, only 3 children's language skills were within normal ranges for their chronological ages. Eight of the children demonstrated receptive and expressive language abilities commensurate with their cognitive abilities, but these abilities were 1-4 years below their chronological ages. The remaining 10 subjects presented uneven language profiles in which their receptive skills were often considerably higher than their expressive skills. Edmonston (1982) studied the speech and language abilities of a child with Prader-Willi syndrome, age 5:8.


302 Journal of Speech and Hearing Disorders She found that the subject's articulatory and language abilities were significantly below the child's intellectual level and motor abilities. Edmonston reported that the speech and language abilities of her subject improved with treatment when dill pickles were used as a contingent reinforcer and felt this type of reinforcement would be helpful in the communicative remediation of other Prader-Willi children. Of note, practitioners would be well-advised to exercise care before using food with these children because of the various dietary problems associated with the syndrome (see Stadler, 1988). Munson-Davis (1988) has described some of the major speech and language characteristics associated with Prader-Willi patients. She noted that delayed speech and articulation development are common, and this is often related to the hypotonia seen in early childhood. Other factors common to many children with the syndrome include a narrow overjet with a high, narrow palatal arch; micronagnathia; and inadequate velopharyngeal movement/closure. Developmental apraxia of speech has also been observed with some Prader-Willi children (Branson, 1981; Munson-Davis, 1988). Problem and Purpose A majority of literature regarding Prader-Willi has focused on the physical identification and medical management of the disorder. The literature often includes general indications of delayed speech and language development, but there is little specific information about the various communicative skills of individuals with the syndrome. The purpose of this study was to examine the various communicative skills associated with children diagnosed as having Prader-Willi syndrome. PROCEDURES Subjects Eighteen children who had been diagnosed medically as having Prader-Willi syndrome were examined. There were 9 boys and 9 girls seen. Ten subjects resided in northern California, 1 in central California, and 7 in southern California. The subjects ranged in age from 8:8 to 17:1 (median age = 11:4). Instrumentation and Methods The children were tested at a university speech, language, and hearing clinic or special education school near their homes. Each child was brought to one of five test sites by a parent or guardian and tested individually during a session that lasted approximately 3 hr. A Maico MA-20 audiometer (ANSI, 1969) was used to determine each subject's hearing acuity. Air conduction pure-tone thresholds were obtained for each ear at 250,

55 300-309 May 1990 500, 1000, 2000, 4000, and 8000 Hz. An extensive oral examination was conducted to determine the adequacy of the speech mechanism. Part of this examination included assessing diadochokinetic rates with the Fletcher Timeby-Count Test of Diadochokinetic Syllable Rate (1978). Additional evaluations were performed for volitional oral tasks and the vocal parameters of pitch, loudness, and quality. A 100-utterance speech-language sample using Tyack and Gottsleben's (1977) procedures was obtained to evaluate each subject's spontaneous abilities. The following formal test instruments were also used in the evaluation. 1. The Goldman-Fristoe Test of Articulation (Goldman & Fristoe, 1969) was used to assess subject's articulation and the stimulability of their sound errors. 2. The Peabody Picture Vocabulary Test-Revised (Form L) (Dunn & Dunn, 1981) was used to assess each subject's receptive vocabulary skills. 3. The Test for Auditory Comprehension of Language (Carrow, 1973) was administered to assess the children's auditory comprehension of various linguistic structures. 4. The Expressive One-Word Picture Vocabulary Test (Gardner, 1979) was administered to assess subjects' expressive vocabulary skills. 5. The Test for Examining Expressive Morphology (Shipley, Stone, & Sue, 1983) was used to evaluate the children's expressive use of morphologic features. All sessions were audiotaped with a Sony TC106A tape recorder for later analysis. Data Analysis The 100-utterance spontaneous speech sample was used to phonetically transcribe the subjects' speech sound productions and to analyze their language abilities. A 200-word representative sample from the 100 utterances was used to evaluate subjects' overall fluency rates and to identify specific disfluency types. Estimates of intelligibility were obtained from each subject's 200-word spontaneous sample. Three graduate students in communicative disorders listened to each tape twice to determine each subject's number of intelligible words. Interjudge reliability was estimated with Pearson rs (Ryan, Joiner, & Ryan, 1981); and coefficients of .87, .88, and .90 (p < .05) were found between the judges' identification of intelligible words. Raw scores were computed for each of the formal receptive and expressive language tests. As appropriate to each instrument, these raw scores were converted into percentile, age-equivalence, age-range, and/or mentalage scores. RESULTS AND DISCUSSION Intelligibility and Articulation The percentage of intelligibility from the three judges was averaged for each subject. The subjects' intelligibil-


KLEPPE ET AL.:

ity ranged from 68% to 96% with a median of 83%. Seven subjects were 68%-79% intelligible, 7 were 80%-89% intelligible, and 4 were 90%-96% intelligible. Weiss and Lillywhite (1976) have noted that normally developing 4-year-olds are typically 100% intelligible. Because all the present subjects were at least age 8:8, all of the children would be considered as having difficulty with overall intelligibility. Each subject's articulation was analyzed phonetically from the 100-utterance samples. The subjects averaged 7.6 different articulation errors in their spontaneous speech. All 18 subjects exhibited at least one consonant error, and 15 children exhibited three or more consonant errors. At least one half of the subjects misarticulated /r/, /1, 11/, /0/, /tS/, and Ifl. Errors on these phonemes were primarily distortions and substitutions. Seventeen subjects misarticulated blends, with distortions being the primary type of error. More than one half of the subjects misarticulated blends containing /rl and /. In addition, 7 subjects misarticulated one or more vowel sounds. The number of children who exhibited spontaneous speech errors by place of articulation, manner of production, and voicing is presented in Table 1. It can be seen in the table that the most prevalent errors of placement were found with linguaalveolars, linguadentals, linguapalatals, and linguavelars. The most frequent errors of manner were found with fricatives, glides, plosives, and affricates. There were generally fewer errors with voicing. The Goldman-Fristoe Test of Articulation examines 23 nonblended consonants in a total of 61 initial, medial, and final positions. All 18 subjects misarticulated at least 1 sound error, and 14 subjects exhibited 3 or more sound errors in at least one position. Of the 23 consonants tested, the subjects misarticulated an average of 4.6 sounds. The /r/, I/f, and /z/ sounds were misarticulated by at least 50% of the subjects, with distortions and substiTABLE 1. The number of Prader-Willi children who exhibited

articulation errors by place, manner, and voicing (n = 18). Type of articulation error Bilabial Labiodental Linguadental Linguaalveolar Linguapalatal Linguavelar Glottal Plosive Fricative Glide Nasal Affricate Voiceless-for-voiced Voiced-for-voiceless Both types of error

Spontaneous speech

Articulation test

Place of articulation 7 3 16 16 12 10 1

2 8 7 16 12 3 0

Manner of production 14 16 16 5 12

6 17 13 1 8

Voicing

3 2 2

7 0 1

Prader-Willi 303

tutions being the prominent types of error. The number of children who exhibited errors on the articulation test by place, manner, and voicing is seen in Table 1. As seen in the table, the most prevalent errors of placement were found with linguaalveolars and linguapalatals. The most frequent errors of manner were found with fricatives and glides. Thus, when viewing the results from the spontaneous speech sample and the Goldman-Fristoe Test of Articulation, the majority of subjects had difficulties with lingual sounds involving fricatives, affricates, and glides. Difficulties with tongue tip sounds and with tongue movement execution have also been noted by MunsonDavis (1988). The articulation test also contains a stimulability subtest. Seven of the 18 children were stimulable for all of their errored sounds. Another 8 subjects were stimulable for at least 50% of their errored sounds. The most frequently misarticulated sounds were /r/, /If, and I/z/.More than 50% of the subjects who misarticulated /f! and /z/ were stimulable, but less than 50% of the subjects were stimulable for I/r/. At least one consonant blend was misarticulated by 16 children. Of these, 15 subjects misarticulated at least one of the four /rl blends tested, and 12 children misarticulated at least one of the five / blends. Less than one half of these /r/ and Ill blends were stimulable.

Oral Examination Nine subjects had normally vaulted palatal contours, 7 had moderately high contours, and 2 had very high palatal contours. Dyken and Miller (1980) and Munson-Davis (1988) have also reported that a high, narrow palatal arch is characteristically seen with Prader-Willi syndrome. Volitional oral movements could be evaluated for 17 of the subjects; 1 subject failed to cooperate sufficiently with these tasks. Eight of the subjects had difficulty elevating the tongue tip. Other primary features included the inability of 4 subjects to retract their lips to the right. Three other subjects did not have equal bilateral retraction of the lips due to weakness on the right side. Muscular weakness is a primary characteristic of flaccid dysarthria (Darley, Aronson, & Brown, 1975), and a number of the subjects exhibited weakness in the lips and difficulties with tongue tip elevation. Results from the Fletcher Time-by-Count Test of Diadochokinetic Syllable Rate (1978) indicated that all of the subjects had some difficulties with rapidly alternating speech movements. The number of children who performed within and below normal expectations is seen in Table 2. When the 17 subjects' performances on the nine Fletcher Time-by-Count Test of Diadochokinetic Syllable Rate tasks were totaled (n = 153), only 29% of these tasks were performed within what might be considered normal limits. The subjects were generally capable of sequencing the target tasks, but their performances were slower than would be expected.


55 300-309

304 Journal of Speech and Hearing Disorders

May 1990

2. The number of subjects who performed within normal expectations and below normal expectations on nine diadochokinetic syllable tasks (n = 17). TABLE

Task Abilities

pA

tA

kA

fA

IA

pAta

pAk

Normal expectations Below expectations

5 12

5 12

7 10

5 12

9 8

2 15

3 14

Voice Only 3 of the children were judged to have completely

normal vocal qualities. Eleven subjects exhibited some degree of hypernasality, and 3 were hyponasal. In addition, 1 child had a hoarse voice. Of the 11 subjects with hypernasality, 5 also exhibited some degree of glottal fry and 1 had a harsh vocal quality. Deviations of vocal quality, particularly hypernasality, are characteristic of flaccid dysarthria (Darley et al., 1975).

Twelve subjects were judged to have appropriate pitch levels for their ages and sexes. Five students' pitch levels were higher than normal, and 1 girl's pitch level was inappropriately low. Of the 12 subjects with generally

appropriate pitch levels, 5 subjects' pitch levels rose inappropriately at times and 2 subjects exhibited intermittent pitch breaks. All subjects were capable of adequate loudness.

Fluency Each subject's fluency was evaluated from the 200word samples. The percentages of fluency ranged from

66% to 99% with a median of 91%. Many of the subjects were disfluent, but only 1 child was considered to be a

tAka

pAtoka

Total

4 13

4 13

44 109

stutterer. Of the total disfluencies exhibited (n = 100%), the following distribution was found: 36% Interjections 26% Revisions 16% Word Repetitions 10% Part-Word Repetitions 9% Phrase Repetitions 3% Incomplete Phrases The primary types of disfluencies were interjections and revisions. A high percentage of disfluencies on smaller units such as sound repetitions and prolongations did not occur, and the Prader-Willi children as a group did not present a clinical picture of stuttering. Branson (1981) also reported the presence of disfluent behaviors in one of her subjects. She felt that her subject's wordrecall difficulties created the repetitions, additions, and circumlocutions found in the subject's spontaneous speech. Some evidence of word-recall difficulties was also seen within subjects in the present study. This was often accompanied by disfluencies such as interjections, revisions, repetitions, and incomplete phrases. A view of each subject's performance on a number of measures employed can be seen in Table 3. This table lists each subject's percentages of intelligibility and fluency, performance on the Goldman-Fristoe Test of Articulation, vocal qualities, and number of /pAtaka/ produc-

TABLE 3. Each subject's age (CA), sex, percentage of intelligibility, fluency, number of articulation errors identified on the articulation test, mean number of /pAtaka/ utterances per second, and voice quality. (CNT means could not test; CNP means could not produce.) M Conson.

/pAtka/

Subject

CA

Sex

% Intell.

Conson. errors

blend errors

per second

% Fluency

Vocal qualities

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

8:8 8:11 9:6 9:9 10:2 10:3 10:5 11:1 11:2 11:6 12:10 13:7 14:4 14:8 15:4 15:7 16:11 17:1

F M F F F M M M F M F F M F M M M F

82 76 75 87 79 96 93 84 93 91 84 87 80 88 74 79 75 68

12 10 7 3 2 2 4 9 1 3 5 4 4 2 5 3 3 6

12 9 6 6 0 2 7 9 5 0 8 6 5 2 5 1 7 2

1.1 1.0 0.5 1.0 CNP 1.2 1.2 CNT 1.1 1.5 1.0 0.6 1.1 CNP 1.3 1.4 1.5 CNP

92 89 91 96 99 90 85 89 92 92 98 83 88 66 89 87 98 95

hyponasal hypernasal hypernasal/glottal fry mild hypernasality normal hypernasal mild hypernasality hypernasal/harsh normal normal hoarse hyponasal hypernasal/glottal fry hyponasal hypernasal/glottal fry hypernasal/glottal fry hyponasal hypernasal/glottal fry


KLEPPE ET AL.:

Prader-Willi 305

Prader-Willi syndrome (Hall & Smith, 1972; MunsonDavis, 1988; Prader-Willi Syndrome Association, 1980a; Schultze, 1979). The receptive and expressive language abilities of the subjects were examined with several measures. Receptive language. The two measures of receptive language were the Peabody Picture Vocabulary TestRevised (PPVT) and the Test for Auditory Comprehension of Language (TACL). Age-equivalence scores from the PPVT ranged from 4:3 to 10:5 years, and 16 of the children's scores were at or below the 6th percentile. No subject's age-equivalence was equal to his or her chronological age. Although all subjects were at least age 8:8, only 3 children achieved at least an 8:0 language-age estimate. On the TACL, the age-equivalence scores ranged from 3:7 to 6:11. Only 1 subject reached the 6:11 ceiling on the test; the remaining 17 subjects failed to reach ceiling and scored well below their chronological ages. Excluding the 1 subject whose TACL score reached ceiling, 12 of the 17 subjects had age-equivalence esti-

tions on one subtest of The Fletcher Time-by-Count Test of Diadochokinetic Syllable Rate (1978). Hearing Three of the 18 subjects failed to respond at 20 dB for at least one frequency between 500 and 8000 Hz. However, these 3 subjects responded at 20 dB or better at 500, 1000, 2000, and 4000 Hz in at least one ear. Because 15 subjects passed the hearing test at each frequency, and the other 3 subjects responded at 0-20 dB between 500 and 4000 Hz in at least one ear, none of the children exhibited any major peripheral difficulties that presently contributed to the various speech problems found. It was unknown, however, whether any of the subjects had experienced early middle ear problems that may have affected their earlier speech and language development. Language Language deficiencies are reportedly characteristic of 17-0 16-6 16-0 15-6 15-0 14-6 14-0 13-6 13-0 12-6 12-0 11-6 n

11-0

5

10-6

M 10-0

9-6 9-0

8-6 8-0 7-6 7-0 6-6 6-0 5-6 5-0 4-6 4-0 3-6 1

2

3

4

5

6

7

8

9 10 11

12 13 14 15

16 17 18

Subjects FIGURE 1. Subjects' chronological ages and receptive language age-level estimates from the Peabody Picture Vocabulary Test (PPVT) and the Test for Auditory Comprehension of Language (TACL). (Subject 10 reached ceiling on the TACL.)


306 Journal of Speech and Hearing Disorders mates that were within 1 year of each other on the TACL and PPVT. Thus, there was a generally close agreement between results from the two receptive measures. Figure 1 depicts the subjects' ages and receptive language performances. Two patterns of performance are found in this figure. One pattern is the discrepancy between the subjects' chronological ages and their presumed language ages. These discrepancies were greater as the subjects' chronological ages increased. The other pattern is the rather flat plane of performance with the children who were near or past their 10th birthday. With the exception of 2 subjects' performances on the PPVT (Subjects 9 and 10), there was a relatively flat language profile for Subjects 5-18, despite their rather large range of chronological ages. Expressive Language Three procedures were used to evaluate the subjects' expressive language skills: the Expressive One-Word Picture Vocabulary Test (Gardner, 1979), the Test for Examining Expressive Morphology (TEEM) (Shipley et al., 1983), and a spontaneous language sample. As seen in Table 4, the mental-age estimates from the Expressive One-Word Picture Vocabulary Test ranged from 3:9 to 11:11. For 15 of the subjects, the mental-age projections fell below the subjects' chronological ages. Scores from the TEEM also resulted in depressed expressive language-age estimates (see Table 4). The age scores ranged from below the 3:0-3:6-year level to above the 7:0-8:0-year level. Sixteen of the subjects were at or below the 7-year language age range despite the children's chronological ages of 8:8-17:1 years. The majority TABLE 4. The subjects' chronological ages (CA) and expressive language estimates. Expressive OneWord Picture Vocabulary Test

Test for Examining Expressive Morphology

Subject

CA

MA a

LA rangeb

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

8:8 8:11 9:6 9:9 10:2 10:3 10:5 11:1 11:2 11:6 12:10 13:7 14:4 14:8 15:4 15:7 16:11 17:1

4:11 5:8 9:1 3:9 7:6 9:7 8:4 9:1 7:4 11:11 6:8 6:11 6:8 5:11 5:0 5:11 10:6 7:0

3:0-3:6 3:0-3:6 7:0-8:0 4:7-5:0 5:0-6:0 7:0-8:0 4:0-4:6 7:0-8:0 7:0-8:0 7:0-8:0 4:0-4:6 3:7-4:0 6:0-7:0 4:7-5:0 3:0-6:0 5:0-6:0 4:7-5:0 4:7-5:0

aMA = mental age. bLA = language age.

55 300-309

May 1990

of the subjects demonstrated difficulties with the use of more difficult allomorphic variations (see Shipley & Sue, 1981; Shipley et al., 1983). The most frequent difficulties were found with /z/ and irregular plurals; /oz/ possessives; /az/ third-person singulars; /ad/ and irregular past tenses; and /ar/, /ast/, and irregular comparative/superlative adjectives. When comparing results from the TEEM to the two vocabulary tests, the subjects scored higher on the vocabulary tests. Although speculative, this may have occurred because (a) the TEEM uses a more difficult sentence-completion response task, (b) the children had experienced more of a vocabulary training emphasis in speech-language treatment and their special education settings, and/or (c) the children actually experienced more difficulties with the area of morphologic development. Previous research (Shipley et al., 1983) with normal children has resulted in relatively high correlation estimates (r = .84) between results from the PPVT and TEEM. Thus, the present discrepancies between the results from the vocabulary measures and the TEEM may be suggestive of Prader-Willi children's difficulties with morphologic development. On the language samples, the subjects also tended to use less difficult allomorphic variations such as present progressives, regular plurals, and regular past tenses. In general, these were the allomorphic variations that the subjects correctly produced on the TEEM. It can be inferred from these comparisons of test performance that the children in this study had specific difficulties within the morphologic areas, particularly with more advanced allomorphic forms. The results from the language samples are displayed in Table 5. Subjects' utterances were typically complete sentences (i.e., contained a noun + verb in a subjectpredicate relationship), but these utterances were not always syntactically and morphologically correct. Of each subject's language sample, the percentage of complete sentences ranged from 46% to 94% (M = 82%). Grammatically correct utterances ranged from 46% to 100% (M = 77%). However, a number of the complete sentences were not grammatically correct (e.g., "I has a dad.")whereas other utterances were grammatically correct but incomplete (e.g., "Loves to play with me."). Prader-Willi children's verbal output often lacks structural completeness but can be understood (Prader-Willi Syndrome Association, 1980a). The subjects' mean length of utterances from the language samples ranged from 3.4 to 6.6 words. Fifteen subjects averaged less than six words per utterance. For purposes of comparison, many normally developing children age 3:0-4:6 exhibit a mean utterance length of six words (Weiss, Lillywhite, & Gordon, 1980). The present subjects' mean utterance lengths computed according to morphemes rather than words ranged from 3.7 to 7.7, with an average of 6.0. Five of the subjects in the present study exhibited a mean utterance length of less than six morphemes. Undoubtedly, the subjects' general language delays influenced the mean utterance lengths on the spontaneous sample. However, the subjects' articulation difficulties may also have contributed to the generally low utterance lengths measured


KLEPPE ET AL.: Prader-Willi 307 TABLE

5. A summary of the results from the language samples. MLU a

Utterances

Form

Subject

CAb

Complete sentences (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14

8:8 8:11 9:6 9:9 10:2 10:3 10:5 11:1 11:2 11:6 12:10 13:7 14:4 14:8

41 65 82 91 81 74 93 94 93 88 83 83 77 94

74 46 86 72 92 100 74 88 93 86 61 70 77 74

3.4 5.5 5.5 5.6 5.5 6.6 5.0 6.1 4.7 6.3 4.5 5.7 5.6 5.0

3.7 5.8 6.5 6.0 6.2 7.7 5.9 6.8 5.4 7.4 5.2 6.4 6.4 5.6

15

15:4

83

59

4.1

16 17 18

4.5

15:7 16:11 17:1

64

86 84 88

36

91 73 72

5.8 4.2 5.5

6.3 5.4 6.3

53 53 51

47 47 49

aMLU = mean length of utterance. bCA

Grammatically correct (%)

Words

Morphemes

Content (%)

Function (%)

69 65 57 54 59 55 60 55 56 58 58 60 64 57

31 35 43 46 41 45 40 45 44 42 42 40 36 43

= chronological age.

in terms of morphemes because many bound morphemes (e.g., -s, -ed) require the production of final consonants. The percentage of content words from each subject's language sample ranged from 51% to 69% (M = 58%), whereas function word use ranged from 31% to 49% (M = 42%). Six of the subjects exhibited a nearly equal distribution (i.e., 45%-55%) of content and function words. The remaining 12 children used more content words than might be expected with normal development.

these were returned, and all 13 subjects were reported to be on some type of diet. A special education placement was reported for 11 subjects, and 2 had been mainstreamed in a regular education classroom. Ten subjects were reported to have been enrolled for speech-language pathology services, and 1 child was presently enrolled in a severe oral language disorder-aphasic classroom. SUMMARY AND CONCLUSION

Birth and Developmental History Each subject's parent or guardian was given a developmental history form to complete, and 17 were returned. Birth difficulties were reported for 8 subjects. Six of the parents reported a headfirst delivery, seven reported a breech birth, and 3 of the subjects were delivered by cesarean section. Reported birth weights ranged from approximately 2 to 8 pounds. Early feeding difficulties were reported for 15 subjects, which is characteristic of Prader-Willi syndrome (Hoefnagel et al., 1967; Landwirth, Schwartz, & Grunt, 1968; Stadler, 1988; Zellweger, 1979). Eight of the 15 had sucking difficulties, and 1 had difficulty swallowing. Gavage feeding was required for 2 subjects, 3 were tube fed, and 1 subject was fed with an eyedropper. However, 16 of the parents or guardians reported that their child ate well at the present time. A separate question dealt with the children's present behavior. All 17 parents or guardians reported that their child presently displayed a temper. Several months after the testing session, a supplemental questionnaire was sent to each subject's parents or guardians requesting additional information regarding dietary, educational, and speech histories. Thirteen of

A number of investigators have suggested that the speech and language abilities of Prader-Willi children are delayed (Hall & Smith, 1972; Prader-Willi Syndrome Association, 1980b; Schultze, 1979). There were a number of communicative problems identified with the present Prader-Willi subjects. The major problems included multiple articulation errors, reduced intelligibility, language difficulties, and voice problems (primarily hypernasality). An above-average number of disfluencies and evidence of flaccid dysarthria were also found in the subjects' speech and oral abilities. Apraxia of speech was not found with the present subjects but has been reported elsewhere (Branson, 1981; Munson-Davis, 1988). Based on the information from the 18 Prader-Willi subjects, speech-language pathology services were warranted because of the multiple articulation errors, reduced intelligibility, and delayed language skills. The prognosis for remediating many of the articulation errors was viewed as being relatively good because of the number of sounds that were stimulable. Dysarthria is also amenable to treatment in most cases (Darley et al., 1975; Rosenbek & LaPointe, 1978); and remediation for the dysarthria would be expected to increase the children's intelligibility, articulation, and phonatory/resonance abilities.


308 Journal of Speech and Hearing Disorders

It was felt that language treatment for these PraderWilli children should emphasize improving their vocabularies, syntax, and morphologic abilities. The need for improved vocabulary skills was seen on the receptive and expressive vocabulary tests, and the generally high percentage of content words on the language sampling. Deficiencies in syntactic and morphologic use were seen in the results from the formal tests and the language samples. In general, language treatment would have focused on improved overall vocabulary skills, using more function words, the increased use of complete and grammatically correct utterances, and the increased use of certain morphologic features. Pragmatic language use was not evaluated directly within the current study, so no suggestions are offered. However, Munson-Davis (1988) has commented that "deficits in pragmatics-awareness of socially appropriate behavior in communication interactions-may also be a problem, particularly in the older child and adolescent" (p. 129). Branson (1981) has suggested that treatment strategies for Prader-Willi children should be individualized because their communicative profiles lack common features. Although the subjects in the present study exhibited some common features-such as errors with certain speech sounds, hypernasality, reduced vocabulary abilities, syntactic errors, and difficulties producing more advanced allomorphic variations-a number of different profiles were also found. These included differences in the severity of the articulation and language difficulties, as well as varying degrees of intelligibility, voice problems, and fluency. Although the Prader-Willi subjects exhibited deficiencies in many common areas, the variations of their communicative skills highlight the need for individualized consideration of each child with Prader-Willi syndrome. Finally, several limitations of the present study need to be noted. Probably the major limitations include the large age range of subjects tested and not controlling subjects' IQs, history of remediative services, and syndrome severity. Another potential limitation involved the test battery because several of the formal tests are not standardized for use with the age and population tested. Although additional control for these factors would seem beneficial for obtaining a more complete picture of the communication skills of individuals with PraderWilli, the present report does identify some of the communicative characteristics associated with the syndrome. It is also potentially important to recall that the outward manifestations of this syndrome, and the severity of these manifestations, vary considerably between patients. Inferentially, this report also helps highlight the need for the early identification and scope of communicative factors that need to be evaluated with children exhibiting Prader-Willi syndrome.

ACKNOWLEDGMENTS The following clinical sites were used for the study: California State University, Fresno; California State University, Long

55

300-309

May 1990

Beach; California State University, Sacramento; the Dubnoff Center for Child Development and Educational Therapy in North Hollywood; and San Jose State University. Specific appreciation is extended to Dr. Mary V. Dickerson, Dr. Joel R. Katzman, Dr. Maryjane Rees, and Dr. Virginia Warren for their help in securing the use of these facilities. We also very much appreciate the help of TerriLynn Cole, Deborah J. Davis, Cynthia DeFuria, Karen M. Jensen, Donald G. Katayama, Keith E. Kleppe, Julie G. McAfee, Joy L. Osumi, Robert F. Scott, Betty Shadelt, and the Prader-Willi children and their parents/guardians for their contributions to the project.

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