Speech, voice, language and cognition in individuals with spinocerebellar ataxia (SCA)

Abstract

Spinocerebellar ataxias (SCA) constitute a group of genetically defined hereditary, degenerative, progressive diseases affecting the cerebellum and its connections. Few previous investigations have focused on how SCA affects different aspects of communication. The aim of the present investigation was to characterize speech and voice in individuals with SCA and to investigate the progression of speech and voice symptoms, using both perceptual and acoustic methodology. In addition, language and cognition in individuals with SCA were studied.

Thirty-two individuals with spinocerebellar degenerative disease participated in the studies. The majority had been diagnosed with SCA using molecular genetic testing and the rest were clinically diagnosed by a specialist in neurology. Matched control subjects were included in study II and III.

Speech and voice in individuals with SCA were assessed perceptually by a group of four speech-language pathologists with long experience of neurogenic communication disorders. Recorded speech samples from individuals with SCA were rated using visual analogue scales, VAS. Speech samples were also used for computer-based acoustic analysis. Speech and voice were characterized by the following perceptual parameters: Equalized stress, imprecise consonants, vocal instability, monotony, strained-strangled voice, stereotypic intonation and reduced speech rate. Factor analysis resulted in two main factors; one associated with temporal aspects of speech and the other with vocal quality. Acoustic analysis confirmed the perceptual findings. Rate of speech and sequential and alternating motion rates were reduced, and duration and variability of syllables and pauses during rapid syllable repetition were increased compared to matched control subjects. Inter-stress intervals (ISIs) were also longer and more variable in subjects with SCA compared to control subjects. Perceived vocal instability was confirmed acoustically by increased coefficient of variation of fundamental frequency, CV of F0, during sustained phonation. This was also found in individuals with SCA with otherwise close to normal speech.

Speech and voice were followed in nine individuals with SCA during three years and speech samples were analyzed both perceptually and acoustically. Perceived imprecision of consonants and stereotypic intonation had increased during the three years. Some acoustic measures had also changed, e g duration of syllables in rapid syllable repetition and duration of inter-stress intervals. In addition, there was a trend towards change in several other perceptual and acoustic measures, especially measures related to temporal aspects. Changes were more substantial in individuals with early disease onset, regardless of disease duration. An increase of mean dysarthria scores was also found.

Language and cognition were assessed in 20 individuals with SCA and control subjects matched for age, gender, length of formal education and estimated cognitive level. Executive functions and attention were most severely affected, but memory and lexicosemantic knowledge were also impaired, especially in individuals with more severely impaired estimated global cognitive level of functioning. Cognitive impairment correlated with low age at disease onset and also with impairment of motor speech function, but not with disease duration.

It was concluded that dysarthria in SCA resembles previous descriptions of ataxic dysarthria, but also includes an element of strained-strangled voice. Equalized stress was more prominent and imprecision of vowels was less common compared to previous studies. Vocal instability may be an early sign of the disease. Progression of symptoms can be seen over a three-year period, especially as increased perceived imprecision of consonants and stereotypic intonation, but also measured with a clinical dysarthria test. Cognition was impaired in individuals with SCA, especially executive functions and attention. Assessment by speech-language pathologists should include testing of cognition and language as it may have implications for treatment. Keywords: Spinocerebellar ataxia, ataxic dysarthria, perceptual analysis, acoustic analysis, cerebellar degenerative disorders, cognitive impairment, language impairment, executive dysfunction, progression of neurological disease.