RESEARCH: Acoustic analysis of inspiratory stridor in multiple system atrophy.

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Acoustic analysis of inspiratory stridor in multiple system atrophy.

Isozaki Eiji, Kazuta Toshinari, Hayashida Tetsuro, Kanda Takemasa, Hirai

Shunsaku

Tokyo Metropolitan Neurological Hospital,Departments of Neurology and

Neurootology

Purpose

To analyze the inspiratory stridor during sleep in multiple system atrophy

(MSA), acoustic analysis of its sound was applied.

Method

The inspiratory stridor during natural sleep from 9 MSA patients were

recorded by a tape-recorder. Then, their sounds were analyzed by the

acoustic analyzer (Kay elemetrics corp., multi-dimensional voice program),

by using the 32 parameters such as F0, APQ, PPQ. The inspiratory stridor

from two of 9 patients were recorded again several months after the first

recording.

Results

Among 32 parameters, F0 (fundamental frequency), vF0 (variance of F0), and

VTI (voice turbulence index) seemed to be useful for the evaluation of vocal

cord abductor paralysis. With the progression of vocal cord abductor

paralysis, F0 was increased, while vF0 and VTI were decreased. VTI came down

to 1.7 in one patient just before sudden death by choking due to vocal cord

abductor paralysis, whose value was almost equal to that of the inspiratory

voice of the normal subject. VTI in the other patient came down to 4, who

was just before tracheostomized against severe vocal cord abductor

paralysis.

Conclusion

VTI, one of the acoustic parameters of the inspiratory stridor, is useful to

evaluate the degree of the vocal cord abductor paralysis in MSA. It may

indicate the time when a tracheostomy should be performed in the patients

with vocal cord abductor paralysis.