Table 2 Summary of the aims, speech assessments, and main findings of the studies

[62]

To examine the correlation between the characteristics of dysphonia and vowel impairment with disease severity and duration. The specific questions in this study are: [1] Are these subsystems’ changes affected by the disease duration and the disease severity? [2] Are these indexes practical for diagnostic processes of MS? And do they increase the accuracy of diagnosis of speech impairments related to MS?

a) Dysphonia Severity Index Acoustic assessment by calculation of the betascore, by means of measuring four vocal parameters including: maximum phonation time, Jitter percent, highest fundamental frequency, and lowest intensity

b) Formant Centralization Ratio by examiner's hand signals, the subjects were asked to read written forms of three words with consonant–vowel-consonant syllable structure

The patients exhibited difficulties: a)Phonation subsystem: loudness control impairment, inability to keep long-term phonation, decrease in habitual pitch, increase in fundamental frequency in MS patients and frequency perturbation in male MS patients, deviations in vocal quality, lower rang of fundamental frequency

b) articulation subsystem: a limited range of motion from the articulatory organs, decrease in the vowel space areas, vowel formants shift to the center of the oral cavity

a) Impairments in the phonation system resulting from neurological conditions may in effect be a symptom indicative of MS presence

b) Impairments affecting the articulation system along with vowel articulation impairments can be a sign of the progression of the disease

c) Phonation subsystem changes not related to the disease severity and the disease duration

[63]

(i) To characterize motor speech disorders in MS including the estimation of prevalence, severity, type and primary manifestations of dysarthria; (ii) to identify relationships between the severity of speech disorder and neurological involvement; and (iii) to examine effect of the pyramidal and cerebellar systems on speech phenotypes

Objective acoustic speech

assessment including subtests on phonation, oral diadochokinesis, articulation and prosody was performed

26 patients (18%) showed spastic-ataxic dysarthria, 9 patients (6%) spastic dysarthria, 4 patients (3%) ataxic dysarthria and 1 patient (1%) had non-specific components of dysarthria

Speech abnormalities in MS (percentage of sample) were related to monopitch (35%), articulatory decay (26%), excess loudness variations (20%), slow rate (19%), irregular pitch fluctuations

(19%), imprecise consonants (15%), slow sequential motion rates (14%), irregular sequential motion rates

(13%), increased noise (13%) and signal perturbations (8%)

Patients with MS developed mainly mild spastic-ataxic dysarthria. They experienced difficulties in all investigated components of speech production including phonation, oral diadochokinesis, articulation and prosody. However, prosodic- articulatory disorder was the most salient with manifestations such as:

monopitch, articulatory decay, excess loudness variations and slow rate

[31]

To investigate the extent and nature of anomic symptoms in people with Rapidly Evolving Severe Relapsing–Remitting Multiple Sclerosis with respect to both accuracy and reaction time in a picture naming assessment task

a) The Addenbrooke’s Cognitive Examination–Revised (Mioshi et al., 2006) tested by asking the patient. b) The National Adult Reading Test (Nelson & Willison, 1991)

c)The Pyramids and Palm Trees (Howard & Patterson, 1992) tested by using either pictures, or written or spoken words to change the modality of stimulus or response items

The patients showed slow latencies, weak phonation, low voice volume and reduced articulatory precision in production of multi-syllabic words

No evidence of severe dysarthria in reading single words

[66]

To identify tongue, lip, and jaw motor deficits in persons with dysarthria due to MS to better understand the speech motor mechanisms that underlie their aberrant

speech

A standard speech evaluation was administered during the study to obtain speech severity ratings, speech intelligibility scores, and speech perceptual characteristics. Specifically, sentence intelligibility scores were calculated based on a standardized reading test consisting of eleven sentences that vary in length (Sentence Intelligibility Test)

The patients in the study exhibited longer movement durations, reduced tongue peak speeds, reduced peak speed/displacement ratios of the lower lips and jaw particularly during the closing gesture

The authors suggested that their findings indicate that speech treatments should specifically target tongue speed when aiming to reduce speech unnaturalness

[67]

Αimed at measuring maximum phonation times, maximum expiratory times, and articulation abilities scores in patients with MS compared to healthy subjects and at investigating if any of these

parameters could be used as a measure of MS progression

a) Articulation subtest from the Fussi assessment

(Dysarthria scores)

b) EDSS

a) MS patients had reduced maximum expiratory times and reduced maximum phonation times as compared to healthy controls

b) Articulation scores in MS patients were abnormal

c)The expiratory times are positively correlated with the maximum phonation times, and the latter are negatively correlated with the articulation scores. The EDSS scores are negatively correlated with the maximum expiratory times

Based on this correlation the authors proposed the use of maximum expiratory times to monitor MS progression

As the expiratory times were significantly correlated with the EDSS scores, they could be used to measure the severity of MS and to monitor its progression

[51]

To compare the results of voice self-assessment with the results of expert perceptual assessment in patients with MS

a) Voice Handicap Index, a standardized 30-point questionnaire (Jackobson et al., 1997). b) GRBAS scale according to the Japanese Society of Logopedics and Phoniatrics

c) EDSS

The patients in this study presented intense vocal difficulties

Symptoms of dysphonia ranged from 30 to 70%

A significant number of patients with MS experienced voice problems. The

Voice Handicap Index is a good and effective tool to assess patient self-perception of voice quality, but it may not reflect the severity of dysphonia as perceived by voice and speech professionals

The authors concluded that almost half of the MS patients feel and describe mild dysphonic difficulties which in turn affect the quality of their lives

[55]

The primary aim of the current study was to describe the

relationship between speech measurements and general

neurological impairment, brain volume, brain lesion

load and quality of life in MS in a single cohort. The

secondary aims were to determine the association

between acoustic metrics and neurological dysfunction

in non-dysarthric pwMS, and to estimate at which

level of neurological disability each speech metric

changes

EDSS scores

Analysis of speech variables through perceptual and acoustic methods. Elicited speech using five standardized speech tasks that fit along a spectrum of automaticity, from

simple to complex (phonetically and/or cognitively), including i) vowel, ii) DDK, iii) reading and iv) unscripted monologue

Dysarthria frequency and severity were associated with EDSS. The three

characteristics with the strongest associations with EDSS were the same for perceptual and acoustic analysis and included DDK rate, speech rate and increase in pauses/intervals. DDK rate and speech rate were

affected mainly in the severe group, whereas the

increase in pauses was observed for both the moderate

and severe groups

The patients exhibited slower speech rate, increased variation in speech rate, increase in pauses and smaller pitch variation (or monotonic speech) during connected speech as this was evident at least for the majority of MS patients in comparison to controls

Both the acoustic composite score and perceptual naturalness, global measurements of speech function, were associated with EDSS-defined disease severity. The degree of speech impairment moderately parallels that of overall MS-related neurological impairment and was not restricted only to the severe phases of MS

[59]

Aimed to

explore the association of tongue motor dysfunction in MS patients with overall clinical disability and structural brain damage

Employed a force transducer based quantitative-motor system to objectively assess tongue function. The TVF output and the mean applied tongue force were measured during an isometric tongue protrusion task

MS patients showed significantly increased tongue force and decreased tongue force compared to controls. TFV but not TF was correlated with the EDSS

TFV might serve as an objective and non-invasive outcome measure to augment the quantitative assessment of motor dysfunction in MS

[61]

Aimed to build an objectively measured speech score that

reflects cerebellar function, pathology and quality of life in MS

a) Analysis of speech variables through perceptual and acoustic methods

b) Scale for the assessment and rating of ataxia (Schmitz-Hu¨ bsch, 2006)

In this study it was noted that the degree of cerebellar dysfunction as this was measured by SARA, was associated mainly with impaired naturalness and intelligibility, slow speech rate, prolonged pauses and inaccurate pronunciation of vowels and consonants

Speech measurements such as an increase in pauses, slower maximum speech rate and subclinical voice tremor are associated with cerebellar dysfunction in MS. When combined, these measures are highly predictive of cerebellar dysfunction in MS

[68]

To propose a method for the evaluation and identification of significant patterns in voice samples acquired from patients affected by MS. This could enhance early detection, differential diagnosis and monitoring of disease progression

Acoustic analysis of parameters F0; Jitter; Shimmer; Harmonic to Noise Ratio and vowel metric, Vowel Space Area to evaluate the vowel articulation) have been used to compare the vocal signals of healthy subjects and the MS affected patients

Acoustic Analysis: a) The results show an increase of the F0 average in men for SPMS; instead, F0 average decreases in women both for Secondary SPMS and

RRMS. b) Showed great differences between healthy subjects and MS patients, with the parameters of relative jitter and relative shimmer to constitute indicators of MS disease

Vowel analysis: The vowel area decreases for pathological subjects. Remarkable reduction of the area for patients with RRMS, even though a tVSA increases can be notified in SPMS

The results showed different values for all parameters, distinguishing normal and pathological subjects as indicated in the literature. The procedure is appropriate to be used in early diagnosis that is critical in order to improve the passions quality of life

[69]

To explore relationships between spastic and ataxic dysarthria patterns evaluated using acoustic analyses and different MRI markers of whole and regional

brain atrophy. Specifically, hypothesized that aspects of ataxic dysarthria such as irregular pitch variability, irregular oral diadochokinesis, and excess loudness variations would reflect cerebellar

white and grey matter loss, whereas slowness of speech associated with

spastic dysarthria would be related to total white and cortical grey matter loss due to widespread brain atrophy

Acoustic speech assessment included:

a) Pitch variability,

b) Diadochokinetic rate,

c) Diadochokinetic regularity,

d) Articulation rate,

e) Loudness variability

A link of brain atrophy with a) slower articulation during reading and with b) a reduced diadochokinetic rate during rapid syllable repetition

Even though the articulation rate is not generally a comprehensive measure in MS, the authors found a strong correlation between brain atrophy and articulation rate, while EDSS and MSFC measurements provided similar results. According to the authors slow articulation rate during reading was particularly associated with bilateral white and grey matter loss while reduced maximum speed during oral diadochokinesis was a result of greater cerebellar involvement

[70]

To investigate the impact of cognitive impairment on speech produced by speakers with MS with and without dysarthria

a) Speakers produced a spontaneous speech sample to obtain speech timing measures of speech rate, articulation rate, and silent pause frequency and duration

b) Twenty listeners judged the overall perceptual severity of the samples using a visual analog scale that ranged from no impairment to severe impairment (speech severity)

a) Speech timing was significantly slower for speakers with dysarthria compared to speakers with MS without dysarthria. b) Silent pause durations also significantly differed for speakers with both dysarthria and cognitive impairment compared to MS speakers without either impairment

c) Significant interactions between dysarthria and cognitive factors revealed comorbid dysarthria and cognitive impairment contributed to slowed speech rates in MS, whereas dysarthria alone impacted perceptual judgments of speech severity. d) Speech severity was strongly related to pause duration

The findings suggest the nature in which dysarthria and cognitive symptoms manifest in objective, acoustic measures of speech timing and perceptual judgments of severity is complex