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Speech Disorders

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MariaCaterinaSilveri

Abstract

Although the term “speech” is generally associated with the motor components of verbal communication, it also denotes the very concept of verbal communication and includes both production and comprehension. At a clinical level, however, “speech disorders” mostly refer to the syndromes produced by disorders of movement of the vocal tract. The present chapter discusses ataxic dysarthria and other disorders of speech associated with cerebellar damage, such as dysprosody, foreign accent syndrome, stuttering and mutism and “covert” articulation decits. The type and localisation of cerebellar lesions associated with speech disorders will also be discussed.

On theoretical grounds, an interpretation of the cerebellar role in speech production is proposed within the hypothesis of the “internal model” of movement. The cerebellum processes sensory feedback and automatically implements the motor patterns stored in the motor cortex; it compares the movements programmed by the motor cortex with actual movements, resolves any mismatches and, through learning processes, progressively improves performance. The cerebellar properties of timing and sequencing ensure the implementation of the correct sequence of events not only during speech production but also in speech sound/phoneme discrimination.

Keywords

Speech · Ataxic dysarthria · Cerebellar mutism · Covert articulation · Timing · Sequencing · Internal model · Voicing onset time · Speech sound/phoneme discrimination · Coarticulation

M. C. Silveri (*) Department of Psychology, Università Cattolica del Sacro Cuore, Milan, Italy e-mail: mariacaterina.silveri@unicatt.it

71.1 Introduction

At the clinical level, speech disorders refer to the strictly motor aspects of verbal production, i.e., disorders related to the inefciency of the structural and neuromuscular components of the vocal tract that implement the articulatory process at the base of verbal production. In fact, the term “speech” actually denotes the very concept of verbal communication, which is achieved by combining the sounds of the language, not limited to verbal production, but also extended to perception.

This chapter will primarily describe disorders of the motor aspects of verbal production controlled by the cerebellum in relation to their clinical relevance. The role of the cerebellum in speech perception will also be mentioned.

71.2 Ataxic Dysarthria

Speech disorders characterise the cerebellar syndrome. In the original study by Darley etal. (1969), observations of co-occurrences of deviant speech dimensions in different brain pathologies drawn in correlation matrices allowed for the emergence of specic clusters in cerebellar damage that point to the main characteristics of cerebellar disorders of speech: these include “articulatory inaccuracy”, “prosodic excess” and “phonatory-prosodic decits”.

Dysarthria manifests as a perceptual disorder that reduces the intelligibility of speech. The analysis of speech disorders in cerebellar patients is mostly based on perceptual and acoustic methods in which speech parameters are identied, analysed and rated by listeners (e.g., see the parameters indicated by Noffs etal. 2020); only more recently have acoustic perceptual analyses been integrated with more sophisticated investigative techniques able to study vocal tract kinematics, for example, with electromyographic recording.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. L. Gruol et al. (eds.), Essentials of Cerebellum and Cerebellar Disorders, https://doi.org/10.1007/978-3-031-15070-8_71

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In classical reports of patients with cerebellar damage, speech production is described as scanning, hesitant, laborious and explosive (Darley etal. 1975). Speech disorders are observed within the broader ataxic syndrome typically generated by cerebellar damage and thus called “ataxic dysarthria”) (Duffy 2012). Ataxic dysarthria, as the ataxic syndrome, is generally explained as the lack of sensorimotor integration and is primarily interpreted as the reection on the vocal tract and respiratory muscles of the lack of sensorimotor coordination of movements that support both articulation and phonation and resonance and prosody.

71.3 Main Features ofAtaxic Dysarthria

In ataxic dysarthria, the speech rate is slow, consonant and vowel sounds are imprecise, phonemes may be prolonged and articulatory breakdown may be irregular. Furthermore, the range of frequency of sounds is reduced (monopitch production) as is the variation of volume (monoloudness). Some authors have also attempted to classify subtypes of dysarthria according to notions of instability (unusual variability) or inexibility (unusual consistency) of speech (Spencer and France 2016).

71.4 Dierent Types ofDysarthria

inDierent Cerebellar Pathologies

Any type of cerebellar damage can be associated with speech disorders, i.e., degenerative, vascular, demyelinating, inammatory/infectious processes, tumours and trauma. Regarding the underlying pathology, although attempts have been made to identify different characteristics of dysarthria, results are only partially conclusive.

Dysarthria is quite frequent in spinocerebellar ataxia (SCA), a rare autosomal dominant neurodegenerative disease. Generally speaking, the characteristics of the speech decit in SCA are the ones typically reported for ataxic dysarthria; however, in SCA the symptoms related to altered phonation seem prominent (Schalling and Hartelius 2013). Some authors suggest that in this pathology it might be possible to detect specic elements in speech and voice that could be of help in differentiating genotypes (Sidtis et al.

2011). For example, hypernasality and phonation disorders

would allow differentiating the dysarthria associated with SCA from that associated with other neurodegenerative diseases, such as Friedreich’s ataxia (FRDA) (Folker et al.

2012). In a sample of 20 patients affected by FRDA, Brendel

etal. (2013) found that respiration, voice quality and instability, articulation and tempo were the most affected speech dimensions; furthermore, some of these had predictive value regarding the severity of ataxia and disease duration.

Both spastic and ataxic dysarthria were documented in olivopontocerebellar atrophy (OPCA) (Kluin etal. 1988). In the latter study, degrees of ataxia and spasticity were rated by means of perceptual analysis; however, only the severity of ataxia, not the severity of spasticity, was correlated with hypometabolism of the cerebellar structures and the brainstem.

Isolated cerebellar infarctions are quite rare because the cerebellar arteries are not only distributed in the cerebellar territories but also supply different regions of the brainstem. Consequently, as well rare is pure dysarthria in cerebellar infarctions (i.e., less than 5% in stroke patients); in most cases, it is transient and associated with other neurological signs. Although dysarthria has been associated with infarction in the distribution territories of all the cerebellar arteries, it is most frequently observed when the infarction is in the territory of the superior cerebellar artery (SCA) with slight prevalence on the right side (Urban 2013). In some studies, no differences were found in the characteristics of speech disorders in patients with vascular lesions encompassing different cerebellar areas (Neau etal. 2000); in other studies, left cerebellar infarcts seemed to be associated with more pronounced difculties in articulation (in particular in vowel articulation) and in the repetition of syllables compared to right-sided lesions; prosody would be more affected in cortical than in subcortical lesions.

Speech disorders are frequently observed in individuals with multiple sclerosis (MS). According to some authors, these disorders are predictive of MS severity; in fact, it was found that an acoustic composite score including different acoustic variables of speech was predictive of cerebellar functions and was correlated with white matter volume, quality of life and manual dexterity performance (Noffs etal.

2020).

71.5 Dysprosody, Foreign Accent

Syndrome andStuttering

Syllable duration, stress and fundamental frequencies characterise speech prosody. Dysprosody has been reported in cerebellar patients, principally consisting of an alteration of syllable duration parameters and fundamental and formant frequencies (Casper etal. 2007). Cerebellar involvement has also been hypothesised in the so-called neurogenic foreign accent syndrome (FAS). FAS is a rather rare prosodic disorder in which, following cerebral damage, a subject speaks with a new accent that sounds foreign to listeners of the language community to which the subject belongs. In the case reported by Priftis etal. (2020), left cerebellar diaschisis was reported in association with a right cortical-subcortical cerebral lesion. The cerebellar involvement was conrmed in two other subjects (Keulen etal. 2017), the rst with a pontine infarct who

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presented bilateral frontal and left cerebellar hypoperfusion at

99m

the

Tc ECD SPECT, and the second with a left cerebellar infarct in the territory of the posterior inferior cerebellar artery (PICA). Overall, these observations conrm that FAS can be generated by damage to complex neural circuits that involve both supra and infratentorial structures. Developmental stuttering is principally associated with abnormal circuitry between the cerebellum lobule VI and the bilateral prefrontal gyrus. This was demonstrated by a resting state functional MRI in adults who stutter (Yang etal. 2016) and a lesion study which reported the emergence of stuttering after a right cerebellar lesion (Tani and Sakai 2010).

71.6 Cerebellar Mutism

Mutism is probably the most severe speech disorder following a cerebellar lesion. It is an acute syndrome characterised by speech arrest. It generally follows the surgical removal of tumours in the posterior fossa, cerebellum and fourth ventricle, principally medulloblastoma, in children. It is only occasionally observed in adults. It can appear several days after surgery and can be associated with other cerebellar symptoms such as ataxia, pharyngeal dyspraxia, bulbar or pseudobulbar signs and behavioural disorders. Cerebellar mutism is a reversible syndrome. It can last from a few days to several months and, in rare cases, years. Residual dysarthria following mutism resolution can persist for months or can even be permanent. However, the characteristics of residual dysarthria are not typical of ataxic dysarthria, but are primarily dominated by a slow speech rate. Sometimes mutism evolves towards a decit of language production, such as agrammatism. There is a large consensus in attributing the syndrome to supratentorial involvement due to diaschisis of the prefrontal lobe cortex resulting from bilateral dysfunction of the dento-thalamocortical pathways. However, damage to other efferent pathways from other deep cerebellar nuclei cannot be excluded.

Some data suggest that cerebellar mutism resolves quickly when the lesion is conned to the vermis and does not encompass the cerebellar hemispheres. When the cerebellar hemispheres are damaged, mutism evolves more slowly towards residual forms of dysarthria, resembling the articulatory disorder associated with frontal lobe damage (Manto 2010). In agreement with this evidence is the nding that mutism is related to bilateral diaschisis of the mesial prefrontal regions, whereas residual dysarthria should be traced back to cerebellar hemispheric injuries during surgery. In fact, the mesial prefrontal cortex intervenes in planning processes and is not involved in speech articulation processes (Ackerman and Brendel 2016); by contrast, articulatory disorders might be generated by diaschisis in the frontal cortical areas involved in speech articulation, due to dysfunctional circuitry between these areas and the cerebellar hemispheres.

The events that cause cerebellar mutism are largely unknown. However, mechanical or thermal injuries during surgery or postoperative increased body temperature have been indicated as the most signicant risk factors for developing mutism (Catsman-Berrevoets and Patay 2018, for discussion).

71.7 Disorders ofCovert Articulation

inCerebellar Damage

The articulatory disturbance, which is one of the fundamental characteristics of ataxic dysarthria, is not limited to the speech level but can also involve the covert components of articulation. This aspect has important implications for phonological short-term memory (ph-STM) and the functions associated with it. The ph-STM system is organised into two main subsystems: the phonological short-term store (phSTS), in which verbal information is transitorily stored, and the rehearsal system, which is a covert articulatory system that “refreshes” information in the store that would otherwise rapidly decay. It has been shown that the rehearsal system, in particular the phonological output buffer component, is dysfunctional in the presence of right cerebellar damage and also in the absence of dysarthria (Silveri etal. 1998). In an event-related MRI study, Chen and Desmond (2005) demonstrated activation of the left opercular regions and the right superior cerebellum during the subvocal rehearsal of letters. Overall, these ndings conrm cerebellar involvement in covert articulation supported by the cerebro-cerebellar networks, and they assign a crucial role to the cerebellum in verbal STM and in all cognitive functions mediated by the STM, primarily in the language domain.

71.8 Neural Substrates ofAtaxic

Dysarthria

The cerebellum has uniform cytoarchitecture with general principles of organisation (Grimaldi and Manto 2012). However, segregated functional zones emerge that are driven by the cerebellar connections with extracerebellar structures, in particular the complex crossed feed-forward cerebellumthalamus- cortico-ponto-cerebellar pathways. Therefore, it is more appropriate to speak of networks that include both cerebellar and supratentorial structures when considering the functional organisation of the cerebellum to support cognition, including speech. There are descriptions of patients with dysarthria and cerebellar damage in the right cerebellar hemisphere, consistently with crossed diaschisis in the left, linguistic hemisphere; note however, that left hemisphere cerebellar lesions have also been reported (Urban 2013). In patients with cerebellar infarctions the lesions associated

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with speech disorders are generally located in the territory of the SCA, i.e., in the superior cerebellum, which is supplied by the medial, as well as the lateral branches (Ogawa etal.

2010; Urban 2013). Paravermal lesions and lesions in hemi-

spheric lobules V and VI have been associated with the pure form of dysarthria (Amarenco et al. 1991; Schoch et al.

2006). Although some evidence from lesion studies suggests

lateralisation on the right, the lateralisation of language functions in the cerebellum is currently an open question. Data obtained from functional neuroimaging studies of normal subjects performing different speech production tasks frequently show bilateral cerebellar activation; however, these data are overall heterogeneous and inconclusive in this respect (see Spencer and Slocomb 2007). It is possible that the heterogeneity of the results depends on the variability of the tasks adopted to elicit the activation; these tasks might engage relatively peripherical stages (motor-articulatory) of language production or properly linguistic competence, implemented by progressively more complex and larger neural networks.

Perhaps neurodegenerative cerebellar pathologies could be useful for identifying the neural substrates of speech and the different subcomponents of speech (such as articulation, phonation or prosody) beyond localisation. In fact, the involvement of different cellular populations, cortical layers and connections to deep nuclei and supratentorial structures characterises different neurodegenerative pathologies. These include, for example, SCA subtypes, FRDA or OPCA, which different subtypes of dysarthria correspond to (Sidtis etal.

2011; Folker etal. 2012; Brendel etal. 2013), thus suggest-

ing the involvement of different neural networks.

Finally, it should be remembered that the cerebellum is part of a highly integrated system of movement control that includes the frontal cortex and the basal ganglia (see Silveri

2021 for a discussion). This might explain why speech motor

disorders associated with damage to the cerebellum, basal ganglia or frontal cortex (i.e., ataxic dysarthria, hypokinetic dysarthria and apraxia of speech, respectively) may share some characteristics.

71.9 The Cerebellar “Internal Model”

ofMovements andtheCerebellar “Timing System” inSpeech Production andSpeech Sounds/ Phonemes Discrimination

Within the general interpretation of dysarthria as the result of a lack of sensorimotor coordination several hypotheses have been put forward to explain the disorders at the basis of the speech decit in cerebellar damage. In an original paper by Ivry and Keele (1989), which also reports Braitenberg’s (1967) earlier observations, the cerebellum is seen as an

“internal clock” because of the difculties of patients with cerebellar damage when they are requested to perform production and perception timing tasks. According to these Authors, the cerebellar role in timing is not limited to the motor domains, but also emerges in perceptual and cognitive processes when time-related predictive computations are needed. These authors associated the cerebellum with a “predictive device”, assuming that in both production and perception tasks correct timing requires the ability to predict when events will occur.

The predictive role of the cerebellum in speech production has been articulated by assuming that the cerebellum generates the “efferent copy”, i.e., a predictive model of the patterns of movements that will be produced. The cerebellum is expected to detect incongruencies between the expected and the actual movements, to correct the incongruency and thus to optimise performance. In more recent literature, the hypothesis of the “internal model” (Wolpert etal.

1998; Ito 2008) assumes that the cerebellum acquires the

model of the movement by the processing of sensory feedbacks and the automatic implementation of the motor patterns stored in the motor cortex. The cerebellum compares the movements programmed by the motor cortex with the actual movements, resolves any mismatches and through learning processes (Fiez 2016) progressively improves the performance. We can hypothesise that during speech production the cerebellum intervenes to facilitate adherence of the oral tract movements to the motor patterns stored in the cerebral cortex according to the frequency of their occurrence in the speaker’s language. The cerebellar properties in timing operations are strictly correlated with the concept of sequencing (Leggio and Molinari 2015). The cerebellum controls the serial movements in the vocal tract and immediately detects any violation of the expected order, thus ensuring the implementation of the correct sequence of events.

The phonetic elements of speech, “the true primitives that underlie linguistic communication” (Liberman and Whalen

2000, p.188), are not sounds but articulatory gestures that

generate sounds. According to Studdert-Kennedy (1998), the hierarchy of language arises from the “particulation” of the vocal tract and related neuromuscular control; the vocal tract is “particulated” into independently controllable movable subcomponents that give the vocal tract high exibility; it is the overall coordination of the activity of these individual components of the vocal tract, which also takes into account the state of the other components (i.e., coarticulation processes), that enables the execution of those fast movements and rapid articulatory routines that are unique to humans, which from a nite set of elements (phonemes) are hierarchically combined into virtually unlimited larger units (i.e., words and sentences).

Evidence of cerebellar involvement in processing speech time parameters (and also in discriminating perceptual com-

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ponents of speech) suggests that the role of cerebellum transcends the articulatory level (Ackermann 2008; Mariën etal.

2014). In fact, time is also crucial in discriminating speech

sounds and in processing phonological stimuli. The cerebellum has been considered as a timing system (“internal clock”) not only in movement but also in perception (Keele and Ivry 1990), and is crucial for estimating the duration of time intervals. The inability to estimate the time interval between two perceived sounds might generate disorders in discriminating sounds as different. For example, the incorrect estimation of the interval between the start of a stop consonant1 and the onset of vibration in the vocal folds (voicing) (Voicing Onset Time) (VOT) prevents discriminating between the sound /ba/ (voiced) and the sound /pa/ (voiceless). In fact, linguistic perception is categorical (Liberman etal. 1957); we can perceive stimuli that we have learned are different, such as /pa/ and /ba/ by means of the categorisation process during language acquisition. The categorisation process “maps” continuous sensorial phenomena such as acoustic stimuli onto a limited number of sound categories (phonemes) that vary across languages. Thus, the brain assigns acoustic stimuli to qualitatively different categories, but never to intermediate categories (the so-called phoneme boundary effect) (Liberman etal. 1957). Patients with cerebellar damage are unable to discriminate different intervals of time demarked by two clicks (Ivry and Keele 1989) and it has been conrmed that VOT is altered in ataxic dysarthria (Ackermann etal. 1997). The impaired phoneme boundary effect was also demonstrated in patients with bilateral cerebellar atrophy by adopting acoustic stimuli that differed only in terms of duration parameters, independently of voicing (Ackermann etal. 1997).

To conclude, there is sufcient evidence to attribute a specic role to the cerebellum not only in speech production but also in speech sound/phoneme discrimination. Both speech production and speech sound/phoneme discrimination are highly dependent on properties such as timing and sequencing, which are typically supported by the cerebellum and must therefore be seen as a fundamental element in the implementation of speech processes. Timing and sequencing are essential to ensure the coordination of the activity of the “particulated” components of the vocal tract, i.e., the “coarticulatory” process, as well as the categorisation of acoustic stimuli. Not only is the actual implementation of linguistic processes based on these processes, but also the evolution of human language (see Liberman and Whalen 2000 for discussion).

In phonetics a stop consonant is the sound produced when the ow of

air is completely blocked and then released.

References

Ackermann H (2008) Cerebellar contributions to speech production and

speech perception: psycholinguistic and neurobiological perspectives. Trends Neurosci 31(6):265–272. https://doi.org/10.1016/j.

tins.2008.02.011. Epub 2008 May 9

Ackerman H, Brendel B (2016) Cerebellar Contributions to Speech

and Language. Neurobiol Lang 7:73–84. https://doi.org/10.1016/

B978- 0- 12- 407794- 2.00007- 9

Ackermann H, Gräber S, Hertrich I, Daum I (1997) Categorical speech

perception in cerebellar disorders. Brain Lang 60(2):323–331.

https://doi.org/10.1006/brln.1997.1826

Amarenco P, Chevrie-Muller C, Roullet E, Bousser MG (1991)

Paravermal infarct and isolated cerebellar dysarthria. Ann Neurol 30(2):211–213. https://doi.org/10.1002/ana.410300215

Braitenberg V (1967) Is the cerebellar cortex a biological clock in

the millisecond range? Prog Brain Res 25:334–346. https://doi.

org/10.1016/S0079- 6123(08)60971- 1

Brendel B, Ackermann H, Berg D, Lindig T, Schölderle T, Schöls

L, Synofzik M, Ziegler W (2013) Friedreich ataxia: dysarthria prole and clinical data. Cerebellum 12(4):475–484. https://doi.

org/10.1007/s12311- 012- 0440- 0

Casper MA, Raphael LJ, Harris KS, Geibel JM (2007) Speech prosody

in cerebellar ataxia. Int J Lang Commun Disord 42(4):407–426.

https://doi.org/10.1080/13682820601056210

Catsman-Berrevoets C, Patay Z (2018) Cerebellar mutism syn-

drome. Handb Clin Neurol 155:273–288. https://doi.org/10.1016/

B978- 0- 444- 64189- 2.00018- 4

Chen SH, Desmond JE (2005) Temporal dynamics of cerebro- cerebellar

network recruitment during a cognitive task. Neuropsychologia 43(9):1227–1237. https://doi.org/10.1016/j.neuropsycholo-

gia.2004.12.015. Epub 2005 Feb 25

Darley FL, Aronson AE, Brown JR (1969) Differential diagnostic pat-

terns of dysarthria. J Speech Hear Res 12(2):246–269. https://doi.

org/10.1044/jshr.1202.246

Darley F, Aronson A, Brown J (1975) Motor speech disorders. Saunders,

Philadelphia, PA

Duffy JR (2012) Motor speech disorders: substrates, differential diag-

nosis, and management, 3rd edn. Elsevier, Mosby, St Louis, MO

Fiez JA (2016) The cerebellum and language: persistent themes

and ndings. Brain Lang 161:1–3. https://doi.org/10.1016/j.

bandl.2016.09.004. Epub 2016 Sep 20

Folker JE, Murdoch BE, Rosen KM, Cahill LM, Delatycki MB, Corben

LA, Vogel AP (2012) Differentiating proles of speech impairments in Friedreich’s ataxia: a perceptual and instrumental approach. Int J Lang Commun Disord 47(1):65–76. https://doi.org/10.1111/j.1460- -

6984.2011.00078.x. Epub 2011 Aug 19

Grimaldi G, Manto M (2012) Topography of cerebellar decits in

humans. Cerebellum 11(2):336–351. https://doi.org/10.1007/

s12311- 011- 0247- 4

Ivry RB, Keele SW (1989) Timing functions of the cerebellum. J Cogn

Neurosci 1(2):136–152. https://doi.org/10.1162/jocn.1989.1.2.136

Ito M (2008) Control of mental activities by internal models in the cer-

ebellum. Nat Rev Neurosci 9(4):304–313. https://doi.org/10.1038/

nrn2332

Keele SW, Ivry R (1990) Does the cerebellum provide a common com-

putation for diverse tasks? A timing hypothesis. Ann N Y Acad Sci 608:179–207; discussion 207–11. https://doi.org/10.1111/j.1749-

6632.1990.tb48897.x

Keulen S, Mariën P, van Dun K, Bastiaanse R, Manto M, Verhoeven J

(2017) The posterior fossa and foreign accent syndrome: report of two new cases and review of the literature. Cerebellum 16(4):772–

785. https://doi.org/10.1007/s12311- 017- 0849- 6

462

https://t.me/medicina_free

M. C. Silveri

Kluin KJ, Gilman S, Markel DS, Koeppe RA, Rosenthal G, Junck

L (1988) Speech disorders in olivopontocerebellar atrophy cor-

relate with positron emission tomography ndings. Ann Neurol

23:547–554 Leggio M, Molinari (2015) Cerebellar sequencing: a trick for predict-

ing the future. Cerebellum 14(1):35–38. https://doi.org/10.1007/

s12311- 014- 0616- x

Liberman AM, Harris KS, Hoffman HS, Grifth BC (1957) The dis-

crimination of speech sounds within and across phoneme bound-

aries. J Exp Psychol 54(5):358–368. https://doi.org/10.1037/

h0044417

Liberman AM, Whalen DH (2000) On the relation of speech to lan-

guage. Trends Cogn Sci 4(5):187–196. https://doi.org/10.1016/

s1364- 6613(00)01471- 6

Manto M (2010) Cerebellar disorders. a practical approach to diagnosis

and management. Cambridge University Press, Cambridge, UK Mariën P, Ackermann H, Adamaszek M, Barwood CH, Beaton A,

Desmond J, De Witte E, Fawcett AJ, Hertrich I, Küper M, Leggio

M, Marvel C, Molinari M, Murdoch BE, Nicolson RI, Schmahmann

JD, Stoodley CJ, Thürling M, Timmann D, Wouters E, Ziegler W

(2014) Consensus paper: language and the cerebellum: an ongo-

ing enigma. Cerebellum 13(3):386–410. https://doi.org/10.1007/

s12311- 013- 0540- 5

Neau JP, Arroyo-Anllo E, Bonnaud V, Ingrand P, Gil R

(2000) Neuropsychological disturbances in cerebel-

lar infarcts. Acta Neurol Scand 102(6):363–370. https://doi.

org/10.1034/j.1600- 0404.2000.102006363.x

Noffs G, Boonstra FMC, Perera T, Kolbe SC, Stankovich J, Butzkueven

H, Evans A, Vogel AP, van der Walt A (2020) Acoustic speech

analytics are predictive of cerebellar dysfunction in multiple

sclerosis. Cerebellum 19(5):691–700. https://doi.org/10.1007/

s12311- 020- 01151- 5

Ogawa K, Yoshihashi H, Suzuki Y, Kamei S, Mizutani T (2010) Clinical

study of the responsible lesion for dysarthria in the cerebellum.

Intern Med 49(9):861–864. https://doi.org/10.2169/internalmedi-

cine.49.2913. Epub 2010 Apr 30

Priftis K, Algeri L, Barachetti L, Magnani S, Gobbo M, De Pellegrin

S (2020) Acquired neurogenic foreign accent syndrome after

right-hemisphere lesion with left cerebellar diaschisis: a longitu-

dinal study. Cortex 130:220–230. https://doi.org/10.1016/j.cor-

tex.2020.05.019. Epub 2020 Jun 25

Schalling E, Hartelius L (2013) Speech in spinocerebellar ataxia. Brain

Lang 127(3):317–322. https://doi.org/10.1016/j.bandl.2013.10.002. Epub 2013 Oct 30

Schoch B, Dimitrova A, Gizewski ER, Timmann D (2006) Functional

localization in the human cerebellum based on voxelwise statistical analysis: a study of 90 patients. NeuroImage 30(1):36–51. https://

doi.org/10.1016/j.neuroimage.2005.09.018. Epub 2005 Oct 25

Sidtis JJ, Ahn JS, Gomez C, Sidtis D (2011) Speech characteris-

tics associated with three genotypes of ataxia. J Commun Disord 44(4):478–492. https://doi.org/10.1016/j.jcomdis.2011.03.002. Epub 2011 Apr 15

Silveri MC (2021) Contribution of the cerebellum and the basal gan-

glia to language production: speech, word uency, and sentence construction-evidence from pathology. Cerebellum 20(2):282–294.

https://doi.org/10.1007/s12311- 020- 01207- 6. Epub 2020 Oct 29

Silveri MC, Di Betta AM, Filippini V, Leggio MG, Molinari M (1998)

Verbal short-term store-rehearsal system and the cerebellum. Evidence from a patient with a right cerebellar lesion. Brain 121(Pt

11):2175–2187. https://doi.org/10.1093/brain/121.11.2175

Spencer KA, France AA (2016) Perceptual ratings of subgroups of

ataxic dysarthria. Int J Lang Commun Disord 51(4):430–441.

https://doi.org/10.1111/1460- 6984.12219. Epub 2016 Feb 24

Spencer KA, Slocomb DL (2007) The neural basis of

ataxic dysarthria. Cerebellum 6(1):58–65. https://doi.

org/10.1080/14734220601145459

Studdert-Kennedy M (1998) The particulate origins of language gen-

erativity: from syllable to gesture. In: Hurford J, Studderto-Kennedy M, Knight C (eds) Approaches to the evolution of language. Cambridge University Press

Tani T, Sakai Y (2010) Stuttering after right cerebellar infarction: a

case study. J Fluen Disord 35(2):141–145. https://doi.org/10.1016/j.

judis.2010.03.001

Urban PP (2013) Speech motor decits in cerebellar infarctions. Brain

Lang 127(3):323–326. https://doi.org/10.1016/j.bandl.2013.10.001. Epub 2013 Nov 1

Yang Y, Jia F, Siok WT, Tan LH (2016) Altered functional connectivity

in persistent developmental stuttering. Sci Rep 6:19128. https://doi.

org/10.1038/srep19128

Wolpert DM, Miall RC, Kawato M (1998) Internal models in the cer-

ebellum. Trends Cogn Sci 2(9):338–347. https://doi.org/10.1016/

s1364- 6613(98)01221- 2

Deficits ofLimbs Movements

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GiulianaGrimaldi

Abstract

This chapter provides a clinical description of the decits

involving limb movements in cerebellar patients. The fol-

lowing cerebellar signs are described: dysmetria (hyper-

metria and hypometria); cerebellar tremor (kinetic,

postural, and isometric tremor); decomposition of move-

ments; disorders of muscle tone (hypotonia, cerebellar

ts); dysdiadochokinesia and dysrhythmokinesia; loss of

check and rebound; isometrataxia; handwriting abnor-

malities; and megalographia. Also, an explanation of the

maneuvers and tests currently used for the clinical evalu-

ation of limb decits in cerebellar patients is provided.

Keywords

Dysmetria · Cerebellar tremor · Decomposition of

movements · Hypotonia · Dysdiadochokinesia · Clinical

evaluation

72.1 Introduction

Ataxia of limbs may be dened as unsteadiness or incoordination of limbs, encompassing an impairment of the control of force and timing of movements. These abnormalities generate errors in speed, range, rhythm, starting, and stopping motor activity (Walker 1990), thus resulting in a jerky or poorly coordinated character of motion in the absence of muscle weakness or sensory decit. The main decits involving limb movements in cerebellar patients include dysmetria, tremor, decomposition of movements, disorders of muscle

tone, and dysdiadochokinesia (Grimaldi and Manto 2012; Grimaldi 2013). Limb ataxia together with ataxic dysarthria and postural/gait decits dene the so-called cerebellar motor syndrome (CMS). These symptoms share a lack of motor coordination between muscles resulting in undershoot or overshoot of the intended target position (Manto and Mariën 2015). This chapter provides a description of the decits of limb movements occurring in cerebellar diseases and an overview of the maneuvers and tests used for clinical examination during daily practice.

72.2 Dysmetria: Hypermetria andHypometria

Dysmetria is an error in trajectory due to a disturbed range, rate, and force of movement (Holmes 1917, 1922; Gilman etal. 1981). In most cases, dysmetria occurs both for proximal and distal joints and is often followed by corrective movements (Hore etal. 1991). Both hypermetria and hypometria occur in cerebellar patients. Hypermetria refers to the overshoot of the target (Fig.72.1, top panel) and is the largest when the movement is made as fast as possible and when the inertia of the moving limb is increased (Manto etal. 1994, 1995a, b). Hypermetria is often associated with abnormal patterns of electromyographic (EMG) activities, namely a delayed onset latency of the antagonist EMG activity. Hypometria is less common. Hypometric movements are characterized by a premature arrest before reaching the aimed target (Grimaldi and Manto 2012).

G. Grimaldi (*) U.O.C. Unità Spinale, Villa delle Ginestre, ASP Palermo, Palermo, Italy

463

464

Accelerometry (Volts)

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G. Grimaldi

0.0

0.1

0.2

0.3

Amplitude (rad)

0.4

0,3

0,2

0,1

-0,1

-0,2

-0,3

100 msec

0.0

0.1

0.2

0.3

Amplitude (rad)

0.4

100 msec

5 sec

Fig. 72.1 Top panel: cerebellar hypermetria. Superimposition of 9 fast wrist exion movements. Left: control subject. Right: cerebellar patient. Movements (lines) are accurate in the control subject and hypermetric in the patient (overshoot of the target). Aimed target (dotted lines) located at 0.4 rad from the start position corresponding to a neutral position of the joint. The target is visually displayed (Adapted from Manto 2009). Middle panel: postural tremor recorded with accelerometer afxed to the right index of a right-handed 49-year-old right-

72.3 Cerebellar Tremor

Tremor in cerebellar disease is mainly composed of lowfrequency oscillations. Tremor may be bilateral. In most cases, oscillations are observed ipsilaterally to the cerebellar

handed woman affected with SCA2; the patient maintains upper limbs motionless, horizontally and parallel to the oor, in front of her (Adapted from Grimaldi etal. 2014). Bottom panel: superimposition of Archimedes’ spirals drawn on a digitized tablet. Left: control subject. Right: patient affected with kinetic tremor. Notice that Archimedes’ spirals performed by the patient are irregular and present swerves. (Adapted from Grimaldi and Manto 2010)

lesion. Eye closure and body displacements tend to enhance the oscillations. Action tremor is common in cerebellar disorders. The term “action tremor” refers to any tremor produced by the voluntary contraction of muscles. It includes kinetic tremor (also named intention tremor), postural

72 Decits ofLimbs Movements

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465

tremor, and isometric tremor (Grimaldi and Manto 2008). The following criteria have to be fullled to diagnose cerebellar action tremor: pure or dominant intention tremor; tremor frequency below 5Hz; postural tremor may be present, but not resting tremor (Deuschl etal. 2007).

Kinetic tremor appears during the execution of a movement and is usually maximal as the limb approaches the target (Holmes 1939). Kinetic tremor tends to involve predominantly the proximal musculature (Gilman et al.

1981; Lechtenberg 1993) and decreases with inertia, unlike

cerebellar dysmetria (Chase etal. 1965; Hewer etal. 1972). Kinetic tremor has a frequency between 2 and 7Hz in the large majority of cases. In most cases, oscillations are perpendicular to the main direction of the intended movement.

Postural tremor appears during postural tasks. Its frequency is usually between 4 and 12Hz (Fig.72.1, middle panel). Tremor appears immediately, but increases in amplitude after a few seconds in the line of gravity. Postural tremor in cerebellar disease can be further described as follows: (a) precision tremor, with a frequency of 2–5Hz, occurring during the execution of precision tasks and involving the distal musculature; (b) asthenic tremor, which is precipitated by fatigue; (c) axial postural tremor; and (d) midbrain tremor (Brown etal. 1997).

Isometric tremor is dened as involuntary oscillations of one or more body regions occurring in situations of isometric muscle contraction against a rigid resistance, e.g., pressing the hand and arm against a heavy table, standing on the feet or hands (orthostatic tremor), or simply holding an object between thumb and other ngers in opposition (Findley and Koller 1995; Nowak etal. 2013).

72.5 Dysdiadochokinesia andDysrhythmokinesia

Dysdiadochokinesia (also called adiadochokinesia) denotes the inability to perform rapid successive movements (Babinski

1902), resulting in irregular and slow alternating sequential

movements. The successive pronation/supination task is typically used to evaluate this decit. In advanced cases, dysdiadochokinesia often results in an abnormal sway of the elbow, and the alternate character of the task may therefore not be detectable (Manto 2002). Dysrhythmokinesia, which is one of the characteristics of adiadochokinesia, consists of a disturbed rhythm associated with repetitive sequential movements (Wertham 1929). Dysrhythmokinesia can be detected in a tapping test (Manto 2010). Interestingly, a relatively preserved accuracy of movements may be found, although the presence of dysrhythmokinesia (Grimaldi 2013).

72.6 Loss ofCheck andRebound

Impaired check causes a large movement called rebound. Disturbed check is assessed by asking the patient to maintain the upper limbs extended with the hands pronated. The examiner exerts a tap on the wrist thus causing a large displacement of the limb, immediately followed by an overshoot at the initial position followed by oscillations (Manto

2002). The lack of check can be evaluated during the

Stewart–Holmes maneuver (1904) (see paragraph Clinical examination of limbs movements).

72.4 Decompositions ofMovement

Decomposition of movement into elementary components is due to a lack of synergy between joints, resulting in a lack of uidity in motion and in ataxic movements (Topka et al.

1998). Decomposition of movement may be assessed by the

index-to-wrist maneuver, during which cerebellar patients demonstrate asynchronous movements of the shoulder and the elbow. For slow multijoint movements, decomposition is manifested by errors in the direction and rate of the movement. Decomposition of movement is often accompanied by an inability to generate independent nger movements, as during the index-thumb test. The attempt to move the thumb and the index alone induces successive exion of the other ngers (“sign of the piano”) (Manto 2002, 2010). For details about index-to-wrist maneuver and index-thumb test, see paragraph clinical examination of limbs movements.

72.7 Disorders ofMuscle Tone: Hypotonia andCerebellar Fits

Hypotonia is a decreased resistance to passive manipulation of the limbs. It might be normally present in children, while in adult it is usually associated with cerebellar damage, namely at the acute stage of disease (Manto 2002). The decline in resistance to the passive manipulation of limbs tends to be more pronounced in proximal joints (Manto

2010). Due to this reduced resistance, pendular tendon

reexes may be observed, notably at the knee, characterized by the distal leg continuing to swing (like a pendulum) ve times or more following elicitation of the patella tendon reex (Holmes 1922, 1939). Disorder of muscle tone in cerebellar injury may also present as “ cerebellar ts,” spasms associated with intermittent opisthotonos (1904), which are included in the category of the cerebellar seizures (Manto

2010).

466

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G. Grimaldi

72.8 Isometrataxia

Isometrataxia is the inability to maintain constant force (impaired isotonic force production) during skilled tasks, especially when requiring hand or nger use (Mai et al.

1989). Isometrataxia may be associated with action tremor.

Isometric tremor often masks isometrataxia, which, therefore, is underestimated. However, isometrataxia can be differentiated from the isometric tremor thanks to two major features: it is not a rhythmic phenomenon and it occurs during slight contractions (Grimaldi 2013).

72.9 Handwriting Abnormalities andMegalographia

Cerebellar patients show difculties in handwriting resulting in irregular writing (Fig. 72.1, bottom panel) (Grimaldi

2013). The observation of letters “unequal in size and irregu-

larly spaced” was reported by Holmes in 1917 in patients with cerebellar lesions following gunshot injuries (Holmes

1917). Megalographia (also called macrographia), charac-

terized by abnormally large handwriting, is another sign of cerebellar dysfunction (Frings etal. 2010).

• Arm outstretched task: holding the upper limbs outstretched with the hands in supination, parallel to the oor at the height of the shoulder.

• Index-to-index test: The patient is asked to maintain the two index ngers medially, pointing at each other at a distance of about 1 cm. Forearms are maintained horizontally at the height of the shoulders.

• Heel-to-knee test: The patient is asked to maintain the heel on the knee for several seconds (Stewart and Holmes

1904; Holmes 1922). The oscillations appearing during

the heel-to-knee test rapidly evolve into lateral sways in severe cases.

The following tests are used to assed decomposition of

movements (Manto 2002):

• Index-to-wrist test: The patient performs a pointing move- ment toward the wrist of the examiner which is maintained horizontally at the height of the patient’s shoulder and at an approximate distance of 85% of the patient’s upper limb’s height.

• Index-thumb test: the patient performs repeated tapping of the index against the thumb (see decomposition of movements and the “sign of the piano”).

72.10 Clinical Examination ofLimbs Movements

Here is a list of the most common tests and maneuvers used for clinical evaluation of limb movements in cerebellar patients.

The following maneuvers are used for the clinical assessment of kinetic tremor (Manto 2002). These tests allow an evaluation of dysmetria (a target has to be reached along a trajectory).

• Finger-to-nose test: Patient (in a seated position) per-

forms movements of one upper limb with the hand ini-

tially on the ipsilateral thigh and then touching the nose

with the index.

• Finger-to-nger test: patient touches the examiner’s n-

ger, which is moved and stopped in different locations in

space.

• Knee-tibia test: This test is executed in the supine posi-

tion. The patient raises one leg and places the heel on the

contralateral knee, which is kept motionless. The patient

slides the heel down the tibial surface in a regular way

toward the ankle. The heel is then raised again up to the

resting knee.

The following maneuvers are used for the clinical assessment of postural tremor (Grimaldi 2013):

The pronation/supination movement is investigated through the pronation/supination task: patients maintains the upper limbs vertically and perform successive pronations/ supinations movements of the hands. Alternate movements of the hands can be tested also with the tapping test over the thigh, by placing the palmar and the dorsal surfaces alternately (Manto 2010).

Stewart–Holmes maneuver (1904) allows the evaluation of the lack of check. The patient is asked to perform a forceful exion of the elbow, while the examiner attempts to extend the joint. When the examiner abruptly releases the forearm, the arm exion continues unopposed and the patient is at risk of hitting him/herself in the shoulder, chest, or face. Possibility which is, of course, prevented by the examiner placing his/her other arm between the patient’s limb and face prior to abruptly releasing the patient’s limb that is being tested.

Muscle tone is assessed by passively moving the wrists, elbows, shoulders, ankles, knees, and hips of the patient and by grasping the patient’s forearm and shaking the relaxed arm.

Isometrataxia is tested by asking the patient to exert a slight and constant pinch force (using his index nger and thumb) on the lateral parts of the examiner’s thumb. The examiner feels an irregular pressure in absence of tremor of the hand (Manto 2002).

Handwriting abnormalities is assessed by asking the patient to write standard sentences, and drawing the

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