Effects of subthalamic nucleus stimulation on parkinsonian dysarthria and speech intelligibility

Abstract

Subthalamic stimulation is known to improve tremor, akinesia and rigidity in Parkinson's disease. However, other signs such as hypophonia and swallowing disorders can be relatively resistant to this technique. The effect on dysarthria remains unclear. The aim of this study was to investigate the effects of implantation of electrode and stimulation of the subthalamic nucleus (STN) on parkinsonian dysarthria. Seven patients were prospectively included. Electrodes (Medtronic) were implanted in both STN. The electrode contacts and stimulation parameters were adjusted to provide best relief of symptoms with fewest side effects. Assessment used global scales (Unified Parkinson Disease Rating Scale, UPDRS II and III), dyskinesia scale, exhaustive dysarthria assessment (bucco-facial movements, voice, articulation, intelligibility) and the 'dysarthria' item from the UPDRS III. Evaluations were performed in six conditions: before and three months after surgery (pre-op, post-op) stimulation turned off or on (off-stim, onstim), and without or with a suprathreshold levodopa dose (offdrug, on-drug). Performance level on the UPDRS III significantly improved following electrode implantation and stimulation. For dysarthria, modest beneficial effects were observed on several motor parameters, especially lip movements. Voice mildly improved, especially for the modulation in loudness and pitch. Articulation was not affected. Furthermore, intelligibility was slightly reduced in the on-stimulation condition, especially when patients received levodopa. At an individual level, negative effects on intelligibility were observed in two patients, and this was associated with a discrete increase in facial and trunk dyskinesias, but not with the electrode position or stimulation parameters. In conclusion, surgery had weak effects on dysarthria. Intelligibility can be worsened, especially in the on-drug condition. Thus, adaptation of the stimulation parameters can be difficult.

Changes induced by levodopa and subthalamic nucleus stimulation on parkinsonian speech

“…37,39,57,58 In order to understand these seemingly conflicting results, the different mechanisms illustrated in our case reports need to be considered: (1) respiratory, phonatory, and articulatory components of speech can be improved like other limb motor function (speech subcomponents are improved); (2) complex coordination of all anatomical substrates involved in speech might not be responsive to STN stimulation (intelligibility is not improved); and (3) current diffusion outside the target or target-related dyskinesias may lead to a worsening of speech intelligibility and seems to be a frequent fact (intelligibility can worsen). 36,39 In other words, item 18 of the UPDRS does not adequately evaluate the often complex speech changes that may result from L-dopa treatment or STN stimulation.…”

“…First, the UPDRS is insufficient to characterize the dysarthria of PD. Alternative perceptual scales 36,59,60 may be used to allow a more accurate description of the presenting dysarthria, including the examination of individual speech subsystems. 61,62 Second, self-evaluation of patients' speech must be taken into account, since the patient's perception of voice seems to reveal more details that can be heard by the clinician.…”

“…However, neither ablative surgeries 30,31 nor stimulation of the pallidum 32 result in any significant improvement in terms of speech. Regarding stimulation of the STN, beneficial effects on specific speech components have been observed, [33][34][35][36] such as phonation 33,34,36 and articulation. 35 No beneficial effect of STN stimulation has been reported on intelligibility.…”

Patient-Specific Model-Based Investigation of Speech Intelligibility and Movement during Deep Brain Stimulation

“…However, several studies have shown that clinically effective stimulation of the STN, with a significant improvement of the motor symptoms, may have an independent influence on speech. Along with substantially improved motor symptoms, some patients may obtain negative stimulation-induced effects on speech during STN DBS [10][11][12][13][14][15][16] . At other times, there may be no effects at all [17,18] , or sometimes positive effects on speech during clinically effective STN stimulation [19][20][21][22] .…”

Learning about language and speech from Deep Brain Stimulation

“…Different approaches have been chosen to study biolinguistic effects of DBS, comprising the assessment of language under active versus inactive stimulation, under variation of DBS parameters and before versus after surgery (Bordini, Garg, Gallagher, Bell, & Garell, 2007;Carpenter et al, 1998;D'Alatri et al, 2008;Klostermann et al, 2008;Puetzer, Barry, & Moringlane, 2008;Rousseaux et al, 2004;Saint-Cyr, Trépanier, Kumar, Lozano, & Lang, 2000;Santens, De Letter, Van Borsel, De Reuck, & Caemaert, 2003;Toernqvist, Schalén, & Rehncrona, 2005;Tripoliti, Limousin, Tisch, Borrell, & Hariz, 2006;Tripoliti et al, 2008;Wang et al, 2006). Most of these studies were performed under clinical rather than neuroscientific aspects, the major concern being the safety of the therapeutic procedure (Ardouin et al, 1999;Dujardin, Defebvre, Krystkowiak, Blond, & Destee, 2001;Saint-Cyr & Albanese, 2006;Saint-Cyr et al, 2000).…”