Speech and language therapy for dysarthria in Parkinson's disease: a comparison of techniques

Background

Dysarthria is a common manifestation of Parkinson's disease that increases in frequency and intensity with the progress of the disease (Streifler 1984). Up to 20% of Parkinsonian patients are referred for speech and language therapy (S&LT), its aim being to improve the intelligibility of the patient's speech.

Objectives

To compare the efficacy and effectiveness of novel S&LT techniques versus standard S&LT to treat dysarthria in patients with Parkinson's disease.
To compare the efficacy and effectiveness of one S&LT technique versus a second form of S&LT to treat Parkinsonian dysarthria.

Search strategy

Relevant trials were identified by electronic searches of MEDLINE, EMBASE, CINAHL, ISI-SCI, AMED, MANTIS, REHABDATA, REHADAT, GEROLIT, Pascal, LILACS, MedCarib, JICST-EPlus, AIM, IMEMR, SIGLE, ISI-ISTP, DISSABS, Conference Papers Index, Aslib Index to Theses, the Cochrane Controlled Trials Register, the CentreWatch Clinical Trials listing service, the metaRegister of Controlled Trials, ClinicalTrials.gov, CRISP, PEDro, NIDRR and NRR; and examination of the reference lists of identified studies and other reviews.

Selection criteria

Only randomised controlled trials (RCT) were included.

Data collection and analysis

Data was abstracted independently by KD and RW and differences settled by discussion.

Main results

Only two trials were identified with only 71 patients. The method of randomisation was good in only one trial and the concealment of allocation was inadequate in both trials. These methodological problems could potentially lead to bias from a number of sources.

The methods used in the two studies varied so much that meta-analysis of the results was not possible. Scott 83 compared prosodic exercises with visual cues with prosodic exercises alone (See Glossary: Table 01). The authors examined prosody and intelligibility as outcome measures immediately after therapy. Ramig 95 compared the Lee Silverman Voice Therapy (LSVT) which emphasises increased vocal effort, with respiratory therapy which aimed to increase respiratory muscle activity. Ramig 95 examined a wide range of vocal characteristics, activities of daily living affected by speech, depression and the carer's impressions of the patient's speech quality. Some of these outcomes were measured up to 24 months after the end of the therapy. However, in neither study were changes in outcomes due to 'Therapy A' compared with the changes due to 'Therapy B' statistically. Therefore no comment on the comparative efficacy of these types of speech and language therapy can be made.

Authors' conclusions

Considering the methodological flaws in both of these studies, the small number of patients examined, and the possibility of publication bias, there is insufficient evidence to support or refute the efficacy of any given form of S&LT over another to treat dysarthria in Parkinson's disease.

Given the lack of evidence from RCTs to support or refute the efficacy of S&LT in Parkinson's disease (see Cochrane review 'Speech and Language therapy for Dysarthria in Patients with Parkinson's Disease'), the consensus as to what is considered 'best-practice' S&LT must be proved first through a large well-designed placebo-controlled randomised trial before examining variations in S&LT methodology. The design of these trials should minimise bias and be reported fully using CONSORT guidelines (CONSORT 1996). Outcome measures with particular relevance to patients, their carers, physicians and speech and language therapists should be chosen and the patients followed for at least 6 months to determine the duration of any improvement.