Directions For Future Research

The Parkinson's-Reversing Breakthrough

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Directions for future research point strongly toward the need to develop both specific and combined behavioral, pharmacotherapeutic, or neurostimulation interventions that might slow, arrest, or even reverse the progression of the speech and language manifestations of atypical parkinsonian disorders (see Table 2 for summary). For example, cholinergic stimulation using centrally active cholinesterase inhibitors may be beneficial in improving cognitive or linguistic performance in the early stages of disease progression. Transcranial magnetic stimulation (TMS) can also be used to investigate the excitability of motor cortices in neurodegenerative diseases, thus providing important information having pathophysiological and clinical relevance. For example, TMS can be used to study the effects of drugs and surgery thus introducing the possibility of monitoring the action of treatment of movement disorders (including dysarthria) on cortical excitability (79). As medical treatments become available for atypical parkinsonian conditions, their effects on speech and language abilities need to be established. Relative to motor speech abilities, for example, medical interventions that may improve limb motor deficits may or may not have a positive effect on speech.

The epidemiology of speech and language disorders must also evolve to a more accurate science. This calls for the development of explicit clinical diagnostic criteria for sensitively and differentially characterizing the features of these disorders and the relative influence of each on communication ability. Currently, comparisons across natural history studies suffer from variability in their assessment methods and descriptions of the various features that constitute dysarthria, apraxia, or aphasia. A second limitation across studies is small sample size. Therefore, multi-institution studies, using consistent and agreed-upon taxonomies in characterizing speech and language functions, and consistent methods in assessing these functions, could increase our understanding of the pathogeneses of these diseases. A solid foundation for such a taxonomy for speech functions has already been established by the extensive work of Darley, Aronson, and Brown (19); any effort to develop explicit criteria for differentiating the dysarthrias should begin with their seminal work.

The efficacy of various approaches to management of communication disorders, including how approaches to management may be influenced by some of the unique characteristics of these diseases (e.g., limb apraxia, visual deficits, deficits of attention) will need to be determined. Also to be determined are the best way to stage management during the course of these conditions. For example, when should management attempt to improve impairment (e.g., LSVT) vs work to compensate for deficits?

Of future interest will also be the combined effects of disease progression and aging, with a normative databank created against which to compare various dimensions of performance. These comparisons may help to parse out the effects of the disease thus increasing clinical management precision. Neuroimaging studies should investigate the effects of neuronal loss from the perspective of studying neural networks and functional connectivity. The methods of probabilistic computational mapping and structural equation modeling will assist with hypothesis-driven studies that can eluci-

Table 2

Summary of Future Research Directions

Study Type

Example

Drug Effect Neurostimulation Medical Intervention Epidemiology

Treatment Efficacy

Natural History Neuroimaging

Genetic

Cholinergic stimulation to improve cognitive and linguistic skills in the early stages of disease progression.

TMS to investigate the effects of surgery and drugs on cortical excitability and their relationship to changes in speech.

Nerve growth implantation and relative effects on motor speech abilities.

Development of explicit clinical diagnostic criteria and an agreed-upon taxonomy for characterizing speech and language disor-

Conventional and new behavioral approaches to speech or language management as influenced by unique disease characteristics (e.g., limb apraxia, visual deficits, attention deficit).

Development of normative databank to determined combined effects of disease progression and aging.

Investigations of the effects of neuronal loss from the perspective of functional connectivity, and their relationships with specific speech and language disturbances.

Identification of gene abnormalities to assist in early diagnosis and increase the effectiveness of preventive therapies. Establish the relationships between specific genetic findings and speech and language manifestations.

date links between neural breakdowns and behavioral effects (8). Finally genetic studies designed to identify gene abnormalities may assist in reducing the incidence and prevalence of atypical parkinsonian disorders and can assist in their early diagnosis and increase the effectiveness of preventive therapies.

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