Catharine M. Pettigrew

Correlation of Quantitative EEG in Acute Ischemic Stroke With 30-Day NIHSS Score Comparison With Diffusion and Perfusion MRI

Background and Purpose— Magnetic resonance imaging (MRI) methods such as diffusion- (DWI) and perfusion-weighted (PWI) imaging have been widely studied as surrogate markers to monitor stroke evolution and predict clinical outcome. The utility of quantitative electroencephalography (qEEG) as such a marker in acute stroke has not been intensively studied. The aim of the present study was to correlate ischemic cortical stroke patients’ clinical outcomes with acute qEEG, DWI, and PWI data. Materials and Methods— DWI and PWI data were acquired from 11 patients within 7 and 16 hours after onset of symptoms. Sixty-four channel EEG data were obtained within 2 hours after the initial MRI scan and 1 hour before the second MRI scan. The acute delta change index (aDCI), a measure of the rate of change of average scalp delta power, was compared with the National Institutes of Health Stroke Scale scores (NIHSSS) at 30 days, as were MRI lesion volumes. Results— The aDCI was significantly correlated with the 30-day NIHSSS, as was the initial mean transit time (MTT) abnormality volume (&rgr;=0.80, P <0.01 and &rgr;=0.79, P <0.01, respectively). Modest correlations were obtained between the 15-hour DWI lesion volume and both the aDCI and 30-day NIHSSS (&rgr;=0.62, P <0.05 and &rgr;=0.73, P <0.05, respectively). Conclusions— In this small sample the significant correlation between 30-day NIHSSS and acute qEEG data (aDCI) was equivalent to that between the former and MTT abnormality volume. Both were greater than the modest correlation between acute DWI lesion volume and 30-day NIHSSS. These preliminary results indicate that acute qEEG data might be used to monitor and predict stroke evolution.

The barriers perceived to prevent the successful implementation of evidence‐based practice by speech and language therapists

BACKGROUND There is currently a paucity of research investigating what speech and language therapists, in particular, perceive are the greatest barriers to implementing evidence-based practice. AIMS The purpose of this study was to investigate the perceived barriers that are faced by speech and language therapists in southern Ireland when attempting to implement evidence-based practice. METHODS & PROCEDURES A 34-item questionnaire was sent to 39 therapists working in several counties in southern Ireland. The survey received an 82.1% (n = 32) response rate. OUTCOMES & RESULTS The results of the study indicated that certain barriers are perceived to prevent evidence-based practice being implemented successfully. The most significant barrier affecting evidence-based practice implementation was reported to be a lack of time to read research (71.9%). Additional barriers that were found to be the most significant were the research having methodological inadequacies (62.5%) and insufficient time to implement new ideas (59.4%). Other important factors identified as being significant barriers to the implementation of evidence-based practice were those associated with the quality and presentation of the research, workplace setting, and lack of skills of the therapist. Associations between specific barriers and workplace setting or grade were also investigated. Some possible reasons for these barriers and the implications for clinical practice are also discussed. CONCLUSIONS & IMPLICATIONS This small study suggests that therapists agreed that evidence-based practice is essential to the practice of speech and language therapy. There are, however, barriers in place that are perceived to prevent its successful implementation. It is hoped that because these barriers have been identified, individual clinicians and organizations can be proactive in aiming to provide an evidence-based service to their clients.

Automatic auditory processing of English words as indexed by the mismatch negativity, using a multiple deviant paradigm

Objective: The aim of this study was to investigate mismatch negativity (MMN) responses to a variety of speech stimuli (/de:/, /ge:/, /deI/ “day”, and /geI/ “gay”) in a multiple deviant paradigm. It was hypothesized that all speech stimulus contrasts in the multiple deviant paradigm, including the fine acoustic speech contrast [d/g], would elicit robust MMN responses and that consonant vowel (CV) real word deviants (e.g., “day” and “gay”) would elicit larger MMN responses than CV nonword deviants (e.g., “de” and “ge”) within and across experimental contrasts. Design: Ten healthy, right-handed, native English–speaking adults (23.4 ± 2.27 yr) with normal hearing were presented with 12 blocks of stimuli, using a multiple deviant oddball paradigm. Each of the four speech stimuli were presented as standards (p = 0.7) in three blocks, with the remaining stimuli acting as deviants (p = 0.1 each). Subjects were also presented with the same stimuli in a behavioral discrimination task. Results: MMN responses to the fine acoustic speech contrast [d/g] (e.g., “de” versus “ge”, “day” versus “gay”) did not reach significance. However, a significant and larger MMN response was obtained at an earlier latency to the real word deviants among nonword standards with the same initial consonant (i.e., de→day, ge→gay) when compared with the responses to nonword deviants among word standards (day→de, gay→ge). Conclusions: The results showed that MMN responses could be elicited by speech stimuli with large, single acoustic deviances, within a multiple deviant paradigm design. This result has positive clinical implications for the testing of subjects who may only tolerate short testing sessions (e.g., pathological populations) in that responses to a wider range of speech stimuli may be recorded without necessarily having to increase session length. The results also demonstrated that MMN responses were elicited by large, single acoustic deviances but not fine acoustic deviances within the speech stimuli. The poor results for the fine acoustic deviances support previous studies that have used single contrast paradigms and found that when carefully controlled methodological designs and strict methods of analysis are applied, robust responses to fine-grained CV syllable contrasts may be difficult to obtain. The enhanced MMN observed in response to the real word deviants among nonword standards may provide further evidence for the presence of long-term neural traces for words in the brain, however possible contextual effects limit the interpretation of these data. Further research is needed to investigate the ability of the MMN response to accurately reflect speech sounds with fine acoustic contrasts, as well as the ability of the MMN to reflect neural traces for words in the brain, before it can be reliably used as a clinical tool in the investigation of spoken word processing in pathological populations.

The Mismatch Negativity (MMN) Response to Complex Tones and Spoken Words in Individuals with Aphasia

Background: The mismatch negativity (MMN) is a fronto-centrally distributed event-related potential (ERP) that is elicited by any discriminable auditory change. It is an ideal neurophysiological tool for measuring the auditory processing skills of individuals with aphasia because it can be elicited even in the absence of attention. Previous MMN studies have shown that acoustic processing of tone or pitch deviance is relatively preserved in aphasia, whereas the basic acoustic processing of speech stimuli can be impaired (e.g., auditory discrimination). However, no MMN study has yet investigated the higher levels of auditory processing, such as language-specific phonological and/or lexical processing, in individuals with aphasia. Aims: The aim of the current study was to investigate the MMN responses of normal and language-disordered subjects to tone stimuli and speech stimuli that incorporate the basic auditory processing (acoustic, acoustic-phonetic) levels of non-speech and speech sound processing, and also the language-specific phonological and lexical levels of spoken word processing. Furthermore, this study aimed to correlate the aphasic MMN data with language performance on a variety of tasks specifically targeted at the different levels of spoken word processing. Methods & Procedures: Six adults with aphasia (71.7 years ±3.0) and six healthy age-, gender-, and education-matched controls (72.2 years ±5.4) participated in the study. All subjects were right-handed and native speakers of English. Each subject was presented with complex harmonic tone stimuli, differing in pitch or duration, and consonant-vowel (CV) speech stimuli (non-word /de:/ versus real word /deI/). The probability of the deviant for each tone or speech contrast was 10%. The subjects were also presented with the same stimuli in behavioural discrimination tasks, and were administered a language assessment battery to measure their auditory comprehension skills. Outcomes & Results: The aphasic subjects demonstrated attenuated MMN responses to complex tone duration deviance and to speech stimuli (words and non-words), and their responses to the frequency, duration, and real word deviant stimuli were found to strongly correlate with performance on the auditory comprehension section of the Western Aphasia Battery (WAB). Furthermore, deficits in attentional lexical decision skills demonstrated by the aphasic subjects correlated with a word-related enhancement demonstrated during the automatic MMN paradigm, providing evidence to support the “word advantage effect”, thought to reflect the activation of language-specific memory traces in the brain for words. Conclusions: These results indicate that the MMN may be used as a technique for investigating general and more specific auditory comprehension skills of individuals with aphasia, using speech and/or non-speech stimuli, independent of the individuals attention. The combined use of the objective MMN technique and current clinical language assessments may result in improved rehabilitative management of aphasic individuals.

Dysphagia Evaluation Practices of Speech and Language Therapists in Ireland: Clinical Assessment and Instrumental Examination Decision-Making

The purpose of this study was to investigate clinical assessment practices and instrumental examination decision-making by speech and language therapists (SLTs) in Ireland. A 21-question survey (including patient scenarios) was sent to 480 SLTs in Ireland. A total of 261 completed surveys were returned (54%), providing demographic information on SLTs currently working in Ireland and their services. Of these 261 surveys, 70 provided the data for the study, focusing on SLTs currently working in dysphagia, with adults/seniors at least some of the time. The results also showed clinician variability regarding which components are included in a bedside clinical examination of swallowing, with a high degree of consistency for only 11 of the 20 components. Clinicians agreed in their instrumental vs. noninstrumental evaluation recommendations for two of the six patient scenarios, with wide variability in clinical decision-making. Possible influences on clinical decision-making are discussed in relation to the findings of similar previous studies, as well as the current status and future needs of dysphagia training and services in Ireland.

The relationship between the mismatch negativity (MMN) and psycholinguistic models of spoken word processing

Background: The results from previous studies have indicated that a pre‐attentive component of the event‐related potential (ERP), the mismatch negativity (MMN), may be an objective measure of the automatic auditory processing of phonemes and words. Aims: This article reviews the relationship between the MMN data and psycholinguistic models of spoken word processing, in order to determine whether the MMN may be used to objectively pinpoint spoken word processing deficits in individuals with aphasia. Main Contribution: This article outlines the ways in which the MMN data support psycholinguistic models currently used in the clinical management of aphasic individuals. Furthermore, the cell assembly model of the neurophysiological mechanisms underlying spoken word processing is discussed in relation to the MMN and psycholinguistic models. Conclusions: The MMN data support current theoretical psycholinguistic and neurophysiological models of spoken word processing. Future MMN studies that include normal and aphasic populations will further elucidate the role that the MMN may play in the clinical management of aphasic individuals.