Language lateralization in children aged 10 to 11 years: a combined fMRI and dichotic listening study

Cortico-cortical evoked potential and language mapping: A meta-analysis

PURPOSE

The purpose of this meta-analysis was to determine the best available evidence for the use of cortico-cortical evoked potential (CCEP) for language mapping.

METHODS

PubMed/Medline/Google Scholar/Cochrane and Scopus electronic databases were searched for articles using CCEP for language mapping. CCEP data was obtained including the area of the cortex generating CCEP, resection data, and post-resection language outcomes. Inclusion criteria were clinical articles reporting the use of CCEP in language regions of the brain, reporting language outcomes and whether there was final resection of the cortex, studies with more than five patients, and studies in either English or Spanish. Review articles, systematic reviews, meta-analyses, or case series with less than five patients were excluded.

RESULTS

Seven studies with a total of 59 patients were included in this meta-analysis. The presence of CCEPs from stimulation of Broca's area or posterior perisylvian region in the resection predicts language deficits after surgery. The diagnostic odds ratio shows values greater than 0 perioperatively (0.69-5.82) and after six months (1.38-11), supporting a high likelihood of a language deficit if the presence of CCEPs from stimulation of Broca's area or posterior perisylvian region are included in the resection and vice versa. The True Positive rate varied between 0.38 and 0.87. This effect decreases after six months to 0.61 (0.30-0.86). However, the True Negative rate increased from 0.53 (0.32-0.79) to 0.71 (0.55-0.88).

CONCLUSION

This meta-analysis supports the utility of CCEP to predict the probability of having long-term language deficits after surgery. .

Cortical mapping of receptive language processing in children using navigated transcranial magnetic stimulation

We used a stepwise process to develop a new paradigm for preoperative cortical mapping of receptive language in children, using temporary functional blocking with transcranial magnetic stimulation (TMS). The method combines short sentences with a lexical decision task in which children are asked to point at a picture that fits a short sentence delivered aurally. This was first tested with 24 healthy children aged 4-16 years. Next, 75 sentences and 25 slides were presented to five healthy children in a clinical setting without TMS. Responses were registered on a separate computer, and facial expressions and hand movements were filmed for later offline review. Technical adjustments were made to combine these elements with the existing TMS equipment. The audio-recorded sentences were presented before the visual stimuli. Sentence lists were constructed to avoid similar stimuli in a row. Two different baseline lists were used before the TMS registration; the second baseline resulted in faster responses and was chosen as the reference for possible response delays induced by TMS. Protocols for offline reviews were constructed. No response, incorrect response, self-correction, delayed response, and perseveration were considered clear stimulation effects, while poor attention, discomfort, and other events were regarded as unclear. Finally, three children (6:2, 14:0, 14:10 years) with epilepsy and expected to undergo neurosurgery were assessed using TMS (left hemisphere in one; both hemispheres in the other two). In the two assessed bilaterally, TMS effects indicated bilateral language processing. Delayed response was the most common error. This is a first attempt to develop a new TMS paradigm for receptive language mapping, and further evaluation is suggested.

Clinical application of advanced MR methods in children: points to consider

The application of both functional MRI and diffusion MR tractography prior to a neurosurgical operation is well established in adults, but less so in children, for several reasons. For this review, we have identified several aspects (task design, subject preparation, actual scanning session, data processing, interpretation of results, and decision-making) where pediatric peculiarities should be taken into account. Further, we not only systematically identify common issues, but also provide solutions, based on our experience as well as a review of the pertinent literature. The aim is to provide the clinician as well as the imaging scientist with information that helps to plan, conduct, and interpret such a clinically-indicated exam in a way that maximizes benefit for, and minimizes the burden on the individual child.

Navigated transcranial magnetic stimulation for preoperative cortical mapping of expressive language in children: Development of a method

We adjusted an object-naming task with repetitive navigated transcranial magnetic stimulation (rnTMS) originally developed for preoperative cortical language mapping in adults in order for it to be used in children. Two series of pictures were chosen for children above and below 10 years of age, respectively. Firstly, the series of pictures and the preferred speed of presentation were assessed for their applicability in children of different ages and abilities. Secondly, these series were used with rnTMS preoperatively in five children with epilepsy. Naming errors induced by the stimulation comprised no response, delayed response, semantic error, phonological error, and self-correction. Language laterality was compared with the results of a dichotic listening test and with neuropsychological tests with respect to general laterality, and general language abilities were considered with respect to the results of stimulation. One participant had below normal general language abilities, two had below-normal rapid naming, and three had slow and indistinct articulation. Laterality was only clear in two of the participants. All children required breaks of various durations during the process, and individual adjustments of the interpicture interval and other stimulation parameters were also made. We conclude that, after adjustment, rnTMS combined with an object-naming task can be useful for preoperative language mapping in children.

Variability in lateralised blood flow response to language is associated with language development in children aged 1-5 years

The developmental trajectory of language lateralisation over the preschool years is unclear. We explored the relationship between lateralisation of cerebral blood flow velocity response to object naming and cognitive performance in children aged 1-5 years. Functional transcranial Doppler ultrasound was used to record blood flow velocity bilaterally from middle cerebral arteries during a naming task in 58 children (59% male). At group level, the Lateralisation Index (LI) revealed a greater relative increase in cerebral blood flow velocity within the left as compared to right middle cerebral artery. After controlling for maternal IQ, left-lateralised children displayed lower expressive language scores compared to right- and bi-lateralised children, and reduced variability in LI. Supporting this, greater variability in lateralised response, rather than mean response, was indicative of greater expressive language ability. Findings suggest that a delayed establishment of language specialisation is associated with better language ability in the preschool years.

Presurgical language lateralization assessment by fMRI and dichotic listening of pediatric patients with intractable epilepsy

Objective

The aim of this study was to evaluate the clinical use of a method to assess hemispheric language dominance in pediatric candidates for epilepsy surgery. The method is designed for patients but has previously been evaluated with healthy children.

Methods

Nineteen patients, 8–18 years old, with intractable epilepsy and candidates for epilepsy surgery were assessed. The assessment consisted of two functional MRI protocols (fMRI) intended to target frontal and posterior language networks respectively, and a behavioral dichotic listening task (DL). Regional left/right indices for each fMRI task from the frontal, temporal and parietal lobe were calculated, and left/right indices of the DL task were calculated from responses of consonants and vowels, separately. A quantitative analysis of each patient's data set was done in two steps based on clearly specified criteria. First, fMRI data and DL data were analyzed separately to determine whether the result from each of these assessments were conclusive or not. Thereafter, the results from the individual assessments were combined to reach a final conclusion regarding hemispheric language dominance.

Results

For 14 of the 19 subjects (74%) a conclusion was reached about their hemispheric language dominance. Nine subjects had a left-sided and five subjects had a right-sided hemispheric dominance. In three cases (16%) DL provided critical data to reach a conclusive result.

Conclusions

The success rate of conclusive language lateralization assessments in this study is comparable to reported rates on similar challenged pediatric populations. The results are promising but data from more patients than in the present study will be required to conclude on the clinical applicability of the method.

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Language lateralization was assessed in 19 pediatric candidates for epilepsy surgery.

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The assessment involved fMRI and an independent behavioral measure; dichotic listening.

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A two step analysis was employed combining fMRI and dichotic listening data.

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For 74% of the subjects a conclusion was reached about hemispheric language dominance.

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The rate of conclusive assessments in this study is comparable to reported rates on similar challenged pediatric populations.