Functional transcranial Doppler sonography assessing language function in children: Validation data in neuropediatric patients

Background: There is a demand to establish complemental methods for the assessment of language lateralization in neuropediatric patients. Today's standard methods for the assessment of language lateralization, functional magnetic resonance imaging (fMRI) and the intracarotid brevital procedure (Wada test) cannot be utilized in every case. Their inherent characteristics circumvent the applicability in children with diminished capacity to cooperate. Functional transcranial Doppler sonography (fTCD) offers a tool to assess the language lateralization in a convenient and non-frightening way even in young children. Here, the first findings on a direct validation of the fTCD procedure are presented comparing fTCD with fMRI and the Wada test.

Methods: Eleven children aged 7 to 14 years (mean age 10.7 years) suffering from medically intractable focal epilepsy were prospectively enclosed. Children were selected if their language lateralization had been investigated before by fMRI or the Wada test. In fTCD, the cerebral blood flow velocities (CBFV) in the middle cerebral arteries (MCA) were continuously recorded during a resting period of 30 seconds (baseline) and a picture description task (PDT) of the same duration. Depending of the child's capacity to cooperate, up to 25 trials of the task were performed. A mean fTCD lateralization index (fTCD-LI) was calculated by a software for automated blood flow analysis (AVERAGE). The fTCD-LI indicates the relative increase of CBFV in one hemisphere compared to the contralateral side in percent during task performance relative to the baseline.

Results: There was no drop-out in the sample due to signal artefacts or an insufficient temporal bow window. On a categorial level, fTCD could confirm left-sided language lateralization in nine children as assessed by fMRI (eight cases) and the Wada test (1 case). One fTCD data set revealed no valid blood flow information about the language processing hemisphere. In one child, the lateralization procedure by fMRI or Wada-test is pending.

Conclusions: The preliminary analysis of the comparison between fTCD and fMRI showed that on a categorial level there was concordance between the two measures on language lateralization. Quantitative analysis will have to be performed to characterize the relationship between the two measures. Further data has to be collected to analyse the relationship between fTCD and the Wada test in determining language lateralization in pediatric patients.