Clinical study
Volumetric analysis of a specific language region – the planum temporale

https://doi.org/10.1016/j.jocn.2005.03.026Get rights and content

Abstract

Planum temporale volumes were determined for 42 control children (ages 4.2–15.7 years) using magnetic resonance imaging. The mean left planum temporale volume was 2729 mm3 (SD = 567) and the mean right planum temporale volume was 2758 mm3 (SD = 546). No significant hemispheric asymmetry was demonstrated. Analysis of co-variance (ANCOVA) showed that the absolute and proportional planum temporale volumes were not significantly associated with age or gender. We also demonstrated a reproducible method for planum temporale volume measurement by acquiring images in the coronal plane and then visualising the sagittal plane to improve accuracy for the posterior border.

Introduction

The planum temporale (PT) represents a triangular structure on the upper surface of the superior temporal gyrus within the sylvian fissure.1 Geschwind and Levitsky2 examined 100 post-mortem brains and noted a longer left PT in 65%. They proposed that the significantly larger left PT may be compatible with functional asymmetry. In the language-dominant hemisphere, the PT coincides with part of Wernicke’s area and functional neuroimaging has demonstrated a role in phonological processing.3 The region is represented by Brodmann area 42.4 Cytoarchitecturally it is believed to consist of secondary auditory cortex.5 Little is known about the morphological changes in the PT that must occur with cognitive and behavioural development.

Initial MR studies of length and surface area demonstrated leftward asymmetry.[6], [7], [8], [9], [10], [11], [12], [13] MRI volume studies of this region[14], [15], [16], [17], [18], [19], [20], [21], [22] have demonstrated variable results in average PT volumes (900 mm3 to 5650 m3) as well as hemispheric asymmetry for control subjects. Differing techniques of volumetric analysis, image acquisition, slice thickness and border definitions were observed in these studies.

In this study, we propose a reproducible method for image acquisition and measurement of PT volumes as well as measuring the PT volume in healthy children.

Section snippets

Materials and methods

Forty-two healthy children (23 males; 19 females; age range, 4.2–15.7 years) were recruited and consent was obtained from parents after standard ethics procedures. Handedness details were obtained for all children. Trained MRI technicians scanned the subjects on a Philips ACS-NT 1.5T machine (Children’s Hospital at Westmead, Sydney) (Philips Medical Systems Australia, North Ryde, NSW, Australia) with the head in the neutral position inside the head coil. A head cradle inside the head coil with

Results

Statistical analyses were performed using the statistical software package SPSS for Windows (Version 10, SPSS Inc., Chicago, IL). The paired t-test was used to compare coronal and sagittal volumes obtained in the preliminary 10 controls. Measurements of the PT volumes for a given patient on two separate occasions, by the same investigator, were used to assess reproducibility of the technique. Pearson’s correlation coefficient was used to quantify the association between the first and second

Methodology

Previous investigators have suggested measurements of the PT were best performed in the coronal plane as it provided direct assessment of the full depth of the sylvian fissure.5 The limitation however, lies posteriorly when the PT angles upward.33 This can be appreciated in the upper images of Fig. 2, Fig. 3. The limitation of the sagittal plane is most laterally when posterior tributaries of the sylvian fissure appear to be a continuation of the PT.33 This is demonstrated in Fig. 4, Fig. 5.

Acknowledgements

The authors would like to thank Mr Allan Kemp and Professor John Morris for their assistance in this study. Dr L. Vadlamudi was the Glaxo-Wellcome Epilepsy Society of Australia Fellow.

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