Brain SPECT scans: A promising research tool for specific learning disability.

Specific learning disability (SpLD) is defined as the performance that children have with difficulties in efficient reading (“dyslexia” or “SpLD1”), writing (“dysgraphia” or “SpLD2”), and/or performing mathematical calculations (“dyscalculia” or “SpLD3”), despite conventional instruction, normal intelligence, proper motivation, intact senses, and adequate sociocultural opportunity.[1] SpLD makes children fail to achieve school grades at a good level and also hinders peer and family relationships as well as social interactions.[2] The longer the children suffer from SpLD, the harder it becomes to overcome and the less likely they can succeed academically. Therefore, it is important to identify SpLD as early as possible.

Because there is no single diagnostic test for SpLD, the method of diagnosing SpLD involves a multidisciplinary analysis, including psychoeducational testing, such as WISC-R and Wechsler Intelligence Scale for Children-Third Edition (WISC-III),[34] and educational testing in specific areas of learning, reading comprehension, oral expression, and listening comprehension, such as Woodcock-Johnson test for achievement/curriculum-based educational test.[5] Conventional computed tomography and magnetic resonance imaging cannot demonstrate visible lesions in these patients under most circumstances. A functional magnetic resonance imaging (fMRI) study of the brain has found that there might be reduced blood flow in the left hemisphere of dyslexic adults and children during reading.[6] Brain single-photon emission computed tomography (SPECT) is a noninvasive and reliable method to assess brain function by measuring regional cerebral blood flow.[7] For instance, Arduini et al.[8] and Chiron et al.[9] performed brain SPECT scans in students with dyslexia and dystrophia, and showed hypoperfusion on visual analysis in areas involved in the reading and writing processes. Moreover, measurements of regional cerebral blood flow during the dichotic task (left stimulation) confirmed that specialization of the left hemisphere was impaired. In conclusion, SPECT could be considered as a promising research tool in the assessment of young students with SpLD.

For the first time, the present study by Karande et al.[10] has attempted a quantitative assessment of brain perfusion in such students. Furthermore, the authors performed brain SPECT scans not only at rest but after stimulation by learning as well.[10] Visual analysis showed reduction of regional blood flow both in the “baseline scans” and the “test scans” in the temporoparietal areas of all nine students. However, when they attempted to compare the data using NeuroGam™ software, there was no statistically significant change in regional perfusion in the temporoparietal areas.[10] Ways for improving on this study include increasing the number of study subjects and locating as many detailed lesions of SpLD as possible. In addition, another fMRI brain study has indicated that this disorder may be caused by specific deficits or atypical asymmetries in the left posterior superior temporal gyrus and left supramarginal gyrus.[11] If we could analyze the SPECT scans combined with fMRI to get more accurate estimations, better results might be achieved.

In conclusion, SPECT scans can be considered reliable to identify changes in regional brain perfusion in SpLD. Future researchers should recruit a larger number of students with SpLD to validate the current findings. Furthermore, investigations using SPECT combined with fMRI may help us to better understand the complex etiology of SpLD.