Tract-based spatial statistical analysis of diffusion tensor imaging in pediatric patients with mitochondrial disease: widespread reduction in fractional anisotropy of white matter tracts.

BACKGROUND AND PURPOSE: Often diagnosed at birth or in early childhood, mitochondrial disease presents with a variety of clinical symptoms, particularly in organs and tissues that require high energetic demand such as brain, heart, liver, and skeletal muscles. In a group of pediatric patients identified as having complex I or I/III deficits on muscle biopsy but with white matter tissue appearing qualitatively normal for age, we hypothesized that quantitative DTI analyses might unmask disturbance in microstructural integrity. MATERIALS AND METHODS: In a retrospective study, DTI and structural MR brain imaging data from 10 pediatric patients with confirmed mitochondrial disease and 10 clinical control subjects were matched for age, sex, scanning parameters, and date of examination. Paired TBSS was performed to evaluate differences in FA, MD, and the separate diffusion direction terms (λr and λa). RESULTS: In patients with mitochondrial disease, significant widespread reductions in FA values were shown in white matter tracts. Mean diffusivity values were significantly increased in patients, having a sparser distribution of affected regions compared with FA. Separate diffusion maps showed significant increase in λr and no significant changes in λa. CONCLUSIONS: Despite qualitatively normal-appearing white matter tissues, patients with complex I or I/III deficiency have widespread microstructural changes measurable with quantitative DTI.

Magnetic resonance spectroscopy in traumatic brain injury.

Magnetic resonance spectroscopy (MRS) offers a unique non-invasive approach for assessing the metabolic status of the brain in vivo and is particularly suited to studying traumatic brain injury (TBI). In particular, MRS provides a noninvasive means for quantifying such neurochemicals as N-acetylaspartate (NAA), creatine, phosphocreatine, choline, lactate, myo-inositol, glutamine, glutamate, adenosine triphosphate (ATP), and inorganic phosphate in humans following TBI and in animal models. Many of these chemicals have been shown to be perturbed following TBI. NAA, a marker of neuronal integrity, has been shown to be reduced following TBI, reflecting diffuse axonal injury or metabolic depression, and concentrations of NAA predict cognitive outcome. Elevation of choline-containing compounds indicates membrane breakdown or inflammation or both. MRS can also detect alterations in high energy phosphates reflecting the energetic abnormalities seen after TBI. Accordingly, MRS may be useful to monitor cellular response to therapeutic interventions in TBI.

Brain imaging and the effects of caffeine and nicotine.

Caffeine and nicotine are the most common psychostimulant drugs used worldwide. Structural neuroimaging findings associated with caffeine and nicotine consumption are limited and primarily reflect the putative relationship between smoking and white matter hyperintensities (WMH), a finding that warrants further appraisal of its clinical implications. The application of newer brain imaging modalities that measure subtle haemodynamic changes or tissue-based chemistry in order to better elucidate brain functional processes, including mechanisms underlying addiction to nicotine and caffeine and the brain functional consequences, provide intriguing findings. Potential influences of caffeine and nicotine on the functional contrast, or metabolic response, to neural activation also necessitates the careful appraisal of the effects that these commonly used drugs may have on the results of functional imaging.