Lactate peak on brain MRS in children with syndromic mitochondrial diseases.

BACKGROUND Brain magnetic resonance spectroscopy (MRS) has been reported to be a valuable noninvasive tool in the diagnosis of some rare diseases. In this study, our aim was to assess lactate peak on single-voxel proton MRS in children with syndromic mitochondrial diseases (MDs). METHODS From March 2004 to November 2010, 14 patients who were diagnosed with syndromic MDs underwent single-voxel proton MRS examination. The volume of interest was positioned on axial magnetic resonance imaging (MRI), and voxels were sampled using short (35 milliseconds), intermediate (144 milliseconds), or long (288 milliseconds) echo times for determination of lactate at 1.33 parts/million. RESULTS Twelve of fourteen patients (85.7%) exhibited lactate peaks on the initial single-voxel proton MRS, and all of them showed abnormal MRI findings. The correlations of lactate level in blood and lactate peak on single-voxel proton MRS were inconsistent. Among the 12 patients, eight (66.7%) had corresponding elevated levels of blood lactate, and four (33.3%) had normal levels of blood lactate. Compared with a positive rate of 85.7% for patients with lactate peaks on the single-voxel proton MRS, the positive rates for diagnosing syndromic MDs by using electron microscopic examination of muscle biopsy, oral glucose lactate stimulation test, and blood lactate level were 100%, 91.7%, and 71.4%, respectively. CONCLUSION Lactate acquisition on single-voxel proton MRS provides a noninvasive and complementary tool for the diagnosis of syndromic MDs, especially in children with abnormal signal changes on the brain MRI or a normal blood lactate level.