Initial experiences with proton MR spectroscopy in treatment monitoring of mitochondrial encephalopathy

Purpose: Mitochondrial encephalopathy (ME) is a rare disorder of energy metabolism. The disease course can roughly be evaluated by clinical findings. The purpose of this study was to evaluate metabolic spectral changes using proton MR spectroscopy (MRS), and to establish a way to monitor ME by neuroimaging. Materials and Methods: Proton MRS data were retrospectively reviewed in 12 patients with muscle biopsy-confirmed ME (M: F = 7: 5, Mean age = 4.8 years). All received 1H-MRS initially and also after a ketogenic diet and mitochondrial disease treatment cocktail (follow up average was 10.2 months). Changes of Nacetylaspartate/creatine (NAA/Cr) ratio, choline/creatine (Cho/Cr) ratio, and lactate peak in basal ganglia at 1.2 ppm were evaluated before and after treatment. Findings on conventional T2 weighted MR images were also evaluated. Results: On conventional MRI, increased basal ganglia T2 signal intensity was the most common finding with ME (n = 9, 75%), followed by diffuse cerebral atrophy (n = 8, 67%), T2 hyperintense lesions at pons and midbrain (n = 4, 33%), and brain atrophy (n = 2, 17%). Lactate peak was found in 4 patients; 2 had disappearance of the peak on follow up MRS. Quantitative analysis showed relative decrease of Cho/Cr ratio on follow up MRS (p = 0.0058, paired t-test, two-tailed). There was no significant change in NAA/Cr ratio. Conclusion: MRS is a useful tool for monitoring disease progression or impro-vement in ME, and decrease or disappearance of lactate peak and reduction of Cho/Cr fraction were correlated well with improvement of clinical symptoms.