Postmortem metabolic and morphologic alterations of the dog brain thalamus with use of in vivo 1H magnetic resonance spectroscopy and electron microscopy.
RATIONALE AND OBJECTIVES: To investigate postmortem metabolic and morphologic alterations in the dog brain thalamus and to contribute diagnostic aids in medicolegal science. METHODS: A homogeneous group of 17 dogs was used for in vivo 1H magnetic resonance (MR) spectroscopy and electron microscopic studies, which were performed under intravenous and intramuscular anesthesia before and after the dogs were killed. All 1H MR spectroscopy and electron microscopy examinations were performed on a 1.5 T MR imaging/MR spectroscopy system using a stimulated-echo acquisition mode pulse sequence and an electron microscope, respectively. RESULTS: The lactate resonance signal, which could be used as a criterion for tissue survival, appeared during the entire postmortem period. The lactate: creatine ratio significantly increased in the early postmortem metabolic process. The inositol: creatine ratio showed a mild gradual increase. However, the N-acetyl-aspartate: creatine and choline/creatine ratios generally were unchanged. The decomposition of proton metabolites was observed in the MR spectrum 48 hours postmortem. In the postmortem period, high power field (x10,000) electron microscopic results showed significant morphologic alterations of the thalamus, revealing nuclear pyknosis and perikaryal condensation, cytoplasmic vacuoles, clumping of nuclear chromatin, and destruction of cellular organelles and nuclear membrane. CONCLUSIONS: Results suggest that the combination of 1H MR spectroscopy and electron microscopy may simultaneously provide good quality metabolic and morphologic information of cerebral tissue in the field of thanatochronology.