DEFINING THE MACROSCOPIC AND MICROSCOPIC FINDINGS OF EXPERIMENTAL FOCAL BRAIN ISCHEMIA IN RATS FROM A FORENSIC SCIENTIST’S POINT OF VIEW

Tatlisumak E , Inan S , Asirdizer M , Apaydin N,

Hayretdag C, Kose C, Tekdemir I.

Xth National Anatomy Congress with International Participation. September 6-10,2006, Bodrum - Turkey. Neuroanatomy. 2006; 5 (Suppl. 2): 4.

ABSTRACT

Stroke is the third leading cause of death in the Western world and approximately 10 % of all deaths occur as a result of stroke in the world. Determination of the time schedule of the occurrence of pathologic events in a stroke patient is invaluable for a forensic specialist. The aim of this study was to define the schedule of macroscopic and microscopic changes occurred in an experimental animal model of permanent focal ischemia. Male Wistar rats weighing 250- 350 g were used in this study. Animals were anesthetized with ketamine and medetomidine. Permanent focal ischemia was applied by the suture occlusion method. The animals were divided in to 7 experimental groups (n= 4) with time schedules including 1.5, 3, 6, 12, 24 and 72 hours and the sham. Brains were harvested at the end of the determined time schedule. Harvested brains which had visible well-demarcated infarcts were used for the study. Images of the brains were recorded. Later, brain samples were fixed in formalin 10 % solutions for 24 hours and routine paraffin procedure was applied. 5 µm sections of frontoparietal cortex were prepared and stained with hematoxilen-eosin (H.E.) and evaluated under light microscope.

Lesions were observed as pink areas in frontoparietal cortex. The impression of the authors by the evaluation of the brains with naked-eye was the enlargement and the darkening of the infarct area until 24 hour period but there were great variations among the animals for proposing an accurate definition of time from the area and colour of the infarct. At 72 hour the infact was seen pale. Edema couldn’t be observed in 1.5 hour and 72 hour periods with naked eye. It was apparent at 6, 12 and 24 hours. Maximum edema was at 24 hour according to the authors’ impression.

Microscopically, the infarct core was evaluated in the cortex. Layers III to V were affected prominently in all animals. Two types of neurons with swelling of the cytoplasm and shrinkage of the cytoplasm and nucleus were observed together at 1.5 hour. Swelling of glial cells and astrocytic processes were other observations in this time point. Triangulations of neurons were observed at 3 hour in addition to the previous findings. Pyknosis and karyorhexis of the nucleus of some neurons were discriminated at 6 hour. There was a diffuse pallor of the eosinophilic background. A few polymorphonuclear leukocytes (PNL) infiltrating the area was present. Neurons with eosinophilic cytoplasm and pyknotic nucleus (red neurons) appeared at 12 hour. Axonal swelling and the prominent increase in the the number of PNLs was observed. The number of neurons was decreased and red neurons were increased prominently at 24 hour. Vacuolation of dendrites were observed. PNLs were more abundant in the region. Astrocytes were increased. Pannecrosis was observed at 72 hour. Red neurons were still present. The number of astrocytes was prominently increased. Histology of the brain tissues of sham operated animals were evaluated as normal.

The results of this study provide clues which can be used by a forensic scientist for the determination of the time of death of stroke. 

Key words: forensic pathology, experimental focal brain ischemia, rats.