External Carotid Artery Territory Ischemia Impairs Outcome in the Endovascular Filament Model of Middle Cerebral Artery Occlusion in Rats

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Abstract
Background and Purpose— Middle cerebral artery occlusion (MCAO) by an intraluminal filament is a widely accepted animal model of focal cerebral ischemia. In this procedure, cutting of the external carotid artery (ECA) is a prerequisite for thread insertion. However, the implications of ECA transsection have not yet been described. Methods— After 90 minutes of filament MCAO or sham surgery, rats were evaluated for up to 14 days in terms of body weight development, core temperature, and motor performance. Repeated in vivo MRI of the head and neck was performed for quantification of brain edema and infarct volume. The temporal muscles were histologically analyzed postmortem. Results— In 47% of all rats, ischemic tissue damage to the ipsilateral ECA area, including temporal, lingual, and pharyngeal musculature, was detectable by MRI. Histology of temporal muscles confirmed acute ischemic myopathy. Animals with ECA territory ischemia (ECA-I) showed delayed body weight development and poorer recovery of motor function. There was no difference in the extent of brain edema or final cerebral lesion size between ECA-I–affected and unaffected rats. Conclusions— Filament MCAO was complicated by the consequences of ECA ischemia in approximately half of all rats. Impaired mastication and swallowing functions restricted ingestion and resulted in postsurgical body weight loss and worse motor performance. Impaired cerebral microperfusion resulting from dehydration and reduced spontaneous motor activity resulting from reduced food and water uptake might have contributed to poorer neurological recovery in ECA ischemic rats. Thus, adverse effects caused by extracerebral ischemia with potential impact on outcome have to be considered in this stroke model.