In vivo MRI assessment of permanent middle cerebral artery occlusion by electrocoagulation: pitfalls of procedure

Investigating cerebral ischemia requires animal models relevant to human stroke. A precise knowledge of the strengths and shortcomings of available models is mandatory for effective research in neuroprotection [1,2]. Initially described in the rat [3] and subsequently adapted in mice [4], permanent middle cerebral artery (MCA) occlusion (pMCAO) by electrocoagulation is a widely used model of focal ischemia. Invasive surgical procedures are required: temporal muscle dissection, in some cases by electrical cauterization [5,6], subtemporal craniotomy and MCA electrocoagulation. This model, by interrupting blood flow at the level of the parietal cerebral artery branch of the MCA (distal occlusion), has the advantage of producing smaller, cortical-restricted, more reproducible and better-tolerated infarcts compared to suture MCAO, which endoluminal occluder is situated in the internal artery, at the birth of the MCA (proximal occlusion) and gives rise to extensive cortico-striatal infarcts [7,8]. It may however induce traumatic brain damage.To our knowledge, sham-operated animals have only been studied using immunohistology at the subacute stage of cerebral ischemia. Early monitoring with magnetic resonance imaging (MRI) may facilitate in vivo identification of traumatic brain injury during pMCAO.We designed an analytic appraisal of pMCAO procedure which included two methods of temporal muscle dissection: cauterization and blade incision. After intraperitoneal anesthesia with 12 mg/Kg xylazine and 90 mg/Kg ketamine, 22 male Swiss mice (28-30 g, Charles River, France) were allotted as follows:？ group A (n = 6): temporal muscle cauterization without craniotomy nor MCA occlusion;？ group B (n = 4): temporal muscle incision without craniotomy nor MCA occlusion;？ group C (n = 4): temporal muscle incision followed by craniotomy without MCA occlusion;？ group D (n = 6): temporal muscle incision followed by craniotomy and MCA electrocoagulation;？ group E (n = 2): temporal muscle c