Cobalt-55 positron emission tomography of ipsilateral thalamic and crossedcerebellar hypometabolism after supratentorial ischaemic stroke

Cobalt-55 (Co-55) is a positron emission tomography (PET) tracer used to de monstrate brain damage, possibly associated to calcium-mediated processes. The degree of Co-55 accumulation correlates with the severity of ischaemia in stroke patients. It is still a matter of debate whether ipsilateral thal amic hypometabolism (ITH) and crossed cerebellar hypometabolism (CCH), occu rring after middle cerebral artery (MCA) infarcts, represent only a metabol ic depression of these remote regions or can lead to structural damage. The present study investigates whether an increased Co-55 influx can be demons trated with PET in ITH and CCH after MCA infarcts. About half of the patien ts with ITH and CCH had a significant degree of Co-55 uptake in, respective ly, the ipsilateral thalamus and the contralateral cerebellar hemisphere. I t was observed in patients with severe signs of stroke on admission and poo r clinical outcome, and correlated well with the degree of Co-55 influx wit hin the supratentorial infarct, The present study demonstrates that ITH and CCH after MCA infarction can represent structural damage in these remote a reas that occurs during the second week after stroke onset.