MALCOLM: Identifying a maximum core lesion threshold in patients undergoing endovascular therapy
Large infarct size has traditionally been a relative contraindication to endovascular therapy; previous studies have reported poorer outcomes in stroke patients with large lesion size and patients with large infarct size have typically been excluded from clinical studies. Recently, Gilgen, et al. published a study in Stroke which suggested that treating large DWI lesions with thrombectomy still confer a benefit, especially in younger patients; however, what still remains unclear is how large is too large. Here, the authors aimed to determine whether the admission infarct volume is predictive of the final infarct volume and to establish the maximum admission core lesion compatible with favorable outcome (MALCOLM), above which the probability of modified Rankin scale (mRS) 0-2 is < 10% for use as a selection tool in endovascular therapy.
Baseline admission infarct volume was calculated on the basis of DWI lesion on MRI (MRI-DWI) or CBV (cerebral blood volume) on CT perfusion (CTP) and compared to final infarct volume as measured on 24-48 hour post-admission non contrast CT scan. 29 patients were evaluated using MRI and 28 patients were evaluated using CTP. Infarct growth was smaller if recanalization was achieved, with lower final infarct volumes following successful recanalization. The authors identified a MALCOLM score of 39 ccs – when recanalization was successful, up to 64% of patients within MALCOLM had a favorable outcome as defined by mRS 0-2; even when recanalization was successful, in patients above MALCOLM, only 12% had a good outcome. The only predictor of favorable outcome was an admission core lesion below MALCOLM. Patients older than age 80 had a lower MALCOLM (15 ccs) compared to younger patients (40 ccs), and a higher MALCOLM was seen on CTP (42 ccs) compared to MRI-DWI (29 ccs).
There are still further studies that will need to be done in this field to address specifics, such as the differences between CTP and MRI-DWI, and whether there are other sequences within CTP which might more accurately estimate initial core volume, but identifying MALCOLM serves to potentially separate out which patients would most benefit from thrombectomy and which would not, putting us closer to answering the question posed previously, “how large is too large?”