Farhani et al. ^{Reference Farhani, Ayoso, Alcock and Shankar1} describe the Critical Area Diffusion Score (CADS) to predict outcome after successful endovascular thrombectomy (EVT) of acute basilar artery occlusion (BAO). It is based on postoperative diffusion-weighted MRI and is modified from the Critical Area Perfusion Score, a preoperative CT perfusion measurement. ^{Reference Cereda, Bianco and Mlynash2} Although a lower CADS score was linked to better outcomes, it was not independently predictive of a favourable prognosis.

The prognosis of EVT of BAO remains guarded, although recent randomised controlled trials and meta-analyses suggest a favourable outcome (mRS 0–3) in 40%–45% of patients at 90 days to 1 year; however, mortality remains high at approximately 40%. ^{Reference Nogueira, Jovin and Liu3,Reference Rui, Tao and Sun4} The major determinants of a favourable outcome are baseline NIHSS, good collaterals and early and successful reperfusion – all confirmed in the present study.

As referenced by the authors, several imaging scales, including a collateral score, ^{Reference Kwak and Park5} have already been proposed to address prognosis in BAO. Few, if any, are used in routine clinical practice. Do we need another one?

Any imaging classification system is tempered by problems of validity, reliability, patient heterogeneity and clinical utility. The posterior fossa is a notoriously complex, compact vascular environment, making these parameters even more challenging to optimise. The authors should be commended on their efforts to improve the care of BAO patients, but the CADS score itself was not predictive of favourable outcome, and it is difficult to know how it might affect management. The authors state that it could aid prognostication, family counselling and rehabilitation planning, but it is doubtful that even a high CADS score would change the quality, intensity and course of care.

The authors believe that the CADS score may be useful as an adjunct to other measures such as pre-EVT imaging, NIHSS and collateral score to improve prognostication in BAO. Perhaps such future research is warranted, but unless the imaging score is thoroughly validated in prospective, multicentre studies and can, like ASPECTS, ^{Reference Barber, Demchuk, Zhang and Buchan6} directly influence patient management, it is likely to join the multitude of classification schemes, which clutter the medical literature, augment CVs and remain unneeded and unused.