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We read with great interest the article of Haussen et al. 1 outlining the problem of identifying patients with minor stroke symptoms (low NIHSS) despite proximal vessel occlusion who should undergo thrombectomy. Intension-to-treat analysis showed significantly higher reduction of stroke severity in the primary thrombectomy group compared to the medical group. But more interestingly, per-protocol analysis revealed a high propo...
We read with great interest the article of Haussen et al. 1 outlining the problem of identifying patients with minor stroke symptoms (low NIHSS) despite proximal vessel occlusion who should undergo thrombectomy. Intension-to-treat analysis showed significantly higher reduction of stroke severity in the primary thrombectomy group compared to the medical group. But more interestingly, per-protocol analysis revealed a high proportion of rescue thrombectomies due to neurological deterioration with a clearly time-dependent effect on outcome after the procedure in the medical group. In our opinion, the problem is multidimensional. In proximal vessel occlusion, intravenous thrombolysis combined with thrombectomy is superior to thrombolysis alone. Current guidelines strongly recommend thrombectomy in these patients and not to stop after intravenous thrombolysis 2. Therefore, it is critical to identify ischemic stroke due to proximal vessel occlusion. High stroke severity measured by the NIHSS has been used as a clinical surrogate to detect major vessel occlusion. Fischer et al. reported an NIHSS threshold of 12 to have a positive predictive value of 91% for central occlusion 3. But this approach can be misleading as the NIHSS represents the amount of ischemic tissue, which is influenced by residual blood supply beyond the occlusion, especially by collateral circulation. Good collaterals can lead to a low NIHSS score in stroke with proximal vessel occlusion. Maas et al. showed that higher NIHSS cutoffs to predict major vessel occlusion missed more proximal occlusions, concluding that there was no NIHSS threshold to identify the majority of clinically important occlusive lesions. An NIHSS threshold of 10, for example had only 48% sensitivity 4. Minor stroke severity resulting in a low NIHSS is not uncommon in proximal vessel occlusion. One group identified 23% of patients with NIHSS <8 in a retrospective database search 5. In another population, approx. 90% of patients presenting with an NIHSS <=10 were found to have major vessel occlusion 4. In our opinion, current data indicate that all stroke patients admitted within the therapeutic time window should undergo vascular imaging. Another question is how to treat these patients. Until a few years ago intravenous thrombolysis was given only to patients with a "significant" neurological deficit, commonly defined as an NIHSS of 4 or higher. Today we know that low NIHSS stroke, even without proximal vessel occlusion, has unfavourable long-term outcome and that intravenous thrombolysis seems to be beneficial in this setting 6 with low risk of intracrcanial bleeding 7. In clinical practice, we today concentrate on individual deficits and try to individualize the treatment decision. In patients with central occlusion and NIHSS 2-7, the natural course is also rather unfavourable. Even in this low NIHSS stratum higher stroke severity was significantly associated with discharge into a facility and gait problems 5. The current study adds important knowledge for decision making in this situation as 41% of the medical group deteriorated a few hours after admission, which was likely caused by failure of the collateral system. Those who were "lucky" to suffer fast breakdown of collateral supply had better functional outcome after rescue thrombectomy than those with later failure. For future treatment algorithms, it will be essential to know more about the dynamics of collateral circulation and to develop a strategy to predict their failure. Currently, it is very difficult to make individual treatment decisions in this subset of patients as the thrombectomy procedure itself has a risk of recurrent stroke, vasospasm and subarchnoid hemorrhage 8.
1. Haussen DC, Bouslama M, Grossberg JA, et al. Too good to
intervene? Thrombectomy for large vessel occlusion strokes with minimal
symptoms: an intention-to-treat analysis. J Neurointerv Surg Published
Online First: 2 Sep 2016. doi: 10.1136/neurintsurg-2016-012633.
2. Powers WJ, Derdeyn CP, Biller J, et al. 2015 AHA/ASA Focused Update of
the 2013 Guidelines for the Early Management of Patients With Acute
Ischemic Stroke Regarding Endovascular Treatment: A Guideline for
Healthcare Professionals From the American Heart Association/American
Stroke Association. Stroke 2015;46:3020-3035.
3. Fischer U, Arnold M, Nedeltchev K, et al. NIHSS score and
arteriographic findings in acute ischemic stroke. Stroke 2005;36:2121-
4. Maas MB, Furie KL, Lev MH, et al. National Institutes of Health Stroke
Scale score is poorly predictive of proximal occlusion in acute cerebral
ischemia. Stroke 2009;40:2988-2993.
5. Mokin M, Masud MW, Dumont TM, et al. Outcomes in patients with acute
ischemic stroke from proximal intracranial vessel occlusion and NIHSS
score below 8. J Neurointerv Surg 2014;6:413-417.
6. Greisenegger S, Seyfang L, Kiechl S, et al. Thrombolysis in Patients
With Mild Stroke. Stroke 2014;45:765-769.
7. Strbian D, Piironen K, Meretoja A, et al. Intravenous Thrombolysis for
Acute Ischemic Stroke Patients Presenting with Mild Symptoms. Int J Stroke
8. Emprechtinger R, Piso B, Ringleb PA. Thrombectomy for ischemic stroke:
meta-analyses of recurrent strokes, vasospasms, and subarachnoid
hemorrhages. Journal of Neurology Published Online First: 20 Jun 2016.