12.1.1 Clinical Presentation

An 84-year-old woman developed acute-onset left-sided weakness and dysarthria. She had a medical history of hypertension, dyslipidemia, and diabetes, and had suffered a TIA 3 months ago with similar clinical manifestations as the current event. She arrived at the hospital approximately 2 hours after symptom onset, at which time she had completely recovered from her deficits (National Institutes of Health Stroke Scale [NIHSS] 0).

12.1.2 Imaging Workup and Investigations

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  Noncontrast computed tomography (NCCT) done 150 minutes after onset of symptoms revealed a hyperdense artery sign in the right MCA (Fig. 12.1). There were no early ischemic changes (ASPECTS score 10).

  
  
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  CTA showed an occlusion of the right M1 segment with an intraluminal clot at the carotid terminus (Fig. 12.2). The patient had excellent collaterals filling the right MCA territory and retrograde filling of the distal part of the MCA.

  
  
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  On CTP, there was a large perfusion abnormality visible in the territory of the right MCA with increased mean transit time and time to peak, and normal to increased cerebral blood volume (Fig. 12.3).

  

  

  

12.1.3 Diagnosis

Transient episode of neurological dysfunction of the right hemisphere with an occlusion of the right MCA and a large area of perfusion mismatch without signs of acute infarction.

12.1.4 Treatment

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  Because of the proximal M1 occlusion in combination with a large area of perfusion mismatch, it was feared that the patient had a high risk of developing an infarct due to failure of collateral circulation, despite the fact that she had no neurological deficits at this time.

  
  
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  After a discussion with the patient and her family, the decision was made to treat the patient with endovascular reperfusion therapy. She was not given intravenous (IV) thrombolysis.

  
  
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  Occlusion of the M1 segment was confirmed on catheter angiography. The vessel was opened with a 4 × 20 mm stent retriever (Trevo). After a single pass, TICI 3 reperfusion was achieved.

  
  
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  There was some irregularity of the proximal M1 segment due to vasospasm (Fig. 12.4). Treatment with 5-mg intra-arterial verapamil resulted in resolution of the irregularity.

  

12.1.5 Outcome

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  There were no complications during the procedure and the patient had no neurological deficits afterward.

  
  
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  MRI was performed 2 days after endovascular treatment, which showed small infarctions in the right basal ganglia, due to prolonged occlusion of the lenticulostriate arteries (Fig. 12.5).

  
  
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  The patient was discharged home on the third day after admission with an NIHSS score of 0.

  

12.2.1 Background

There is almost no evidence from randomized trials on the use of endovascular therapy in patients with mild or no neurological deficit. Most of the recent thrombectomy studies excluded this patient population. ^{1 ,​ 2 ,​ 3 ,​ 4 ,​ 5} The protocols of the EXTEND-IA and Mr Clean trial did allow randomization of patients with mild deficits. In the case of Mr Clean, a minimum baseline NIHSS score of 2 was required for randomization. ⁴ The EXTEND-IA protocol did not specify a minimal NIHSS score, but stated that the patient had to be eligible for IV thrombolysis treatment. ⁶ However, despite the fact that these studies allowed recruitment of patients with mild deficits, hardly any of these patients were actually included. In EXTEND-IA and Mr Clean, the median NIHSS scores of the patients randomized to intervention were 17 (IQR: 13–20) and 17 (IQR: 14–21), respectively. ^{4 ,​ 5}

Even before the widespread introduction of endovascular therapy, there was already uncertainty about the optimal strategy to manage patients with acute ischemic stroke and rapidly improving or mild symptoms (RIMS). Cohort studies have shown that RIMS is one of the most common reasons to withhold IV thrombolysis, despite the fact that the outcome in about a third of these patients is unfavorable. ^{7 ,​ 8} In a retrospective single-center study, Rajajee et al examined risk factors for poor outcome in patients with RIMS. ⁹ Among 39 patients with RIMS who did not receive reperfusion therapy, 8 (21%) were dead or dependent at the time of discharge. The strongest predictor of a poor outcome was the presence of a large vessel occlusion in the territory of the stroke, which was present in 8 of 39 patients. Of these, four patients (50%) had a poor outcome and infarct expansion was found on MRI in three patients. In contrast, of the patients without a large-vessel occlusion, only 13% (4/31) had a poor outcome. Thus, the odds of a poor outcome were seven times higher in patients with an occlusion, compared to those without an occlusion. The 95% confidence interval of this risk estimate, however, is wide (1.2–38), due to the low sample size of the study. Alexandrov et al used transcranial Doppler and they also found that large vessel occlusion was the strongest predictor of poor outcome in patients with RIMS. ¹⁰ Secondary deterioration occurred in 62% of patients with an occlusion, compared to only 4% of patients with a normal flow in the intracranial arteries. Finally, results from a prospective study from Canada in which patients with TIA or minor stroke were evaluated with MRI and MRA confirmed that a proximal occlusion is an important predictor of recurrent stroke. ¹¹

Based on the presence of a proximal occlusion and the CT perfusion abnormalities, our patient was feared to have a high risk of developing an infarct. Although the pathophysiology of infarct expansion in patients with a proximal occlusion and RIMS is incompletely understood, the most plausible mechanism is failure of collateral flow. Patients with RIMS and an occlusion of a major supplying artery probably initially have sufficient perfusion from collateral circulation, similar to our patient. This is the likely reason for the mild neurological deficits. If no recanalization of the proximal occlusion has occurred by this time, either spontaneously or after therapy, this process can result in expansion of the infarct.

Because of the high risk of poor outcome in patients with RIMS and a proximal occlusion, reperfusion therapy should be considered in these patients. In a recent phase 1 study in which the safety of IV tenecteplase for patients with RIMS and a proximal occlusion was examined, patients in whom recanalization occurred had a higher chance of a good clinical outcome at follow-up compared to those with persistent occlusion (relative risk: 1.65). ¹² Despite the fact that our patient arrived at the hospital within the timeframe for IV treatment, we decided not to use IV thrombolysis. In the guideline of the American Heart Association, RIMS is listed as a relative (but not an absolute) contraindication for IV thrombolysis. ¹³ However, it also states that for the use of IV thrombolysis, a patient should have a “measurable neurological deficit,” which was not the case in our patient. In fact, according to the most recent AHA definition, our patient had a TIA at the time of admission, not an ischemic stroke. ¹⁴ Other arguments against the use of IV thrombolysis were the risk of symptomatic hemorrhage, ¹⁵ and the fact that proximal M1 occlusions generally respond poorly to IV therapy. ¹⁶ Based on these considerations, we decided to treat the patient directly with mechanical thrombectomy, instead of bridging with IV thrombolysis.