Patients who experience ischemic stroke in the posterior circulation are at greater risk of impaired functional outcomes compared to those with anterior circulation stroke (ACS)—particularly if their time to hospital arrival exceeds 4.5 hours, according to an Austrian registry study published Oct. 8 in Stroke.
“Our results urge for implementation of symptoms found in the posterior circulation into preclinical patient-triage tools,” wrote Peter Sommer, MD, and colleagues.
Posterior circulation strokes (PCS) account for about 20 percent of all ischemic strokes, the authors noted. But previous studies have yielding conflicting results on whether PCS and ACS are associated with varying functional outcomes, and those analyses were limited by small sample sizes and variations in the rates of treatment with recombinant tissue-type plasminogen activator (r-tPA).
Sommer et al. used propensity-score matching to balance patient characteristics and stroke severity between 4,604 patients with PCS and the same number with ACS. A total of 477 individuals in each group were treated with r-tPA.
Overall, patients with ACS had 19 percent greater odds of a better functional outcome, as assessed by the modified Rankin scale at three months. However, the deficit in the PCS group was mostly driven by patients who presented to the hospital at least 4.5 hours after stroke onset, who showed 34 percent greater odds of worse functional outcome.
PCS patients with unknown onset-to-door times had a 26 percent greater chance of a worse degree of disability, but there was no significant difference between groups when hospital arrival occurred within 4.5 hours.
“Relevantly, these results were independent of age, sex, stroke severity, and vascular risk factors,” the authors wrote. “Our data, therefore, demonstrate that patients with PCS only experience worse outcome compared with patients with ACS if they arrive late in hospital or if their onset of symptoms is unknown.”
Sommer et al. pointed out the National Institute of Health Stroke Scale (NIHSS)—which they used to balance stroke severity between groups—may be inherently weighted toward ACS and “tends to underestimate stroke severity in PCS.”
“Symptoms such as vertigo or gait disturbance are not examined in the NIHSS but have relevant impact on disability,” they wrote. “As we used the NIHSS for assessment of stroke severity in the matching process, we cannot rule out that there might have been imbalances when matching patients with PCS to ACS.”
Another plausible explanation was that prehospital delays resulted in larger onset-to-treatment gaps in PCS patients, leading to noneligibility for r-tPA treatment. Patients in the study fared equally well regardless of stroke location if they were given r-tPA.
The authors reiterated the need for stroke triage tools to pay more attention to the possibility of PCS, as current techniques may be less sensitive in detecting those types of strokes.
“The face-arm-speech test does not include ataxia or hemianopia which is often seen in PCS,” Sommer and colleagues noted. “It has been demonstrated that the sensitivity of the face-arm-speech test increases from 60% to 80% if ataxia and visual symptoms are added.
“Furthermore, transient isolated brain stem symptoms commonly precede PCS. These symptoms, such as vertigo, dysarthria, dizziness, or confusion, do not classify as transient ischemic attack-related symptoms. Therefore, taking these symptoms into account may help to identify patients at risk for PCS in patient triage.”