Stroke patients who also have Covid-19 showed increased systemic inflammation, more serious stroke severity and a much higher rate of death, compared to stroke patients without coronavirus, warn researchers.

The study published in the journal Brain, Behavior & Immunity - Health, is a retrospective, observational, cross-sectional study of 60 ischemic stroke patients admitted to the University of Alabama at Birmingham (UAB) Hospital between late March and early May 2020.

Ischemic stroke occurs when a blood vessel for the brain is blocked by a clot, depriving some brain tissue of oxygen. All patients were tested for Covid-19 at admission.

"The ratio of the number of neutrophils to the number of lymphocytes, or the NLR, as calculated from blood count data, served as an index of the systemic inflammatory response," said study author Chen Lin from UAB in the US.

"While other researchers have associated NLR with Covid-19 disease severity, refractory disease and even as an independent factor for mortality, our study is the first to associate the NLR in patients with Covid-19 and ischemic stroke and stroke severity," Lin added.

Of the 60 hospitalised patients with acute systemic stroke, nine were positive for a COVID-19 infection.

The research had four major findings. First, patients who were positive for Covid-19 presented a more severe neurological deficit at admission, as measured by the National Institutes of Health Stroke Scale, or NIHSS, score, which averaged 18.4.

Second, all patients with an NIHSS score higher than four -- including uninfected patients -- had a significantly higher NLR than those with lower scores. The NIHSS is used to predict lesion size and gauge stroke severity.

Third, patients with Covid-19 had an increased inflammatory response, including significantly higher neutrophil counts, lower lymphocyte counts and an increased NLR, compared with uninfected patients.

Finally, stroke patients with Covid-19 had a significantly higher mortality rate -- 44.4 per cent, versus 7.6 per cent for uninfected stroke patients.

"Interestingly, in our patients with stroke and Covid-19, the neutrophil and lymphocyte levels were only borderline high and low, respectively, yet the NLR was almost twice as high as in patients without Covid-19," Lin said.

"This potentially indicates that the systemic inflammatory response triggered by Covid-19 can cascade from multiple components," Lin noted.