A population-based, case-control study in Canada found that neonatal hemorrhagic stroke occurred in at least one of every 6,300 live births. That incidence rate was higher than previously reported.

Most of the strokes occurred within a week of birth when infants had seizures and encephalopathy. Infants who suffered neonatal hemorrhagic strokes also had poor outcomes.

Lead researcher Lauren Cole, BScH, of the Calgary Pediatric Stroke Program at the University of Calgary in Alberta, Canada, and colleagues published their results online Jan. 17 in JAMA Pediatrics.

The researchers analyzed data from the Alberta Perinatal Stroke Project, a registry established in 2008 that includes more than 900 MRI-confirmed perinatal stroke cases. They included infants who had radiographic neonatal hemorrhagic stroke, were residents of Southern Alberta and had a term birth, which they defined as being in the womb for at least 35 weeks. They defined neonatal hemorrhagic stroke as “imaging evidence of blood within the brain parenchyma with or without intraventricular or subarachnoid blood.”

The researchers identified 86 cases of neonatal hemorrhagic stroke, of which 62 percent occurred in males. They said that their prevalence estimates suggest at least 1,000 Canadian children are living with neonatal hemorrhagic stroke.

During the study, the mean live births in Southern Alberta were 24,650 per year, which yielded a neonatal hemorrhagic stroke incidence of 15.9 in 100,000 per year or approximately one in 6,300 live births. The incidence for pure neonatal hemorrhagic stroke and presumed perinatal hemorrhagic stroke was 10.5 in 100,000 per year or approximately one in 9,500 live births.

The incidence rates were similar during the retrospective period (1992 to 2010) and the prospective period (2008 to 2015).

The researchers mentioned that 94 percent of infants with neonatal hemorrhagic strokes presented within the first 28 days of life, while 69 percent were imaged in the first week. They added that 67 percent presented with seizures, 83 percent presented with encephalopathy and 42 percent presented with hypotonia. In addition, 88 percent were admitted to the neonatal intensive care unit, but only three patients (3.5 percent) had an acute neurosurgical intervention.

Further, they noted that idiopathic neonatal hemorrhagic stroke was independently associated with lower maternal age, primiparity, prior spontaneous abortion, difficult fetal transition and low Apgar scores.

A follow-up of 50 cases found that 44 percent of patients had poor neurological outcomes at a median of 37 months.

The researchers acknowledged the study had a few limitations, including a potential reporter bias during medical record review. They also mentioned that neurological outcomes data were only available at the most recent clinic visit. In addition, they excluded subdural and subarachnoid hemorrhages, which made it difficult to compare the results with some previous studies.

The causes of neonatal hemorrhagic stroke are also unclear, but the researchers said they may include genetic disorders and quantified arterial tortuosity.

“Collectively, evidence suggests [neonatal hemorrhagic stroke] pathophysiology involves rare events occurring in uniquely susceptible individuals rather than any controllable external factors, limiting opportunities for prevention,” the researchers wrote.