Vertebral artery insufficiency as a possible mechanism for sudden infant death – in vivo evidence does not support findings from postmortem studies

Recent postmortem studies have suggested that sudden infant death syndrome (SIDS) might involve an underlying, gradual brain stem injury caused by repeated episodes of transiently compromised brain stem circulation. Autopsy studies have also reported that vertebral artery occlusion due to head rotations, such as occurs, e.g. during prone sleeping, would be a physiological phenomenon of infant atlantooccipital junction. The present study was undertaken to examine whether vertebral artery insufficiency does truly occur in live infants during such head rotations. We studied by transcranial doppler sonography the blood flow velocity of the basilar artery (BA) in 27 infants during head rotation from straight position to maximal rotation in three directions (left, right, dorsiflexion). No significant change in BA blood flow was seen between any head positions. Weight and gestational age, but not arterial pressure or hematocrit, of the infants were correlated with blood flow velocity. Our results suggest that brain stem circulation in live infants may not be compromised due to changing the head position, which is inconsistent with the postmortem findings showing insufficiency of brain stem circulation in both controls and those succumbed to SIDS. We hence propose that the brain stem pathology observed with SIDS is likely caused by other factors (e.g. systemic disturbance) rather than by mechanical obstruction of brain stem circulation.