Hypoperfusion of the Brainstem – A Possible Cause of the Sudden Infant Death Syndrome: Dopplersonographic Screening of the Blood Flow in the Basilar Artery in Dependency on Head and Body Position

Introduction: Hypoperfusion of the brainstem may be a cause of sudden infant death. With spectral Doppler sonography the flow in the basilar artery to the brain stem can be measured noninvasively. From the flow profile the flow velocities can be calculated. Patients and methods: To prove the hypothesis of hypoperfusion of the brain stem as a cause of SIDS we performed Doppler sonographic flow measurements in the basilar artery of healthy newborns. We measured the peak and time average flow velocity in neutral position (infant supine and head in midline) and after rotation to the right and left: These measurements were performed either supine or prone. Possible alterations of the flow velocities during head rotation were compared with the intra individual normal values in neutral position. We interpreted our results as followed: If the flow during head rotation did not fall under 50% of the initial value in neutral position this was declared normal. If the flow velocities fell below 50% of the initial value this was declared abnormal. If a retrograde or biphasic flow could be shown during head rotation this was pathologic. In patients with abnormal or pathologic flow during head rotation the flow in both vertebral arteries was additionally measured. Patients: From 1998 till 2016 we investigated 31.945 infants (15.521 girls and 16.424 boys). The mean gestational age was 38, 76 + 2, 13 weeks, the mean birth weight 3288 + 585 g. 4122 newborns without the voluntary screening program served as a control collective. We compared the incidence of SIDS in both groups. Results: In 31.544 newborns (98, 74%) the flow in the basilar artery was independent on head and body position. 323 newborns (1, 01%) showed a reduction of the peak and/or time average flow velocity under 50% of the value in neutral position. In 78 patients (0, 24%) a pathologic retrograde or biphasic flow could be found. The flow alterations were more pronounced in prone than in supine position. Patients with pathologic flow were assumed to have a greater risk for SID. The parents were encouraged to avoid potentially dangerous head rotations. In all patients flow normalized within the first year of life. Normalization occurred earlier in supine than in prone position. Occurrence of SIDS: None of our patients with abnormal or pathologic flow died of SIDS. 2 infants (0, 06 ‰) with normal Doppler sonographic screening died of SIDS. In the control group without Doppler sonographic screening 5 infants (1, 21‰) died of SIDS. Statistical analysis between both groups was significant. Discussion: Pathologic flow occurred predominantly in infants with ahypoplastic or aplastic vertebral artery if the leading contra lateral vertebral artery was compressed at the craniocervical junction during head rotation. This may cause hypoperfusion of the brain stem. Repeated or longer lasting hypoperfusion episodes may cause lesions in the brain stem and lead to SIDS. Conclusion: Doppler sonographic screening of position dependent blood flow in the basilar artery of healthy newborns may detect infants with increased risk of SIDS. Avoiding head rotations to the pathologic side may reduce the risk of SIDS. Central Bringing Excellence in Open Access   Deeg (2017) Email: JSM Allergy Asthma 2(1): 1010 (2017) 2/6 INTRODUCTION The cause of sudden infant death (SID) is still unclear. We only know some risk factors which are associated with SID. An important risk factor is sleeping in prone position: More than 85% of SID victims are found lying on their stomach. In contrast to supine position the head is maximally turned to one side lying on the stomach. This may cause compression of the vertebral arteries at the cranio-cervical junction and cause hypoperfusion of the brainstem. Frequent or longer lasting hypoperfusion episodes of the brain stem may cause apnea and bradycardia and may be a cause of SID. Brain stem gliosis, found in victims of SID, may be a consequence of frequent and longer lasting hypoperfusion episodes to the brainstem [1]. Hypoperfusion of the brainstem may be caused by compression of the vertebral arteries at the cranio-cervical junction during head rotation. The compression of the vertebral arteries could clearly be shown by pathologic anatomic investigations of SIDS victims by Pamphlett and coworkers [2]. They investigated SID victims and performed serial sections through the cranial cervical junction [2]. They showed that during head rotation the vertebral arteries can be significantly compressed between the transverse process of the atlas and the occipito-cervical membrane [2]. MATERIALS AND METHODS Doppler sonographic screening of the flow in the basilar artery in neonatology As long as the fontanelles are open the intracranial anatomic structures can excellently be displayed by 2d sonography [3,4]. With color Doppler all intracranial arteries especially the basilar artery and both vertebral arteries can be displayed within the 2d image [3,4]. With spectral Doppler the flow in these arteries can be measured. From the flow curve the peak systolic and time average flow velocities can be measured [3,4]. To evaluate a possible dependency of the flow in the basilar artery in different body positions and during head rotation the flow was measured in different head and body positions: Head in neutral position (supine – midline) vs head rotation to the right and left in supine and prone position. We performed a voluntary Doppler sonographic screening program in healthy newborns since 1998.This program was offered to the parents of all newborns born in our department on a voluntary basis. Our study was approved by the ethics commission of the University of Erlangen-Nuremberg. After informed consent of the parents, blood flow in the basilar artery was measured in neutral position (infant supine with head in the midline). From the flow profile the peak systolic flow velocity and the time average flow velocities were measured. After rotation of the head to the right and left these flow velocities were additionally measured in supine and prone position. These flow velocities were compared with the values in neutral position. The values in neutral position were the intra individual normal value of the infant (100%). We assumed that the flow velocities in the basilar arteries did not significantly change during head rotation. We estimated that they were independent on body position and head rotation. This was the case in the great majority of our newborns. In dependency on possible flow alterations during head rotation we divided the infants in 3 groups: • Infants in which the flow velocities didn ́t fall under 50% of the flow velocities in neutral position during head rotation. This was the case in the great majority of our newborns. These infants were judged as normal • Infants with a fall of one or both flow velocities under 50% of the initial value in neutral position were judged as abnormal (Figure 1a,b). Inspite of the fall of the flow velocities still an ante grade flow could be found. • Infants with a biphasic or retrograde flow during head rotation were judged as pathologic (Figure 2a,b). In these infants the time average flow velocity fell dramatically.