Dependency of blood flow in the basilar artery on head and body position -A possible cause of SIDS? Results of a Doppler sonographic screening programme of 3840 newborns

Hypoperfusion of the brainstem during head rotation may be a risk factor fo r the development of SIDS. On this background we established a Doppler sono graphic screening programme of the basilar cerebral arteries to evaluate th e dependency of blood flow on head and body position. patients and method: We investigated 3840 newborns (1872 girls and 1968 boys) with a birth weigh t of 3399 +/- 497 g and a gestational age of 39,2 +/- 1,4 weeks. The invest igations were performed in the neonatal period with an average age of 4,7 /- 3 days. In all infants blood flow was measured in the basilar artery (BA ) in supine position with the head in the midline. From the flow profile pe ak systolic flow velocity Vs and time average Row velocity TAV were measure d. Additionally flow measurements were performed in supine and prone positi on with rotation of the head to the right and left side. A decrease of bloo d flow velocities below 50% of the value in neutral position was considered to be abnormal. Retrograde or biphasic flow profiles during rotation were considered to be pathologic. In infants with abnormal or pathologic flow du ring rotation of the head flow measurements in the vertebral arteries (VA) were additionally performed. Blood flow velocities in the VA were measured in su pine and prone position with the head in the midline position and aft er rotation to the right and to the left. In neutral position unilateral ve rtebral hypoplasia, aplasia and normal VA were differentiated. The judgemen t after rotation was performed such as in the BA. Results: In 3807 infants (99.14%) blood flow velocities during head rotation did not decrease below 50% of the value measured in neutral position. In 33 infants (0.86%) a decr ease of blood flow velocities below 50% could be found during rotation. In 7 infants (0.18%) a pathologic flow could be found during head rotation. 27 of the 33 infants with abnormal and pathologic blood flow in the BA during rotation showed anatomic abnormalities of the VA. 20 of these infants (61% ) had unilateral vertebral hypoplasia (11 right, 9 left side), 7 (21%) had unilateral vertebral aplasia (4 right, 3 left side). 32 of the 33 infants w ith abnormal flow in the BA showed a decrease of blood flow in the contrala teral VA during head rotation. 9 infants had an abnormal, 19 a pathologic f low within the contralateral VA. In 4 infants the corresponding VA could no t be measured during head rotation. The decrease of blood flow velocities i n the BA during heed rotation was caused by compression of the contralatera l VA at the craniocervical junction. Conclusion: Blood flow within the basi lar artery of healthy infants is independent of body position and rotation of the head. A decrease of the flow velocities below 50% during rotation ha s to be considered as an abnormality. The incidence of pathologic blood flo w during head rotation with 1.8%0 approximates the incidence of SIDS. Hypop erfusion of the brainstem during head rotation may be a risk factor of SIDS .