“In some infants when the head is brought into extension, the posterior arch of atlas inverts through the foramen magnum. This often caused mild to severe vertebral artery compression.
10 of 17 infants studied demonstrated this atlas inversion. All ten were SIDS deaths.
Giles FH; Bina M; Sotrl A; Infantile Atlanto-occipital Instability/ The Potential Danger of Extreme Extension. Am J Dis Child 19/9; 133 (1): 30-7 / Medline ID:79101175
A Possible Cause of SIDS
Vertebral artery compression that cuts off blood flow to the brainstem has been suggested as an underlying cause of sudden infant death syndrome (SIDS). This study, published in the journal Pediatrics, involved postmortem examination of the vertebral arteries of 20 infants who died of SIDS or other causes.
In five of the cases the deceased infant’s neck was extended; in nine cases it was rotated 90 degrees, and in six cases the head was held in the neutral position. Both macroscopic and microscopic evidence of vertebral artery compression was found in some of the extended or rotated necks of infants. No vertebral artery compression was detected in the necks held in the neutral position.
According to the investigators:
· This study provides direct evidence that both neck extension and rotation in infants can compress the vertebral arteries between the atlas and the occiput or at the C1 transverse foramen.
· Architectural anomalies in arteries at the base of the brain are risk factors threatening reduced vertebrobasilar flow that could cause acute brainstem ischemia and death.
· Because an infant tends to rotate or extend its head in the prone sleeping position to clear its nose from the bedding, vertebral artery compression caused by these head movements could explain why the prone position is a major risk factor for SIDS.
Because most infants die of SIDS between one and six months of age, the combination of risk factors seems to be greatest in that period. Before that, an infant probably lacks the strength and coordination to rotate or extend its neck enough to cause artery compression. After that, as the infant’s neck anatomy develops, it has greater protection from the risks of SIDS. In those critical months, the dangers of the prone sleeping position are greatest.
Pamphlett R, Raisanen J, Kum-Jew S. Vertebral artery compression resulting from head movement: A possible cause of the sudden infant death syndrome. Pediatrics, Feb. 1999;103(2), pp460-63.
Vertebral Artery Compression Resulting From Head Movement: A Possible Cause of the Sudden Infant Death Syndrome
From the * Neuropathology Unit, Department of Pathology, University of Sydney, Sydney, and the New South Wales Institute of Forensic Medicine, Glebe, Australia.
Objective. Vertebral artery compression causing brainstem ischemia has been suggested to underlie the sudden infant death syndrome. Vertebral artery distortion from neck movements has been demonstrated by angiography in infants, but direct evidence for arterial compression is lacking. In an attempt to demonstrate vertebral artery compression from head movement, we examined at postmortem the vertebral arteries of infants after neck extension or rotation.
Methods. The C1-C7 spinal column, together with a 2-cm rim of skull base, was removed from 20 infants dying from sudden infant death syndrome or other causes. In 5 cases the neck was extended, in 9 cases it was rotated 90° to the right, and in 6 cases the neck was held in the neutral position. The neck was maintained in these positions during formalin fixation, and serial sections of selected blocks were examined microscopically.
Results. In 3 of 5 extended cases, bilateral vertebral artery compression was seen between the occipital bone and C1. In 3 of 9 rotated cases, the left vertebral artery was compressed adjacent to C1 before the artery entered the transverse foramen. No vertebral artery compression was seen in the necks held in the neutral position.
Conclusions. The vertebral arteries of some infants can be compressed by neck movement. This could induce lethal brainstem ischemia in infants with inadequate collateral blood flow or with poor compensatory arterial dilatation, and may underlie some cases of sudden infant death syndrome.
Pamphlett, R, Raisanen, J & Kum-Jew, S. Pediatrics Vol. 103 No. 2 February 1999, pp. 460-468