A new hypothesis for sudden infant death syndrome: the occlusion of vertebral arteries as a major cause

Abstract

Many factors, such as prematurity, low weight and minor infection, may predispose to Sudden Infant Death Syndrome (SIDS) but not cause it. It is suggested that the ultimate act of dying is due to the occlusion of one or both verebral arteries triggered by the position of the head and cervical spine. When the head is turned to one side, the ipsilateral vertebral artery may be occluded at mid-cervical level along its length, or the contra lateral artery at atlanto-axial level or on both sides with the head in the initial position. Extension of cervical spine, with or without rotation, may produce obstruction of one or both vertebral arteries. If the degree, the levels and duration of occlusion are exceeded, particularly if there is a degree of failure of the collateral circulation (including one from carotid arteries via posterior communicating arteries), this can lead to prolonged apnoea, a ‘near-miss’ or cot death. The factors which may predispose to SIDS among others are hypoplasia or ‘unexercised’ vertebral arteries (in utero) and/or hypermobility of the immature cervical spine with lax joint capsules and ligaments. These factors allow the undue stretch or kinking of the vertebral arteries resulting in occlusion when the head or cervical spine are turned. The hypothesis explains the reduction of mortality of SIDS in infants in sleeping supine position to those in the prone position. In prone position, the infant's head is rotated 90 degrees which may put stress on atlas and axis thus occlude vertebral arteries by stretching and kinking. Infants under 6 months are unable to change position unaided so duration of obstruction is an aggravating element. These factors are about 50% less in the supine position.