Letters to the Editor

摘要

'The evidence base for retinal haemorrhages in shaken baby syndrome'SIR-Dr Squier's review1 analyses the evidence base for subdural haemorrhages which we agree is an important finding in 'shaken baby syndrome' (non-accidental head injury [NAHI]). However, it provides a skewed perspective on the subject by focusing on subdural haemorrhages in isolation. It ignores another important rinding - the presence of retinal haemorrhages which, along with the history, clinical examination, radiology, and pathology findings help arrive at the diagnosis.The severity of retinal haemorrhages in NAHI closely parallels the degree of brain injury, and the neurological outcome. There is ample evidence that the same mechanism is responsible for the eye and brain findings. Of the theories that have been proposed for the mechanism of retinal haemorrhages in NAHI, rotational and shearing traction between the vitreous gel and the retina is the likeliest mechanism. The infant eye has strong adhesions between the vitreous gel and the internal limiting membrane of the retina, especially around the optic disc and in the retinal periphery. The differential movement at the interface between the vitreous and retina due to acceleration-deceleration forces is believed to result in shearing of retinal vessels, which may be dilated as a result of increased intracranial venous pressures secondary to raised intrathoracic pressure.7 Moreover, macular retinoschisis and retinal folds, characteristic but not invariable findings in NAHI,5 result from mechanical separation of the retinal layers. This cannot occur without repeated traction between the retina and the vitreous gel, lending further support to this theory.