“2.1 The normal fetal brain consists of two halves. Each half is called a cerebral hemisphere and each hemisphere contains a ventricle (a thin fluid filled space). These ventricles communicate towards the front of the brain and then there is a midline channel through which fluid passes (third ventricle), which then communicates with the posterior part of the brain (cerebellum). There is a further fluid space within the cerebellum (fourth ventricle) which communicates with the outside of the brain and this is where the fluid (cerebral spinal fluid) leaves the brain and then is absorbed over the surface of the brain. 2.2 In holoprosencephaly the process by which the brain separates into two halves does not occur. The result is a spectrum of abnormalities in which many of the midline structures are absent and there is a variable shaped single ventricular cavity. The brain usually separates into two halves during the fourth and fifth weeks of pregnancy. There are three main types of holoprosencephaly. 2.3. The most severe type is alobar holoprosencephaly. In this condition there is a single ventricular cavity and the thalami are fused. There is also absence of the midline structures such as the cavum septum pellucidum, corpus callosum and falx. This diagnosis of holoprosencephaly is quite straightforward as the brain is severely disordered and there is a large central fluid filled space within the brain. 2.4 Semilobar holoprosencephaly is a more difficult diagnosis to make, however once again there is a single ventricular cavity around the thalami, which are partially fused. The anterior parts of the ventricles are fused in a sickle or horseshoe shape and there is absence of the corpus callosum, cavum septum pellucidum and anterior portion of the falx. The posterior parts of the lateral ventricles will appear relatively normal. 2.5 Lobar holoprosencephaly is the least severe form and in this condition the ventricles are almost normally formed however there is fusion of the most anterior parts of the lateral ventricles. The corpus callosum, cavum septum pellucidum and part of the falx are absent. 2.6 It should be noted therefore that in all forms of holoprosencephaly there is absence of the cavum septum pellucidum. In both alobar and semilobar forms there is absence of the anterior horns of the lateral ventricles.”
‘unable to visualise septum pelucidum and normal anatomy in the anterior brain. ? absent corpus callosum ? normal’
‘We acknowledge that this is a selected group where there have been difficulties establishing a definitive diagnosis at ultrasound for patient or technical factors.’, and ‘Despite the bias and the above assumptions, we suggest that in cases where there are diagnostic difficulties at ultrasound due to patient size, gestational age, fetal lie and technical limitations in utero magnetic resonance should be considered.’
“In my view the court is not bound to hold that a defendant doctor escapes liability for negligent treatment or diagnosis just because he leads evidence from a number of medical experts who are genuinely of the opinion that the defendants’ treatment or diagnosis accorded with sound medical practice … the court has to be satisfied that the exponents of the body of opinion relied on can demonstrate that such opinion has a logical basis. In particular in cases involving, as the often do, the weighing of risks against benefits, the judge before accepting a body of opinion as being responsible, reasonable or respectable will need to be satisfied that in forming their views, the experts have directed their minds to the question of comparative risks and benefits and have reached a defensible conclusion on the matter.”