Pathogenesis
The exact pathogenesis of iniencephaly is still unknown though there are proposed theories, most of which view the neural tube malformation from the primary neural anomaly standpoint. Marin-Padilla and MarinPadilla have proposed that the cause for the abnormalities has to do with a deficiency in the primary mesoderm. P. Erdinçler, et al. suggests from their findings that the cause of the anomaly is actually a defect in the occipital bone and rachischisis of the posterior vertebral arches leading to herniation of neural tissue through the opening in the bone during gestation. Diagnosis
The most accurate method of diagnosis is prenatal screening through real-time fetal images. However, since maternal body habitus leads to diagnostic difficulties using this method, MRI and sonography are the most commonly used technique since there is no exposure to ionizing radiation. At the beginning of the second trimester, the central nervous system (CNS) and anatomic structures of the fetus can be clearly visualized and the characteristic malformations of iniencephaly, such as a shortened trunk, marked lordosis in the cervicothoracic vertebrae, absence or partial absence of the occipital squama, abnormal fusion of vertebrae, closed vertebral arches, formation of an encephalocele (for iniencephaly apertus), and dorsiflexion of the head in respect to the spine, can be precisely diagnosed as well as the severity and location established. Once established, further decisions can be made with regard to terminating the pregnancy or providing a plan of adequate postnatal care.
Iniencephaly is a rare type of cephalic disorder characterised by three common characteristics: a defect to the occipital bone, spina bifida of the cervical vertebrae and retroflexion (backward bending) of the head on the cervical spine. Stillbirth is the most common outcome, with a few rare examples of live birth, after which death almost invariably occurs within a short time. The disorder was first described by Étienne Geoffroy Saint-Hilaire in 1836. The name is derived from the Ancient Greek word ἰνίον inion, for the occipital bone/nape of the neck. Classifications
There are two types of iniencephaly. The more severe group is iniencephaly apertus (open iniencephaly), involving the development of an encephalocele. In the other group, iniencephaly clausus (closed iniencephaly), the encephalocele is absent. Signs and symptoms
The affected infant tends to be short, with a disproportionately large head. The fetal head of infants born with iniencephaly are hyperextended while the foramen magnum is enlarged and opens through the widened pedicles. The defective neural arches directly into the upper cervical reach of the spinal canal, causing the formation of a common cavity between most of the spinal cord and the brain. The skin of the anterior chest is connected directly to the face, bypassing the formation of a neck, while the scalp is directly connected to the skin of the back. Because of this, those born with this anomaly either have a highly shortened neck or no neck at all. This causes extreme retroflexion, or backward bending, of the head in a "star-gazing" fashion.