There is a 25% chance that both parents will pass the gene to their child, resulting in hydranencephaly. Genetic hydranencephaly afflicts both males and females in equal numbers. Post-natal brain injury
Though hydranencephaly is typically a congenital disorder, it can occur as a postnatal diagnosis in the aftermath of meningitis, intracerebral infarction, ischemia, or a traumatic brain injury. Diagnosis
An accurate, confirmed diagnosis is generally impossible until after birth, though prenatal diagnosis using fetal ultrasonography (ultrasound) can identify characteristic physical abnormalities. After birth, diagnosis may be delayed for several months because the infants early behavior appears to be relatively normal. The most accurate diagnostic techniques are thorough clinical evaluation (considering physical findings and a detailed patient history); advanced imaging techniques, such as angiography, computerized tomography (CT scan), and magnetic resonance imaging (MRI); and (more rarely) transillumination. However, diagnostic literature fails to provide a clear distinction between severe obstructive hydrocephalus and hydranencephaly, leaving some children with an unsettled diagnosis.Preliminary diagnosis may be made in utero via standard ultrasound, and can be confirmed with a standard anatomy ultrasound. Hydranencephaly is sometimes misdiagnosed as bilaterally symmetric schizencephaly (a less destructive developmental process on the brain), severe hydrocephalus (cerebrospinal fluid excess within the skull), or alobar holoprosencephaly (a neurological developmental anomaly). Once destruction of the brain is complete, the cerebellum, midbrain, thalami, basal ganglia, choroid plexus, and portions of the occipital lobes typically remain preserved to varying degrees.
Hydranencephaly is a condition in which the brains cerebral hemispheres are absent to a great degree and the remaining cranial cavity is filled with cerebrospinal fluid. "Cephalic" is the scientific term for "head" or "head end of body". Hydranencephaly is a type of cephalic disorder. These disorders are congenital conditions that derive from damage to, or abnormal development of, the fetal nervous system in the earliest stages of development in utero. These conditions do not have any definitive identifiable cause factor. Instead, they are generally attributed to a variety of hereditary or genetic conditions, but also by environmental factors such as maternal infection, pharmaceutical intake, or even exposure to high levels of radiation.Hydranencephaly should not be confused with hydrocephalus, which is an accumulation of excess cerebrospinal fluid in the ventricles of the brain. In hemihydranencephaly, only half of the cranial cavity is affected. Signs and symptoms
An infant with hydranencephaly may appear normal at birth or may have some distortion of the skull and upper facial features due to fluid pressure inside the skull. The infants head size and spontaneous reflexes such as sucking, swallowing, crying, and moving the arms and legs may all seem normal, depending on the severity of the condition. However, after a few weeks the infant sometimes becomes irritable and has increased muscle tone (hypertonia). After several months of life, seizures and hydrocephalus may develop, if they did not exist at birth.