Subdural hematomas also enlarge the child’s head and cause bulging of the fontanels and separation of the sutures. The infant is usually irritable and listless, taking nourishment poorly. Infants and children with neurofibromatosis, osteogenesis imperfecta, and achondroplasia also have enlarged heads; in the last of these, some degree of hydrocephalus appears to be responsible. Ultrasonography, which can be performed in the prenatal and neonatal periods, is usually diagnostic in all these cranial enlargements. Also MRI and CT will disclose the size of the ventricles and the presence of subdural blood or fluid (hygroma).
Apart from patients with these pathologic states, there are individuals whose heads and brains are enlarged but who are normal in all other respects. Many of them come from families with large heads. Schreier and colleagues, who traced this condition through three generations of several families, declared it to be an autosomal dominant trait. This group represented 20 percent of 557 children referred to a clinic because of cranial enlargement, according to Lorber and Priestley.
Hemimegalencephaly This term refers to a marked enlargement of one cerebral hemisphere as a result of a developmental abnormality. The cortical gray matter and sometimes the basal ganglia are greatly increased in volume and weight. The cerebellum, brainstem, and spinal cord retain their normal dimensions. The cranium may be misshapen or enlarged but is normal in size in some cases. Rarely, the face and body are enlarged on the side of the enlarged hemisphere. The cortex of the giant hemisphere is thick and disorganized. Neurons are in disarray and some are enlarged; in some places the natural lamination of the cortex is effaced. Nothing is known about causation, but clearly embryogenesis has been deranged at the stage of neuroblast formation.
Clinically, these individuals are cognitively delayed and some have epilepsy. A degree of hemiparesis may be present but severe hemispheral neurologic deficits are generally not reported. However, hemimegalencephaly has been discovered at autopsy in a few individuals who had no mental or neurologic deficits.
Some of the most startling cranial deformities are caused by premature closure of the cranial sutures (membranous junctions between bones of the skull). Such conditions are estimated to occur in 1 of every 1,000 births, with predominance in males (Lyon and Evrard). The growth of the cranium is inhibited in a direction perpendicular to the involved suture(s), creating a compensatory enlargement in other dimensions as allowed by the patent sutures. For example, when the lambdoid and coronal sutures are both affected, the thrust of the growing brain enlarges the head in a vertical direction (tower skull, or oxycephaly, also referred to as turricephaly and acrocephaly). The orbits are shallow, the eyes bulge, and imaging of the skull shows islands of bone thinning (lückenschädel). When only the sagittal suture is involved, the head is long and narrow (scaphocephalic) and the closed suture projects, keel-like, in the midline. With premature closure of the coronal suture, the head is excessively wide and short (brachycephalic). The nervous system is usually normal in these restricted craniosynostoses. If this condition is recognized before 3 months of age, the surgeon can make artificial sutures that may permit the shape of the head to become more normal (Shillito and Matson). Once brain growth has been completed, little can be done aside from complex reconstructive surgery. When several sutures (usually coronal and sagittal) are closed, so as to diminish the cranial capacity, intracranial pressure may increase, causing headache, vomiting, and papilledema. An operation is then needed to increase the capacity of the skull.