Macrocephaly

MACROCEPHALY, or macrocephalia, megalocephalia (from the Greek makros or megalos - large and kephale - head), an increase in the head in all dimensions due to an increased size of the brain without the presence of hydrocephalus (Virchow's megalocephaly). In this condition, the brain is distinguished by its particular weight and massiveness (macroencephalia). Sometimes an increase in the brain is observed without an increase in the skull. It is usually difficult to determine whether the issue is a congenital or acquired condition. True hypertrophy, or hyperplasia of the brain, is distinguished from pseudohypertrophy; in the former, hyperplasia of nerve elements is observed, while in the latter, there is an overgrowth of glia (interstitial megalencephaly). Cases of the first form are rare. One can speak of them only after a thorough histological examination. Most cases of macrocephaly belong to pseudomacrocephalies, caused by various pathological processes. The surface of the brain in macrocephaly usually differs little from the normal. The convolutions are not flattened, but are often very voluminous. The ventricles are sometimes enlarged. The bones of the skull are for the most part thin and porous. There is not always a parallelism observed between the development of the psyche and the weight of the brain; therefore, one cannot draw a conclusion about the intellect of its possessor from the size of the brain. According to Marchand, the highest weight of a male brain is 1,600 g, and for women, 1,450 g. A large brain weight has been discovered in some prominent people (Turgenev - 2,012 g, Byron - 1,807 g, Cromwell - 2,000 g), but a large weight is also observed in deeply retarded individuals; thus, Walsen described a brain weighing 2,250 g in a 21-year-old idiot. A large brain weight has also been described in normal people (2,028 g, 2,222 g, 2,155 g, etc.). Hypertrophy of the brain can proceed without any symptoms, and often it is only during an autopsy that abnormal brain dimensions are discovered. It is necessary to remember that during many diseases, edema of the brain can occur and cause an increase in its weight. The symptoms sometimes observed in macrocephaly are explained by the pressure of the skull on the surface of the brain and are expressed primarily in convulsions, reaching the point of status epilepticus and easily triggered reflexively by visual and auditory stimuli. Local cerebral symptoms are not observed. General symptoms develop only after the end of the first year of life, after the closure of the fontanelles, because until this time the soft skull yields to internal pressure. In infants, a relatively large head size represents a physiological phenomenon. An excessively enlarged skull is often observed in rachitic children. In premature infants, an enlarged head in the shape of a balloon with a tense fontanelle is often observed several months after birth as a consequence of rapid brain growth, which subsequently disappears. It is interesting to note that sometimes in hypertrophy of the brain, a persistent thymus, enlargement of the pineal gland, changes in the thyroid gland, and aplasia of the adrenal glands are observed.