Macrocephaly


Macrocephaly is a condition in which the human head is abnormally large; this includes the scalp, the cranial bone, and the contents of the cranium. It may be pathological or benign, even a familial genetic characteristic. People diagnosed with macrocephaly will have further testing done to determine if the syndrome if accompanied by any other disorders. Those with benign or familial macrocephaly are considered to have megalencephaly, another form of macrocephaly that will not result in the development of neurological disorders in the patient.

Causes

Many people with abnormally large heads or large skulls are healthy, but macrocephaly may be pathological. Pathologic macrocephaly may be due to megalencephaly, hydrocephalus, cranial hyperostosis, and other conditions. Pathologic macrocephaly is called "syndromic", when it is associated with any other noteworthy condition, and "nonsyndromic" otherwise. Pathologic macrocephaly may be caused by congenital anatomic abnormalities, genetic conditions, or by environmental events.
Many genetic conditions are associated with macrocephaly, including familial macrocephaly related to the holgate gene, autism, PTEN mutations such as Cowden disease, neurofibromatosis type 1, and tuberous sclerosis; overgrowth syndromes such as Sotos syndrome, Weaver syndrome, Simpson-Golabi-Behmel syndrome, and macrocephaly-capillary malformation syndrome; neurocardiofacial-cutaneous syndromes such as Noonan syndrome, Costello syndrome, Gorlin Syndrome, and cardiofaciocutaneous syndrome; Fragile X syndrome; leukodystrophies such as Alexander disease, Canavan disease, and megalencephalic leukoencephalopathy with subcortical cysts; and glutaric aciduria type 1 and D-2-hydroxyglutaric aciduria.
At one end of the genetic spectrum, duplications of chromosomes have been found to be related to autism and macrocephaly; at the other end, deletions of chromosomes have been found to be related to schizophrenia and microcephaly.
Environmental events associated with macrocephaly include infection, neonatal intraventricular hemorrhage, subdural hematoma, subdural effusion, and arachnoid cysts.
In research, cranial height or brain imaging may be used to determine intracranial volume more accurately.
Below is a list of causes of macrocephaly from noted in The Little Black Book of Neurology:

Hydrocephalus

Noncommunicating:

Meningeal fibrosis/obstruction

Vascular

Neurocutaneous syndromes

Subdural fluid

Thick skull or scalp (hyperostosis)

Diagnosis

Macrocephaly is customarily diagnosed if head circumference is greater than two standard deviations above the mean. Relative macrocephaly occurs if the measure is less than two SDs above the mean, but is disproportionately above that when ethnicity and stature are considered. Diagnosis can be determined in utero or can be determined within eighteen 18-24 months after birth in some cases where head circumference tends to stabilize in infants. Diagnosis in infants includes measuring the circumference of the child's head and comparing how significant it falls above the 97.5 percentile of children similar to their demographic. If falling above the 97.5th percentile then the patient will be checked to determine if there is any intracranial pressure present and whether or not immediate surgery is needed. If immediate surgery is not needed then further testing will be done to determine if the patient has either macrocephaly or benign macrocephaly.
Diagnosis for macrocephaly involves the comparison of the infant's head circumference to that of other infant's of the same age and ethnicity. If a patient is suspected of having macrocephaly molecular testing will be used to confirm diagnosis. Symptoms vary on the cause of macrocephaly on the child and if the child has any other accompanying syndromes which will be determined through molecular testing.

Benign or familial macrocephaly

Benign macrocephaly can occur without reason or be inherited by one or both parents. Diagnoses for familial macrocephaly is determined by measuring the head circumference of both parents and comparing it to the child's. Benign and familial macrocephaly is not associated with neurological disorders. While benign and familial macrocephaly does not result in neurological disorders, neurodevelopment will still be assessed.
Although neurological disorders do not occur, temporary symptoms of benign and familial macrocephaly include: developmental delay, epilepsy, and mild hypotonia.
Neurodevelopment is assessed for all cases and suspected cases of macrocephaly to determine if and what treatments may be needed and whether or not other syndromes may be present or likely to develop.

Treatment

Treatment varies depending on whether or not it occurs with other medical conditions in the child and where cerebrospinal fluid is present.
Below is a list of syndromes associated with macrocephaly that are noted in .

Include multiple major and or minor anomalies

Secondary to a metabolic disorder

Associated with a skeletal dysplasia

With no obvious physical findings