Hemimegalencephaly
Hemimegalencephaly is an extremely rare form of macrocephaly and is characterized by uneven development of brain hemispheres (one-half of brain is larger than other). The syndrome can be presented by itself or in association with phakomatosis or hemigigantism. Additionally, hemimegalencephaly will frequently cause severe epilepsy, focal neuro-logical deficits, macrocrania, and mild to severe intellectual disability. MCAP
Megalencephaly-capillary (MCAP) is one of the two major syndromes of megalencephaly. Typically, MCAP and MPPH can be distinguished by somatic features. MCAP includes many characteristics that are observed at birth including: cutaneous vascular malformations, especially capillary malformations of the face and cutis marmorata, polydactyly, connective tissue dysplasia, and focal or segmental body overgrowth. Furthermore, MCAP can occasionally be linked with asymmetric brain overgrowth (hemimegalencephaly) as well as segmental overgrowth of the body (hemihypertrophy). MPPH
Megalencephaly-polymicrogyria-polydactyly-hydrocephalus (MPPH) is one of the two major syndromes contributing to megalencephaly. Typically MCAP and MPPH can be distinguished by somatic features. In differentiation to MCAP, MPPH lacks consistent somatic features other than postaxial polydactyly. Furthermore, brain and body development is normally symmetric in the majority of patients that appear to have MPPH symptoms. Presentation
Autism
There is an extremely high association between megalencephaly and autism. Approximately 20% of autistic children have megalencephaly, making it the most common physical characteristic of autism. People who present both megalencephaly and autistic characteristics usually also show signs of hyperactivity as a major symptom.
Prognosis
The prognosis of megalencephaly depends heavily on the underlying cause and associated neurological disorders. Because the majority of megalencephaly cases are linked with autism, the prognosis is equivalent to the corresponding condition. Since hemimegalencephaly is associated with severe seizures, hemiparesis and intellectual disability, the result is a poor prognosis. In most cases, those diagnosed with this type of megalencephaly usually do not survive through adulthood. Epidemiology
Approximately one out of every 50 (2%) children in the general population are said to have megalencephaly. Additionally, it is said that megalencephaly affects 3–4 times more males than females. Those individuals that are classified with macrocephaly, or general head overgrowth, are said to have megalencephaly at a rate of 10–30% of the time. History
It is believed that megalencephaly was discovered in 1972. Prior to diagnoses that used MRI scanning as a way to confirm brain overgrowth, cases of megalencephaly were diagnosed by autopsy in which the physical brain was measured and weighed. Research
Future research is targeted at further understanding mutations and how they lead to MCAP and MPPH syndromes. The majority of studies of megalencephaly have included mice who present brain abnormalities and overgrowth. The next step is to move to clinical trials involving humans in order to determine the exact genetic mutation causing the sequences. Additionally, scientists and pharmaceutical companies have begun to show interest in mutation inhibition and designing preventative methods to eliminate the underlying cause of megalencephaly altogether. Other relations
Intracranial volume also affects this pathology, since it is related with the size of the brain.