Shannon Higgins a special girl born with Polymicrogyria (PMG)

What is PMG?

What is PMG?
Shannon's Story

Dr. Christopher A. Walsh Laboratory gives a comprehensive explanation of Polymicrogyria.

Here is my version: Polymicrogyria (PMG) is a rare brain disorder. It's a neuronal migration disorder in which neurons fail to migrate normally up into the brain from where they are born resulting in structurally abnormal cerebral hemispheres. The name Polymicrogyria broken down describes its characteristics: Poly (many) micro (small) gyria (folds in the surface of the brain).

PMG is also characterized by shallow sulci, a slightly thicker cortex, neuronal heterotopia and enlarged ventricles. When many of these small folds are packed tightly together, PMG may resemble pachygyria (a few "thick folds" - a mild form of lissencephaly) in parts of the brain. The difference between PMG and pachygyria/lissencephaly can be difficult to see on an MRI or CT scan, even for an experienced radiologist.

The diagnosis of PMG is merely descriptive and is not a disease in itself nor does it describe the underlying etiology or cause of the brain malformation. In the past, PMG was often classified under the umbrella term of Cerebral Palsy but with recent advances in neuroimaging technology and molecular biology, many neuronal migration disorders have been categorized further enabling a more accurate diagnosis, treatment plan and prognosis.

PMG results from several different causes that are both genetic and non-genetic in nature as follows: (1) a genetic disorder with recessive inheritance; (2) damage or mutation to a specific genetic region on a chromosome; (3) viral infections of the baby during the 2nd trimester (i.e., CMV); (4) insufficient blood supply to the baby's brain during the 2nd trimester (i.e., umbilical cord entanglement); and, (5) other causes which have not yet been identified. Research is ongoing in this area.

Most children with Polymicrogyria, but not all, have some degree of global developmental disabilities or delays, seizures, feeding difficulties, respiratory problems, motor dysfunction and mental retardation. It is difficult to make a predictable prognosis for children with the diagnosis of PMG because each child is very unique in their presentation of this disorder

DISCLAIMER: I am a parent, not a medical professional. All the information here and throughout my web site is true and accurate to the best of my knowledge.