Polymicrogyria is characterized by excessive folding of the surface gyri and a thickening of the cerebral cortex, rather than the sulcal scarring that is typical of ulegyria. In addition to morphological differences, the period in which polmicrogyria and ulegyria emerge is also different. Polymicrogyria typically forms while the embryos central nervous system is maturing. Ulegyria is acquired later in development during the perinatal period after neuronal migration has already occurred. It is also suspected that polymicrogyra is genetically linked, whereas ulegyria is caused by environmental factors—namely lack of oxygen.Polymicrogyria can lead to similar conditions that are linked to ulegyria such as mental retardation, cerebral palsy, and epilepsy. It has been observed that patients with polymicrogyria are not receptive to epilepsy surgery. However, responses of patients with ulegyria to similar surgeries are still not fully known, which makes distinction of these two disorders significant. In vivo neuroimaging techniques, namely MRI, have been instrumental in making this distinction. An MRI image of ulegyria is identified by mushroom shaped gyri, deformities in white matter, and localization mainly in the posterior cerebral region. Polymicrogyria is typically recognized by a scalloped appearance at the bordering region between grey and white matter. Although these distinctions have been made with many patients, there is still some difficulty in defining distinct boundaries between these two similar conditions. Detection
Primarily, the main method of detecting ulegyria is through the use of MRI screening for epilepsy. Normally an MRI of an ulegyria affected region will reveal groups of deteriorated neurons with gliosis present.
In addition, unaffected gyri are also present in especially bilateral watershed regions indicating delayed effects of perinatal hypoxic damage. However, there are three main criteria for diagnosing ulegyria using MRI in addition to the features mentioned above:
1.The presence of a poorly demarcated lesion
2. Atrophy and thinning of the cortex resulting in the characteristic “mushroom” like shape of ulegyria. 3. Presence of white matter signal abnormalities as a result of FLAIR signaling (fluid attenuated inversion recovery).Another sign of ulegyria that is visible on an MRI scan is the presence of a widened subarachnoid space, signifying cortex atrophy. FLAIR signaling can help visualize the depths of the parietal-occipital sulci, which also allows ulegyria-affected gyri to be identified. Though there is still confusion in differentiating ulegyria and polymicrogyria in patients, MRI allows for the proper identification in the majority of the cases. In addition, most of the current research regarding ulegyria is focused on improving this identification. Furthermore, MRI can diagnose whether ulegyria presence is unilateral or bilateral. Electroencephalography, EEG, can also be used to screen for ulegyria, though MRI is still preferred. This is mainly done for epilepsy patients as abnormalities in EEG recordings indicate the presence of ulegyria in the area of the brain being tested. For example, when EEG tests in epileptic patients show deviations in the frontal and central-parietal regions, ulegyria can be considered to be present in that area. Treatment
Presently, there is no well-defined treatment for ulegyria mainly because of the irreversible ischaemic damage done to neurons of an affected area.