Mild malformation of cortical development

Last revised by Avni K P Skandhan on 2 Aug 2021

Mild malformations of cortical development (mMCD), previously known as microdysgenesis 4, correspond to microscopic malformations of cortical development with heterotopic neurons and an abnormal cortical architecture 1

For a broader view on malformations of cortical development refer on classification system for malformations of cortical development and more specifically focal cortical dysplasia

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    It is related as one cause of drug-resistant partial epilepsy 1,3, however mMCD were also described in autopsy studies of asymptomatic patients.  

    mMCD correspond to microscopic changes that constitute cortical laminar disorganization, abnormal cortical myelinated fibers, neuronal clustering, and heterotypic or excessively numerous neurons in white matter, subcortical areas, or cortical layer I 3.
    It is important to emphasizes that isolated single neurons are usually present in the white matter of normal brains. On the other hand, a large groups of mispositioned cortical neurons in the white matter are found in types malformations of cortical development associated with epilepsy. mMCD may lie between these extremities, but the point at which white matter neuronal numbers become abnormal and represent a significant malformation is controversial and not well defined 2.

    The fact that several types of cortical dysplasia may be observed in the same patient illustrates the complexity of this broad spectrum of pathological processes that affect cortical mantle formation 3

    mMCD is recognized in the Palmini classification of focal cortical dysplasia

    These features correspond to microscopic abnormalities in which MRI scans usually are normal.

    The literature describes both favorable and worse outcomes after epilepsy surgery in patients with increased numbers of white matter neurons and mMCD 1.  

    In 1984, Meencke and Janz described microdysgenesis in post-mortem tissue from patients with generalized epilepsy 2,5.  

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