Cortical dysplasia and epilepsy

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  • 1. FOCAL CORTICAL DYSPLASIA Dr Ashraf Abdou Professor of neurology Neuropsychiatry department Alexandria university
  • 2. Normal Cortical Development 1) Proliferation  proliferation of neurons in the ventricular zone and glia in the subventricular zone 2) Migration  Migration of postmitotic neurons to the cortical plate  Heading for the deepest layers and then for the superfricial layer  Between the 8th and 24th weeks of gestation 3) Cortical organization :  vertical and horizontal organization of neurons within the cortex and elaboration of axonal and dendritic branch  terminal differentiations, apoptosis, synapse elimination, cortical remodeling
  • 3. Proliferation and Migration  Germinal matrix adjacent to the lumen of neural tube (future ventricles) contains stem cells of the neurons and two types of glial cells.  Neuronal precursor cells migrate along specialized cells called radial glial cells, to one of the six layers of cerebral cortex.  Once at adult site – establish synaptic connections with neighbouring neurons & send axons to targets  Generally migrate centrifugally towards brain surface
  • 4. Timing of Neuroblast migration  Cerebrum – neuroblasts – begin by 6 weeks – last till 34th weeks  Cerebrum – glioblast – migrate till early post natal period  Brainstem – migration of neuroblast complete by 2 months  Cerebellum – continue till 1 year
  • 5. Formation of sulci & gyri  Migrating neuroblasts necessitate more surface area without increasing volume  Proliferation of Glia  Growth of dendrites & axons
  • 6. Neuronal Migration Disorders I. True migration disorders Neurons fail to reach their intended destination. 1. Lissencephaly (agyria, pachygyria and sub-cortical band heterotopia). 2. Cobble stone complex malformation. 3. Heterotopias. II. Malformations of cortical organization. Microscopic abnormality in cortical arrangement. 1. Polymicrogyria. 2. Schizencephaly. 3. Focal cortical dysplasia.
  • 7. Lissencephaly with sub cortical band heterotopia. Clinical features  Normal at birth.  Seizures uncommon on 1st day of life.  Seizures at 3-6 months, later infantile spasm and Lennox- gastaut syndrome.  Profound MR .  Early hypotonia, later spastic quadriplegia and opisthotonus.
  • 8. Subcortical band heterotopia-Double cortex Sub-cortical, symmetric, circumferential bands of gray matter, separated from cortex by thin band of white matter. “Double cortex” appearance.
  • 9. Heterotopias  Group of neurons is an inappropriate location – either below or above the cerebral cortex.
  • 10. Periventricular nodular heterotopia
  • 11. Sub-ependymal nodular heterotopia
  • 12. Periventricular laminar heterotopia
  • 13. Focal Cortical dysplasia èè
  • 14. Focal Cortical dysplasia with normal cell types Pure architectural Dysplasia * Abnormal cortical lamination. * Ectopic neurons in white matter. Present with – Epilepsy / learning disability. MRI: Lobar / gyral hypoplasia, atrophy of underlying white matter blurring of gray- white border. Increased T2 & decreased T1 signal intensity.
  • 15. Focal cortical dysplasia with abnormal cell types (balloon cells)  Cytoarchitectural dysplasia  It is clear only with histopathology, not with MRI
  • 16. Incidence  Autopsy studies 1.7% incidence of FCD in normal brains.1  The incidence was significantly higher (46.5%) in patients with epilepsy  In surgical treated epilepsy:  In pediatric patients the incidence was 25%  In an adult population: 15%
  • 17. Cortical dysplasia and epilepsy  77 to 90% of patients with cortical malformations had seizures.  Cortical dysplasia is the most common substrate in pediatric and the second or third most frequent etiology in adult epilepsy surgery patients
  • 18. Cortical dysplasia and epilepsy  Epilepsy typically manifests during the first decade of life, usually after 2 or 3 years of age  Seizure semiology depends on the anatomic location of the malformation.  Partial  Partial with 2ry generalization  Many patients have more than one seizure type
  • 19. Focal cortical dysplasia MRI : Focal abnormal gyral(cotical) thickening Blurring of the cortical-white matter junction
  • 20. Cortical dysplasia; other clinical presentations  Dysplasia involving extratemporal regions demonstrates earlier age at presentation, more severe epilepsy, higher incidence of mental retardation and developmental delay.
  • 21. Imaging studies  Milder forms of dysplasia may remain invisible to current imaging techniques. Other studies report MRI detection of cortical abnormalities in 60 to 90% of the patients with FCD.  Characteristic MRI findings include:  abnormal gyral patterns  shallow sulci  increased cortical thickness  poor gray-white matter differentiation  increased subcortical signal intensity on T2-weighted imaging
  • 22. Focal cortical dysplasia (A1) T1WI : cortical thickening (A2) Proton-density-WI : blurring of interface between GM and WM (A3) T2WI : increased signal change (A4) FLAIR image : increased signal change
  • 23. Focal Cortical dysplasia
  • 24. There is : •cortico-subcortical blurring of the left paramedian frontal cortex •streak of high T2 signal extending from the depth of the sulcus to the ventricular wall. • T1 hyperintensity of the cortex Coronal T2WI Axial T2WI Axial T1 MPRAGE Coronal T1 MPRAGE recon
  • 25. 5-year-old boy with refractory epilepsy. Coronal T2WI imaging done on 1.5 T MR scanner was read as normal. Imaging done at 3T with 32 channel head coil demonstrates subtle blurring of the gray-white junction in the left frontal lobe with mild T2 prolongation in the underlying white matter. Increased T1 hyperintensity of the left frontal cortex is also noted. Findings consistent with FCD. Axial T2WI Coronal T1 MPRAGE recon Coronal FLAIR Axial FLAIR
  • 26. 13 month old male with medically refractory focal seizures. Coronal & axial T2WI MRI done at 1.5 T MR scanner was read as normal. Same patient as above scanned on a 3T MR scanner. Imaging demonstrates cortical thickening and blurring of gray-white junction in the left temporal lobe. Findings consistent with cortical dysplasia. Coronal T2WI Coronal T2WI Axial T2WI Coronal T1 MPRAGE recon
  • 27. Surgical outcome  Approximately 33–75% of individuals becoming seizure-free. [80% of patients became seizure-free after surgical treatment for mTLE related to HS or lesional epilepsy, such as primary brain tumor or vascular malformations]6,20.  Most important factor:  complete removal of dysplastic cortex [70% compared with 22% of those with incomplete resections - 82% compared with 47% with incomplete resections]