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FOCAL CORTICAL DYSPLASIA
Dr Ashraf Abdou
Professor of neurology
Normal Cortical Development
proliferation of neurons in the ventricular zone and glia in the
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
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
Once at adult site – establish synaptic connections with
neighbouring neurons & send axons to targets
Generally migrate centrifugally towards brain surface
Timing of Neuroblast migration
Cerebrum – neuroblasts – begin by 6 weeks – last till
Cerebrum – glioblast – migrate till early post natal
Brainstem – migration of neuroblast complete by 2
Cerebellum – continue till 1 year
Formation of sulci & gyri
Migrating neuroblasts necessitate more surface area
without increasing volume
Proliferation of Glia
Growth of dendrites & axons
Neuronal Migration Disorders
I. True migration disorders
Neurons fail to reach their intended destination.
1. Lissencephaly (agyria, pachygyria and sub-cortical
2. Cobble stone complex malformation.
II. Malformations of cortical organization.
Microscopic abnormality in cortical arrangement.
3. Focal cortical dysplasia.
Lissencephaly with sub cortical band heterotopia.
Normal at birth.
Seizures uncommon on 1st day of
Seizures at 3-6 months, later
infantile spasm and Lennox-
Profound MR .
Early hypotonia, later spastic
quadriplegia and opisthotonus.
Subcortical band heterotopia-Double cortex
Sub-cortical, symmetric, circumferential bands of gray
matter, separated from cortex by thin band of white matter. “Double
Group of neurons is an inappropriate location –
either below or above the cerebral cortex.
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.
Focal cortical dysplasia with abnormal cell
types (balloon cells)
It is clear only with histopathology, not with MRI
Autopsy studies 1.7% incidence of FCD in
The incidence was significantly higher
(46.5%) in patients with epilepsy
In surgical treated epilepsy:
In pediatric patients the incidence was
In an adult population: 15%
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
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 with 2ry generalization
Many patients have more than one seizure type
Focal cortical dysplasia
Blurring of the
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.
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
increased cortical thickness
poor gray-white matter differentiation
increased subcortical signal intensity on T2-weighted
Focal cortical dysplasia
(A1) T1WI : cortical thickening
(A2) Proton-density-WI : blurring of interface between GM and
(A3) T2WI : increased signal change
(A4) FLAIR image : increased signal change
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
• T1 hyperintensity of the cortex
Coronal T2WI Axial T2WI Axial T1 MPRAGE
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.
MPRAGE recon Coronal FLAIR Axial FLAIR
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
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
Most important factor:
complete removal of dysplastic cortex
[70% compared with 22% of those with
incomplete resections - 82% compared with
47% with incomplete resections]