grey matter heterotopia
The grey matter heterotopias are a relatively common group of conditions characterized by interruption of normal neuronal migration from near the ventricle to the cortex, thus resulting in "normal neurons in abnormal locations" . They are a subset of disorders of cortical formation .
Grey matter heterotopias can be divided macroscopically into:
- nodular heterotopias
- subependymal heterotopia: most common
- subcortical heterotopia
- diffuse heterotopias
- band heterotopia: also known as double cortex heterotopia and X-linked lissencephaly (chromosome Xq22.3)
- lissencephaly: types 1 and 2
- laminar heterotopia (a problematic term variably defined)
These are discussed in detail separately. The rest of this article concerns itself with a general overview.
Epidemiology
Although heterogeneous, some forms are X linked as such there is an overall predilection.
Clinical presentation
Patients most commonly present with partial seizures in the second decade of life. Additionally, and depending on the extent, children may demonstrate developmental delay or intellectual disability . Grey matter heterotopias are seen with greater frequency in patient with other congenital central nervous system anomalies, and these associated anomalies will also affect symptomatology. Associated anomalies include :
- agenesis of the corpus callosum
- pachygyria
- schizencephaly
- polymicrogyria
- Chiari II malformation
- basilar cephalocoeles
Pathology
Grey matter heterotopias are believed to be due interruption of the normal migration of neurons from the periventricular telencephalic germinal matrix to the cortex and may be due to either genetic abnormalities or infection/trauma.
Neuroblasts proliferate in the germinal matrix between 7 and 8 weeks of gestation. Migration take place from 8 to 26 weeks gestation, and is maximal between 8 and 16 weeks .
Radiographic features
As is the case with most imaging of the central nervous system, MRI is the modality of choice in assessing heterotopic grey matter due to its as yet unsurpassed contrast resolution.
Ultrasound
Antenatal and neonatal ultrasound has difficulty identifying heterotopic grey matter as the echogenicity of such grey matter is not sufficiently different from the surrounding white matter .
CT
Grey matter heterotopia has a slightly higher density than the surrounding white matter and can thus be seen if sufficiently large. Thin or small regions may not be apparent.
MRI
On MRI the heterotopic tissue follows grey matter on all sequences. Their margins are often indistinct. Careful examination of the remainder of the brain is necessary to identify associated anomalies.
In general MR spectroscopy demonstrates a decrease in NAA/Cr ratio in the heterotopic grey matter compared to normal control subjects. It is important to note that comparing the spectrographic trace to the 'normal-appearing contralateral side' is not necessarily valid as a control as metabolic abnormalities in patients with malformations of cortical development may be widespread .
fMRI (BOLD imaging) can demonstrate activation in heterotopic nodules and these can match epileptogenic EEG discharges .
See also
Siehe auch:
- Arnold-Chiari-Malformation Typ 2
- Schizenzephalie
- Lissenzephalie
- Polymikrogyrie
- Dysembryoplastischer neuroepithelialer Tumor
- periventrikuläre Heterotopie der grauen Substanz
- BOLD-Kontrast
- laminar heterotopia
- subcortical heterotopia
- pachygyria - lissencephaly spectrum
- Dysgenesie des Corpus callosum
- Band-Heterotopie
- Zephalozele
- kortikale Malformation
- closed-lip-Schizenzephalie
- subcortical grey matter heterotopia
und weiter:
Assoziationen und Differentialdiagnosen zu Heterotopie der grauen Substanz:
