classification system for malformations of cortical development.It is important to note that comparing the spectrographic trace to the 'normal-appearing contralateral side' is not necessarily valid as control as metabolic abnormalities in patients with malformations of cortical development may be widespread 7.įMRI ( BOLD imaging) can demonstrate activation in heterotopic nodules and these can match epileptogenic EEG discharges 8. In general MR spectroscopy demonstrates a decrease in NAA/Cr ratio in the heterotopic grey matter compared to normal control subjects. Their margins are often indistinct. Careful examination of the remainder of the brain is necessary to identify associated anomalies. On MRI the heterotopic tissue follows grey matter on all sequences. Thin or small regions may not be apparent. Grey matter heterotopia has a slightly higher density than the surrounding white matter and can thus be seen if sufficiently large. UltrasoundĪntenatal 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 6. Radiographic featuresĪs 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. Migration takes place from 8 to 26 weeks gestation and is maximal between 8 and 16 weeks 10.
Neuroblasts proliferate in the germinal matrix between 7 and 8 weeks of gestation. Grey matter heterotopias are believed to be due to 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.
Grey matter heterotopias are seen with greater frequency in patients with other congenital central nervous system anomalies, and these associated anomalies will also affect symptomatology.
Additionally, and depending on the extent, children may demonstrate developmental delay or intellectual disability 3. Patients most commonly present with focal seizures in the second decade of life. Although heterogeneous, some forms are X-linked as such there is an overall predilection.
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