Diagnosis of grey matter heterotopia on cerebral ultrasound in a newborn: lessons from a case report for daily clinical practice

Grey matter heterotopias result from premature arrest of neuronal migration from the germinal matrix in the lateral ventricular wall to the developing cortex. To date, heterotopias have been exclusively diagnosed on magnetic resonance imaging (MRI). We present a case of heterotopia primarily detected with transfontanellar cranial ultrasonography (CUS) and review the literature for sonographic signs to suggest the presence of this pathological entity. Transfontanellar CUS evaluation of a preterm twin revealed a prominent rectangular-shaped left lateral ventricle. Subsequent angled views identified an abnormally increased echogenicity within the ipsilateral cortex. MRI confirmed subependymal and possibly subcortical heterotopia. A literature review using the search words ‘grey matter heterotopia’ was undertaken and further refined for specific information related to imaging criteria on MRI or sonography. Neuroradiologists classify heterotopias on MRI by location and appearance into three types: subependymal, subcortical and band types. Signs of subependymal heterotopia on CUS include ventricular wall irregularity, hyperechoic periventricular band and isolated hyperechoic periventricular nodules protruding into the ventricle. They are rarely associated with cortical lesions. CUS signs of subcortical heterotopia include abnormal hyperechoic regions in the white matter. Our sonographic imaging revealed an irregular shape of the left ventricle suggestive of subependymal heterotopia. Other abnormalities described with subependymal heterotopia were not found. A hyperechoic structure in the left cortical region next to the affected lateral ventricle could represent enfolded cortex as is seen in subcortical heterotopia. We propose an extended search for cerebral lesions outside the usual field of view (i.e. white matter and cortex) using angled coronal and parasagittal CUS views to display frontal, occipital and lateral cortices as optimally as can be achieved whenever an angular or irregular lateral ventricle shape is encountered. The differential diagnoses including haemorrhagic, ischaemic and structural parenchymal lesions should be extended to include grey matter heterotopia.