[Ultrasound differentiation between benign enlargement of the subarachnoid space and brain atrophy]

Fluid collections surrounding the brain (pericerebral fluid collections) in infants can be caused by a variety of conditions: benign enlargement of the subarachnoid space, passive dilatation of the subarachnoid space due to brain atrophy, subdural hygroma and subdural effusion as a result of meningitis or subdural haematoma. An enlarged frontal subarachnoid space and normal or minimally enlarged ventricular size, with normal or increase head circumference is relatively common finding in infancy. Without associated brain anomalies, this finding predicts normal development of the child. In our study, we have followed up psychomotor development of 22 children, with increased diameters of subarachnoid spaces, detected by ultrasound examination of the brain, without associated brain anomalies. The inclusion criterion for study was enlarged subarachnoid space, measured at the conventional coronal section at the level of the interventricular foramen. The upper limits of each measurements were: 3 mm for sinocortical width, 4 mm for craniocortical width and 6 mm for the interhespheric width. The patients have been followed up to the age of 24 months. Each of them had normal development. 16 of them had normal head circumference. 6 of them had head circumference above the 97th percentile and their head circumference measurements have been plotted for the next 6 months after the diagnosis, to be certain that growth is paralleling the normal curve. It is important to differ benign enlargement of subarachnoid space from brain atrophy, which is quite "serious" diagnosis, with poor neurodevelopmental prognosis. The brain atrophy has been presented with passive dilatation of subarachnoid space and ventriculomegaly, as well. In the case of benign enlargement of subarachnoid space normal or minimally enlarged ventricular size is present. For proper interpretation of this ultrasound finding, correlation with head circumference is necessary. We recommend the head circumference percentile chart to be enclosed to the each brain sonography finding. The algorithm of the further neurological evaluation differs significantly in the case of benign enlargement of subarachnoid space and brain atrophy. In the case of benign enlargement of subarachnoid space further neuroimaging procedures are not needed (in our study it has been done for 6 patients). If the brain atrophy is suspected, further complete neurological examination is necessary.