CT AND MR IN INFANTS WITH PERICEREBRAL COLLECTIONS AND MACROCEPHALY -BENIGN ENLARGEMENT OF THE SUBARACHNOID SPACES VERSUS SUBDURAL COLLECTIONS

PURPOSE: To compare CT and MR in the differentiation of benign enlarge ment of the subarachnoid spaces and subdural collections in infants wi th macrocephaly. METHODS: MR was performed in 19 infants with macrocep haly, showing bifrontal enlargement of the subarachnoid spaces on CT. RESULTS: In 11 patients, a single fluid layer could be distinguished o n MR of the pericerebral collections, suggesting benign enlargement of the subarachnoid spaces. In eight patients, two separate layers were clearly differentiated, an outer layer that was hyperintense on all se quences and an inner layer with the same intensity as the cerebrospina l fluid. This indicated the presence of subdural collections. These co llections were mainly frontal in six and extended over the entire hemi sphere in two patients. On CT, these separate lesions were seen only i n three patients and missed in three others. In two final patients, CT findings were equivocal with evidence of membrane formation within th e hypodense collections. In seven patients with a subdural collection, subdural-external drainage was performed. In three patients, the coll ection was hemorrhagic. The protein content of the fluid showed a mean of 1381.7 +/- 785.6 mg/dL. The MR and surgical findings of a subdural collection correlated with the absence of a family history of macrocr ania, an age under 5 months, and acute clinical signs of vomiting, som nolence, and hypotonia. CONCLUSION: MR appears essential in the differ ential diagnosis between benign enlargement of the subarachnoid spaces and subdural collections in infants.