Sonographic nomogram of the leptomeninges (pia-glial plate) and its usefulness for evaluating bacterial meningitis in infants

BACKGROUND AND PURPOSE: To our knowledge, the upper limits of the thickness of normal meninges on neurosonograms are not known, We therefore establish ed a nomogram for sonographic measurements of the leptomeninges (pia-glial plate) and assessed its usefulness in neurosonographic examinations of chil dren with bacterial meningitis. METHODS: The pia mater-cortical glia limitans complex on the surface of the brain and in the sulcus of a frontal gyrus was measured on neurosonograms in 100 infants without meningeal disease in order to establish a nomogram o f the thickness of this pia-glial plate, referred to as the leptomeninx, Ef fects of prematurity, age, sex, and single-layer (surface) versus double-la yer (sulcus) measurements were analyzed. Meningeal thicknesses derived from a retrospective analysis of the neurosonograms of 33 patients with purulen t meningitis and a prospective study of 22 patients with bacterial meningit is were compared with the nomograms, Clinical outcomes of children with men ingeal thickening were compared with those of affected children with normal meninges. RESULTS: The distribution of sulci measurements was significantly asymmetri cal around the mean, Statistical data showed no influence of prematurity an d sex, but showed surface measurements to be more consistent than sulcal me asurements, Older chronological age was related to slightly larger sulci, b ut did not influence the surface measurements, In children with bacterial m eningitis, the surface meninges were less frequently thickened than were th e sulci, Sulcal enlargement occurred often in combination with echogenic de posits in the subarachnoid space. CONCLUSION: Leptomeninges are best measured on the surface of a gyrus rathe r than in a sulcus, as the normal thickness of the sulci shows much more va riability, Clinical outcome of bacterial meningitis cannot be predicted by presence or absence of meningeal thickening as the only sonographic abnorma lity.