DEC 12, 2012
The authors investigated the anatomical abnormalities of the distal nasolacrimal duct (NLD) in children with congenital obstruction using high-resolution computed tomographic (CT) imaging. The results provide anatomic evidence of a bony or membranous obstruction at the distal portion of the NLD or of a postductal obstruction at the inferior meatus in children with congenital NLD obstruction.
The authors retrospectively reviewed CT scans of the anatomy of the bone and soft tissue of the NLD and the postductal anatomy of the inferior meatus in six children with a wide spectrum of NLD obstructions. The images were reconstructed in a 3-D viewer. They were taken from prior axial (five children) or coronal (one child) CT facial scans at 0.625- or 1.25-mm resolution, respectively.
The axial CT images and 3-D reconstructions showed bony obstructions of the distal NLD in three children, membranous obstructions of the distal NLD in one child, and a postductal obstruction in the inferior meatus in one child. One child had a combined soft tissue obstruction of the NLD and post-NLD obstruction.
The authors note that the distal portion of the NLD complex was the anatomic site of obstruction in each of the patients. They say they have demonstrated by high-resolution CT imaging that NLD obstruction results from one of three mechanisms:
- The increased proportion of the bony wall relative to the central lumen at the distal portion of the NLD.
- The abnormal persistence of a membrane, presumably nasal and lacrimal mucosa in apposition, at the distal portion of the NLD.
- The narrowing of the inferior meatus with apposition of the nasal mucosa.
They propose that each type of distal duct obstruction falls on a continuum that represents distinctive stages in the developmental process that leads to a continuous channel between the NLD and the inferior meatus.
They say a limitation of the study is that four of the six cases represent more extreme developmental abnormalities of the distal NLD.