Absence of Nasolacrimal Canal
From bonepath
This could possibly be a very rare condition, as there appears to be a lack of literature (at least in English) on the lack of a bony nasolacrimal canal. The incidence of the condition, therefore, is unclear. The nasolacrimal canal is the communication through which tears drain from the orbital to nasal cavities. Absence of the nasolacrimal canal would manifest clinically in epiphora (excessively teary eyes) unless the lacrimal gland was also absent or functionless.
Whereas the literature on the absence of a bony nasolacrimal canal is scant, there is a good deal of information about dysgenesis of the (soft tissue) nasolacrimal duct. Such dysgenesis can result from a number of syndromes, including: Saethre-Chotzen, Kallman Syndrome, Branchial Oculofacial Syndrome, CHARGE, Apert’s, and Amniotic Band Syndromes (Yuen et al. 2004). However, it is not clear whether any of these also cause a failure of bony canalization. It is improbable that conditions resulting in facial clefting or tissue lysis (i.e. Amniotic Band Syndrome) could cause the absence of a bony nasolacrimal canal. Similarly, it is not clear how craniosynostotic conditions (e.g. Saethre-Chotzen Syndrome) could affect bony nasolacrimal morphology, although “tear duct anomalies” apparently affect roughly half of the reported Saethre-Chotzen cases (Fries and Katowitz 1990). In sum, while a good deal of research has been done on the dys- or agenesis of the soft-tissue nasolacrimal system, research into the subsequent bony development is an area for further study.
Following Moss’s functional matrix model of craniofacial growth (Moss and Young 1960), absence of the bony nasolacrimal canal could reflect the embryonic agenesis of the (soft tissue) lacrimal excretory system (e.g. de la Cuadra-Blanco et al. 2004). If the embryonic lacrimal lamina (Carnegie Stage 16-18) or cord (CS 19-22) fail to develop, there would be no reason for the nasolacrimal groove to develop, either. To the best of our knowledge, this is the first time the developmental etiology of an absent bony nasolacrimal canal has been hypothesized.
[edit] Examples from Ford Collection
[edit] References
Fries PD, Katowitz JA. 1990. Congenital craniofacial anomalies of ophthalmic importance. Survey of ophthalmology 35:87-119
de la Cuadra-Blanco C, Peces-Peña MD, Jáñez-Escalada L, Mérida-Velasco JR. 2006. Morphogenesis of the human excretory lacrimal system. J Anat 209:127-35
Moss ML, Young RW. 1960. A functional approach to craniology. Am J Phys Anthropol 18:281-92
Yuen SJ, Oley C, Sullivan TJ. 2004. Lacrimal outflow dysgenesis. Ophthalmology 111:1782-90
