Nasal dermal sinuses--new concepts and explanations.

Utilizing a series of 13 consecutive patients with nasal dermal sinus-cyst (NDSC) as a basis for study, this area of embryopathology was re-examined in light of the known and also the speculative knowledge available. Four of these patients had NDSC that involved the intracranial cavity and these served as a basis for correlating preoperative radiologic findings with what was actually found at the time of surgery. In so doing, we have been able to show that the pathogenesis of these lesions is consistent and the predictability of their intracranial involvement is based on this consistency. The repeated penetration through the prenasal space and into the foramen cecum is accompanied by a characteristic deformity of the base of the skull that is entirely recognizable radiographically. A protocol of findings has been developed, therefore, that allows the surgeon to be forewarned regarding the depths to which NDSC extends, and as such to design the surgical procedure to fit the lesion. The more basic findings for this study relate to the demonstration in human embryos of an anatomic reason why intracranial dermal cysts grow in the manner in which they do, i.e., in the substance of the falx cerebri; and even more basically, with additional human embryo studies we have been able to demonstrate a neuroectodermal pathway through the prenasal space, thus definitively confirming previous speculated embryomorphologic information. By corroborating the placement of the dermal displacement in the prenasal space, we have speculated that the NDSC is often but one disorder in a spectrum of aberrations which involves not only dermal and neural displacement, but also cranial floor deformities.