The infraorbital nerve constitutes a branch of the maxillary nerve, the second branch of the V pair of cranial nerves. It emerges from a canal of the same name on the malar surface and conducts the sensitivity of the skin and mucous membranes of the middle third of the face. Once out, it is divided into 4 distal branches, dedicated to the skin areas of competence, and 3 proximal ones – the latter correspond to the upper, anterior, middle, and posterior alveolar nerves, which together form the plexus that serves the entire upper dental arch.
The canalis sinuosus was first described in 1939 by Jones as a nerve that emerges from the posterior portion of the infraorbital canal and then flows into a tortuous bone channel, about 2 mm in diameter, beside the nasal cavity.
The canal originates froCanalis sinuosusm the terminal tract of the infraorbital canal (i.e., before it flows into the respective canal), running initially forward towards the nasal cavity and then moving downwards after describing an “S.” The canal, after an intraosseous path of more than 5 cm, finally emerges from a secondary canal at the palatal level – the latter tract is subject to important anatomical variability.
The structure houses the course of the anterior superior alveolar nerve (with the respective comitant vessels) and is, therefore, not underestimated, especially in the area’s implant surgery. Fortunately, the final tract of the nerve, which, as mentioned, participates in the plexus dedicated to the upper arch, presents a series of anastomoses that are able to vicariate any damage; in some cases, however, it is possible to find neurological disorders related to traumatic events. Moreover, these symptoms are often difficult to interpret from a clinical point of view as they are not properly evaluated previously.
Ferlin’s group has conducted a systematic review on the subject, obtaining a total of 70 records from the Scopus, Medline, and Web Of Science databases, 11 of which have been evaluated qualitatively. Most of the studies consist of CT cone beams to evaluate accessory channels. However, 90% of the evidence, relating to these documents, was evaluated as being of moderate or high quality.
The study concluded by observing the possible variability of the canalis sinuosus in terms of position, diameter, route, and presence of accessory channels. The canalis sinuosus is present between 88 and 100% and its accessories between half and 70% of the time.
As far as clinical management in surgical cases is concerned, the authors underline the importance of not underestimating the problem, especially during the surgical programming phase; the most recommended diagnostic measure, from this point of view, is CT cone beam.