SummaryThe dentigerous cyst or temporal teratoma in horses is a well‐known congenital malformation that occurs in the temporal region and usually contains dental tissue. This case report describes two horses with a previously unreported variant of the dentigerous cyst associated with an exostosis arising from the temporal bone. The principal clinical sign was a draining tract opening at the margin of the right pinna in both horses. There was no evidence of an ectopic tooth on the radiographs or at ultrasonographic examination. Computed tomography combined with positive contrast sinography of the draining tract revealed bone formation arising from the supramastoid crest of the right temporal bone extending towards a cyst‐like structure but without direct connection in both cases. This bone formation was located at a site on the supramastoid crest, close to the external acoustic meatus, where ectopic teeth may also occur. Both cysts were removed surgically with a good long‐term outcome.

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This basically anatomical study focuses on two items; firstly, the establishment of a system for the cartographic subdivision of the neopallium; secondly, the topographical correlation of extracranial landmarks and intracranial sites on the neopallium. The surface of the neopallium was subdivided into 15 Sectors with reference to a newly introduced pattern of Primary Sulci. The topographical link between extracranial landmarks and certain intracranial sites (i.e., neopallium Sectors) was elaborated by using a simple stereotactic device and a computer-assisted measurement device.Measurements were performed between points on the head´s outer surface and on the isolated brain.The introduction of an anatomical three-dimensional Coordinate System was an essential key issue for this investigation. This setting facilitated the measurements and calculations of the so-called Indirect Distances that were characterized by their alignment along the three orthogonal axes (x, y, z) of the anatomical Coordinate System. The inter-individual comparison (16 adult horses [Equus caballus]) of the Indirect Distances revealed that each Sector Center lay within a distinct morphometric Residence Area. The measured and calculated data also showed that each Sector Center could be assigned to its proper extracranial landmark thatin comparison with other landmarkswas best suited for the optimal allocation of the Sector Center Point.