Although the infratemporal region is well defined anatomically, its complex topography has been the subject of numerous, and sometimes, opposite works. That is the reason why it appeared necessary for the authors to re-evaluate this topic using the original method of Combelles and Boyer, allowing to define three referential planes, and thereby, a tridimensional shape and the volume of this region. This study allows to conclude that the infratemporal region is a triangular prism with an horizontal main axis 47 mm long. Its anterior base has a mean area of 733 mm2. The posterior top consists of the Juvara slot and has a mean area of 490 mm2. This infratemporal prism contains another one, the pterygomandibular space, prismatic too. It widens out from coronoïd plane (93 mm2) to mandibular foramen plane (169 mm2) before ending as a narrow groove between the neck of the mandibular condyle and the interpterygoïd fascia. The volume of the pterygomandibular space is quite superior to the value usually reported in the dental literature. It is of 4.8 ml to 5.8 ml according to denture. These results point out the opportunity to accomodate more important volumes of anesthesic solutions, than the 1.8 ml usually performed, without any leak out of the infratemporal region.

RÉSUMÉLe diagnostic différentiel entre névralgie trigéminale essentielle (NTE) et symptomatique est facilité lorsque le tableau clinique d'une NTE est constitué, et que l'examen clinique et neurologique est négatif. En revanche, ce diagnostic différentiel s'avère plus hasardeux lorsqu'une névralgie trigéminale symptomatique imite parfaitement les caractères cliniques d'une NTE. Cet article rapporte le cas d'une patiente de 81 ans avec des antécédents de dépression se plaignant d'une part, d'accès douloureux en décharge évoluant depuis les 3 dernières semaines et limités à une petite partie du territoire du nerf mandibulaire, et d'autre part de pertes de connaissances brèves dont la fréquence a augmenté récemment. Ce dernier point a conduit à pratiquer un examen tomodensitométrique qui a révélé la présence d'un anévrysme intracaverneux de la carotide interne. Les auteurs discutent les différentes hypothèses étiopathogéniques impliquant les conflits neurovasculaires dans le déclenchement des NTE, et soulignent l'importance de garder à l'esprit le fait qu'une cause tumorale cachée peut toujours être à l'origine d'une algie d'apparence essentielle. Cette observation d'une névralgie trigéminale en rapport avec un anévrysme intracaverneux de la carotide interne est la seule répertoriée à notre connaissance SUMMARY The differential diagnosis between so-called idiopathic trigeminal neuralgia and symptomatic trigeminal neuralgia is easy when the clinical criteria of tic douloureux are gathered and the neurologic examination is negative. Actually it is much more difficult, when a symptomatic neuralgia mimics the main features of an idiopathic trigeminal neuralgia. This paper reports the case of a women, aged 81 , with a history of depression and a complaint for painful epidodes during the last three weeks characterised by short-lasting attacks of intense , electric shocklike pain limited to the distribution of third division of the left trigeminal nerve and frequent fainting fits. This last criterion led us to ask for CT examination. CT images evidenced an aneurysm of the left intracavernous internal carotid artery probably related to the observed neuralgia. Authors discuss the etiopathogenic hypotheses reported by litterature about neurovascular conflicts and underline the necessity of keeping always in mind the possiblity of an hidden tumoral etiology to idiopathic trigeminal neuralgia-like syndroms. This case of trigeminal neuralgia related to an aneurysm of the left intracavernous internal carotid artery is to