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On the basis of 15 CT scan and MRI studies of normal volunteers, the authors describe the features the lateral pterygoid muscle. A good correlation appears between CT and MR images which would be useful in the staging of tumors in this space, and in the pathophysiology of internal derangements of the temporomandibular joint (TMJ).

The modern imaging techniques (computed tomography, MRI), allow a new approach of the limits and contents of the infratemporal fossa. This better anatomical knowledge allows distinguishing three distinct subregions, hence providing better interdisciplinary understanding.

The infratemporal and paratonsillar regions can be the site of propagation of parotid tumors. Our personal experience with 3 cases of malignant parotid tumors extending into the infratemporal region and the study of the literature seem to show that: benign tumors, such as pleiomorphic adenomas, develop in depth towards the paratonsillar regin and not towards the infratemporal region; and conversely, malignant tumors rather invade the infratemporal regin and not the paratonsillar region. This extension occurs along the neurovascular axis through Juvara's retrocondylar buttonhole. If this notion was confirmed, it might have a semiological and therapeutic interest.

The infratemporal fossa (ITF) is a hidden, subracranial part of the retrofacial region, which is concealed by the mandible. While its definition corresponds to bony relationships, it goes far beyond these. The classical pyramid with a lateral mandibular base and a superomedial apex, the pterygopalatine fossa, actually is a passage for the neurovascular elements it contains. It also is the hidden aspect of the manducatory apparatus, accommodating the pterygoid muscles. Besides these bony limits, the ITF has fasciomuscular boundaries formed posteriorly by the sphenomandibular ligament and the lateral insertion of the styloidian curtain on the angle of the mandible. The anterior limit, under the maxillozygomatic bones, is formed by the pterygomandibular ligament, on which spread the fibers of the buccinator muscle. The inferior limit is only theoretic and corresponds to the lower margin of the mandible. Within these limits, the ITF is connected with the mandible and the lateral manducatory muscles, the parotid gland, the peripharyngeal spaces, the submandibular region. However, it primarily is a passage into the neighboring regions with which it communicates through openings that are either endo- or exocranial, parotid, pharyngeal, nasal, orbital. Thus this fossa is one of the paths of the expansile processes that arise from the neighboring regions and invade it, being guided by the various anatomical openings we have described.

The authors show the interest of C.T. examination of pterygo-maxillary region, principally in the pre-therapeutic staging of the maxillo-facial neoplasy. The anatomical division of the fossa in four regions (pterygoïd muscle area, lateropharyngeal area, pterygo-palatine fossa and retro-maxillary-malar area) can be easily applied to C.T. study. Cuts must be taken axially, in the orbito-meatal plane, and coronally always if possible, before and after administration of contrast medium. Six, out of thirty six cases studied were demonstrative. It appears that C.T. examination must be performed immediately after conventional radiology in the staging of maxillo-facial neoplasy. It shows with considerable accuracy not only the bony involvement, but also the extension in the soft tissues (interest of the densitometric study of fat) and aeric structures. It sometimes brings the solution of special clinical problems (Trismus, neuralgia of the facial nerve).