Masticator Space Neoplasms

Abstract

The masticator space (MS) is a deep facial space delineated by a splitting of the deep cervical fascia which encloses the four muscles of mastication: the medial and the lateral pterygoid, the masseter, and the temporalis muscles – hence the denomination of “masticator space” (Harnsberger 1995; Mukherji and Chong 2004). The MS also contains the ramus and posterior body of the mandible and the third division of the fi fth cranial nerve (mandibular trigeminal branch or V3). The V3 nerve gives motor innervation to the mastication muscles and relays sensory information from the inferior teeth, gums and lower lip/chin region through the inferior alveolar nerve. The nerve emerges from the endocranium to the MS through the foramen ovale. The space is easy to identify on both CT and MR images (Figs. 10.1, 10.2) because of easily recognizable shape and location of the mastication muscles (Harnsberger and Osborn 1991; Mukherji and Castillo 1998). The inferior limit of the MS is the attachment of the medial pterygoid muscle to the mandible. The space has two distinct superior margins. The base of the skull is the superior limit of the “infratemporal fossa” or “nasopharyngeal masticator space” which encompasses all soft tissue below the foramen ovale. The second superior margin is the attachment of the temporalis muscle to the outer table of the skull; this part is called the “temporal fossa”, or the “suprazygomatic masticator space” because it is above the zygomatic arch (Fig. 10.2). The MS is separated from the parapharyngeal space by a fascial layer extending from the medial pterygoid muscle to the skull (Curtin 1987). The fascia is also attached to the anterior aspect of the mandibular ramus, has an interface with the oral cavity, and reaches the posterior margin of the ramus, where the masticator space constitutes the anterior border of the parotid space.