Schuknecht, B; Stergiou, G; Grätz, K W (2008). Masticator space abscess derived from odontogenic infection: imaging manifestation and pathways of extension depicted by CT and MR in 30 patients. European Radiology, 18(9):1972-1979. Postprint available at: http://www.zora.uzh.ch University of Zurich Posted at the Zurich Open Repository and Archive, University of Zurich. Zurich Open Repository and Archive http://www.zora.uzh.ch Originally published at: European Radiology 2008, 18(9):1972-1979. Winterthurerstr. 190 CH-8057 Zurich http://www.zora.uzh.ch Year: 2008 Masticator space abscess derived from odontogenic infection: imaging manifestation and pathways of extension depicted by CT and MR in 30 patients Schuknecht, B; Stergiou, G; Grätz, K W Schuknecht, B; Stergiou, G; Grätz, K W (2008). Masticator space abscess derived from odontogenic infection: imaging manifestation and pathways of extension depicted by CT and MR in 30 patients. European Radiology, 18(9):1972-1979. Postprint available at: http://www.zora.uzh.ch Posted at the Zurich Open Repository and Archive, University of Zurich. http://www.zora.uzh.ch Originally published at: European Radiology 2008, 18(9):1972-1979. Masticator space abscess derived from odontogenic infection: imaging manifestation and pathways of extension depicted by CT and MR in 30 patients Abstract Propagation of odontogenic masticator space abscesses is insufficiently understood. The purpose was to analyse pathways of spread in 30 patients with odontogenic masticator space abscess. The imaging findings in 30 patients (CT in 30, MR in 16 patients) were retrospectively analysed. CT and MR imaging depicted a masticator space abscess within: medial pterygoid muscle in 13 patients (43.3%), lateral masseter and/or pterygoid muscle in 14 (46.7%) and superficial temporal muscle in 3 patients (10%). In the lateral masticator space intra-spatial abscess extension occurred in 7 of 14 patients (50%). The sub-masseteric space provided a pathway in seven (70%). Extra-spatial extension involved the submandibular space only in 3 of 14 patients (21.4%). Medial masticator space abscesses exhibited extra-spatial spread only. Extension affected the parapharyngeal space and/or soft palate in 7 of 13 lesions (53.8%). MR imaging in comparison to CT increased the number of abscess locations from 18 to 23 (27.8%) and regions affected by a cellular infiltrate from 12 to 16 (33.3%). The sub-masseteric space served as a previously underestimated pathway for intra-spatial propagation of lateral masticator abscesses. Medial masticator space abscesses tend to display early extra-spatial parapharyngeal space and/or soft palate extension. Eur Radiol (2008) 18: 1972–1979 DOI 10.1007/s00330-008-0946-5 HEAD AND NECK B. Schuknecht Masticator space abscess derived G. Stergiou K. Graetz from odontogenic infection: imaging manifestation and pathways of extension depicted by CT and MR in 30 patients Abstract Propagation of odontogenic exhibited extra-spatial spread only. Received: 21 July 2007 Revised: 1 January 2008 masticator space abscesses is insuffi- Extension affected the parapharyngeal Accepted: 28 January 2008 ciently understood. The purpose was space and/or soft palate in 7 of 13 Published online: 17 April 2008 to analyse pathways of spread in 30 lesions (53.8%). MR imaging in com- # European Society of Radiology 2008 patients with odontogenic masticator parison to CT increased the number of space abscess. The imaging findings abscess locations from 18 to 23 B. Schuknecht Section Neuroradiology, MRI in 30 patients (CT in 30, MR in 16 (27.8%) and regions affected by a Medizinisch Radiologisches Institut, patients) were retrospectively ana- cellular infiltrate from 12 to 16 Bahnhofplatz 3, lysed. CT and MR imaging depicted a (33.3%). The sub-masseteric space CH 8001 Zurich, Switzerland masticator space abscess within: me- served as a previously underestimated G. Stergiou . K. Graetz dial pterygoid muscle in 13 patients pathway for intra-spatial propagation Department of Cranio-Maxillofacial (43.3%), lateral masseter and/or pter- of lateral masticator abscesses. Medial Surgery, University Hospital of Zurich ygoid muscle in 14 (46.7%) and su- masticator space abscesses tend to Switzerland, perficial temporal muscle in 3 patients display early extra-spatial parapha- Frauenklinikstr 24, (10%). In the lateral masticator space ryngeal space and/or soft palate CH 8091 Zurich, Switzerland intra-spatial abscess extension oc- extension. B. Schuknecht (*) curred in 7 of 14 patients (50%). The MRI, sub-masseteric space provided a path- Keywords Masticator space abscess . Bahnhofplatz 3, way in seven (70%). Extra-spatial Odontogenic infection . CH 8001 Zurich, Switzerland . e-mail: [email protected] extension involved the submandibular Submasseteric space Tel.: +41-442252090 space only in 3 of 14 patients (21.4%). MR imaging . CT Fax: +41-442118754 Medial masticator space abscesses Introduction muscle. The infrazygomatic part of the masticator space is separated by the mandibular ramus into a medial and lateral A masticator space abscess represents an advanced stage of compartment [8, 9]. The medial part contains the medial a commonly odontogenic infection indicated by facial pain, pterygoid muscle. The lateral masticator space harbours the swelling and trismus [1–3]. Anatomically (Fig. 1), the masseter muscle, which communicates with the lateral masticator space is defined by the superficial layer of the pterygoid and temporal muscle superiorly. In 1948 deep cervical fascia [4–8]. As it splits at the lower margin Bransby–Zachary [10] described a “sub-masseteric” of the mandible, the medial fascia follows the medial space lateral to the mandibular ramus. As a virtual space pterygoid muscle where it joins the levator veli palatini between separate attachments of the masseter muscle [10, fascia to attach to the skull base. The lateral sleeve covers 11], it is prone to inconspicuous abscess accumulation. the masseter and superficial temporal muscle and attaches The vertical orientation of the fascia layers within the to the zygomatic arch and the inferior oblique line of the masticator space predisposes to a far more extensive temporal squama [4]. cranio-caudad (intra-spatial) extension of infection than is For descriptive terms, the masticator space is subdivided clinically anticipated [4, 5, 9]. Extension beyond the into a suprazygomatic portion that contains the temporal confines of the masticator space (extra-spatial) at least 1973 Fig. 1 a, b Line drawing of the coronal (a) and axial anatomy (b) with schematic delineation of the preferred pathways of intra- and extraspatial extension of infection initially is considered rare [4]. It subsequently may affect MR system with an eight-channel phased array head the parapharyngeal space medially, the submandibular coil and a field of view of 180 mm. The sequences space inferiorly, the buccal space anteriorly, or the parotid employed were axial and coronal T2 fast spin echo space posteriorly [5]. sequences (TR 4,000–4,200, TE 90ms, three excitations, The precise pathways of intra-spatial abscess propaga- 3.5-mm-thick sections, matrix 448×224, ETL 13) and tion remained undetermined [1, 2, 12] or were assumed to axial/coronal T1 sequences (TR 400–450, TE 10–14 ms, be via the parotid and parapharyngeal space [3]. In the two excitations, 3.5-mm slice thickness, matrix 448× present series of 30 patients, the imaging manifestations 224) obtained before and after intravenous GD admin- were assessed in order to support understanding of intra- istration (20 ml 0.1 mmol/l). A fat saturation pulse was and extramasticator space extension of odontogenic added to the axial and coronal contrast-enhanced T1- abscesses. weighted sequences. The CT and MR images were retrospectively and Patients and methods The imaging findings of 30 patients independently reviewed by a neuro-radiologist (B.S), and with a masticator space abscess confirmed by surgery in a maxillo-facial surgeon with particular experience in 28 patients and follow-up imaging in 2 patients were maxillo-facial and dental radiology (G.S). In each retrospectively reviewed. The patients had been included individual patient the CT images were analysed first into the study prospectively with the clinical diagnosis of followed by the MR examination when available. The odontogenic infratemporal fossa abscess. review was performed blinded to the results of surgery. The patients had been treated between 2000 and 2006 at Images were assessed with respect to the presence of the Department of Cranio-Maxillo-Facial Surgery in abscess (A), sub-masseter abscess (smA) and cellulitis (x) Zurich under the surveillance of the senior author and and bone changes. head of the department (K.G.). The patients had given Based on the nomenclature and descriptions of the fascia consent for retrospective evaluation of the imaging and lined spaces in previous publications [4, 5], including surgical findings. definition of the sub-masseteric space [11], each observer Imaging consisted of contrast-enhanced CT (100 ml at attributed the location of an abscess or cellulitis to the 2 ml/s, 40-s data acquisition delay) performed in every of different components of the masticator space: medial 30 patients using a 4- or 64-multi-detector CT (MDCT) pterygoid muscle (MPTM), masseter muscle (MM)/ with a slice collimation of 1 mm reconstructed to submasseteric space (sm), lateral pterygoid muscle 1.25/0.7 mm increment for the 4 MDCT, a slice collimation (LPTM) and temporal muscle (TM).