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Table of Contents
LETTER TO EDITOR
Year : 2022  |  Volume : 5  |  Issue : 1  |  Page : 185-186

M. masseter pars coronoidea: Gateway between the masticator space and infratemporal fossa


Department of Radiodiagnosis & Imaging, Homi Bhabha National Institute, Tata Memorial Hospital, Tata Memorial, Center, Mumbai, Maharashtra, India

Date of Submission10-Jan-2022
Date of Decision19-Jan-2022
Date of Acceptance19-Jan-2022
Date of Web Publication24-Feb-2022

Correspondence Address:
Abhishek Mahajan
M.D., Fellowship In Cancer Imaging, MRes(KCL, London), FRCR (UK). Room No 125, Department of Radiodiagnosis & Imaging, Homi Bhabha National Institute, Tata Memorial Hospital, Tata Memorial Centre, Dr E Borges Road, Parel, Mumbai, Maharashtra, 400 012
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/crst.crst_9_22

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How to cite this article:
Mahajan A, Smriti V. M. masseter pars coronoidea: Gateway between the masticator space and infratemporal fossa. Cancer Res Stat Treat 2022;5:185-6

How to cite this URL:
Mahajan A, Smriti V. M. masseter pars coronoidea: Gateway between the masticator space and infratemporal fossa. Cancer Res Stat Treat [serial online] 2022 [cited 2022 May 21];5:185-6. Available from: https://www.crstonline.com/text.asp?2022/5/1/185/342417



We read with great interest and congratulate the authors on their discovery of the new muscle of mastication named “M. masseter pars coronoidea” which will have significant implications in the management of oral cancers [Figure 1].[1] As per the American Joint Committee on Cancer staging system, involvement of the masticator space in oral cancer is staged as T4b disease. T4b disease has the worst overall and progression-free survival of all T-stages of oral cancer.[2],[3],[4] The masticator space is an anatomical space between the superficial (investing) layer of the deep cervical fascia which divides into two layers at the level of the inferior border of the mandible and forms the masticator space which is bounded by the medial pterygoid fascia medially and the masseter muscle laterally. The space medial to the mandible contains the medial pterygoid muscles and temporalis tendon; the masseter muscle is lateral to the mandible.[3],[4] Another overlapping space known as “infratemporal fossa (ITF)” shares some of its contents with the masticator space and is known to determine the management and outcomes in oral cancers. ITF is a complex surgical space bounded medially by the parapharyngeal space and laterally by the inner border of the mandible. The space contains the following muscles: medial and lateral pterygoid, temporalis, tensor veli palatini, levator veli palatini, and superior constrictor muscle. The masseter muscle is not a component of the ITF.[3],[4] The ITF is further divided into high and low ITFs by the mandibular notch. Above the notch, the space is known as “high ITF” and below, “low ITF.” Oral cancers reaching up to the high ITF tend to have poor local control and are deemed to be unsuitable for radical surgery.[4],[5],[6] The discovery of M. masseter pars coronoidea may have a huge clinical impact on the management of oral cancers. At the level of the mandibular notch (high ITF), this new muscle bridges the two important spaces, namely the “masticator space” and the “ITF.”[1] The coronoid part of the masseter muscle which is now named M. masseter pars coronoidea forms the cross-connection between the masseter muscle laterally and the temporalis muscle medially [Figure 1] and [Figure 2]. The fibers of the M. masseter pars coronoidea muscle at the level of the mandibular notch run laterally from the masticator space over the mandibular notch and medially into the ITF having close proximity to the temporalis tendon [Figure 1] and [Figure 2]. This muscle may also serve as a landmark to divide the ITF into high and low ITFs.[3],[5] The M. masseter pars coronoidea muscle at the level of the mandibular notch will redefine the boundary of the masticator space and the ITF, shifting the masticator space medially at this level. The anterior part of the supranotch space will become the masticator space. As part of it originates from the temporalis fascia, its margin with the temporalis muscle becomes indistinct at this position and the two spaces merge into each other.[1],[3]
Figure 1: Sagittal computed tomography image showing the coronoid part of the masseter originating superiorly from the temporal side of the zygomatic arch and running obliquely anteroinferiorly to attach to the coronoid process of the mandible

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Figure 2: Axial computed tomography scan at the level of the high infratemporal fossa (at the mandibular notch level): Temporalis muscle (blue), coronoid process of masseter (brown), and deep layer of masseter (green)

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Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Mezey SE, Müller-Gerbl M, Toranelli M, Türp JC. The human masseter muscle revisited: First description of its coronoid part. Ann Anat 2021;240:151879.  Back to cited text no. 1
    
2.
Vaidya T, Desai S, Mahajan A. 8th edition AJCC and imaging TNM: Time to break-in and assert in the staging process! Indian J Cancer 2019;56:271-3.  Back to cited text no. 2
    
3.
Mahajan A, Ahuja A, Sable N, Stambuk HE. Imaging in oral cancers: A comprehensive review. Oral Oncol 2020;111:104956.  Back to cited text no. 3
    
4.
Mahajan A, Suthar M, Agarwal U, Shukla S, Thiagarajan S, Sable N. Imaging-based T stage (iT) as a predictive and prognostic marker for outcome in T4 stage tongue carcinomas: A narrative review. Cancer Res Stat Treat 2021;4:677-83.  Back to cited text no. 4
  [Full text]  
5.
Liao CT, Ng SH, Chang JT, Wang HM, Hsueh C, Lee LY, et al. T4b oral cavity cancer below the mandibular notch is resectable with a favorable outcome. Oral Oncol 2007;43:570-9.  Back to cited text no. 5
    
6.
Liao CT, Chang JT, Wang HM, Ng SH, Hsueh C, Lee LY, et al. Survival in squamous cell carcinoma of the oral cavity: Differences between pT4 N0 and other stage IVA categories. Cancer 2007;110:564-71.  Back to cited text no. 6
    


    Figures

  [Figure 1], [Figure 2]



 

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