CASE 11444 Published on 08.02.2014
0

Quadruple mental foramina detected by CBCT: a case report

Section

Head & neck imaging

Case Type

Anatomy and Functional Imaging

Authors

Dimitar Yovchev

Medical University - Sofia,
Faculty of Dental Medicine,
Department of Imaging and Oral Diagnostic;
Georgi Sofiiski str 2,
Sofia, Bulgaria;
Email:dr.iovchev@dir.bg
Connected authors
Patient

15 years, male

Categories
Area of Interest Anatomy, Head and neck ; Imaging Technique CT-High Resolution
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Clinical History
We present a case of a 15-year-old Bulgarian Caucasian patient who underwent Cone Beam Computed Tomography (CBCT) to evaluate his jaws and temporomandibular joints for orthodontic treatment. On the CBCT we found an incidental finding at the right side of the mandible (Fig. 1).
Imaging Findings
On CBCT, four mandibular foramina were found on the right side of the mandible. One of these was just as large as the left mandibular foramen (MF) and in the same position. The additional foramina on the right were smaller. Two of these were positioned medially to the right MF, one was positioned laterally (Fig. 1 and 2).
Discussion
The mental foramen (MF) is an anatomic opening on the outer surface of the mandible through which the mental nerve branches and blood vessels ensure innervation and vascularization of the skin and mucosa of the lower lip, gingiva, cheeks, and chin. Earlier studies showed that the number of mental foramina can vary and reach up to four on one side [1]. The presence of accessory foramina is much more common than absence of the foramen [1]. Supplementary blood vessels or nerves in accessory MF may be significant for anaesthesia procedures and the knowledge about their presence could be used to avoid post-operative complications (haemorrhages and sensory disturbances) during implant installations [1, 2].
Near to the MF there are other important structures - i.e. lingual concavity, mandibular incisive canal and anterior loop of the inferior alveolar nerve [3, 4].These should also be taken into account before implant placement.
Cone beam computed tomography (CBCT) makes it possible to visualize the MF and possible variations with high spatial resolution.
In cases of surgical interventions (e.g. endosseous dental implantation) it is very important to preserve the neurovascular bundle in the mandibular canal and mental foramen. Accessory MF are defined as bony foramina originating from the mandibular canal - as in this case (Figure 3). It is important to differentiate accessory mental foramina from nutritive vascular channels/foramina and fistulas.
Panoramic and intra-oral radiographs, widely used in dental practice, may not always demonstrate the presence of (small) accessory MF (Fig. 4) [5, 6].
Earlier studies reported that the general incidence of double mental foramina ranges from 1.8% to 10.6 % [2, 7-9]. Triple or four mental foramina are very rare findings. Gershenson et al. described triple foramina in 0.7 % of 525 dry mandibles and four foramina only in one mandible - 0.19%. Katakami et al. reported triple foramina in 0.6% of 150 patients investigated by limited CBCT, Naitoh et al. - 1.2 % [8-10]. We found only one study reporting quadruple MF [8].
Using CBCT, all bony structures in the mental region including the mental foramina (i.e. accessory foramina), mandibular incisive canal, lingual concavity and anterior loop of the inferior alveolar nerve can be depicted [3, 4, 11-13].
In the literature, we did not find quadruple mental foramina detected by CBCT.
We conclude that anatomical variants such as double, triple and quadruple mental foramina have to be recognized in order to avoid potential neurosensory disturbances and haemorrhages during and after surgical procedures.
Differential Diagnosis List
Quadruple mental foramina on the right side of the mandible
Nutritive canals
Fistulas
Final Diagnosis
Quadruple mental foramina on the right side of the mandible
Case information
URL: https://www.eurorad.org/case/11444
DOI: 10.1594/EURORAD/CASE.11444
ISSN: 1563-4086
Figure 1

Three-dimensional reconstruction

Three-dimensional reconstruction
Three-dimensional reconstruction of the lower jaw.
Figure 2

Four mental foramina seen on cross-sections on right mandibular side.

Four mental foramina seen on cross-sections on right mandibular side.
Ovoid openings in the buccal cortex of the right mandible constituting a well-defined four mental foramina seen on cross-sections and VR panoramic reconstruction.
Figure 3

CBCT panoramic reconstruction

CBCT panoramic reconstruction
CBCT panoramic reconstruction demonstrating moderate to poor visibility of the mental foramina.
Figure 4

Three-dimensional and sagittal CBCT images

Three-dimensional and sagittal CBCT images
Three-dimensional and sagittal images showing three additional canals which originate from the right mandibular canal (MC) and the corresponding accessory foramina.