The morphological variations of the lateral pterygoid muscle: A systematic review

Abstract

Background: The lateral pterygoid muscle (LPM) has been described in many anatomical and functional studies. The morphology of the LPM is still under debate because of its deep location in the infratemporal fossa and the difficulties to approach this area with different anatomical methods. Although it has been generally accepted that this muscle is mainly composed of two separate parts, other forms have been described in the past. Objectives: To conduct a systematic literature review regarding the anatomy and variations of the LPM. Methods: We included studies published in English, German or French employing anatomical and imaging methods or a combination of the two methods. The cadavers used in the dissections had to be human and without any pathological alterations. Studies were only included when focusing on the anatomy of the LPM or its morphological variations or when taking the frequency of variations into account. We searched 26 biomedical databases including MEDLINE, EMBASE, BIOSIS Previews and Science Citation Index Expanded (part of Web of Science) through October 2014. The review was followed by the dissection of a hemisected head in two different planes. Results: We identified 4279 records (2200 after deduplication) in the databases searches plus 17 articles from manual searches. 81 studies out of these articles were included in this review. 69 articles used anatomical methods, 5 imaging methods and 7 studies a combination of the two methods. 11 studies took into account that the LPM may have variations and also considered the relative frequency of each variation. The frequency of one-headed LPMs ranged between 7.7% and 26.7%, of two-headed LPMs between 61.4% and 91.1% and of three-headed LPMs between 4.0% and 35.0%. Our own dissection showed a three-headed version of the LPM. Discussion: In anatomical studies, different preparation techniques seem to be the main reason for diverging results.

Effects of Botulinum Toxin Therapy on Health-Related Quality of Life Evaluated by the Oromandibular Dystonia Rating Scale

“…Nevertheless, the number of lateral pterygoid muscle heads remains controversial. It is commonly a two-headed muscle, but one-headed or three-headed muscles have also been reported [ 46 , 49 , 50 ]. Detailed findings of the origins and insertions of an anatomical study suggest that the lateral pterygoid muscle is a single muscle with no clear border, containing fibers in various directions, indicating that a two-head muscle pattern would be indicated by the differences in the convergences of the muscle fibers [ 49 ].…”

“…Detailed findings of the origins and insertions of an anatomical study suggest that the lateral pterygoid muscle is a single muscle with no clear border, containing fibers in various directions, indicating that a two-head muscle pattern would be indicated by the differences in the convergences of the muscle fibers [ 49 ]. In contrast, a recent systematic review reported that the frequency of one-headed lateral pterygoid muscles ranged from 7.7% to 26.7%, two-headed muscles from 61.4% to 91.1%, and three-headed muscles from 4.0% to 35.0% [ 50 ]. The difference in efficacy of BoNT therapy between jaw closing and jaw opening dystonia may be associated with the anatomical variability of the lateral pterygoid muscle.…”

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“…The lateral pterygoid muscle crosses the upper part of the ITF from anteromedial to posterolateral [ 19 , 22 ]. In most of the cases (61.4–91.1%), it is formed by two heads, one arising from the infratemporal surface of the greater wing of the sphenoidal bone and from the infratemporal crest (superior head) and one from the lateral surface of the lateral pterygoid plate (inferior head) [ 22 , 23 ]. Possible variations of lateral pterygoid muscle with single or triple heads have been reported respectively between 7.7 and 26.7%, and 4.0 and 35.0% of cases [ 23 ].…”

“…In most of the cases (61.4–91.1%), it is formed by two heads, one arising from the infratemporal surface of the greater wing of the sphenoidal bone and from the infratemporal crest (superior head) and one from the lateral surface of the lateral pterygoid plate (inferior head) [ 22 , 23 ]. Possible variations of lateral pterygoid muscle with single or triple heads have been reported respectively between 7.7 and 26.7%, and 4.0 and 35.0% of cases [ 23 ]. These heads converge in a postero-lateral direction to insert into the pterygoid fovea (a convex space on the neck of the mandible), the articular disc, and the capsule of the temporomandibular joint [ 22 , 23 , 24 ].…”

“…Possible variations of lateral pterygoid muscle with single or triple heads have been reported respectively between 7.7 and 26.7%, and 4.0 and 35.0% of cases [ 23 ]. These heads converge in a postero-lateral direction to insert into the pterygoid fovea (a convex space on the neck of the mandible), the articular disc, and the capsule of the temporomandibular joint [ 22 , 23 , 24 ]. Particularly, the most frequent attachment is at the level of both the condyles and disc and capsule of the temporomandibular joint (55.5%), while insertions only at the level of the condyles (27.8%) or of the disc and capsule (16.7%) were more rarely observed [ 24 ].…”