Scientific article

What do we need to know about “Ankyloglossia” or “Tongue Tie”?

Prof. Ali Mirjalili

 Ankyloglossia is a clinical diagnosis, when the lingual frenulum is thought to be restricting tongue mobility. However, as the relationship between structure and functional limitation is still uncertain, diagnosis of ankyloglossia remains subjective. With ankyloglossia now being discussed widely in social media forums, the term “tongue tie” has gained popularity to describe both the condition of restricted tongue mobility and the lingual frenulum itself.

Current popular grading systems for ankyloglossia utilize a single feature of frenulum appearance, the height of attachment of the frenulum on the ventral surface of the tongue.1,2 As these grading systems encompass all possible morphological variants of the lingual frenulum, they create the possibility of any frenulum being allocated a grade of ankyloglossia and therefore be considered “abnormal.” The use of these grading systems, together with a paucity of knowledge of frenulum anatomical structure seem to have contributed to confusion regarding what is “normal” frenulum anatomy.

As lingual frenulum is present in almost all infants3, the presence of a frenulum should not in itself be considered abnormal or diagnostic of ankyloglossia. Furthermore, no direct correlation has been shown between these gradings and the presence of breastfeeding difficulties or outcomes following frenotomy. This suggests that there is a wider range of anatomical variables that impact on the tongue mobility and function than this single feature of lingual frenulum appearance used in isolation. The subjective nature of ankyloglossia diagnosis is a major dilemma for both clinical practice and research, as well as potentially creating parental confusion. It has become a source of conflict within breastfeeding support communities, when beliefs around the diagnosis of ankyloglossia and promotion of frenotomy become divergent. With a dramatically increasing rate of diagnosis and concomitant surgical intervention for ankyloglossia reported in extensive audits in a number of countries4-6, there is concern that this reflects a trend for potential over-diagnosis, such that a number of infants with a normal anatomy and tongue function are being recommended for intervention. 

The popular structural concept of the lingual frenulum being a midline submucosal string, band, or “mast”7-9 has recently been replaced with the understanding that the adult lingual frenulum is formed by a layer of fascia that spans the floor of mouth.10 Tongue movement creates tension in the fascial layer, dynamically raising the fascia and overlying oral mucosa into a midline fold, recognizable as the lingual frenulum. This research has provided a structural explanation for the spectrum of lingual frenulum morphology. Variability in the relative gliding of the mucosal and fascial layers with tongue movement (together with the underlying suspended genioglossus) alters the transparency, thickness, and shape of the lingual frenulum. The research on anatomy of the fetal and neonatal clearly showed no differences to adult lingual frenulum.11 Interestingly, embryological studies have also shown that the oral mucosa and associated connective tissues develop by 22 weeks gestation.12

In conclusion, the lingual frenulum is a dynamic structure formed by a fold in the floor of mouth fascia. There is significant variability in morphology of the lingual frenulum relating to midline attachment of the floor of mouth fascia, and variability in how the mucosa, fascia, and genioglossus are drawn into the fold of the frenulum with tongue movement. Lingual frenulum anatomy has recently been clearly defined, but there are still large gaps in knowledge, particularly correlating variability in structure with function. More detailed biomechanical research is required, with a more holistic approach needed to understand the potential impact of a broad range of variables in infants oral anatomy on task-specific tongue function. Until more research provides these answers, I strongly encourage a considered clinical approach that includes ruling out other potential causes of breastfeeding difficulties (e.g., nipple shape, high-arched palate etc) before proceeding to surgical intervention.

Prof. Ali Mirjalili

Associate Professor S. Ali Mirjalili Faculty of Medical Health Science, University of Auckland, New Zealand
 Specialist in paediatric clinical anatomy

Professor Ali Mirjalili, from University of Auckland in New Zealand, is specialist in paediatric clinical anatomy. Ali is the section editor in the world-famous textbook Gray's Anatomy. Ali is also the editor and author of the textbook Last's Anatomy. 

Ali has investigated the lingual frenulum and has spent the last 12 months in Graz, Austria investigating the biomechanics of the tongue.

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12 Winning T, Townsend G. 2000. Oral mucosal embryology and histology. Clin Dermatol 18: 499–511.