International Journal of Anatomical Sciences 2010, 1: 45-47.

Case Report

Levator Glandulae Thyroideae with the absence of Pyramidal Lobe – A  case report

Gunapriya R, Varsha S, Senthil Kumar B.

Department of Anatomy, Saveetha Medical College, Thandalam, Chennai 602 105, India

Key  Words: levator glandulae thyroideae, pyramidal lobe,  infrahyoid muscles, thyroglossal duct,  ectopic thyroid

 Abstract: Levator glandulae thyroideae is a fibromuscular band, if present is usually on the left side connecting the pyramidal lobe of thyroid gland and the hyoid bone. The presence of levator glandulae thyroideae and its anatomical variations gain importance, in the pathologies related to thyroid gland and their treatment modalities. Hence, this case has been presented here for such a clinical significance.

 Case Report

 During routine dissection of neck, in a male cadaver aged about 60 years, the presence  of  levator  glandulae  thyroideae  was observed on the right side. It was dissected with utmost care to look for its attachments above and below and for its innervation. A thin band of muscular like tissue stretched from the   upper border of isthmus  of  thyroid  gland,  to    the  lower border of the lamina of thyroid cartilage, on the right side (Fig. 1). Hence, according to Mori’s classification, the levator glandulae thyroideae in this case belongs to Thyreoglandularis type. It measured 1 cm in length and 0.6 cm in breadth.   Careful dissection revealed that there was no pyramidal lobe and this band did not have innervation from any nerve and did not extend up to hyoid bone. The thyroid gland and other structures in the vicinity appeared normal

As this tissue appeared to be muscular, it was subjected to microscopic study. The tissue was dissected out from the cadaver and sectioned at four levels. The tissues were then processed, and stained by hematoxylin and eosin stain, as described by Culling (1974). The study revealed the presence of thyroid follicles lined by cuboidal epithelium, with moderate amount of colloid in their lumina and surrounding fibrous tissue, at the lower levels (Fig. 2) and only fibrous tissue in the section taken at the upper level (towards the thyroid cartilage).

(TC-Thyroid cartilage; LGT-Levator glandulae                (TF – Thyroid follicle with colloid; FT – Fibrous

Thyroideae; TG- Thyroid gland)                                        tissue)

 Musculus levator glandulae thyroideae  stretches   from  the  pyramidal lobe or upper border of isthmus of thyroid, usually on the left side, to the body of the hyoid bone above (Standring, 2006). It may receive its innervation from external laryngeal nerve (Sinnatamby, 2007). Moore and Persaud (1999) have stated that pyramidal lobe is seen in 50% of population and the muscular band may be made up of smooth muscle fibres and that the pyramidal lobe and the associated smooth muscle represent the  persistent part of distal end of thyroglossal duct. Another study done in 90 male cadavers revealed that, pyramidal lobe was  present  in  37.77%,  frequently arising from   the   left   lobe,   while   the   levator glandulae thyroideae was present in 30% instances, mostly attached above to body of hyoid bone (Joshi et al., 2010).

 The levator glandulae thyroideae observed in the present study is of thyreoglandularis type, which was found to be attached to thyroid cartilage on the right side, with no innervation from any nerve. The pyramidal lobe was also totally absent (Fig.  1).  The  microscopic  study  revealed that it was mainly made up of glandular tissue and partly by fibrous tissue towards  the thyroid cartilage. Hence in this case, the levator glandulae thyroideae did not have innervation and it was made up of fibroglandular tissue (Fig. 2), which represents the persisting distal end of thyroglossal duct.

 Accessory nodules / ectopic thyroid tissue of the thyroid are usually found at the embryonic origin of thyroid, at the foramen caecum and along the thyroglossal tract (Bergman et al., 2007; Ranade et al., 2008). Therefore the anterior cervical region has to be  investigated  very  carefully  during surgery, in order not to  leave behind  any residual thyroid tissue, during total thyroidectomy (Braun et al., 2007).

Conclusion

This  study  highlights  the significance  of  thorough  understanding  of the thyroid anatomy and its associated anatomical variations, which thus form a cornerstone for safe and effective thyroid surgery.

References

Bergman RA, Afifi AK, Miyauchi R (2007) Thyroid gland In: Illustrated Encyclopedia of Human Anatomic Variation: Opus IV Organ Systems: Endocrine System (www.anatomyatlases.org/Anatomic variants/organ system/text/thyroidgland.html/)