“Because the beauty of the human body is that it hasn’t a single muscle which doesn’t serve its purpose; that there’s not a line wasted; that every detail of it fits one idea, the idea of a man and the life of a man.”
Salivary Glands: What We Already Know
Presently, all major research institutions across the world are engaged in applying advanced scientific knowledge in the disciplines of immunology, virology, biotechnology, etc. to search for a preventive or curative remedy for the COVID-19 virus. Ironically, at the very same time, an unexpected discovery has come to light which has the potential to change the basic tenets of human anatomy. A discovery, which I believe in some ways is a testament to the technical ingenuity and brilliance of human anatomy and also, a timely reminder to mankind of how incomplete our knowledge about the human body actually is.
Even those of you, who are not health professionals will recall studying the classification of human salivary glands, as far back as high school. Till a few days back, it was believed that three pairs of major salivary glands i.e. the parotid, sub-mandibular and sublingual glands, and around 1000 minor salivary glands existed in the human body.
The New Find: What and How?
However, in a recently published study, a team of researchers from the Netherlands led by Dr Valstar announced, that they have discovered the presence of previously unnoticed macroscopic salivary tissue in the human nasopharynx. So, basically, that means there actually may exist a fourth set of major salivary glands in the human body, which despite the countless cadaver dissections and radiographic analysis of the past, has still been missed by researchers across the world, right up till now. Astonishing isn’t it?
Well, the findings of Dr Valstar and the team were also incidental in nature, to be honest. They were actually engaged in studying prostate cancer using an advanced radiographic imaging method called positron imaging tomography/computed tomography with radio-labelled ligands to the prostate-specific membrane antigen (PSMA1 PET/CT).
This imaging modality enables researchers to simultaneously visualize the major salivary glands with a high range of sensitivity and specificity. This particular group of researchers, while studying the PSMA1 PET/CT, were taken aback to discover a fourth unknown area in the nasopharynx, which depicted similar radiographic characteristics as the known major salivary glands. The researchers confirmed their findings by retrospectively evaluating similar radiographic images of 100 patients of prostrate/ urethral cancer. All 100 images showed the presence of a fourth salivary gland location.
Further, they were also able to isolate this tissue on two human cadavers and confirm that it had salivary gland characteristics with immunochemistry. For now, the researchers have named these salivary glands as ‘tubarial’ glands, due to its anatomic proximity to the auditory tube. They have hypothesized that these glands were never observed before by researchers or medical professionals due to their poorly accessible anatomic location which cannot be clearly visualized on conventional modalities like MRI, ultrasound/CT.
The relevance of the Discovery
While we can all agree, that is definitely a landmark study in the field of medicine, the more discerning amongst may wonder on the clinical implications of this find. It is well-accepted that dysphagia and xerostomia are the common adverse effects seen, post-radiotherapy in head neck cancer patients. Interestingly, the same group of researchers have shown a significant correlation between radiotherapy doses given at the location of the tubarial glands and the occurrence of dysphagia and xerostomia in these patients.
This indicates that the tubarial glands may be responsible for moistening and lubricating the nasopharynx and oropharynx. Thus, their inadvertent exposure to radiotherapy may be a strong reason for dysphagia and xerostomia experienced by patients, which substantially affect their quality of life post-radiation. The discovery of the tubarial glands has the potential to revolutionise the radiation treatment protocols used in head and neck cancer patients. Perhaps, in future, this finding could afford them a more comfortable quality of life, after undergoing radiation therapy.
Of course, like every other major scientific discovery of the past, this one too has been met with cynicism from some quarters, but most researchers and medical professionals have welcomed Dr Valtzar’s findings. At the same time, it is important that similar studies should be conducted in different populations across the world to externally validate the presence of the tubarial glands in the human body. At a later stage, interventional studies could be conducted to modulate the radiation dose, these glands are exposed to during radiotherapy.
In conclusion, a lesson for all of us to learn from this breakthrough is progress in medicine can only occur, when we accept that our knowledge of the field can never remain static in any arena, even in areas as basic as human anatomy. Change is our only constant!
- M.H. Valstar, B.S. de Bakker, Roel J.H.M. Steenbakkers et al., The tubarial salivary glands: A potential new organ at risk for radiotherapy, Radiotherapy and Oncology.2020