Etiopathogenesis of lacrimal sac mucopeptide concretions: insights from cinematic rendering techniques

[Concrements of the lacrimal apparatus]

Concrements of the lacrimal apparatus, known as dacryoliths, can occur at different localizations and can cause a variety of symptoms. A common clinical sign is chronic inflammation, possibly exhibiting acute exacerbation. Based on a literature review and descriptive clinical cases with histopathological correlations, this contribution summarises the most important information concerning epidemiology, aetiopathogenesis, composition, histology, and therapy of lacrimal concrements. Furthermore, factors known to affect lacrimal lithogenesis are addressed. Concrements of the lacrimal gland cause a swelling at the lateral canthus. With only mild pain, this manifests as circumscribed conjunctival hyperaemia. Histologically, the gland tissue is characterised by acute-erosive to chronic inflammation. The concrements consist of amorphic material. Inflammatory infiltration is dominated by neutrophil granulocytes. Canalicular concrements are highly correlated with chronic canaliculitis. Besides epiphora, patients present with purulent discharge at the affected canaliculus. Actinomyces are frequently found inside these deposits and form drusen-like formations. The surrounding tissue reacts with plasma-cellular and granulocytic inflammation. Dacryoliths (concrements of the lacrimal sac) are associated with dacryocystitis, whereby acute and chronic types are common. Stones can be found in up to 18% of patients undergoing dacryocystorhinostomy or dacryoendoscopy. Preoperative diagnostic testing is challenging, as many lacrimal sac stones cannot be reliably visualised by diagnostic procedures. Recurring episodes of epiphora, mucopurulent discharge, and dacryocystitis are common indicators of dacryoliths. Lacrimal syringing is often possible and shows that total blockage is not present. Histology of the lacrimal mucosa reveals lymphocytic infiltration and submucosal fibrosis. The immediate vicinity of the dacryoliths shows acute inflammation. Therapy consists of stone extraction and improving lacrimal drainage, as the latter is recognised as the main risk factor for dacryolith formation.

Internal vascular anatomy of the human lacrimal gland: A protocol based on cadaver dissection and three-dimensional micro-computed tomography

PURPOSE

To evaluate the feasibility of studying the vascular supply of the orbital and palpebral lobes of the human lacrimal gland using micro-computed tomography (micro-CT) and microscopic dissection.

METHODS

The lacrimal gland artery of a fresh parasagittalized cadaver head (male, aged 76 years) was infused with a lead oxide-latex mixture near the occipital pole of the gland. The entire lacrimal gland was imaged using micro-CT and 3D cinematic rendering (CR) and then dissected under a surgical microscope.

RESULTS

Micro-CT and CR images showed well-demarcated internal vascular branches of the lacrimal artery and their distribution within the orbital and palpebral lobes. The entire course of the artery and its branches could be visualized by CR and microscopic dissection, with the former showing better spatial orientation and finer branching. The main artery runs along the free edge of the aponeurosis of the levator palpebrae superior muscle and lies in the isthmus portion of the gland (between the orbital and palpebral lobes). The branches of the main lacrimal artery include one branch to the orbital adipose tissue just before entering the gland, two branches to the orbital lobe (medial and lateral), and two branches to the palpebral lobe (medial and lateral). The main artery terminates as palpebral and orbital lobe branches in the lateral half of the lacrimal gland.

CONCLUSION

Latex and contrast-enhanced micro-CT is very well suited to visualize the vascular anatomy of the lacrimal artery within the gland. A large number of lacrimal gland examinations using the method presented here are required to demonstrate and understand the variability of the vascular anatomy of the human lacrimal gland.

Dacryolithogenesis or Dacryolithiasis-The Story So Far

The term dacryoliths refers to the concretions found within the lacrimal system. When the term dacryoliths is unspecified, it usually refers to the noninfectious dacryoliths commonly isolated from the lacrimal sac and the nasolacrimal duct. More often, they are diagnosed incidentally during a dacryocystorhinostomy, and the reported incidence among all dacryocystorhinostomy surgeries is 5.7% to as high as 18%. Dacryolithiasis is a complex process occurring within the lacrimal system, and current evidence suggests a multifactorial etiology. The sequence of events can be summarized broadly into 4 stages: stage of susceptibility, stage of initiation/trigger, stage of development, and stage of maintenance. The triggering event is the breach of the lacrimal sac or nasolacrimal duct epithelium, resulting in microtrauma with blood leakage. The blood clots act as a nidus for subsequent sequential laying of mucopeptides, cellular debris present locally, debris washed from the ocular surface, and extraneous agents in tears. This process is aided by altered rheology and composition of the tear film. After the formation of dacryoliths, extracellular neutrophil traps usually form on the surface, which help to maintain the dacryoliths (which do not dissolve). This review highlights and discusses the possible sequence of events during dacryolithiasis.

Neutrophil Extracellular Traps Drive Dacryolithiasis

Mucopeptide concretions, previously called dacryoliths, are macroscopic stones that commonly obstruct the lacrimal sac. The mechanism behind dacryolithiasis remains unclear; however, the involvement of various immune cells, including neutrophils, has been confirmed. These findings remain limited, and no information on neutrophil extracellular traps (NETs), essentially involved in the pathogenesis of other lithiases, is available yet. Here, we employ microcomputed tomography, magnetic resonance tomography, histochemistry, mass spectrometry, and enzyme activity analyses to investigate the role of neutrophils and NETs in dacryolithiasis. We classify mucopeptide concretions into three types, with respect to the quantity of cellular and acellular material, polysaccharides, and mucosubstances. We propose the role of neutrophils and NETs within the existing model of gradual formation and growth of mucopeptide concretions, with neutrophils contributing to the initial stages of dacryolithiasis, as they localized on the inner (older) parts of the tissue. As NETs localized on the outer (newer) parts of the tissue, we link their role to the late stages of dacryolithiasis, presumably maintaining the proinflammatory environment and preventing efficient clearance. An abundance of IgG on the surface indicates the involvement of the adaptive immune system later as well. These findings bring new perspectives on dacryolithiasis, in which the innate and adaptive immune system are essentially involved.

Cinematic rendering to improve visualization of supplementary and ectopic teeth using CT datasets

OBJECTIVES

Ectopic, impacted, and supplementary teeth are the number one reason for cross-sectional imaging in pediatric dentistry. The accurate post-processing of acquired data sets is crucial to obtain precise, yet also intuitively understandable three-dimensional (3D) models, which facilitate clinical decision-making and improve treatment outcomes. Cinematic rendering (CR) is anovel visualization technique using physically based volume rendering to create photorealistic images from DICOM data. The aim of the present study was to tailor pre-existing CR reconstruction parameters for use in dental imaging with the example of the diagnostic 3D visualization of ectopic, impacted, and supplementary teeth.

METHODS

CR was employed for the volumetric image visualization of midface CT data sets. Predefined reconstruction parameters were specifically modified to visualize the presented dental pathologies, dentulous jaw, and isolated teeth. The 3D spatial relationship of the teeth, as well as their structural relationship with the antagonizing dentition, could immediately be investigated and highlighted by separate, interactive 3D visualization after segmentation through windowing.

RESULTS

To the best of our knowledge, CR has not been implemented for the visualization of supplementary and ectopic teeth segmented from the surrounding bone because the software has not yet provided appropriate customized reconstruction parameters for dental imaging. When employing our new, modified reconstruction parameters, its application presents a fast approach to obtain realistic visualizations of both dental and osseous structures.

CONCLUSIONS

CR enables dentists and oral surgeons to gain an improved 3D understanding of anatomical structures, allowing for more intuitive treatment planning and patient communication.

Concrements of the Lacrimal Apparatus

Concrements of the lacrimal apparatus, known as dacryoliths, can occur at different localizations and can cause a variety of symptoms. A common clinical sign is chronic inflammation, possibly exhibiting acute exacerbation. Based on a literature review and descriptive clinical cases with histopathological correlations, this contribution summarises the most important information concerning epidemiology, aetiopathogenesis, composition, histology, and therapy of lacrimal concrements. Furthermore, factors known to affect lacrimal lithogenesis are addressed. Concrements of the lacrimal gland cause a swelling at the lateral canthus. With only mild pain, this manifests as circumscribed conjunctival hyperaemia. Histologically, the gland tissue is characterised by acute-erosive to chronic inflammation. The concrements consist of amorphic material. Inflammatory infiltration is dominated by neutrophil granulocytes. Canalicular concrements are highly correlated with chronic canaliculitis. Besides epiphora, patients present with purulent discharge at the affected canaliculus. Actinomyces are frequently found inside these deposits and form drusen-like formations. The surrounding tissue reacts with plasma-cellular and granulocytic inflammation. Dacryoliths (concrements of the lacrimal sac) are associated with dacryocystitis, whereby acute and chronic types are common. Stones can be found in up to 18% of patients undergoing dacryocystorhinostomy or dacryoendoscopy. Preoperative diagnostic testing is challenging, as many lacrimal sac stones cannot be reliably visualised by diagnostic procedures. Recurring episodes of epiphora, mucopurulent discharge, and dacryocystitis are common indicators of dacryoliths. Lacrimal syringing is often possible and shows that total blockage is not present. Histology of the lacrimal mucosa reveals lymphocytic infiltration and submucosal fibrosis. The immediate vicinity of the dacryoliths shows acute inflammation. Therapy consists of stone extraction and improving lacrimal drainage, as the latter is recognised as the main risk factor for dacryolith formation.

The Translational Role of MUC8 in Salivary Glands: A Potential Biomarker for Salivary Stone Disease?

Mucin (MUC) 8 has been shown to play an important role in respiratory disease and inflammatory responses. In the present study, we investigated the question of whether MUC8 is also produced and secreted by salivary glands and whether it may also play a role in the oral cavity in the context of inflammatory processes or in the context of salivary stone formation. Tissue samples from parotid and submandibular glands of body donors (n = 6, age range 63–88 years), as well as surgically removed salivary stones from patients (n = 38, age range 48–72 years) with parotid and submandibular stone disease were immunohistochemically analyzed targeting MUC8 and TNFα. The presence of MUC8 in salivary stones was additionally analyzed by dot blot analyses. Moreover, saliva samples from patients (n = 10, age range 51–72 years), who had a salivary stone of the submandibular gland on one side were compared with saliva samples from the other “healthy” side, which did not have a salivary stone, by ELISA. Positive MUC8 was detectable in the inter- and intralobular excretory ducts of both glands (parotid and submandibular). The glandular acini showed no reactivity. TNFα revealed comparable reactivity to MUC8 in the glandular excretory ducts and also did not react in glandular acini. Salivary stones demonstrated a characteristic distribution pattern of MUC8 that differed between parotid and submandibular salivary stones. The mean MUC8 concentration was 71.06 ng/mL in female and 33.21 ng/mL in male subjects (p = 0.156). Saliva from the side with salivary calculi contained significantly (15-fold) higher MUC8 concentration levels than saliva from the healthy side (p = 0.0005). MUC8 concentration in salivary stones varied from 4.59 ng/mL to 202.83 ng/mL. In females, the MUC8 concentration in salivary stones was significantly (2.3-fold) higher, with an average of 82.84 ng/mL compared to 25.27 ng/mL in male patients (p = 0.034). MUC8 is secreted in the excretory duct system of salivary glands and released into saliva. Importantly, MUC8 salivary concentrations vary greatly between individuals. In addition, the MUC8 concentration is gender-dependent (♀ > ♂). In the context of salivary stone diseases, MUC8 is highly secreted in saliva. The findings support a role for MUC8 in the context of inflammatory events and salivary stone formation. The findings allow conclusions on a gender-dependent component of MUC8.

Lacrimal Intrasaccal Polyp With Inspissated Mucopeptide Concretions

Lacrimal sac mucopeptide concretions are not uncommon and usually identified following the lacrimal sac marsupialization during a dacryocystorhinostomy. A 39-year-old female presented with epiphora and discharge of 8 months duration and was diagnosed as primary acquired nasolacrimal duct obstruction. During the endoscopic dacryocystorhinostomy, a large intrasaccal polyp arising from the posterosuperior wall of the lacrimal sac with multiple inspissated mucopeptide concretions was noted. The lesion was excised, and the mucopeptide concretions were removed. Histopathology was suggestive of an intrasaccal polypoidal granuloma. To the best of the authors' knowledge, this is the first report of an intrasaccal polyp-like lesion secondary to a granulomatous response to a lacrimal sac mucopeptide concretion. It is important to be aware of this entity. The retrieval of mucopeptide concretion or lacrimal sac dacryoliths should prompt the surgeon to initiate an intraoperative endoscopic assessment of the sac before proceeding with the surgery.

Neutrophil Extracellular Traps Promote the Development and Growth of Human Salivary Stones

Salivary gland stones, or sialoliths, are the most common cause of the obstruction of salivary glands. The mechanism behind the formation of sialoliths has been elusive. Symptomatic sialolithiasis has a prevalence of 0.45% in the general population, is characterized by recurrent painful periprandial swelling of the affected gland, and often results in sialadenitis with the need for surgical intervention. Here, we show by the use of immunohistochemistry, immunofluorescence, computed tomography (CT) scans and reconstructions, special dye techniques, bacterial genotyping, and enzyme activity analyses that neutrophil extracellular traps (NETs) initiate the formation and growth of sialoliths in humans. The deposition of neutrophil granulocyte extracellular DNA around small crystals results in the dense aggregation of the latter, and the subsequent mineralization creates alternating layers of dense mineral, which are predominantly calcium salt deposits and DNA. The further agglomeration and appositional growth of these structures promotes the development of macroscopic sialoliths that finally occlude the efferent ducts of the salivary glands, causing clinical symptoms and salivary gland dysfunction. These findings provide an entirely novel insight into the mechanism of sialolithogenesis, in which an immune system-mediated response essentially participates in the physicochemical process of concrement formation and growth.