^99mTcO4 Sialoscintigraphy in Pre and Post-Transplant Evaluation of Submandibular Gland Transfer in a Case of Bilateral Congenital Alacrimia

INTRODUCTION

Tear ducts are already formed by the time of a child's birth, but produce visible tears at around 2 weeks to 3 months of age, as the lacrimal glands mature. These tear ducts are often blocked by a membrane called the “valve of Hasner” which usually opens up by itself before birth. Thus, children with alacrimia (absence of tear production) fail to shed tears but instead produce a sticky/no discharge on crying at birth, which may be due to either a blocked or absent tear duct. Although it is rarely present as an isolated lacrimal system pathology, it is more often associated with multisystem involvement from underlying genetic birth disorders such as anhidrotic ectodermal dysplasia and familial dysautonomia.^[1,2]An important secondary cause is lacrimal gland agenesis^[3],which may be a part of a systemic rheumatological pathology. Timely diagnosis and management of subtle ocular signs are essential to avoid potential life-threatening consequences. This lacrimal gland agenesis may be associated with lacrimal punctum abnormalities and salivary gland aplasia in hereditary syndromes.^[4]

CASE REPORT

A 23-day-old male child presented to neonatology with acute lower respiratory infection, bilateral eye discharge, and skin excoriation along inner and outer canthi, which was diagnosed as associated bilateral conjunctivitis. Broad-spectrum systemic antibiotics, local antibiotic eye drops, and a refresh gel were instituted. An ophthalmologist performed a detailed eye examination. Parents reported that while crying, the amount of tears was not obvious. Ocular examination revealed a visual acuity of 1/60 in both eyes, not improving with spectacles or pinhole. He was orthotropic with a full range of ocular movements and no nystagmus. Ocular examination revealed normal lids with conjunctival xerosis involving bulbar, palpebral, and forniceal conjunctiva in both eyes. Although the fornices were deep with no keratinisation, there was evidence of subconjunctival fibrosis in the superior fornix. Schirmer's test (under anaesthesia) for tear production reported 20 mm tear production for the right eye (RE). In comparison, the left eye (LE) showed a complete absence of tear production (normal tear production is 15–25 mm). LE also showed a lack of fornix space to fit a strip, suggesting a contracted socket, potentially due to scar tissue. Local examination of both eyes revealed keratinisation of the bulbar conjunctiva. The cornea had superficial vascularisation extending to the central cornea for 360°. No tear meniscus seen. On fundal dilatation, RE showed fundal glow, but details were not visible; LE showed no fundal glow. Tear film stability was grossly reduced. Tear breakup time (T-BUT) in our patient was 0 s (normal is 10–45 s), as well as increased tear osmolality, which are the hallmarks of dry eyes.^[5,6]

After an extensive dry eye workup, the patient was diagnosed with congenital bilateral membranous conjunctivitis due to congenital alacrimia with bilateral conjunctival cicatrisation. Symptomatic treatment includes tear substitutes for the mild form of dry eyes. In this patient, the surgical option (gland transfer) was the mainstay of treatment due to the severity of the condition and involvement of the conjunctiva.^[7] Although parotid glands are larger with more volume, the submandibular gland (SM) provides an optimal replacement for lacrimal tissue as its secretions are mucinous and nearly compatible with original tears. Therefore, vascularized autologous submandibular gland transfer on both sides was considered as a viable and vision saving surgical for this case. Sialoscintigraphy was performed [Fig 1] pre and postoperatively. Baseline images reveal normal functioning bilateral SM and parotid (P) glands (T 1/2 of 9 min and 24 min, range 4–24 min and 12–48 min, respectively for SM and P) with good excretion post sour lime intervention.

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Fig 1:

(A) Preoperative ^99mTcO4 Sialoscintigraphy with 2 mCi of Tc04 injected IV. Findings reveal normal functioning bilateral submandibular (SM) and parotid (P) glands. Parotid (bold arrow) and submandibular glands (dotted arrow) exhibited prompt extraction and good excretion with sour lime intervention at 10 min of the dynamic study. (B) Post-SM transplant sialoscintigraphy was performed with 2 mCi of ^99mTcO4 IV. Dynamic images showed focal symmetrical good tracer uptake in transplanted SM glands in both sides of the scalp in the temporalis trough, along with prompt tracer uptake in bilateral parotid glands. No lemon intervention was done for native parotids (dotted arrow) as the aim was to check good tracer uptake in transplanted SM gland sites (thin arrows), which was proved on imaging with region of interest (ROI) showing rising curves. (C) Preoperative markings on skin post-induction. (D) Harvested right SM with Wharton’s duct. (E) A 3 cm × 3 cm trough was created by excising the central portion of the temporalis muscle to accommodate the submandibular salivary gland (arrow). A subcutaneous tunnel was made up to the upper lateral fornix to create an opening for the duct. (F) Three-dimensional (3D) reconstructed single-photon emission computed tomography (SPECT) CT of posttransplant right SM gland at lacrimal fossa (black arrow). The yellow arrow shows the parotid salivary gland. 3D SPECTCT images 3 months after surgery, showing good functional status and viability of the transplanted right SM gland placed superior to the lateral canthus. In addition, there is normal and significant technetium uptake in the parotid glands bilaterally, and the thyroid gland

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Post SM transplant sialoscintigraphy was performed with 2 mCi of 99m Tc04 IV. Dynamic images showed focal symmetrical tracer uptake in transplanted SM glands in both sides of the scalp in the temporalis trough, along with prompt tracer uptake in bilateral native parotid glands. Previously seen SM glands are not seen in their native position as they have now been transplanted to the bilateral scalp trough. Please note no lemon intervention was done for native parotids (dotted arrow) as the aim was to check prompt and good tracer uptake in transplanted SM gland sites both visually and quantitatively.

Gland transfer was performed by our specialised head and neck surgical team after the child attained 5 years of age, as per the parents' wish. Transplant surgery was undertaken for each eye separately; hence, it was performed as a 2-step procedure with an interval of 1 year and 5 months. The patient was under follow-up for 2 years postoperatively.

^99mTc Pertechnetate sialoscintigraphy is an important functional investigation used for assessment of parotid and submandibular salivary gland ;^[8] but in this case, it has an additional utility of assessing preserved functionality before surgery and also to rule out any autoimmune degeneration, given the congenital lacrimal gland anomaly already documented. It also provides a yardstick to document postoperative tear flow and drainage improvement (3 months post-surgery).

Clinically, RE improved from counting fingers close to the face (6/120) to counting fingers at 3 m (3/60) [Table 1]. Parents also noted definite improvement in vision. Systemic pilocarpine (5 mg thrice daily) was started for the first 3 months postoperatively to stimulate salivary secretion. After 2 months, the secretion started improving and stabilised. Slit lamp examination showed a notable difference in the ocular surface [Fig 2]. A moist, shiny surface replaced the dry, lustreless conjunctiva and cornea. The tear meniscus height improved from 0 to 1 mm. T-BUT increased to 4 s, Schirmer's values ^[9] also dramatically improved to > 10 mm at 5 min. Ocular surface staining showed remarkable improvement. NEI score^[10] was 0/15 for conjunctiva (preoperative 12.5/15) and 7.5/15 for cornea (15/15 preoperatively). However, LE improvement was not as dramatic as for RE.

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Fig 2:

Right eye (RE) images (A) Preoperative and (B) 2 weeks’ postoperative status. RE improved from counting fingers close to the face (6/120) to counting fingers at 3 m (3/60). After 2 months, the secretion started improving and stabilised. However, left eye (LE) improvement was not as dramatic as for RE. (C and D) Postoperative RE and LE. Eyes became moist with a Schirmer’s value of >10 mm. Ocular surface improved with some reversal of surface keratinisation and reduction in corneal fluorescein staining

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Postoperatively, the eyes became moist with a Schirmer's value of >10 mm. The ocular surface also improved with some reversal of surface keratinisation and reduction in corneal fluorescein staining. Postoperative biochemical analysis of transposed submandibular gland secretion was assessed and compared with the normal submandibular gland secretion and normal tear secretion to be near normal to lacrimal secretion [Tables 1 and 2]. There was a dramatic improvement in tear flow through LE by 7 months postoperatively, while RE took 2 years.

DISCUSSION

Dry eyes are a vexing problem. It can get easily exacerbated with air exposure, weather conditions, medications, prolonged screen time, as well as low humidity, which may worsen symptoms and damage the corneal surface. Agenesis of the lacrimal glands can be an isolated finding or sometimes associated with ectodermal defects in branchial arches, lacrimal punctum abnormalities, and major salivary gland agenesis. Corrective management is surgery.^[11] Indications for transplant surgery in dry eyes include;

1. Schirmer's test <2 mm

2. Corneal ulceration documented by rose bengal staining

3. T-BUT <5 s.

Filatov and Chevaljev originally described parotid duct transposition in 1951^[12], whereas Murube-Del-Castillo was the first to try SM gland transfer.^[13] In fact, all three salivary glands have been used for transplant. However, high surgical expertise is necessary for SM gland transfers due to prolonged surgical time and physical activity-related epiphora. In this patient, there was significant improvement in visual acuity, corneal morphology, and function.

Dry eye status also showed significant clinical and quantitative improvement in tear flow. Biochemical analysis of tear fluid posttransplant showed amylase. It must be noted that the mere presence of amylase in tear fluid does not lead to corneal damage, as it does not have any proteolytic and lipolytic activity against the corneal epithelium. In addition, it provides bactericidal activity and secretory immunoglobulin A, which also provides immunological protection against bacteria.

CONCLUSION

Sialoscintigraphy is an essential and important investigation in documenting the functional status of native and transplanted salivary glands, as highlighted in this case. Treatment with lubricant eye drops and anti-drainage procedures has been successful in managing most symptoms associated with lacrimal gland agenesis. Early detection of this condition is crucial to prevent permanent complications such as severe scarring, perforation, or blindness. SM gland transfer is a promising surgical option for severe dry eye.