The sensitivity and specificity of methylene blue spray to identify the parathyroid gland during thyroidectomy

Real-time imaging of ipsilateral parathyroid glands by retrograde injection of methylene blue into the superior thyroid artery: a new intraoperative parathyroid protection method

BACKGROUND

Postoperative hypoparathyroidism caused by parathyroid injury is a problem faced by thyroid surgeons. The current technologies for parathyroid imaging all have some defects.

METHODS

Patients with differentiated thyroid carcinoma (DTC) who underwent unilateral thyroidectomy plus ipsilateral central lymph node dissection were recruited. We dissected the main trunk of the superior thyroid artery entering the thyroid gland and placed the venous indwelling tube into the artery. The sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were calculated.

RESULTS

A total of 132 patients enrolled in this single-arm clinical trial, 105 of them completed retrograde catheterization via the superior artery. The sensitivity was 69.23 and 83.33% respectively. The specificity was 72.91 and 64.89%. The accuracy was 72.91 and 64.89%. The PPV was 85.71 and 81.08%. The NPV was 22.58 and 45.45%. There were no patients with allergic reactions to the methylene blue, or methylene blue toxicity.

CONCLUSIONS

Retrograde injection of methylene blue via the superior thyroid artery is an effective and safe method to visualize parathyroid glands. This method can accurately locate the target organ by ultraselecting the blood vessel and injecting the contrast agent while avoiding background contamination and reducing the amount of contrast agent.

TRIAL REGISTRATION

Clinical trial registration numbers and date of registration: ChiCTR2300077263、02/11/2023.

Ultrasound characteristics of normal parathyroid glands and analysis of the factors affecting their display

BACKGROUND

Parathyroid glands are important endocrine glands, and the identification of normal parathyroid glands is crucial for their protection. The aim of this study is to explore the sonographic characteristics of normal parathyroid glands and analyze the factors affecting their display.

METHODS

Seven hundred three subjects who underwent physical examination at our hospital were included. The number, location, size, morphology, echogenicity and blood flow distribution of parathyroid glands were recorded. The ultrasound characteristics and display rate were also summarized. Meanwhile, shear wave elastography was performed in 50 cases to provide the stiffness measurements, and 26 cases received contrast-enhanced ultrasonography for the assessment of microcirculatory perfusion. Furthermore, we analyzed the factors affecting parathyroid display, including basic information of the subjects and ultrasound features of the thyroid.

RESULTS

① A total of 1038 parathyroid glands were detected, among which, 79.29% were hyperechoic, 20.71% were isoechoic, 88.15% were oval-shaped, and 86.71% had blood flow of grade 0-I. ② 81.79% of the subjects had at least one parathyroid gland detected. ③ The Emean, Emax, PI and AUC of the parathyroid glands were significantly lower than those of the adjacent thyroid tissue (P < 0.05). ④ The display of normal parathyroid glands was related to BMI, thyroid echogenicity and thyroid volume of the subjects (P < 0.05).

CONCLUSIONS

Normal parathyroid glands tend to appear as oval-shaped hyperechoic nodules with blood flow of grade 0-I. BMI, thyroid echogenicity and thyroid volume are independent factors affecting the display of parathyroid glands.

Prevention of hypoparathyroidism: A step-by-step near-infrared autofluorescence parathyroid identification method

BACKGROUND

Hypoparathyroidism is an important factor that seriously affects the quality of life of patients after thyroidectomy. This study aimed to optimize the surgical procedure for parathyroid identification using near-infrared autofluorescence (NIRAF) during thyroidectomy.

METHODS

This was a prospective controlled study that included 100 patients with primary papillary thyroid carcinoma diagnosed in Beijing Tongren Hospital between June 2021 and April 2022 who were awaiting total thyroidectomy and bilateral neck dissection. The patients were randomly divided into an experimental group in whom step-by-step NIRAF imaging was used to identify parathyroid glands, and a control group in whom NIRAF was not used.

RESULTS

The number of parathyroid glands identified in the NIRAF group was higher than that in the control group (195 vs. 161, p=0.000, Z=-5.186). The proportion of patients with parathyroid glands inadvertently removed in the NIRAF group was lower than that in the control group (2.0% vs. 18.0%, respectively; p=0.008, χ^{2 =} 7.111). In the NIRAF group, we found that more than 95% of the superior parathyroid glands and more than 85% of the inferior parathyroid glands were identified before the dangerous phase, which was much higher than that in the control group. The incidences of temporary hypoparathyroidism, hypocalcemia, and symptomatic hypocalcemia were higher in the control group than those in the NIRAF group. On the first postoperative day, the average parathyroid hormone (PTH) level in the NIRAF group decreased to 38.1% of the preoperative level and that in the control group decreased to 20.0% of the preoperative level (p=0.000, Z=-3.547). On the third postoperative day, the PTH level in 74% of the patients in the NIRAF group recovered to normal levels, whereas it recovered in only 38% of the patients in the control group (p=0.000, χ^{2 =} 13.149). The PTH levels in all patients in the NIRAF group had recovered within 30 days after surgery, whereas one patient in the control group failed to return to the normal level 6 months after surgery and was diagnosed with permanent parathyroidism.

CONCLUSIONS

The step-by-step NIRAF parathyroid identification method can effectively locate the parathyroid gland and protect its function.

Epineural Methylene Blue Injection May Aid Localization of Digital Nerves in Dupuytren's Surgery

Background

In Dupuytren's surgery, limited fasciectomy is still the gold-standard treatment. A relatively high risk of iatrogenic nerve injury has been observed especially when the spiral cords of the Dupuytren's tissue pull digital nerves away from their normal anatomical location. Intraoperative neural marking could facilitate locating the potentially displaced nerves. Hence, surgery could be undertaken more quickly with a lower risk of iatrogenic nerve injury.

Objectives

We hypothesize that digital nerves may be stained with methylene blue (MB) in vivo providing a visual aid to distinguish them from Dupuytren's tissue. We aim to (a) test an in vivo nerve staining technique using MB in a rat sciatic nerve model and to (b) assess the safety of epineural MB injection.

Methods

Three experiments were performed: first, the effects of (a) sham surgery, (b) epineural needle insertion, and (c) 40 μL epineural saline injection were tested in the rat sciatic nerve. Second, we determined the (a) histoanatomical localization of the epineurally injected 40 µL 1 m/m% MB stock solution and (b) we tested which saline dilution (i.e., 1:40, 1:80, and 1:160) of the stock solution does provide optimal blue color upon 40 µL epineural injection. Third, the functional and morphological effect of 40 µL 1:80 diluted MB injection was compared with that of saline, injected into the contralateral sciatic nerve. The functional effects were tested by assessing the pain threshold by using a dynamic plantar esthesiometer (DPA) and by examination of the animal's gate and paw posture. Sciatic nerves were subjected to histological examination and morphometry to test structural damage.

Results

Neither epineural needle insertion nor saline injection caused any functional or morphological changes. Histological examination revealed that the MB stained the epineural compartment. Epineural injection of 40 μL 1:80 diluted MB into the sciatic nerve stained an 18.18-mm segment of the nerve distal to the puncture point. DPA revealed unchanged pain threshold values on the plantar surface of the limbs. Normal gait and foot posture suggested normal motor functions in all groups. No histological changes were seen in the stained nerves, and the nerve fiber density remained unchanged.

Conclusion

We demonstrated that in vivo nerve staining with MB is a suitable method to mark nerves without causing detectable negative effect to the stained nerve. Human trials are required to prove the efficacy of the technique in Dupuytren's disease.

Endoscopic parathyroidectomy using a three-port submental approach

PURPOSE

The three-port submental endoscopic approach and its variations were introduced in 2016 and have been used for thyroidectomy since. However, there has been no report of this approach being used for parathyroidectomy [1, 2]. The objective of this paper was thus to report our experience using a three-port submental approach for endoscopic parathyroidectomy in challenging cases such as tertiary parathyroidism.

METHODS

We compared the outcomes before and after endoscopic removal of the parathyroid glands using a three-port submental endoscopic approach.

RESULTS

Endoscopic subtotal parathyroidectomy was performed using submental approach in five patients with tertiary hyperparathyroidism from January 2018 to June 2019. The parathyroid hormone levels of the patients dropped significantly after undergoing subtotal parathyroidectomy (mean difference 2260 pg/ml; 95% CI 1883.74 to 2636.65), as did calcium levels (mean difference 2.84 mg/dl; 95% CI 1.90 to 3.78). No major adverse events occurred in this study.

CONCLUSIONS

Submental approach parathyroidectomy allows for visualization of all parathyroid glands. Surgical scarring was minor and was hidden under the chin. The surgical outcomes were promising, and there were no major complications.