Retinoic acid-mediated down-regulation of ENO1/MBP-1 gene products caused decreased invasiveness of the follicular thyroid carcinoma cell lines

Retinoic acid (RA) acts as an anti-proliferative and redifferentiation agent in the therapy of thyroid carcinoma. Our previous studies demonstrated that pretreatment of follicular thyroid carcinoma cell lines FTC-133 and FTC-238 resulted in decreased in vitro proliferation rates and reduced tumor cell growth of xenotransplants. In addition to the previous results, we found that RA led to decreased vitality and invasiveness of FTC-133 and FTC-238 cells as they reacted with reduction of intracellular ATP levels and number of migrated cells respectively. However, the molecular mechanisms by which RA mediates these effects are not well understood. Two-dimensional (2D) screening of the proteins related to ATP metabolism and western blot analysis revealed alpha-enolase (ENO1) to be down-regulated in FTC-133 and FTC-238 cells after RA treatment. 2D gel detection and mass spectrometric analysis revealed that ENO1 existed as three separate protein spots of distinct pIs (ENO1-A1-A3). Comparative 2D difference gel electrophoresis analysis of fluorescently labeled protein samples of RA-treated and untreated FTC-133 demonstrated a selective down-regulation of ENO1-A1 which we identified as a phosphoprotein. RA caused the dephosphorylation of ENO1-A1. Both, RA-mediated and specific knock-down of ENO1/MBP-1 resulted in the reduction of MYC oncoprotein, and simultaneously decreased proliferation rates of FTC-133 and FTC-238 cell lines. In summary, the RA-mediated down-regulation of the ENO1 gene products and MYC oncoprotein provides a novel molecular mechanism facilitating the anti-proliferative effect of RA in human thyroid carcinoma cells and suggests new pathways for supportive RA therapies.

Premonitory symptoms preceding metastatic medullary thyroid cancer in MEN 2B: An exploratory analysis

BACKGROUND

More than 90% of M918T carriers with multiple endocrine neoplasia type 2B (MEN 2B) harbor de novo mutations in the REarranged during Transfection (RET) protooncogene. DNA-based screening for RET germline mutations is rarely useful for early diagnosis, which thus is contingent on the clinical ascertainment of MEN 2B-specific symptoms as soon as they emerge. Little information exists about the presence of these symptoms in infancy.

METHODS

Detailed information was gathered regarding the development of MEN 2B-associated symptoms from the parents of 25 M918T RET carriers and 50 age- and sex-matched controls with the use of a disease-specific questionnaire.

RESULTS

Until the end of the study, at a median age of 16.2 (range, 0.5-34.9 years), all 25 M918T RET carriers had developed medullary thyroid cancer. By that time, 96%, 91%, 71%, 75%, and 28% of carriers displayed oral manifestations, ocular abnormalities, intestinal symptoms, musculoskeletal malformations, and pheochromocytoma, respectively. During the first year of life, fewer than 20% of carriers were found to express the typical MEN 2B phenotype, whereas 86% and 61% of these children, but none of the controls, were noted for their inability to cry tears and for constipation.

CONCLUSION

Because the classic MEN 2B phenotype is rare during the first year of life, more emphasis should be placed on the more subtle features of the syndrome. Additional studies are needed to validate the usefulness of the symptoms "inability to cry" and "constipation" for earlier diagnosis of MEN 2B.

Limitations of intraoperative adrenal remnant volume measurement in patients undergoing subtotal adrenalectomy

BACKGROUND

Recent studies have shown that a minimum of approximately one-third of one normal adrenal gland is required for sufficient adrenocortical stress capacity. Correlation between intraoperative measurement, determination of remnant size by computed tomography (CT), and adrenocortical stress capacity has not been examined so far.

METHODS

Twenty-two patients with familial pheochromocytoma (n=13), sporadic pheochromocytoma (n=3), and adrenocortical tumors (n=6) who underwent unilateral or bilateral subtotal adrenalectomy (STAE, 28 adrenal remnants) were prospectively studied. Patients were examined in a multi-slice CT to determine residual adrenal tissue and by ACTH test 4 days and 3 months postoperatively.

RESULTS

There was a slight significant correlation between intraoperative and CT calculated volumes (r=0.77; p<0.001). However, volumes assessed by CT were almost doubled compared with intraoperative determination (p<0.001). Although recovery of adrenal function could be observed, no significant changes of remnant volumes could be detected within 3 months. In patients with familial pheochromocytoma, there was a significant correlation between residual adrenal volume and stimulated cortisol levels (P<0.001). A distinct minimum of adrenal volume for intact adrenocortical stress capacity could not be exactly determined; however, in one patient with only 10% residual adrenal tissue intact stress capacity was found.

CONCLUSIONS

Residual adrenal tissue of approximately 10-15% offers intact stress capacity. However, an exact determination of the size of an adrenal remnant after STAE has limitations. CT gives larger volumes compared with intraoperative determination. For calculation of a volume-function correlation of residual adrenal tissue, in clinical practice, the determination of relative adrenal residual volume is acceptable.

Total parathyroidectomy without autotransplantation for renal hyperparathyroidism: experience with a qPTH-controlled protocol

BACKGROUND

Controversy regarding the optimal surgical treatment for secondary hyperparathyroidism (sHPT) continues. Subtotal parathyroidectomy (PTX) with a small remnant and total parathyroidectomy with autotransplantation prevail, although impaired by considerable recurrence rates. Concerns about postoperative management and long-term supplementation prevent broader acceptance of total parathyroidectomy without autotransplantation.

MATERIALS AND METHODS

The standardized surgical procedure with intraoperative PTH assessment (qPTH) included cervical thymectomy, histological proof of four parathyroid specimens and obligatory cryopreservation of parathyroid tissue in all 23 patients undergoing total PTX without autotransplantation. Whenever qPTH did not normalize, complete cervical exploration of ectopic sites was performed. Another 64 patients with subtotal PTX for sHPT served as comparison for the postoperative course.

RESULTS

There were 13 primary and 10 completion (5 persistent, 5 recurrent sHPT) total PTX with 14 concurrent thyroid resections performed. Mean preoperative PTH was 1.351 pg/ml (12-72 pg/ml) and serum calcium was 2.5 mmol/l (2.25-2.5 mmol/l). PTH showed intraoperative normalization in 15 patients and a 50% PTH reduction from preoperative values in all. Postoperative course was not significantly different from the subtotal PTX group and showed PTH within the normal range for 5 patients (4 < 35 pg/ml), 7 with PTH < 12 pg/ml, and 4 without measurable PTH. In 4 patients PTH did not normalize postoperatively. Serum calcium levels were below normal in all patients: < 2.25 mmol/l in 9, < 2.00 mmol/l in 7, and <1.8 mmol/l in 6 patients. Only 1 patient required intermittent early postoperative i.v. calcium supplementation, 6 patients received oral calcium and vitamin D supplement for low calcium levels, but no severe hypocalcemic symptoms were encountered. Mean postoperative hospital stay was 5 days. No recurrent laryngeal nerve palsies were encountered. Complications were two cervical bleedings following postoperative hemodialysis requiring evacuation.

CONCLUSIONS

Total PTX without autotransplantation proves to be an equally safe and successful procedure for sHPT as subtotal PTX or total PTX with autotransplantation. Measurable PTH after total PTX as demonstrated in this study, supports the idea of uncontrollable isolated cell nests that are inevitably prone to stimulated growth with time. Therefore, total PTX is superior with regard to prevention of recurrence. Adequate supplementation with calcium and vitamin D, often necessary after subtotal PTX to suppress inadequate PTH and protect from recurrence, will prevent severe hypocalcemia and with the modern aluminium-diminishing dialysis regimen, development of adynamic bone disease appears less likely than feared. If necessary, cryopreserved parathyroid tissue can be autotransplanted on demand.

Prognostic Significance of Disseminated Tumor Cells in the Connective Tissue of Patients with Medullary Thyroid Carcinoma

INTRODUCTION

Disseminated tumor cells in the connective tissue (CT-DTCs) do not have any connection to a primary tumor or the lymph nodes. They are identified quite often in patients with medullary thyroid carcinoma (MTC), but nothing is known regarding their prognostic significance.

METHODS

Among 450 patients with MTC, 69 (15%) were identified as having CT-DTCs. A case-control group of patients without CT-DTCs was selected. The two groups were matched concerning TNM classification, age, heredity, and sex. Because many patients with CT-DTCs had extrathyroidal tumor extension (pT4 category), distant metastases (M1 category), or both, only 35 matched pairs could be identified. The TNM classification in both groups was as follows: pT1, n = 8; pT2, n = 15; pT3, n = 4; pT4, n = 8; pN0, n = 4; pN1, n = 31; M0, n = 30; M1, n = 5. The mean age was 46.8 +/- 17.0 years in the CT-DTC group and 44.4 +/- 15.0 years in the case-control group (NS).

RESULTS

In both groups, 23 patients had sporadic MTC, and 12 patients had hereditary MTC. Neither mean basal preoperative nor postoperative calcitonin levels differed significantly between the two groups. In contrast, none of the patients with CT-DTCs was biochemically cured (normal calcitonin level after pentagastrin stimulation) compared to eight patients without CT-DTCs (P < 0.005). The two groups did not differ concerning other parameters (basal calcitonin level > 3000 pg/ml, more than 10 lymph node metastases, more than two involved locoregional lymph node compartments, mediastinal lymph node metastases) that have been reported to correlate with the lack of or almost (< 10%) lack of biochemical cure.

CONCLUSIONS

In patients with MTC, disseminated tumor cells in the connective tissue correlate with advanced tumor stages and appear to be of prognostic significance.

[Thyroid surgery: generalist or specialist?]

BACKGROUND

Thyroid surgery is done in Germany in a considerable numbers of operations (about 110,000 per year). To perform thyroid operations by so called "generalists" or "specialists" have been discussed intensively, however, this issue have not been analyzed in detail.

METHODS

Study material comprised 16,500 consecutive thyroid operations with 30,000 operated sites that have been prospectively documented in the German Thyroid Multicenter Study performed 1998 through 2001. Quality of surgery were analyzed by calculating the inverse relationship between volume and outcome (complication rate).

RESULTS

To achieve complication rates (permanent unilateral recurrent laryngeal nerve paralysis and hypocalcemia) of < 1 % (primary surgery) or < 3 % (redo surgery) the minimum number of thyroid operations of lower level of experience (e. g. benign nodular goiter) per year was n=30. The minimum number of operations with higher level of experience was significantly lower (n=3-12) due to the higher level of experience of operating surgeons. In contrast to the rates of postoperative hypocalcemia the rates of postoperative recurrent laryngeal nerve paralysis was clearly related to the number of thyroid operations performed.

CONCLUSIONS

The high number of thyroid operations in Germany with about 20 % of operations of high level experience are requiring surgical curricula and hospital structures that offer as well generalists as specialists to treat the broad spectrum of thyroid diseases accordingly. To lower the complication rate especially of difficult thyroid operations the level of specialization in Germany have to be increased.

Selective arterial chemoembolization for hepatic metastases from medullary thyroid carcinoma

BACKGROUND

Hepatic metastases from medullary thyroid carcinoma (MTC) may impair quality of life by hypercalcitonemia-associated diarrhea and pain. In this prospective study, the effect of selective arterial chemoembolization (SACE) was evaluated.

METHODS

Eleven patients with hepatic metastases from MTC received 1 to 9 courses of SACE using epirubicine. Symptomatic, biochemical, and morphologic responses on SACE were recorded.

RESULTS

Symptomatic response was observed in all symptomatic patients. However, biochemical and radiologic response occurred only in 6 patients. Liver function was not affected by SACE. One patient with unexpected concurrent pheochromocytoma metastases died after the first course. Development of side effects in the course was observed in 8 patients but were only World Health Organization grade 1. Patients' satisfaction with SACE was excellent. Long-term follow-up found 7 patients alive (1-72 months). Three patients died with tumor 6, 12, and 24 months after SACE, respectively.

CONCLUSION

SACE provided good symptom palliation for the majority of patients with hepatic metastases from MTC. However, transient remission or stabilization of hepatic metastases resulted in only 60%. Further studies using a randomized protocol are required.

Risk factors of paralysis and functional outcome after recurrent laryngeal nerve monitoring in thyroid surgery

BACKGROUND

Recurrent laryngeal nerve monitoring (RLNM) has been suspected to reduce postoperative RLN paralysis (RLNP). However, functional outcome of RLNM in comparison with no nerve identification and visual nerve identification only has not been analyzed.

METHODS

Analysis of 16,448 consecutive multi-institutional operations resulted in 29,998 nerves at risk. Three groups of different RLN treatment were compared: group 1, no RLN identification; group 2, visual RLN identification; and group 3, visual RLN identification and electromyographic monitoring. RLNM was performed with a bipolar needle electrode that was placed through the cricothyroid ligament into the vocal muscle.

RESULTS

Risk factors for permanent RLNP were recurrent benign and malignant goiter (odds ratios, [ORs]), 4.7, and 6.7, respectively), primary surgery in thyroid malignancy (OR, 2.0), lobectomy (OR, 1.8), no nerve identification (OR, 1.4), low or medium volume hospital (OR, 1.3), and low volume surgeons (OR, 1.2).

CONCLUSIONS

Based on these data, visual nerve identification was identified to be the gold standard of RLN treatment in thyroid surgery. RLNM is a promising tool for nerve identification and protection in extended thyroid resection procedures. However, because of the overall low frequency of RLNP, no statistical difference compared with visual nerve identification only was reached in the setting of this study.

Multiple endocrine neoplasia 2B syndrome due to codon 918 mutation: clinical manifestation and course in early and late onset disease

More than 50% of patients with typical MEN-2B have a de novo M918T germline mutation of the RET protooncogene. However, even in typical MEN-2B, extrathyroidal manifestations of MEN-2B can be found to be differently expressed. We analyzed the clinical manifestation and course in 21 patients harboring a de novo RET M918T mutation. Mean age at MEN-2B diagnosis was 14.2 years (range: 1-31 years). All patients had medullary thyroid carcinoma (MTC). At the time of syndrome diagnosis, oral manifestations (bumpy lips, ganglioneuroma), ocular manifestations (corneal fibers, conjunctivitis sicca), intestinal dysfunctions, musculoskeletal manifestations, and pheochromocytoma were found in 86%, 90%, 74%, 79%, and 19% of the patients, respectively. At the time of follow-up examination, the symptoms were found at higher frequency. Severe intestinal manifestation was predominantly found in patients with prepubertal onset (< or = 12 years) of MTC (n = 4/10) compared with patients with late onset (> 12 years) of MTC (n = 0/11) (40% versus 0%; p = 0.019). Although biochemical cure was found only in four patients with early onset of MTC, the long-term prognosis for patients with early onset of MTC was poorer than for patients presenting with late onset of MTC (p = 0.005). During mean follow-up of 55.8 months (range: 3-161 months), seven patients (33%) died from MTC. In conclusion, whereas most typical MEN-2B symptoms were found to be age-related, severe intestinal manifestation was found to be predominantly expressed in patients with early onset of MTC. Furthermore, in patients with early onset of MTC who could not be biochemically cured, the long-term prognosis was found to be worse than that of non-cured patients with late onset of MTC, suggesting an additional pathological process in the younger subgroup reinforcing the very high transforming in vitro activity of the M918T RET mutation.

[Not all vocal cord failure following thyroid surgery is recurrent paresis due to damage during operation. Statement of the German Interdisciplinary Study Group on Intraoperative Neuromonitoring of Thyroid Surgery concerning recurring paresis due to intubation]

Since the phoniatrician H. Bauer described the first case of recurrent laryngeal nerve palsy most likely caused by intubation some 45 years ago, several case reports have been published. However, systematic analyses regarding the frequency of recurrent laryngeal nerve palsies due to intubation are scarce, and none of them has used the proper methods to demonstrate clearly that such a mechanism exists. Currently available data justify the assumption that not every recurrent laryngeal nerve palsy following thyroid surgery is due to the operation itself and that the damage caused by intubation, however, may only account for a minority of these cases. The differential diagnosis of postoperative recurrent laryngeal nerve palsy requires the use of specific tools which go beyond simple laryngoscopy and include stroboscopy as well as intra- and extralaryngeal electromyography. A partial palsy of recurrent laryngeal nerve due to intubation would be associated with severe dysphonia or aphonia, not with dyspnea because of the typical intermediate position of the paralyzed vocal folds with a normal electromyographic function of the cricothyroid muscle. The use of these methods to identify the nature of postoperative recurrent laryngeal nerve palsy is recommended in cases of regular intraoperative neuromonitoring but postoperatively impaired function of the vocal cords.

Zuverl�ssigkeit und Konsequenzen des intraoperativen Neuromonitorings in der Schilddr�senchirurgie

Intraoperative neuromonitoring (IONM) has yielded an increasing effect on thyroid surgery. During IONM, the recurrent laryngeal nerve is stimulated electrically and an acoustically transformed electromyographic signal is derived via either a needle electrode placed in the vocalis muscle or an electrode adjusted to the intubation tube. The IONM is used for identifying and predicting the function of the recurrent laryngeal nerve. Especially under difficult anatomic conditions, IONM has proven a valuable tool for identification of recurrent laryngeal nerves. This can lead to decreased occurrence of nerve palsy rates, as shown in numerous studies. The reliability of the IONM signal (defined as the correlation between intraoperative signal interpretation and postoperative vocal cord function) is reflected by a specificity as high as 98.2%, as shown by German multicenter studies. Thus, normal vocal cord function could be demonstrated postoperatively in over 98.2% of patients with intraoperatively unchanged neuromonitoring signals. If the neuromonitoring signal changed during operation, 39% of the patients suffered from transient vocal cord immobility and 12% had permanent loss of vocal cord function.

[Morbidity after subtotal and total thyroidectomy in patients with Graves' disease: the basis for decision-making regarding surgical indication and extent of resection]

Compared to radioiodine therapy the surgical treatment of Graves' disease aims to combine high therapeutic efficacy with low morbidity. According to the literature the risk for complications concerning recurrent laryngeal nerve paralysis and hypocalcaemia is lower after subtotal (0.6% and 0.9% respectively) than after total thyroidectomy (1.1% and 1.7% respectively). In contrast, the rate of persistent or recurrent thyrotoxicosis (3.2% and zero respectively) and the rate of worsening or newly developing endocrine ophthalmopathy is higher after subtotal resection than after total thyroidectomy (8% and 2% respectively). On the basis of these data, total thyroidectomy performed by an experienced surgeon is recommended in the case of complicated Graves' disease and in special situations (e.g. pregnancy and breastfeeding, suspected or proven concomitant thyroid malignancy, severe side effects of antithyroid drug treatment). Subtotal thyroidectomy should be reserved for patients with low activity of Graves' goitre, where radioiodine treatment has a similar effect but without the risks associated with surgery.

Ambulante und kurzzeitstation�re Schilddr�sen- und Nebenschilddr�senchirurgie

Outpatient or short-stay thyroid and parathyroid surgery is still uncommon in Germany. Although a substantial number of these operations are performed with low morbidity, nearly zero mortality, and short operation time, some potentially lethal complications, especially postoperative hemorrhage, are strong arguments against liberal shortening of hospital stay. Symptomatic hematomas after thyroid and parathyroid surgery are observed in about 1-2% of cases. They frequently occur during the first 8 h after operation (40%). However, two thirds of these major complications occur later, about 20% of them more than 24 h postoperatively. Therefore, an outpatient procedure cannot be generally recommended. Short-stay (<23 h, overnight) thyroid and parathyroid surgery may be attractive, but this concept requires clear release-criteria and professional outpatient structures. Compared to general anesthesia, local and regional anesthesia did not emerge as helpful to shorten hospital stay. Also, prophylactic calcium supplementation is not recommended to enhance early hospital discharge after bilateral thyroid or parathyroid surgery.

Validity of intra-operative neuromonitoring signals in thyroid surgery

BACKGROUND

Although intra-operative neuromonitoring (IONM) is widely used in thyroid surgery, the validity of the received IONM signals are still unknown.

METHOD

Prospective collection of data forms in 29 hospitals from 8,534 patients with 15,403 nerves at risk, who underwent surgery for benign and malignant goitre disorders between August 1999 and January 2001. IONM was performed by indirect stimulation via the vagal nerve and by direct recurrent laryngeal nerve (RLN) stimulation in 12,486 cases. IONM signals were compared with early (<14 days) and late (6 months) postoperative vocal cord function findings.

RESULTS

The transient and permanent RLN palsy rate was 2.8% and 0.7%, respectively. Monitoring of the RLN function was significantly more reliable via the indirect IONM stimulation route than via the direct IONM stimulation route (specificity P<0.05). IONM by indirect stimulation via the vagal nerve reliably excluded postoperative, permanent, vocal cord palsy (specificity 97.6%, negative predictive value 99.6%). However, a changed IONM was insufficient to predict permanent RLN palsy (sensitivity 45.9%, positive predictive value 11.6%). IONM was not associated with increased general morbidity.

CONCLUSIONS

For intra-operative neuromonitoring, indirect stimulation of the RLN is superior to direct stimulation. An intact acoustic IONM signal is highly predictive of intact postoperative RLN function. When the IONM signal is abnormal or absent, a one-stage extensive thyroid resection should be performed only if the surgeon is absolutely convinced that the first RLN is not harmed or a total thyroidectomy is mandatory.

[Is primary total thyroidectomy justified in benign multinodular goiter? Results of a prospective quality assurance study of 45 hospitals offering different levels of care]

INTRODUCTION

After subtotal resection of multinodular goiter, rates of up to 40% are reported for recurrent goiter in the long-term follow-up. Because of the increased morbidity of surgery for recurrent goiter, this study evaluated the preconditions that would justify total thyroidectomy as part of the primary therapy concept for benign multinodular goiter.

MATERIAL AND METHODS

The Quality Assurance Study of Benign and Malignant Goiter covering the period from 1 January to 31 December 1998 assessed 5195 patients treated for benign goiter by primary bilateral resection. With respect to the extent of resection three groups were analyzed: bilateral subtotal resection (ST+ST, n=4580), subtotal resection with contralateral lobectomy (ST+HT, n=527), and total thyroidectomy (TT, n=88).

RESULTS

The age of the patients was significantly higher (60.3 years) in the TT group than in the ST+ST (52.5 years) and ST+HT (55.6 years) groups. ASA classification grades III and IV were significantly more frequent in the TT group. The postoperative morbidity increased with the extent of resection. The rate of permanent recurrent laryngeal nerve (RLN) palsy was 0.8% for ST+ST, 1.4% for ST+HT, and 2.3% for TT and of permanent hypoparathyroidism 1.5% for ST+ST, 2.8% for ST+HT, and 12.5% for TT. Multivariate analysis showed that the extent of resection significantly increased the risk of RLN palsy (transient RR 0.5, permanent RR 0.4) and hypoparathyroidism (transient RR 0.2,permanent RR 0.08). The surgeon's experience (RR 0.6) and identification of the RLN (RR 0.5) reduced the risk of permanent RLN palsy. Additionally, the development of permanent hypoparathyroidism was reduced if at least two parathyroid glands (RR 0.4) were identified.

CONCLUSION

Total thyroidectomy is associated with an increased rate of RLN palsies and hypoparathyroidism in comparison to less extensive thyroid surgery. In the hands of well-trained surgeons using an appropriate intraoperative technique, primary thyroidectomy is justified if the patient has an increased risk of recurrent goiter. Due to the increased postoperative morbidity after total thyroidectomy, subtotal thyroid resection based on the morphologic changes in the thyroid gland is still recommended as the standard treatment regimen for multinodular goiter.

The impact of surgical technique on postoperative hypoparathyroidism in bilateral thyroid surgery: a multivariate analysis of 5846 consecutive patients

BACKGROUND

Limited information exists about risk factors for postoperative hypoparathyroidism after bilateral thyroid surgery.

METHODS

Between January 1 and December 31, 1998, bilateral thyroid surgery was performed on 5846 patients for benign and malignant thyroid disease. Data were prospectively collected by questionnaires from 45 hospitals. A logistic regression model was used to determine independent risk factors.

RESULTS

The overall incidence of transient and permanent hypoparathyroidism was 7.3% and 1.5%, respectively. On logistic regression analysis, total thyroidectomy (odds ratio [OR], 4.7), female gender (OR, 1.9), Graves' disease (OR, 1.9), recurrent goiter (OR, 1.7), and bilateral central ligation of the inferior thyroid artery (OR, 1.7) constituted independent risk factors for transient hypoparathyroidism. When the multivariate analysis was confined to permanent hypoparathyroidism, total thyroidectomy (OR, 11.4), bilateral central (OR, 5.0) and peripheral (OR, 2.0) ligation of the inferior thyroid artery, identification and preservation of no or only a single parathyroid gland (OR, 4.1), and Graves' disease (OR, 2.4) emerged as independent risk factors.

CONCLUSIONS

Extent of resection and surgical technique had a greater impact on the rates of permanent postoperative hypoparathyroidism than thyroid pathologic condition. In bilateral thyroid surgery, peripheral ligation of the inferior thyroid artery at the thyroid capsule should be favored over central ligation, and at least 2 parathyroid glands should be identified and preserved. High-risk procedures, such as total thyroidectomy and Graves' disease, require special surgical training and expertise.

Thyroid surgery with intraoperative neuromonitoring of the recurrent laryngeal nerve: a prospective multicentre study in Germany with 7617 patients

Background

Injury to the recurrent laryngeal nerve (RLN) is a frequently noted and serious complication in thyroid surgery. Several studies have established that identification of the RLN may reduce the incidence of RLN palsy. To date, no prospective study has evaluated whether the RLN palsy rate can be further reduced by intraoperative neuromonitoring of the RLN.

Methods

Between 1 January and 31 December 1998, surgery for benign and malignant goitre was performed on 7607 patients in 45 hospitals. Data were collected prospectively by questionnaire. RLN function was evaluated before and after operation in all patients. RLN palsy was defined as permanent when there was no evidence of recovery within 6 months after surgery. The RLN palsy rate was adjusted to nerves at risk in the three groups ‘no identification of the RLN’, ‘intraoperative identification of the RLN without neuromonitoring’ and ‘identification of the RLN with neuromonitoring’. Statistical analysis was by χ2 test.

Results

Mean patient age was 51·8 years; 72·7 per cent were women. Some 7256 patients were treated for benign goitre (multinodular goitre 74·0 per cent, uninodular goitre 16·6 per cent, recurrent goitre 6·1 per cent, Graves' disease 3·3 per cent, Hashimoto and De Quervain thyroiditis less than 0·1 per cent) and 351 patients for thyroid carcinoma, with a negative selection of recurrent goitre and thyroid carcinoma for the two groups with intraoperative RLN identification (P &lt; 0·0001). With respect to the extent of resection, in cases of lobectomy the rate of permanent RLN palsy was 1·5 per cent with intraoperative neuromonitoring which was significantly lower than rate with intraoperative RLN identification without neuromonitoring (2·6 per cent) or no RLN identification (6·3 per cent) (P &lt; 0·0001). Detailed analysis of the complete spectrum of extent of resection and indications for surgery showed a positive trend for intraoperative neuromonitoring in comparison to the group with RLN identification without the use of neuromonitoring, but this trend was not statistically significant because of the small number of permanent RLN palsies.

Conclusion

Intraoperative neuromonitoring of the RLN has a beneficial effect for high-risk patients with recurrent goitre and thyroid carcinoma in whom the RLN is at greatest risk in cases of lobectomy or total thyroidectomy.

An update on thyroid surgery

Surgery has been the treatment of choice for many disorders of the thyroid gland, both benign and malignant, for many decades. However, surgery has not been invariable but has continued to change in accordance with research results. In benign cases, surgery has generally evolved to be as organ preserving as possible. In several instances, however, a more radical extent of resection seems justified in order to ensure that the risk of recurrence is as low as possible. For instance, total thyroidectomy may be beneficial in patients with endemic multinodular goitre or young patients with Graves' disease and accompanying cold nodules or high levels of autoantibodies. Several tools, e.g. magnifying glasses, bipolar coagulation forceps and neuromonitoring, are available to identify and preserve the recurrent laryngeal nerve and the parathyroid glands, hence keeping the morbidity at a low level. Most recently, minimally invasive surgery has been successfully used in treating both benign and malignant disorders of the thyroid gland. In the case of malignant disorders, minimally invasive surgery may become an attractive alternative to open surgery if a limited surgical extent is justified, e.g. in patients with micro-PTC (papillary thyroid carcinoma, diameter less than 1 cm). Whether a limited surgical approach is also justified in other cases, e.g. in any patient with intrathyroidal PTC or patients with micro-FTC (follicular thyroid carcinoma), remains to be shown and is the subject of ongoing investigations. One of the most intriguing recent discoveries is the identification of genotype-phenotype correlations in patients with hereditary medullary thyroid carcinoma. In these patients, the timing and extent of surgery may depend not only on the patient's age and serum levels of the tumour marker calcitonin but also on the specific germline RET proto-oncogene mutation. Surgery will certainly continue to play an important role in the treatment of thyroid diseases and may be increasingly based on individual findings instead of general recommendations.

Intraoperative neuromonitoring of surgery for benign goiter

BACKGROUND

Recurrent laryngeal nerve (RLN) palsy is one of the most serious complications in thyroid surgery. No prospective studies are available that evaluate if the additional use of intraoperative neuromonitoring reduces the rate of RLN palsy.

METHODS

Between January 1 and December 31, 1998, surgery for histologically benign goiter with intraoperative identification with and without additional intraoperative RLN neuromonitoring was performed on 4,382 patients in 45 hospitals. Data were collected prospectively by questionnaire.

RESULTS

The rate of transient and permanent RLN palsy based on nerves at risk were 1.4% and 0.4% with intraoperative neuromonitoring. These rates were significantly lower (P <0.05) compared with intraoperative visual RLN identification without intraoperative neuromonitoring which resulted in rates of 2.1% and 0.8%, respectively. A multivariate logistic regression analysis confirmed that the use of intraoperative neuromonitoring decreases the rate of postoperative transient (P <0.008) and permanent (P <0.004) RLN palsies as an independent factor by 0.58 and 0.30, respectively.

CONCLUSIONS

Intraoperative neuromonitoring of the RLN in thyroid surgery is recommended because of significantly lower rates of transient and permanent RLN palsy rates in comparison with conventional RLN identification.

[Does intraoperative nerve monitoring reduce the rate of recurrent nerve palsies during thyroid surgery?]

Two different aspects of the influence of neuromonitoring on the possible reduction of post-operative recurrent laryngeal nerve palsies require critical examination: the nerve identification and the monitoring of it's functions. Due to the additional information from the EMG signals, neuromonitoring is the best method for identifying the nerves as compared to visual identification alone. There are still no randomized studies available that compare the visual and electrophysiological recurrent laryngeal nerve detection in thyroid operations with respect to the postoperative nerve palsies. Nevertheless, comparisons with historical collectives show that a constant low nerve-palsy-rate was achieved with electrophysiological detection in comparison to visual detection. The rate of nerve identification is normally very high and amounts to 99 % in our own patients. The data obtained during the "Quality assurance of benign and malignant Goiter" study show that in hemithyreoidectomy and subtotal resection, lower nerve-palsy-rates are achieved with neuromonitoring as compared to solely visual detection. Following subtotal resection, this discrepancy becomes even statistically significant. While monitoring the nerve functions with the presently used neuromonitoring technique, it is possible to observe the EMG-signal remaining constant or decreasing in volume. Assuming that a constant neuromonitoring signal represents a normal vocal cord, our evaluation shows that there is a small percentage of false negative and positive results. Looking at the permanent recurrent nerve palsy rates, this method has a specificity of 98 %, a sensitivity of 100 %, a positive prognostic value of 10 %, and a negative prognostic value of 100 %. Although an altered neuromonitoring signal can be taken as a clear indication of eventual nerve damage, an absolutely reliable statement about the postoperative vocal cord function is presently not possible with intraoperative neuromonitoring.