Place and value of the recurrent laryngeal nerve (RLN) palpatory method in preventing RLN palsy during thyroid surgery

The Anatomical Relationship of Inferior Thyroid Artery and Recurrent Laryngeal Nerve: A Review of the Literature and Its Clinical Importance

Background

Thyroidectomy is a quite common daily operation in general surgery. However, the anatomical structures of the region, mainly the relationship of recurrent laryngeal nerve (RLN) and inferior thyroid artery (ITA) makes the procedure challenging. The current review of the literature aims to report the anatomical variations of this relationship.

Methods

The preferred reporting items for systemic reviews and meta-analyses (PRISMA) guidelines were used for the systematic review of the articles found after an extensive research through PubMed, Science Direct, EMBASE and Web of Science. A total of 16 studies were included for the statistical analysis.

Results

The results showed that the most common type of RLN was posterior to the ITA. However, according to Higgins I² statistics the heterogeneity of the studies was quite high.

Conclusions

The relationship between the RLN and the ITA is quite variable. Anatomical knowledge of the region is vital for attempting to eliminate the risk of injuring the nerve during thyroidectomy.

[Modern thyroid surgery - the surgeon's endocrine-surgical understanding and his responsibility for the extent of surgery and complication rate]

Die hohe Qualität der Schilddrüsenchirurgie impliziert ein endokrin-chirurgisches Verständnis des Operateurs mit dem Ziel einer bestmöglichen Ergebnisqualität. Das beinhaltet ein befundadäquates Resektionsausmaß und eine möglichst niedrige Komplikationsrate. Der Chirurg sollte frühzeitig in die Operationsindikation eingebunden sein und auch selbst die Diagnostik, speziell den Schilddrüsen- und Halslymphknotenultraschall, sowie die Interpretation der Schnittbild- und nuklearmedizinischen Verfahren beherrschen. Im Besonderen sollte er über zeitgemäße Radikalitätsprinzipien in der Chirurgie Bescheid wissen.

Bei der gutartigen Struma ist eine individualisierte Operationsstrategie anzuwenden: Solitärknoten können auch einer gewebeschonenden Knotenresektion unterzogen werden. Bei multinodulärer Knotenstruma ist nicht zwingend eine totale Thyreoidektomie notwendig, die Vermeidung eines permanenten Hypoparathyreoidismus hat Priorität. Bei Rezidivstrumen ist oft die einseitige Operation des dominanten Befundes zu bevorzugen. Auch besteht zunehmend der Trend, die Indikation zur Entfernung der Schilddrüsenlappen seitengetrennt zu stellen. Die Basedow Struma erfordert eine Thyreoidektomie. Auch die hypertrophe Thyreoiditis Hashimoto kann eine Operationsindikation darstellen.

Die Radikalitätsprinzipien bei maligner Struma haben sich ebenfalls deutlich gewandelt als auch die strenge Indikation zur Radiojodtherapie. Das gilt speziell für papilläre Mikrokarzinome und minimal invasive follikuläre Tumortypen. Selbst bei medullären Schilddrüsenkarzinom stehen die Radikalitätsprinzipien im Hinblick auf synchrone oder metachrone laterale Halsdissektion in Diskussion.

Der Hypoparathyreoidismus stellt derzeit das Hauptproblem in der radikalen Schilddrüsenchirurgie dar. Recurrensparese und Nachblutung sind durch die subtile Operationstechnik selten geworden. Spezielle extrazervikale Operationszugänge sind nach wie vor in der Erprobungsphase und unter strengen Studienbestimmungen nur Zentren vorbehalten. Die Radiofrequenzablation stellt für gewisse Läsionen wie Zysten und autonome Adenome bei chirurgischer Kontraindikation ein alternatives Ablationsverfahren dar.

The Reliability of the Tracheoesophageal Groove and the Ligament of Berry as Landmarks for Identifying the Recurrent Laryngeal Nerve: A Cadaveric Study and Meta-Analysis

Purpose. The aim of this meta-analysis was to provide a comprehensive evidence-based assessment, supplemented by cadaveric dissections, of the value of using the Ligament of Berry and Tracheoesophageal Groove as anatomical landmarks for identifying the Recurrent Laryngeal Nerve. Methods. Seven major databases were searched to identify studies for inclusion. Eligibility was judged by two reviewers. Suitable studies were identified and extracted. MetaXL was used for analysis. All pooled prevalence rates were calculated using a random effects model. Heterogeneity among included studies was assessed using the Chi² test and the I² statistic. Results. Sixteen studies (n = 2,470 nerves), including original cadaveric data, were analyzed for the BL/RLN relationship. The RLN was most often located superficial to the BL with a pooled prevalence estimate of 78.2% of nerves, followed by deep to the BL in 14.8%. Twenty-three studies (n = 5,970 nerves) examined the RLN/TEG relationship. The RLN was located inside the TEG in 63.7% (95% CI: 55.3-77.7) of sides. Conclusions. Both the BL and TEG are landmarks that can help surgeons provide patients with complication-free procedures. Our analysis showed that the BL is a more consistent anatomical landmark than the TEG, but it is necessary to use both to prevent iatrogenic RLN injuries during thyroidectomies.

Extralaryngeal branching of the recurrent laryngeal nerve: a meta-analysis of 28,387 nerves

Introduction

The recurrent laryngeal nerves (RLN) are branches of the vagus nerve that go on to innervate most of the intrinsic muscles of the larynx. Historically, the RLN has been considered to branch after it enters the larynx, but numerous studies have demonstrated that it often branches before. The wide variability of this extralaryngeal branching (ELB) has significant implications for the risk of iatrogenic injury. We aimed to assess the anatomical characteristics of ELB comprehensively.

Methods

Articles on the ELB of the RLN were identified by a comprehensive database search. Relevant data were extracted and pooled into a meta-analysis of the prevalence of branching, branching pattern, distance of ELB point from the larynx, and presence of positive motor signals in anterior and posterior ELB branches.

Results

A total of 69 articles (n = 28,387 nerves) from both intraoperative and cadaveric modalities were included in the meta-analysis. The overall pooled prevalence of ELB was 60.0 % (95 % CI 52.0–67.7). Cadaveric and intraoperative subgroups differed with prevalence rates of 73.3 % (95 % CI 61.0–84.0) and 39.2 % (95 % CI 29.0–49.9), respectively. Cadavers most often presented with a ELB pattern of bifurcation, with a prevalence of 61.1 %, followed by no branching at 23.4 %. Branching of the RLN occurred most often at a distance of 1–2 cm (74.8 % of cases) prior to entering the larynx. A positive motor signal was most often noted in anterior RLN branches (99.9 %) but only in 1.5 % of posterior branches.

Conclusions

The anatomy of the RLN is highly variable, and ELB is likely to have been underreported in intraoperative studies. Because of its high likelihood, the possibility of ELB needs to be assessed in patients to prevent iatrogenic injury and long-term postoperative complications.

Electronic supplementary material

The online version of this article (doi:10.1007/s00423-016-1455-7) contains supplementary material, which is available to authorized users.

"Mystic" transient recurrent nerve palsy after thyroid surgery

BACKGROUND

The mechanism of transient recurrent laryngeal nerve (RLN) palsy remains unclear.

METHODS

Samples were harvested from the RLN adjacent thyroid capsule and perineural fascia during 223 lobectomies and 89 RLNs from cadavers were used for histologic and immunohistologic evaluation. Intraoperative chromoendoscopic features of the RLN were compared with postoperative ear, nose, and throat examinations.

RESULTS

Those nerves that macroscopically seem to be single-branched (35 of 89 = 39.3%), microscopically consist of multiple fascicles in most of the cases (23 of 35 = 65.7%), resembling a plexus more than a single cord. Chronic lymphocytic infiltration of the thyroid capsule adjacent to the RLN was present in 29% (65 of 223) of the cases. The perineural fascia showed lymphocytic (18 of 223 = 8.1%) or granulocytic (7 of 223 = 3.1%) infiltration.

CONCLUSIONS

The origin of transient RLN palsy is multifactorial: plexus shaped microscopic nerve structure with or without branches, frame-like adventitial tissue, variable epineurium, inflammatory changes that involve not only the thyroid capsule but the perineural fascia, resultant nerve edema, and diffuse microhemorrhages by injury of fragile capillaries.

Risk Factors for Recurrent Laryngeal Nerve Neuropraxia Postthyroidectomy

Objective. Despite preservation of the recurrent laryngeal nerve (RLN), transient vocal cord paralysis (VCP) occurs after 1.2% to 10.9% of thyroidectomies. The objective of this study was to study risk factors for transient VCP after thyroidectomy.

Study Design. Prospective cohort study.

Setting. Academic teaching hospital.

Subjects and Methods. Two hundred fifteen consecutive thyroid surgeries performed by a single surgeon. All patients underwent preoperative and postoperative laryngoscopy. Patients with preexisting VCP or without postoperative laryngoscopy were excluded. Clinical and operative data were recorded prospectively at the time of thyroid surgery. The association between possible risk factors and occurrence of postoperative transient VCP was studied.

Results. Six patients were excluded (2 with preexisting VCP and 4 without postoperative laryngoscopy). There was 1 intentional sacrifice of an RLN and 1 unintentional RLN transection. Of the remaining 322 RLNs at risk, 15 (4.7%) had postoperative VCP. Operative findings of cancer invading the RLN requiring sharp dissection to separate the nerve ( P = .006) and operative findings of RLN extensively draped along the thyroid or intimately associated with the thyroid parenchyma at Berry’s ligament ( P = .03) were significantly associated with VCP. Revision surgery ( P = .06) trended toward significance. Malignancy, central compartment neck dissection, extralaryngeal RLN branching, hyperthyroidism, and retrosternal extension were not significant. Of cases with follow-up laryngoscopic documentation of vocal function, 85% (11/13) showed full resolution of VCP, with 1 further case showing partial recovery.

Conclusion. Invasive cancer and variants in the anatomic course of the RLN are risk factors for transient VCP after thyroidectomy.

Risk factors for recurrent laryngeal nerve palsy after thyroidectomy

This study investigates the incidence of temporary and permanent recurrent laryngeal nerve palsy (RLNP) and possible risk factors for patients with different types of thyroid gland diseases. 1224 consecutive patients who underwent thyroidectomy for treatment of various thyroid diseases between the years 2001–2005. The rates of RLNP were evaluated. The surgeon and type of thyroid gland disorder were recognised as possible risk factors for RLNP. The incidence of temporary/permanent RLNP for the whole group was 4.5/0.8%. The rates of temporary RLNP for groups, classified as multinodular goitre, Graves’ disease, thyroid cancer or Hashimoto’s disease were 4.3%, 4.3%, 5.2% and 5.7%, respectively. The rates of permanent RLNP for the same groups were 0.4%, 0.9%, 1.6% and 1.9%, respectively. The frequency of temporary RLNP for individual surgeons ranges from 2.8 to 7.0% and the rates of permanent RLNP is between 0–3.1%. There was no relationship between the surgeon’s experience (the number of procedures performed) and RLNP rates. Total thyroidectomy is a safe procedure associated with a low incidence of RLNP not only for benign multinodular goitre, but also for Graves’disease, thyroid cancer and Hashimoto’s disease. The rates of RLNP among individual surgeons are acceptable with small inter-individual differences.