Case Report: A pyramidal lobe coexisting with a left-sided thyroid goiter displacing trachea and esophagus: A cadaveric finding with clinical implications

Neck vessels displacement

In the current case, the development of an enlarged left-sided TGo in the anterolateral direction displaced the LCCA and the LIJV, probably resulting in vessel compression. The trachea had a lateral right-side displacement from the midline, and consequently further displaced the RCCA and RIJV. Ovchinnikov et al.¹¹ pointed out that vessel dysfunction can be detected when the TG volume is increased by 1.4 times, however in the current case, it is unknown if the TG lobe was increased, resulting in a compression effect.

Common carotid artery (CCA) compression and/or stenosis may cause dizziness, weakness, and hypomnesia. Meanwhile, the potential outcomes are worse for the IJV¹¹ (with phlebectasia, decreased blood flow at the compression point, and increased velocity beneath that point). Both CCA and IJV compression outcomes were released with TGo resection, and the anatomy was reorganized.¹¹ Atherosclerosis tends to occur more often in arteries with inclined (angled) parts. Hence, in the current case, TGo and the resulting CCA deviation may potentially favor the development of atherosclerosis; however, larger angiographic studies should confirm this hypothesis. Stula et al.¹³ highlighted that the repeated mechanical force exerted by sternocleidomastoid muscle contraction on the arterial wall has a slight impact on atherosclerotic plaque development.¹⁴ In the current case, the existence of TGo further guided the CCA in proximity to or on the sternocleidomastoid muscle.

Trachea and esophagus displacement

In the current case, both tracheal and esophageal displacements were compressed on the RCCA. Tracheal inclination may lead to airway distress.¹⁴ In Shaha’s study,¹⁴ 18% of patients with TG had acute airway problems requiring emergency care (and some of them intubation). Shaha¹⁴ more often recorded tracheal (25%) than esophageal (18%) compression. In cases of esophageal compression, the most common clinical sign is dysphagia.¹⁴ The symptoms of tracheal and esophageal displacement could lead to an earlier surgical intervention to relieve pulmonary and gastrointestinal symptoms.¹⁵ It is of paramount importance to identify the tracheal location with clinical examination (palpation), as an indication of pulmonary pathology (e.g., pneumonia and atelectasia) or any other anomaly (TG).

Surgical outcomes

Airway problems due to an enlarged TGo may be an indication for mass resection.¹⁵ Difficult airway management is a challenge for anesthesiologists, requiring proper assessment, planning, and sometimes a multidisciplinary approach to establish a secure airway.¹⁶ Fiberoptic intubation is challenging in extreme cases of enlarged TGo coexisting with tracheal narrowing. In such cases, awake fiberoptic intubation and intraoperative anesthetic management of the patient are proposed to obtain a definitive airway through venovenous extracorporeal membrane oxygenation.¹⁶

However, the type of TGo resection remains controversial.¹⁵ Bann et al.,¹⁷ after investigating the effect of age on the distance of the TG from the sternal notch, observed that the TG was 15 mm closer to the sternal notch in patients aged 80 years and over than in patients age group–18-39 years. Thus, surgeons should direct their incision at a mean distance of 20 mm cephalad to the sternal notch. In the current case, the TG was identified 31.9 mm cephalad to the sternal notch, as supported by Bann et al.¹⁷ This close incision to the TG may lead to iatrogenic injury of the adjacent neurovascular structures or even the TG. In cases of enlarged TGos, surgeons usually intraoperatively identify the mass development anteriorly and displacement of the adjacent structures (CCA) posteriorly, such as the posterior cervical triangle area.¹⁸ Thus, in the current case, the CCA and IJV were displaced laterally rather than posteriorly. Linhares et al.¹⁹ recorded the prevalence of substernal extension of the TGo in 10% of patients (109/1080 patients who underwent surgical resection for multinodular TGo). Patients with substernal TGo and progressive enlargement and/or compressive symptoms should undergo surgical excision.

As in the current case, TGos may also coexist with TG variants, such as accessory lobes or tissues found superiorly, inferiorly, externally, and posteriorly to the TG. Such variants may be a source of pitfalls during preoperative diagnosis using scintigraphic imaging for thyroidectomies.²⁰ Rarely, thyroid tissue within the tracheal lumen could be a cause of upper respiratory obstruction and must be investigated to determine whether it is an ectopic tissue or malignant invasion of the trachea.²⁰

The pyramidal lobe overall pooled prevalence has been calculated at 42.82%, according to Ostrowski et al.²¹ meta-analysis. The most common type of pyramidal lobe is its origin from the left lobe, similar to the current case, with a pooled prevalence of 40.10%. The second most common type is its origin from the right lobe (25.39%). The presence of this variant lobe can implicate thyroidectomy. If the variant lobe is affected by carcinoma along with the rest of the gland, its incomplete dissection could lead to metastasis to the adjacent lymph nodes.²¹ Therefore, it is very important for head and neck surgeons to preoperatively identify this variation before thyroidectomy.²¹