Diagnostic Work-up and Anesthesiologic Considerations
The diagnostic workup of a goiter begins with simple palpation of the
neck and performing an ultrasound. Regarding the former, Pattashanee and
colleagues have shown that clinical examination in modified Rose’s
position (i.e. , supine, a roll under the shoulders, and by
hyperextending the neck) has an excellent sensitivity (98%) and a
variable specificity (46.7-91.1%) to identify substernal
extension36. Another interesting result is that, in
the absence of the Pemberton’s sign, the probability of getting a false
positive finding of a substernal extension was only 4%, and this is
quite relevant in the context of low-income countries where the
availability of CT scan is scarce3633, an 89%
sensitivity and 87% specificity for any degree of tracheal narrowing
were registered (AUC = 0.90)37.
CT scan of the neck and thorax remains the gold standard for a full
assessment and classification of RG because it evaluates the dimensions,
the morphology, and the relationships to the adjacent mediastinal
anatomical structures (Figure 2 ). It is usually performed with
the aid of intravenous iodine contrast agents, despite a theoretical
more than a real risk of precipitate thyrotoxicosis (Jod-Basedow
phenomenon)5,21. Some authors have proposed a simple
yet not validated rule-of-thumb: if the RG remains cranial to the aortic
arch in the sagittal plane of CT performed while the patients maintain a
full neck extension, then sternotomy is usually not
necessary38. Classical predictors of the need for
sternotomy are based on the craniocaudal length of the retrosternal
extension, the ratio between the retrosternal portion and the diameter
of the upper thoracic inlet (so-called “iceberg” or “cone-shaped
RG”), and the anterior or posterior relationships with major
vessels2,393 had a negative predictive value for the
extra-cervical approach of 100%40. Volume was
manually outlined on axial sections by two radiologists, but interrater
agreement and kappa coefficients were not calculated thus leaving doubts
on the applicability of this technique. The value of imaging in the
prediction of an exclusive transcervical approach to RG will be
discussed further in the next sections.
CT scan lets a clear assessment of both tracheal deviation and extrinsic
compression, which are both reasons why airway management is usually
labeled as difficult in RG patients, and a very low threshold for
endoscopic-assisted awake intubation is kept by anesthesiologists. This
fear mostly derives from anecdotal evidence of extreme RG where
emergency tracheostomy29, or the need for a pediatric
flexible bronchoscope were necessary41. In the most
extreme case, the application of extracorporeal membrane oxygenation
(ECMO) before the induction of general anesthesia has been described
with success42,43. Actual evidence instead dispels the
myth of a difficult airway, in the absence of classical risk factors
(mouth opening less than 4 cm, a thyromental distance less than 6 cm,
Mallampati Class III or higher, etc.)39. In a 2020
paper, 22 cases of “giant” type I RG (defined as trespassing the
aortic arch on CT scan), with a mean maximum diameter of 114.2 ± 19.5 mm
were all successfully intubated with standard laryngoscopy or awake
tracheal intubation (for 5 patients, 22%) using flexible
bronchoscopy44. A larger multi-institutional series
from the USA, confirmed that direct laryngoscopy or videolaryngoscopy
techniques were sufficient in 162 patients (90.5%), while transnasal of
transoral fiberoptic was intubation used for the remaining 17
patients45. The authors did not give a clear-cut
definition of RG, yet they performed a multivariate analysis where the
body mass index was the only factor to positively correlate with the
number of attempted intubations45.