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\begin{document}

\title{Undescended Superior Parathyroid: A Case Report}



\author[1]{Elliott Sina}%
\author[2]{Chihun Han J}%
\author[2]{Elizabeth Cottrill}%
\affil[1]{Thomas Jefferson University Sidney Kimmel Medical College}%
\affil[2]{Thomas Jefferson University Hospital}%


\vspace{-1em}



  
  \date{May 26, 2024}


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\selectlanguage{english}
\begin{abstract}
\textbf{Background:} Aberrant migration of parathyroid glands from their
embryologic origin may result in undescended parathyroid glands. We
present a case of an ectopic parathyroid adenoma at the level of the
pyriform sinus. \textbf{Methods:} A 41-year-old female was evaluated for
primary hyperparathyroidism. Following non-localizing ultrasound and
planar sestamibi imaging, the patient underwent%
\end{abstract}%



\sloppy


\textbf{1. Introduction}

Parathyroid glands normally descend from their embryologic origin in the
pharyngeal pouches to their final locations in the central neck.
However, aberrant migrations can lead to one or more parathyroid glands
being in non-anatomic locations, including retroesophageal space,
thymus, mediastinum, or within the thyroid gland. Rarely they fail to
migrate, resulting in an undescended gland. Adenomas arising from these
locations should be considered when initial preoperative imaging fails
to identify a target adenoma or after unsuccessful surgery. Here we
present a case of an ectopic parathyroid adenoma arising at the level of
the pyriform sinus.

\textbf{2. Case Report}

A 41-year-old female presented to our institution for evaluation of
primary hyperparathyroidism. She had a 7-year history of hypercalcemia,
with levels up to 11.5 mg/dL (reference range: 8.7 - 10.2 mg/dL) and PTH
levels up to 101 pg/mL (reference range: 10 -- 73 pg/mL). She has no
pertinent family history and is a former smoker (0.25 ppd, 5
pack-years). Initially, she underwent an ultrasound (US) of the neck
and\textsuperscript{99m}Tc-MIBI single photon emission computed
tomography (SPECT) imaging, which failed to identify any suspicious
lesions or localizing parathyroid adenomas. Subsequent SPECT/CT
(\emph{Figure 1} ) and 4-D computed tomography (CT) (\emph{Figure 2} )
demonstrated evidence of a 1.3 cm lesion superior to the thyroid at the
level of the pyriform sinus on the left side, likely representative of
an ectopic or undescended parathyroid adenoma. Given its unusual
location patient was preoperatively counseled on the risk of injury to
the hypoglossal nerve, marginal mandibular nerve, and the possible need
for a second incision for four gland exploration if the candidate lesion
was not an adenoma.

On the day of surgery, pre-operative PTH level was 80 pg/mL. In the
operating room, an upper transcervical incision was performed to obtain
access to the identified site. The subplatysmal flap was raised
superiorly and inferiorly to expose the inferior aspect of the
submandibular gland. Then the investing fascia was incised just caudal
to the submandibular gland, which was retracted superiorly to reveal the
posterior belly of the digastric muscle. The digastric muscle was
dissected along its anterior face and subsequently retracted superiorly
to identify the hypoglossal nerve and the internal jugular vein. A
crossing facial vein was encountered that required ligation to gain
appropriate access. An enlarged and undescended parathyroid measuring
1.5 x 1.5 cm located deep and slightly inferior to the anterior belly of
the digastric muscle, anterior and slightly medial to the carotid
artery, was identified and carefully resected (\emph{Figure 3, Figure 4}
). 10 minutes following the excision of the adenoma, PTH fell to 16
pg/mL and at 15 minutes post-excision remained stable at 14 pg/mL
indicating biochemical cure.

\textbf{3. Discussion}

Undescended parathyroid glands are typically defined as those located at
or above the carotid bifurcation.\textsuperscript{1} This classification
of parathyroid glands only constitutes 2-7\% of parathyroid adenomas,
making it the least common form of parathyroid glands found in ectopic
locations.\textsuperscript{2} While rare, undescended parathyroid
adenoma should be considered when initial preoperative imaging fails to
identify a target adenoma or after unsuccessful parathyroid surgery.

Pre-operative localization studies are critical in the identification of
possible undescended parathyroid adenomas. Imaging modalities typically
include high resolution neck ultrasound, SPECT, parathyroid
scintigraphy, CT and/or magnetic resonance imaging (MRI). In a
meta-analysis of 1276 patients, Wong et al. demonstrate a sensitivity of
86\% {[}Confidence Interval: 0.81-9.90{]}
for\textsuperscript{99m}Tc-sestamibi SPECT/CT in identifying ectopic
parathyroid adenomas, which is superior to the sensitivity of SPECT and
planar imaging modalities alone.\textsuperscript{3} The addition of
anatomical imaging can further enhance the diagnostic localization of
the candidate lesion. In a review of 656 patients at a single
institution, Zerizer et al. found that
combining\textsuperscript{99m}Tc-MIBI with anatomical scans (CT or MRI)
significantly improved diagnostic accuracy (improving sensitivity and
specificity to 100\%).\textsuperscript{4} Anecdotally, the localization
of parathyroid adenomas can be complicated by false positive signals
generated by thyroid nodules as well as the salivary glands, as was the
case for our undescended parathyroid. Additional imaging modalities,
such as CT neck with contrast or MRI can be helpful to pinpoint the
location and distinguish it from the neighboring structure as it did in
this case. A recent review article demonstrated that MRI had both a
sensitivity and specificity of up to 97\% in the detection of
parathyroid adenomas.\textsuperscript{5} Common MRI traits of adenomas
can include elongated morphology, T2 fat saturation hyperintensity, and
strong enhancement T1 post-contrast.\textsuperscript{5}

Four-dimensional CT has shown promise for the detection of ectopic
parathyroid glands, but has the drawback of a greater radiation exposure
compared to the sestamibi SPECT
modality.\textsuperscript{6}Four-dimensional CT specifically used for
localization of ectopic parathyroids has not been clearly defined in the
literature, however, it demonstrates a higher sensitivity (82\%) and
specificity (92\%) compared to other imaging modalities, suggesting its
benefit as a useful adjunct to localizing ectopic parathyroid
adenomas.\textsuperscript{7}

Importantly, in pre-operative planning, it is imperative to consider the
potential need to perform a second incision in order to conduct a
four-gland exploration in the case that the PTH did not decrease by
\textgreater{} 50\% after the removal of the adenoma. The unique
location of the surgical incision employed for this patient lends itself
to potential surgical complications that are otherwise uncommon in
standard parathyroidectomies. Specifically, surgeons must consider the
increased risk of injury to the hypoglossal and marginal mandibular
nerves, and injuries to the carotid artery, internal jugular vein, and
vagus nerve if dissection of the gland is required from these
structures. Furthermore, the use of a two-incision surgical approach
necessitates the surgeon to counsel patients on potentially managing two
scars post-surgery. As such, it is important to note that pre-operative
discussions with patients regarding surgical risks may differ from that
of a standard parathyroidectomy.

\textbf{4. References}

\begin{enumerate}
\tightlist
\item
  Fraker DL, Doppman JL, Shawker TH, Marx SJ, Spiegel AM, Norton JA.
  Undescended parathyroid adenoma: an important etiology for failed
  operations for primary hyperparathyroidism.~\emph{World J Surg} .
  1990;14(3):342-348. doi:10.1007/BF01658522
\item
  Phitayakorn R, McHenry CR. Incidence and location of ectopic abnormal
  parathyroid glands.~\emph{Am J Surg} . 2006;191(3):418-423.
  doi:10.1016/j.amjsurg.2005.10.049
\item
  Wong KK, Fig LM, Gross MD, Dwamena BA. Parathyroid adenoma
  localization with 99mTc-sestamibi SPECT/CT: a
  meta-analysis.~\emph{Nucl Med Commun} . 2015;36(4):363-375.
  doi:10.1097/MNM.0000000000000262
\item
  Zerizer I, Parsa\selectlanguage{ngerman}ï A, Win Z, Al-Nahhas A. Anatomical and functional
  localization of ectopic parathyroid adenomas: 6-year institutional
  experience.~\emph{Nucl Med Commun} . 2011;32(6):496-502.
  doi:10.1097/MNM.0b013e32834557a3
\item
  Morris MA, Saboury B, Ahlman M, et al. Parathyroid Imaging: Past,
  Present, and Future.~\emph{Front Endocrinol (Lausanne)} .
  2022;12:760419. Published 2022 Feb 25. doi:10.3389/fendo.2021.760419
\item
  Petranovi\selectlanguage{polish}ć \selectlanguage{english}Ov\selectlanguage{polish}č\selectlanguage{english}ari\selectlanguage{polish}č\selectlanguage{english}ek P, Giovanella L, Carri\selectlanguage{ngerman}ó Gasset I, et al. The EANM
  practice guidelines for parathyroid imaging.~\emph{Eur J Nucl Med Mol
  Imaging} . 2021;48(9):2801-2822. doi:10.1007/s00259-021-05334-y
\item
  Beland MD, Mayo-Smith WW, Grand DJ, Machan JT, Monchik JM. Dynamic
  MDCT for localization of occult parathyroid adenomas in 26 patients
  with primary hyperparathyroidism.~\emph{AJR Am J Roentgenol} .
  2011;196(1):61-65. doi:10.2214/AJR.10.4459
\end{enumerate}

\textbf{5. FIGURES}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

Figure 1. Sestamibi Single Photon Emission Computed Tomographic
(SPECT/CT)) Study. Yellow arrow points to the candidate lesion.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

Figure 2. Preoperative 4D-CT scan. Yellow arrow points to the candidate
lesion.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image5/image5}

\end{center}
\end{figure}

Figure 3. Removed ectopic parathyroid gland with the illustration of
relevant anatomical structures.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image6/image6}

\end{center}
\end{figure}

Figure 4. Intraoperative image of surgical incision site.

\selectlanguage{english}
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