UNIVERSITY OF SANTO TOMAS
FACULTY OF MEDICINE AND SURGERY
DEPARTMENT OF CLINICAL EPIDEMIOLOGY
AN EVIDENCE BASED MEDICINE APPROACH TO
THYROGLOSSAL DUCT CYST
Eugenio, Clarisse Marie
Evangelista, Kristy Elleza
Facton, Rosabelle
Fajardo, Revie Anne
Fang, Mark David
Fontano, Michael Jeff
Francisco, Therese Pauline
Gabuat, Harry
Gaffud, Prima Bianca
Gagtan, Majelle
Gallardo, Estee Lauren Heart
Garan, Aileen Elizabeth
Garcia, Cholson Banjo
Garcia, Louise Fatima
Garcia, Mark Jezreel
February 11, 2010
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CASE SCENARIO
CA, 20, Female has an anterior cystic mass that started to grow in the area since she was
3 years old. The cystic mass is exactly at the midline at the level of the thyroid cartilage.
This is smooth, well circumscribed, non tender and moves up when the tongue is
protruded.
Salient Features



20 y/o, female
Anterior cystic mass; exactly at midline, level of thyroid cartilage
Smooth, well circumscribed, non tender and moves up when the tongue is
protruded
Clinical Impression
THYROGLOSSAL DUCT CYST
Thyroglossal duct cysts often present as anterior midline masses in the 1st decade of life.
More than 25% of thyroglossal duct cysts present before the age of 5, and 40% present by
the age of 10. Thyroglossal duct cysts appear at a constant rate of almost 10% per decade
in the ensuing years (Hechtman et al 2007).
Embryology
An appreciation of the embryology of the thyroid gland is important for an understanding
of the surgical approach to excision of thyroglossal duct cysts. During the 3rd week of
gestation, an epithelial thickening develops at the tuberculum impar on the anterior
pharyngeal wall. This thickening, the median thyroid anlage, divides into a bilobed
structure representing the developing thyroid gland. Rostral growth of the embryo results
in caudal displacement of the median thyroid anlage with persistence of a median stalk
stretching to the tuberculum impar. Canalization of the median stalk produces the
thyroglossal duct, which typically courses ventral to the hyoid anlage, but can pass
through or dorsal to it. In the 5th week of gestation, the duct degenerates and is resorbed.
Secretion by epithelium – lined remnants of the duct can lead to thyroglossal duct cyst.
The stimulus for secretion is unknown but can occur any time, accounting for the
appearance of the cysts later in life.
Clinical Presentation and Evaluation
A thyroglossal duct cysts usually presents as a suddenly appearing, unsightly, or inflamed
midline neck mass, or is discovered on routine physical examination. The cyst is located
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within 2 cm of the midline and typically overlies the hyoid bone, although it may be
found anywhere along course of the thyroglossal duct. Unless infected, the cyst is smooth
and mobile without communication with the overlying skin.
Diagnosis requires nothing more than a careful history and physical examination. A
typically positioned mass that rises in the neck with swallowing or with protrusion of the
tongue is diagnostic (Hechtman et al 2007). Confirmation of the thyroid in its normal
location by palpation or demonstration by ultrasonography may be important to avoid
incidental excision of a partially descended thyroid. Routine thyroid scintigraphy is
advocated by some to identify this extremely rare phenomenon. In the typical patient with
a recently identified upper midline neck mass, however the likelihood of this diagnosis is
remote and routine testing is not indicated.
Dermoid cysts are occasionally identified at the time of surgery or pathologically after
excision of a presumed thyroglossal duct cyst. Dermoid cysts can usually be
distinguished intraoperatively by the finding of thick, white sebaceous contents.
Additional diagnoses to be considered include lymphadenitis, enlargement of the thyroid
pyramidal lobe, and either locally occurring or metastatic neoplasia.
An operation is scheduled at the earliest convenience to avoid the morbidity of
intervening infection. If infection is present, the operation is deferred until the
inflammatory process is fully resolved. Incision and drainage are rarely required.
Surgical Technique
The contemporary approach to excision of thyroglossal duct cysts is attributed to
Sistrunk, for whom the procedure is named. He incorporated resection of central hyoid
bone and the tract extending to the foramen cecum with excision of the cyst. This
maneuver reduces the incidence of recurrence to less than 5% from 25% when
cystectomy alone is performed (Hechtman et al 2007).
Complications and Recurrence
The most potentially dangerous complication after thyroglossal duct excision is
postoperative wound hemorrhage with resultant airway compromise. Careful hemostasis,
not routine drainage of the wound, is the optimal approach in avoiding this uncommon
complication. Wound infections are infrequent and respond to treatment with oral
antibiotics.
Recurrence after thyroglossal duct excision occurs in approximately 5% of patients,
typically within 1 year of the procedure (Hechtman et al 2007). Inflammation of the
anterior neck associated with localized swelling or a draining sinus is the characteristic
presentation. Drainage may or may not occur at the incision scar. Recurrence is usually
attributed to inadequate excision of thyroglossal duct remnants.
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Spectrum of Disease
5%
7%
20%
Higher threshold
Pre-test probability
Lower threshold
The pre – test probability was set in 7% for this reason:
Thyroglossal tract remnant occurs in 7% (which is usually asymptomatic) of the total
population and only 20% occur at ages 20-30 years age. TTR/TDC is more common on
pediatric patients which occur at around 30%. The incidence of ectopic thyroid tissue,
misdiagnosed as a thyroglossal tract remnant, is probably between 1 and 2%, according
to a series by Radkowski et al which makes our pretest probability much lower Mostly
thyroglossal duct cyst is diagnosed early and intervention is well established. Most adult
patient at peak of around 4th decade has greater incidence for a malignancy.
The lower threshold was set at 5 percent for this reason:
The diagnosis of TDC can be established with good history and physical examination.
Physical examination reveals a midline mass at or below the hyoid bone, firm, nontender,
and mobile with protrusion of the tongue. This makes the diagnosis more cost efficient.
TDR are the most common midline neck masses representing more than 75% so higher
probability of diagnosing the disease in our patient.
The higher threshold was set at 20 percent for this reason:
Incidence of primary malignancy is estimated at only 1%. Since complication of not
having treatment has a low chance of occurrence, we therefore place the high threshold
father from the pre-test probability. Major complications of TDC surgery are rare. They
include recurrence, abscess or hematoma requiring surgical drainage, entry into the
airway, the need for tracheotomy, nerve paralysis, hypothyroidism, and death. Minor
complications such as seroma, local wound infection and stitch abscesses were reported
in 9 - 29% of the case. Recurrence rate after Sistrunk surgery is averaging of about 6.6%.
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CLINICAL DECISION ON DIAGNOSIS
CLINICAL QUESTION:
Is there a role for ultrasonography in the pre-operative diagnosis of thyroglossal duct cyst?
Population: thyroglossal duct cyst
Intervention: ultrasonography
Outcome: preoperative diagnosis
Methodology: retrospective cohort
Search:
Finding the Evidence:
1. Visited http://www.ncbi.nlm.nih.gov/pubmed/
Search terms: Thyroglossal duct cyst, sonography, preoperative diagnosis.
First search term is “thyroglossal duct cyst” and the result is a total of 1,038.
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Second search term is “sonography” and the total result is 285,674.
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Using MESH terms search we combined the result from thyroglossal duct cyst and sonography
by typing #1 AND #2.
The combined result of search #1 and #2 showed a total study of 81.
Third search term is “preoperative diagnosis” and the total result is 102,718.
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Using MESH terms we combined the result from thyroglossal duct cyst, sonography and
preoperative diagnosis by typing #3 AND #4.
The combined result of search #3 and #4 showed a total study of 17.
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With the list of journals narrowed down and limited, the right journal was found.
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______________________________________________________________________________
CRITICAL APPRAISAL ON DIAGNOSIS
Article:
“Preoperative Sonography in Presumed Thyroglossal Duct Cysts”
Gupta P., Maddalozzo J.
RELEVANCE
 Is the objective of the study relevant to your clinical question?
YES. To understand the role of the diagnostic tool, some things are to be considered.
Most literature would suggest that the diagnosis of thyroglossal duct cyst in through a
thorough history and physical exam: being it a midline cystic neck mass at the vicinity of
the hyoid that moves with deglutition. This could however be problematic since a in a
few number of cases there have been reports of the inadvertent removal of an ectopic
thyroid gland that was mistaken for a TGD cyst. Thus there could be a need to truly
characterize the midline neck mass through imaging.
VALIDITY GUIDES
 Was there an independent and blind comparison with a reference standard?
It was not stated in the article whether or not there was an independent comparison
between sonography and the reference standard used, histopathology findings

Did the patient sample include an appropriate spectrum of patients to whom the test
will be used?
YES. Although, there was no mention of the age range of the pediatric patients, all
patients had cystic midline neck masses at the vicinity of the hyoid which is a
characteristic of thyroglossal duct cysts.

Was the reference standard done regardless of the result of the diagnostic test being
evaluated?
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YES. A pathologic examination was done post-operatively to characterize the midline
neck mass lesion.

Were the methods for performing the test described in sufficient detail to permit
replication?
YES. It was mentioned in the methods and ‘patients and methods box’ on page 2.
OVERALL, IS THE STUDY VALID?
Yes, the study met most of the criteria for a valid study.
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WHAT ARE THE RESULTS?
Diagnostic Test
Ultrasonography
Positive
Negative
Thyroglossal Duct Cyst
(Histopathology)
Present
Absent
37
2
0.37
38
Based from the results tabulated in above table, the sensitivity and specificity of
ultrasonography is 99% and 95%, respectively.

What are the likelihood ratios for the different possible test results?
Positive LR: 19.8, negative LR: 0.01. Since the positive LR is more than 10 (19.8), it is
expected that there will be conclusive changes from the pre – to post test probability. A
negative LR of 0.01, which is less than 0.05, it is expected to alter the probability to a
small (and rarely important) degree.
Shown below is how the group was able to compute for the post test probability:
Pre test probability to pre test odds: (p/1-p)
Pre test odds = 0.07 / (1 - 0.07)
= 0.08
Post test odds: pretest odds x likelihood ratio
If positive = 0.08 x 19.8 = 1.58
If negative = 0.08 x 0.01= 0.0008
Post test odd to post test probability:
If positive = 1.58 / (1.58+1) = 60%
If negative = 0.0008 / (0.0008+1) = 0%
Spectrum of Disease
0% 5 %
7%
20%
Higher threshold
60%
Positive Post Test Probability
Pre-test probability
Lower threshold
Negative Post Test Probability
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CAN THE RESULTS HELP ME IN CARING FOR MY PATIENTS?

Will the reproducibility of the test result and its interpretation be satisfactory in my
setting?
There was no clear way of how the results were actually interpreted and how they were
able to come up with the sensitivity and specificity of the test.

Are the results applicable to my patient?
YES. Since the disease is actually very rare and the findings of ultrasonography are
highly specific, then it may be applied to our patient and although the age range of the
patients (pediatric) is different from our patient (20 years old- adult), their clinical
presentation is similar.

Will the results change my management?
Generally, the management will be dependent on which part of the spectrum the
computed post test probability will fall. If the post test probability falls beyond the set
upper testing threshold, a diagnosis of rabies is made and immediate treatment will be
initiated to prevent the further spread and development of the disease. But if the value
will fall below the lower testing threshold, the probability of having rabies can be ruled
out and the patient can be sent home.
RESOLUTION OF THE PROBLEM IN THE SCENARIO
Our patient, having all the classical findings of a thyroglossal duct cyst may therefore
undergo surgical intervention without the necessity of an ultrasonography.
CATMAKER
Preoperative Sonography in Presumed Thyroglossal Duct Cyst
Clinical Bottom Line: Ultrasound maybe used as a preoperative diagnostic tool for thyroglossal
duct cyst however the clinical findings may already suffice.
Citation/s:
Gupta, Pankaj and Maddalozzo, John, Preoperative Sonography in Presumed Thyroglossal Duct
Cyst. Arch Otolaryngolol Head Neck Surg/Vol 127, Feb 2001
Three-part Clinical Question: Is there a role for ultrasonography in the pre-operative diagnosis
of thyroglossal duct cyst?
Search Terms: thyroglosal duct cyst AND sonography AND preoperative diagnosis
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The Study:
The Study Patients: 20y/o, female, anterior midline neck mass at the level of thyroid cartilage,
smooth, well circumscribed, cystic, non-tender, moves up when tongue is protruded
Couldn't tell if there was an independent, blind comparison with a reference (gold) standard.
There was an appropriate spectrum of patients. The gold standard was applied regardless of the
test result.
Target disorder and Gold Standard: Thyroglossal duct cyst confirmed by histopathology
Diagnostic test: Ultrasonography
The Evidence:
TR> TR>
Target Disorder: thyroglossal
duct cyst
Test:
ultrasonography
Present
Absent
Test Result
Num
Prop
Num
Prop
Positive
37
a
2
b
Negative
.37
c
38
d
Likelihood
Ratios
5.13 to
19.80
76.48
0.00 to
0.01
0.26
Sensitivity: 99%; CI: 96 to 100
Specificity: 95%; CI: 88 to 100
Prevalence: 48%; CI: 37 to 59
Positive Predictive Value: 95%; CI: 88 to 100
Negative Predictive Value: 99%; CI: 96 to 100
Comments:
Appraised by: Fajardo, RA; Fontamo, MJ; Gaffud, PB; Garcia, MJ, February 7, 2010.
Kill or Update by Tuesday, February 09, 2010
Particular to my patient:
Pre-test probability:
7%
Test Result
Post-test probability
Positive
60%
Negative
0%
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