Pyriform sinus fistula is the rarest of the cervical branchial anomalies. A recurrent left sided lower neck infection may be the only clue to this elusive entity. The ambiguity of the presentation, its diagnosis, delineation of its possible anatomical course and treatment options are highlighted in this review article.
Development of the neck takes place from the
branchial apparatus which is an embryological
complex. Abnormal development gives rise to
branchial anomalies that most commonly present
with neck masses and occasionally with external
opening on the skin forming sinuses. Most often
they are undiagnosed till multiple surgeries have
been performed. Of the various branchial anomalies,
the 2nd branchial anomaly is the most common.
Third and 4th branchial anomalies account for only
about 3 to 10% . The latter are in close proximity or
pass through the thyroid gland and originate in the
pyriform fossa, hence they are called pyriform sinus
fistula (PSF) . Most reported cases are found on the
left side with very few being reported on the right.
This may be related to normal embryology of the
branchial apparatus, where the fourth arch artery on
the left side becomes part of aortic arch, whereas
on the right side it becomes proximal part of right
subclavian artery .
A 19 year old male presented with complaints
of recurrent swelling in the anterior aspect of left lower neck. He had undergone multiple incision
and drainage of the abscess and had received antituberculosis
medications and various antibiotics
empirically. However, this therapy only resulted
in temporary relief. On presentation to us, he had
tenderness and mild swelling in the left lower
neck with scars of previous procedures. Barium
esophagram (BO) suggested the presence of a
pyriform sinus (Figures 1,2).
Figure 1: Barium esophagogram AP view showing tract delineated by barium. (white arrow)
Figure 2: Barium esophagogram LAT view proximalshowingbarium filled tract with ‘air pockets’ in thedistal part, leading to skin surface. (White arrow)
Computed tomogram (CT) showed a small tract
containing air pockets and a streak of contrast,
located anterior to the left carotid artery, leading
to apex of the left pyriform sinus (Figure 3). He was
reluctant to try non-invasive treatment and opted to
undergo surgery. He successfully underwent excision
of the tract along with a left hemithyroidectomy as
the tract was going through the thyroid gland. He
made an uneventful recovery and has not had any
recurrence for the last 6 years.
Figure 3: CT scan axial image showing ‘air-pockets’ with streaks of contrast near apex of left pyriform sinus. (White arrow)
PSFs occasionally present as a discharging sinus
along the anterior part of sternomastoid, often with
localised swelling and recurrent infection. The more
typical presentation is with a recurrent neck abscess
with a history of repeated surgical drainages, resulting
in fistula formation. If a PSF courses through thyroid
gland it may also present with acute suppuratives
Knowledge of the embryological relationships of
the branchial clefts to the adjoining structures, can
predict a probable course of 3rd and 4th branchial
fistulas. A typical course of the 3rd branchial fistula is to pierce the platysma, ascend along carotid
sheath, pass over superior laryngeal nerve, deep to
glossopharyngeal nerve (4th arch nerve), pass behind
the internal carotid artery, pierce the thyrohyoid membrane and enter upper lateral pyriform sinus .
The expected course of a 4th branchial fistula would
also pierce platysma; ascend along carotid sheath
but pass under superior laryngeal nerve and over the recurrent laryngeal and hypoglossal nerve. Then
it would dip back into mediastinum, passing the
aortic arch on the left and the subclavian artery on
the right side. Finally, the fistula would ascend to
enter larynx near cricothyoid joint or lower part of
thyroid cartilage, pass through inferior constrictor
muscle and enter apex of pyriform sinus4. Other
differentiating features may include presence of
thymic tissue in the third sinus and thyroid tissue in
the fourth sinus. Although the above description is of
interest, there is considerable overlap between the
two. None of the PSF has been reported to follow
the above course entirety. Fibrosis developing after
infection makes correct identification of anatomical
An alternative embryological process is perhaps
pertinent to the clinical presentation of branchial
cleft fistulas. As the thymus descends during fetal
development, a thymo-pharyngeal duct is formed.
The thymus is derived from ventral portion of third
pouch and it descends through fourth arch during
7th t o 8th week of intrauterine life. It fuses with its
counterpart in the midline forming a single organ.
The thymopharyngeal duct soon gets obliterated.
Failure of this duct to close results in the formation
of a branchial sinus lined by endodermal cells. These
cells arise from the pyriform fossa and pass in close
association to the thyroid gland as they head towards
cervical inlet. This is analogous to the formation of a thyroglossal cyst between tongue base and thyroid
Clinically a non-communicating cyst or
communicating non infected cyst may present as
a cold thyroid nodule or can be confused with a
thyroglossal cyst . The most common presentation is
that of recurrent abscess with a repeated history of
incision and drainage. A history of recurrent upper
respiratory tract infections, neck or thyroid pain
and tenderness as well as a neck mass is common.
Other manifestations include cellulitis, hoarseness,
odynophagia, thyroiditis, abscess and stridor.
Diagnosis of a PSF is based on demonstration
of a sinus or a fistula, originating from pyriform
sinus. BO has been widely used to demonstrate
the sinus tract . If there is acute inflammation, the
chance of a false negative result increases due to the
tract obliteration by inflammatory oedema . Real
time ultrasound can also be used to establish the
connection of an abscess cavity to the pyriform sinus
by performing the ‘trumpet, manoeuvre (exhale
with pursed lips to distend the pyriform sinus) . A
CT scan is considered the investigation of choice,
since it can delineate the location and extent of a
PSF. If the scan is performed soon after BO, the
sensitivity is considerably increased . Carbonated
beverages have also been used as alternative to
barium to demonstrate air in the fistula’s tract . In
addition, the Trumpet manoeuvre can be used to facilitate demonstration of sinus tract during BO and
CT. Indirect laryngoscopy often shows the internal
opening of the tract. Catheterization of the internal
opening with small Fogarty embolectomy catheters
may facilitate dissection. Some authors have used
methylene blue dye to delineate the entire tract but
extravasation can hinder identification of important
structures around the tract during surgery .
Meticulous dissection to identify superior and
recurrent laryngeal nerve should be taken. The
tract should be traced and dissected as high as
possible towards pyriform fossa, ligated and excised.
An oblique thyrotomy is performed above the
cricothyroid joint to expose the apex of the pyriform
sinus, thus, preventing injury to recurrent laryngeal
nerve. Recurrence of the fistula can occur if the
thyroid lobe is not removed with the tract, if the
tract passes through the thyroid or if the resected
specimen shows an absence of the epithelial lined
tract. However, recurrent infection can destroy the
epithelial lining. Chemo cauterization of the internal
opening using trichloroacetic acid has been described
with short term symptom free follow up . Using a laser to obliterate the epithelium has also been
advocated in the treatment of PSF. An endoscopic
approach with use of a carbon dioxide laser has been
reported to produce good outcomes [16,17]. These less
invasive treatments are an attractive option, since
they have a shorter surgical time and a low morbidity
and can be performed as an outpatient procedure.
PSFs are uncommon developmental abnormalities
of the branchial apparatus which are often
misdiagnosed, resulting in multiple operations prior
to making the correct. A barium esophagram often
reveals the presence of a tract communicating with
the pyriform sinus. However, a CT scan is considered
as the investigation of choice. Complete excision of
the tract, including its entry into the pyriform sinus
with or without hemithyroidectomy, is essential to
prevent recurrence. However, there have also been
an increasing number of case reports managed by
less invasive procedures, such as chemo or electrocauterization
that have obtained good clinical
outcome and reduced morbidity. More research in
this area is needed.
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