Description
General anesthesia is used. Partial thyroidectomy is the removal of an entire thyroid
lobe and isthmus or a portion of a lobe. The nature of the lesion has almost always
been determined prior to the operation. Nodules are confi ned to a single thyroid
lobe or the isthmus. Most often a certain or suspected diagnosis of malignancy is
the indication for surgery; less often the nodule(s) is either hyperfunctional or is
enlarged and causing obstructive symptoms. The patient is supine with a roll placed
transversely under the scapulae to allow optimal neck extension.
To prevent neck
hyperextension, the head is supported on a supporting “donut” head ring. A curved
transverse “skin crease” incision is made in the anterior neck about two fi ngerbreadths
above the clavicular heads, continuing deep to the platysma muscle. The
strap muscles are separated in the midline after incision of the fascia and retracted
laterally. The non-diseased thyroid lobe is inspected, and the thyroid lobe to be
removed is mobilized anteromedially by transecting vessels laterally. This exposes
the thyroidal vessels and fi ne attachments of Berry’s ligament. The vessels supplying
the thyroid must be dissected carefully and divided as close to the gland as
possible. Care must be taken to identify the upper and lower parathyroid glands and
the recurrent laryngeal nerve early, before starting to remove the thyroid lobe. The
nerve is most easily identifi ed where the inferior thyroid artery crosses it and is followed
until it enters the larynx. Great care should be taken not to injure the nerve
by applying too much traction, direct pressure, or injuring it with electrocautery.
The external branch of the superior laryngeal nerve can be identifi ed before dividing
and ligating the superior pole vessels. Identifi cation of the cricothyroid avascular
space can assist to localize the nerve as described elsewhere. The use of nerve
monitoring devices may improve the localization and detection of nerve branches
to preserve. If the blood supply to a parathyroid gland cannot be preserved with
certainty, it should be removed, sliced into 1 mm slivers, placed into iced saline,
and implanted into muscle pockets in a strap (or forearm) muscle at the end of the
case. The thyroid lobe should always be removed from lateral to medial, and as the
last step it is sharply removed from the trachea. The cut edge of the thyroid should
be sutured for hemostasis. If the removed nodule is found to be malignant, either
by frozen section examination or the presence of metastatic disease in the cervical
lymph nodes, a total or near total resection of the contralateral lobe is indicated during
the same operation. Frozen section may not discern benign from malignant, and
delayed completion thyroidectomy may be performed later. Meticulous dissection
and impeccable hemostasis may obviate the need for a drain in the neck, but many
surgeons still use a drain.
Anatomical Points
The thyroid gland arises from the foramen caecum of the posterior base of the
tongue and descends in the midline of the neck to reach the 2nd tracheal ring
in the adult. Variations in the course of the recurrent laryngeal nerve, typically
on the right side, occur in about 1 % of cases. The nerve may be anterior, posterior,
or between branches of the inferior thyroid artery. The right subclavian artery
can arise directly from the descending aorta so that the right nerve is “nonrecurrent,”
exiting from the vagus nerve at a 45° angle. The nonrecurrent nerve may
be mistaken for a vessel and divided, resulting in paralysis of the ipsilateral vocal
cord. About 0.2 % of patients have both a recurrent and nonrecurrent laryngeal
nerve on the right. Left- sided “nonrecurrent” laryngeal nerves are very rare and
are seen with situs inversus. The course of the superior laryngeal nerve, including
its external and internal branches, is also variable. The external branch of the
superior laryngeal nerve is usually closely associated with the inferior pharyngeal
constrictor and may be covered entirely by its muscle fi bers. In 15 % of patients
the nerve travels with the superior thyroid artery. In 6 % of patients it continues
to accompany the superior thyroid artery even after branching of the main
trunk. During embryogenesis, the parathyroid glands migrate a great distance, and
their anatomical location may vary greatly. The presence of a large thyroid nodule
may further complicate the identifi cation of these structures, and it takes great
patience and tenacity to identify them. Fifteen percent of patients have more than
four parathyroid glands. The inferior parathyroid glands arise from the third pharyngeal
pouch and are closely associated with the thymus. As they migrate during
development, they may fi nally rest anywhere from the pharynx to the posterior
mediastinum. The superior glands are more reliable in their position because they
arise from the fourth pharyngeal pouch along with the lateral thyroid. Intrathyroid
parathyroids occur in about 1 % of patients. Some patients have large pyramidal
lobes of the thyroid. Other variations include lingual thyroid and thyroglossal duct
cysts. Dysphagia lusoria or lusus naturae describes dysphagia due to extrinsic
compression by an aberrant right subclavian artery. This congenital vascular problem
occurs in 0.5–1.8 % of the general population, being the most common congenital
non-valvular aortic root anomaly.
Perspective
The major risk from unilateral thyroid lobectomy is damage to the
recurrent or superior laryngeal nerves. Any damage may not be apparent until any
vocal cord swelling from the endotracheal tube settles on the second or third postoperative
day. Intraoperative electromyography electrode monitoring may reduce the
incidence of recurrent laryngeal nerve injury. Damage to both parathyroid glands
may go unnoticed, unless the contralateral parathyroid glands have been damaged
or removed. In this situation parathyroid gland grafting/transplanting usually averts
permanent hypoparathyroidism. Hypocalcemia is due to temporary or permanent
disruption of normal parathyroid function. This may be due to manipulation of
the blood supply, direct trauma, or removal of the glands. Most hypocalcemia is
transient, and the glands will resume function after several days or weeks. If the
glands have been permanently injured or removed, then the patient will require
lifelong calcium and vitamin D supplementation, together with appropriate clinical
oversight. Bleeding is uncommon, unless the thyroid mass is very large and
associated with increased vasculature in the neck. Drains rarely provide adequate
drainage if the bleeding is heavy. Severe bleeding can cause tracheal compression
and acute respiratory failure, requiring prompt recognition, surgical decompression,
and control of bleeding. Cutaneous numbness and tingling of the anterior neck is
common and due to division of cervical plexus branches during incision. It often
improves with time, but can make shaving and application of cosmetics diffi cult.
Although very rare, Horner’s syndrome is caused by retraction damage to the cervical
sympathetic chain. It usually resolves, but may not. Neck wounds usually heal
rapidly with low infection risk and are rarely unsightly. Keloid reaction at the scar
may occur being diffi cult to prevent or treat.
Major Complications
A serious complication is damage to the recurrent laryngeal nerve or to the
external branch of the superior laryngeal nerve. Some factors for increased risk
or nerve injury are the inexperienced surgeon, invasive malignancy, very large thyroid
masses, and reoperative surgery. With time the changes in phonation associated
with these injuries will improve; however, in patients who depend on their voice
for a livelihood, the injuries can be devastating. Management of a divided recurrent
laryngeal nerve is controversial. Anastomosis of the nerve restores some bulk to the
vocal cord; however, there is anomalous regeneration, and phonation may not return
to normal. When the recurrent laryngeal nerve is known to be intact, the patient
should be referred for a trial of speech therapy. An injection of a material (e.g.,
gelatin, Tefl on, Silastic fat) into the vocal cord may be helpful in voice restoration.
In some cases, regardless of the integrity of the nerve, medialization thyroplasty
(using a variety of methods) may be indicated to improve the vocal quality and
decrease aspiration. There is little that can be done to restore the integrity of a damaged
external branch of the superior laryngeal nerve. Pre- and postoperative videostrobic
testing can be useful in defi ning preexisting or surgically induced voice and
laryngeal functional changes. Transient mild hypocalcemia is not uncommon after
surgery. Major hypocalcemia in the postoperative period is indicative of injury to
the parathyroid glands , which is usually transient, but in some cases may be permanent,
although uncommon after a partial thyroidectomy because the two glands
on the contralateral side typically remain untouched. Oral calcium and vitamin D
therapy for several weeks usually corrects this and is then reduced to test for recovery.
Meticulous surgical technique, sometimes with autotransplantation, can almost
prevent this complication. Serious postoperative bleeding <48 h, requiring urgent
reoperative drainage, is a rare but well-recognized complication patients should be
informed about. Thorough hemostasis and Valsalva testing before closure at the
completion of surgery are two risk reduction strategies often used.
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