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Surgical Anatomy Thyroid and Parathyroid Glands

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Surgical Anatomy Thyroid and Parathyroid Glands Bastaninejad Shahin MD, ORL&HNS, TUMS, Amiralam Hospital Thyroid Laboratory Tests Thyroid Function Tests TSH FT4, (T4 ... – PowerPoint PPT presentation

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Title: Surgical Anatomy Thyroid and Parathyroid Glands


1
Surgical Anatomy Thyroid and Parathyroid Glands
  • Bastaninejad Shahin
  • MD, ORLHNS, TUMS, Amiralam Hospital

2
Presentation outlines
  • Thyroid Gland
  • General measures
  • Vascular supply
  • Important proximities
  • Surgical approaches and important Landmarks
  • Parathyroid glands
  • General measures
  • Surgical localization
  • Thyroid Function Tests

3
Thyroid Gland
4
General measures
  • Two lateral lobes connected with isthmus
  • Total weight is about 15 to 25 g
  • Each lobe 4 x 1.5 x 2cm (height/width/depth)
  • Extends from C5 to T1 vertebra
  • Isthmus is over 2nd 3rd tracheal ring
  • Approximately 40 of patients have a pyramidal
    lobe that arises from either lobe or the midline
    isthmus

5
40 present
6
General measures...
  • Cervical Fascia
  • True Thyroid Capsule
  • Surgical Capsule
  • Berrys Ligament (connecting the lobes of the
    thyroid to the cricoid cartilage and the first
    two tracheal rings)
  • Surgical Approaches regarding to the Fascia
  • Intracapsular Thyroidectomy
  • Extracapsular Thyroidectomy
  • Combine!?

7
Berrys Ligament
8
Vascular Supply
  • Two pairs of arteries
  • Three pairs of veins
  • Connecting vessels within the thyroid true
    capsule
  • In less than 10, there is a midline arterial
    supply to the gland, named as Thyroid Ima artery

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Important proximities
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? About 12cm
? About 5-6cm
16
Non-recurrent LN, Less than 1
17
Can be find in only 10-30 of the times
1 cm
18
Surgical approaches and Landmarks
  • The course of the inferior laryngeal nerve is
    highly variant
  • Incidence of nerve paralysis is three to four
    times greater in cases in which the recurrent
    nerve was not localized compared with cases in
    which it was
  • Try to seek, expose and identifying the nerve,
    instead of avoiding it!
  • ?Extracapsular approach with nerve identification
    is the method of choice

19
The most common course of the nerve is within TE
Groove (48.5 - not depicted here)
Incidence is more higher in Revision cases
42.2
5.4
3.9
20
Extralaryngeal Branching (35.5 in some reports
up to 80!)
21
Surgical approaches and Landmarks
  • Lateral Approach
  • Inferior Thyroidal Artery
  • Tubercle of Zuckerkandl (ZT)
  • Inferior Approach
  • Lores triangle
  • Tracheoesophageal Groove
  • Superior Approach
  • Posterolateral aspect of the Cricoid
  • Berrys ligament
  • Inferior border of the inferior Constrictor
  • Inferior horn of the thyroid cartilage

22
...Lateral Approach
  • Used most commonly
  • RLN is identified typically at the thyroid
    midpole level (?less nerve dissection required)
  • This approach is less useful for Revision

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ZT is Present in 63-80 of the patients
25
...Inferior Approach
  • Used for Revision cases and Goiter surgery (not
    substernal)
  • Problem Longer nerve dissection and probability
    of Parathyroid glands ischemia
  • Benefit nerve will be find before any
    extralaryngeal branching

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...Superior Approach
  • Used for large substernal Goiters
  • Nerve is at the lower edge of the lateral aspect
    of the cricoid cartilage
  • Nerve should be identified just caudal to the
    lowest fibers of the inferior constrictor

28
Parathyroid Glands
29
General measures
  • Two pairs Superior and Inferior
  • Weight is about 50 to 70 mg
  • Size 5 x 3 x 1 mm
  • Color of normal parathyroid glands ranges from
    yellowish brown to reddish brown
  • 87 there are four glands (super numerary glands
    are usually in the mediastinum or thymus gland)
  • Their Arterial supply is usually from Inferior
    Thyroid artery (80)

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Surgical Localization
  • Superior Parathyroid Glands
  • 80 they are at the cricothyroid junction
    approximately 1 cm cranial to the juxtaposition
    of the recurrent laryngeal nerve and the inferior
    thyroid artery.
  • Ectopic glands it cloud be intrathyroid,
    paraesophageal, retroesophageal and mediastinal
    (posterior superior compartment)

32
...Surgical Localization
  • Inferior Parathyroid Glands
  • More variable location
  • More than 50 of the inferior parathyroid glands
    are situated near the lower pole of the thyroid
    gland
  • Ectopic glands it could be situated in
    thyrothymic ligament (28) or mediastinum
    (Anterior superior compartment)

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Thyroid Laboratory Tests
35
Thyroid Function Tests
  • TSH
  • FT4, (T4)
  • FT3, (T3)
  • Thyroglobulin
  • Thyroid stimulating immunoglobulin (TSI)
  • Antithyroid peroxidase antibodies (Anti-TPO)
  • RAIU

36
Serum TSH
  • Single best initial test of the thyroid function
  • Normal range 0.5 5.0 mU/L
  • If TSH alone is the first line test, what
    diagnoses will be missed?
  • Pituitary disease or tumors
  • Hypothyroidism develops within 12 months of
    treatment for thyrotoxicosis (the TSH value
    remains suppressed)
  • Thyroid hormone resistancy
  • Non-thyroidal illness (NTI)
  • Pregnancy
  • ? In these cases testing of free thyroid hormones
    is recommended in addition to the TSH assay (FT4
    TSH)

37
Screening Recommendations
  • Various societies and authors disagree about
    population-based screening
  • There are insufficient evidences to recommend for
    or against routine screening for thyroid disease
    in adults.
  • The AAFP recommends screening high-risk
    populations
  • women with a family hx of thyroid disease
  • women gt35 y.o.
  • pregnant women
  • abnormal physical exam
  • diabetic patients
  • Hx of autoimmune disorder
  • The American Thyroid Association (ATA) recommends
    screening start at age 35 (and q 5 years after
    that)

38
Serum T4
  • Serum total T4 assays measure both bound and
    unbound (free) T4
  • Levels are high in approximately 90 of
    hyperthyroid patients and low in approximately
    85 of hypothyroid patients.

39
Serum Free T4
  • FT4 is measured by equilibrium dialysis
    techniques or estimated indirectly by calculation
    of free-thyroxine index (FTI)
  • FT4 assay is preferred test with TSH or when TSH
    is high

40
T3, Free T3, and rT3
  • T3
  • binding protein dependent
  • Levels can be misleading in patients with acute
    illness, cirrhosis, uremia, or malnutrition
  • FT3
  • Useful to distinguish T3 toxicosis from
    subclinical thyrotoxicosis
  • When TSH is low, a free T3 assay should be
    obtained
  • Measurement of fT3 is not indicated in
    hypothyroidism
  • Reverse T3 (rT3)
  • - increased in NTI
  • - it is an inactive hormone
  • - helpful to exclude central hypothyroidism

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Other Ancillary Tests
  • Serum thyroglobulin
  • produced and released by thyroid gland
  • marker for recurrent thyroid cancer
  • differentiate Graves disease from factitious
    thyrotoxicosis
  • Serum thyroid-stimulating immunoglobulin (TSI)
  • Expensive test
  • Graves disease.
  • Antithyroid peroxidase antibodies (Anti TPO)
  • organ-specific and sensitive.
  • Hashimotos thyroiditis
  • predict overt hypothyroidism (use in subclinical
    hypothyroidism)

43
Other
  • Radioactive iodine uptake (RAIU)
  • A very high RAIU is seen in individuals whose
    thyroid gland is overactive (hyperthyroidism)
  • A low RAIU is seen when the thyroid gland is
    underactive (hypothyroidism)

44
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