Aortic arches😊

• 6 pairs of aortic arch arteries
• 1st, 2nd and 5th arch arteries disappear
• 3rd, 4th and 6th arch arteries remain

Development of Aortic Arches

• During development, 2 arteries join with the 4th arch arteries.

• Aortic sac divides into 2 horns:
• Left horn of Aortic Sac
• Right horn of Aortic Sac

Key Structures and Their Origins

• Arch of Aorta: Formed by
• Left horn of Aortic Sac
• Left 4th arch artery.

• 7th cervical intersegmental artery on both sides
• Between 4th and 5th aortic arches

• Brachiocephalic Trunk: Formed by
• Right horn of Aortic Sac.

• Common Carotid Artery: Formed by
• 3rd Arch Artery
• Proximally → CCA
• Distally → ICA
• Gives a bud for the external carotid artery.

• Left Subclavian Artery:
• Left 7th cervical intersegmental artery.

• Right Subclavian Artery:
• Right 7th cervical intersegmental artery
• Right 4th arch artery.

• Ductus Caroticus:
• A small part of the dorsal aorta.
• Between the 3rd and 4th arch arteries.
• Disappears on both sides.

• Left Dorsal Aorta: Forms the descending thoracic aorta

• Right Dorsal Aorta: Disappears.

• Pulmonary artery:
• Proximal part of 6th arch artery

• Ductus arteriosus
• Distal part of 6th arch artery
• Connects the pulmonary artery to the aorta.
• Obliterated ductus arteriosus → ligamentum arteriosum
• If patent → PDA

• Lung bud
• 6th Arch Artery
• invaded by Pulmonary Artery

Aberrant Right Subclavian Artery (ARSA)

 

• Right 4th arch artery obliterates (Normally persists)

• Persisting Arteries
• Right caudal dorsal aorta +
• Right 7th cervical intersegmental artery
• = abnormal right subclavian artery.

• Compresses the esophagus
• "dysphagia lusoria" (difficulty swallowing)

Double aortic arch

Persistence of both sides.

• 4th arch arteries &

• Dorsal aorta.

Recurrent Laryngeal Nerve

• Branch of the vagus nerve.

• Course
• Left RLN
• Longer course than right
• It turns under the remnant of left 6th arch artery.
• Ligamentum arteriosum (fibrous remnant).
• Right RLN
• winds around the Right subclavian artery.

• RLN injury
• Runs near Inferior Thyroid Artery
• Important for voice preservation
• Injured: Left > Right



• Commonest RLN injured:
• Left RLN (longer course)

• Commonest cause bilateral RLN palsy:
• Surgical trauma (esp. Total thyroidectomy)

• B/L RLN Palsy
• ⛔ Posterior Cricoarytenoid → Safety muscle of VC → Abductor
• Stridor, aphonia, breathlessness (Life threatening)
• Inability to extubate

ㅤ	U/L RLN injury	SLN Injury
Presentation	• Unilateral vocal cord paralysis • Hoarseness • Post-op dysphonia • Dyspnea • Difficulty in deglutition	• ILN → Aspiration → Absent cough reflex • ELN → Low pitch
Vocal cord appearance	• RLN injury = Paramedian	• RLN + SLN injury = Cadaveric/intermediate

Types of Vocal Cord Palsy



• Complete/adductor palsy
• SLN + RLN palsy
• VC in cadaveric/intermediate position (3.5 mm from midline)

• Incomplete/abductor palsy
• RLN palsy
• Cricothyroid intact
• VC in median/paramedian position (1.5 mm from midline)

Clinical Features





• Lateralisation of VC
• Kashima → Type 2 thyroplasty
• Woodmans → cordectomy + Arytenoidectomy

Surgical Trauma

Site of injury	Nerve injured
Base of skull	Complete vagus / SLN
Carotid triangle	ILN / ELN / SLN
Upper pole of thyroid	ELN ↳ most common injured in thyroid surgery
Lower pole of thyroid	RLN ↳ 2nd most common injured in thyroid surgery ↳ Rt > Lt
Mediastinal	Left RLN ↳ also in Ortner’s / cardiovocal syndrome

Normal VC position	during
Lateral	Deep inspiration
Paramedian	Rest
Median	Phonation

During total thyroidectomy for papillary carcinoma thyroid in a thirty-six-year-old lady, the
recurrent laryngeal nerve of right side was sacrificed for oncological safety. The next day, the patient complained of breathy voice. A fiberoptic laryngoscopy on the second post-operative day showed vocal cord paralysis of the right side. What would be the positions of the right and left vocal cords in this patient, on phonation?
(A) Right cadaveric, left intermediate
(B) Right intermediate, left intermediate
(C) Right paramedian, left median
(D) Right paramedian, left paramedian

ANS

C

Treatment of Vocal Cord Palsy

Isshiki’s thyroplasty types



• Type I (Medialisation/Proximalisation)
• Thyroid cartilage pushed medially
• Indication: U/L complete (adductor palsy)

• Type II (Lateralisation)
• Thyroid cartilage pulled laterally
• Indication: B/L RLN palsy

• Type III (Shortening)
• Part of thyroid cartilage cut
• Vocal cord shortened → pitch ↓
• Indication: Puberphonia
• Shorten the long man (shortening) who has guts (Gutzmann manoevre) but female sound (Puberphonia)

• Type IV (Tightening/Tensing)
• Indication: Androphonia
• Lengthen () the short female with male voice (androphonia)

Note

• Laryngeal inlet = epiglottis + arytenoid

• ILN injury → loss of cough reflex

Galen’s anastomosis:

• Between:
• Internal laryngeal nerve (from SLN)
• Recurrent laryngeal nerve (from RLN)

---

Clinical Testing

• Hypoglossus (CN 12)
• Test: ask patient to protrude tongue
• If lesion present: tongue deviates towards the affected side (ipsilateral deviation)

• Glossopharyngeal N (CN 9)
• Test: pressure on soft palate/uvula
• Also supply Glossopharyngeus

• Circumvallate papillae
• Present in the anterior 2/3rd part of the tongue
• But special sensation carried by glossopharyngeal

• Jugular canal
• Carries the glossopharyngeal nerve (IX)
• Fracture of the jugular canal
• Loss of taste sensation in the posterior 1/3rd of the tongue