A 45-year-old male patient presents with difficulty swallowing and hoarseness that has progressively worsened over the past month. During physical examination, the physician notices that the patient's left vocal cord is paralyzed. The paralysis is most likely due to compression of which of the following nerves?

Right recurrent laryngeal nerve

A 10-month-old boy is brought to the clinic with a history of recurrent episodes of stridor and wheezing. His mother reports that his wheezing is exacerbated by crying, feeding, and flexion of the neck, and is relieved by extension of the neck. Occasionally he vomits after feeding. What is the most likely diagnosis?

Gastroesophageal reflux disease

A 27-year-old man comes to the physician because of a 1-day history of right-sided facial weakness and sound intolerance. Three days ago, he hit the right side of his head in a motor vehicle collision. He neither lost consciousness nor sought medical attention. Physical examination shows drooping of the mouth on the right side. Sensation over the face is not impaired. Impedance audiometry shows an absence of the acoustic reflex in the right ear. Which of the following muscles is most likely paralyzed in this patient?

Anterior belly of the digastric

A 54-year-old man comes to the physician because of dysphagia and hoarseness of voice for the past 3 months. Initially, he had difficulty swallowing solid food but now has difficulty swallowing porridge and liquids as well. He has recently been choking on his oral secretions. During this period, he has had an 8.2-kg (18-lb) weight loss. He has noticed increasing weakness of both arms over the past year. He appears ill. His temperature is 36.8°C (98.2°F), pulse is 74/min, respirations are 14/min, and blood pressure is 114/74 mmHg. Examination shows tongue atrophy and pooled oral secretions. There is diffuse muscle atrophy with occasional twitching. He is unable to lift his arms above the chest level. Deep tendon reflexes are 3+ in all extremities. Sensation to pinprick, light touch, and vibration is intact. Laboratory studies show: Hemoglobin 16.1 g/dL Leukocyte count 10,900/mm3 Erythrocyte sedimentation rate 20 mm/h Serum Na+ 133 mEq/L K+ 4.2 mEq/L Cl- 101 mEq/L Urea nitrogen 12 mg/dL Creatinine 1.1 mg/dL Creatine kinase 320 U/L Albumin 4.3 mg/dL Lactate dehydrogenase 307 U/L An esophagogastroduodenoscopy shows no abnormalities. Which of the following is the most likely cause of this patient's symptoms?

Destruction of upper and lower motor neurons

Autoimmune destruction of acetylcholine receptors

Dilation of the central spinal canal

Demyelination of peripheral nerves

A 63-year-old man comes to the physician because of a 1-month history of difficulty swallowing, low-grade fever, and weight loss. He has smoked one pack of cigarettes daily for 30 years. An esophagogastroduodenoscopy shows an esophageal mass just distal to the upper esophageal sphincter. Histological examination confirms the diagnosis of locally invasive squamous cell carcinoma. A surgical resection is planned. Which of the following structures is at greatest risk for injury during this procedure?

Bronchial branch of thoracic aorta

Esophageal branch of thoracic aorta

A 75-year-old man is referred for thyroidectomy for treatment of thyroid nodules. A portion of the thyroid gland is resected, and the neck is closed with sutures. After awakening from anesthesia, the patient complains of ‘hoarseness’. His vital signs are normal and his incisional pain is minimal. The surgeon realizes he most likely damaged the recurrent laryngeal nerve. Which of the following should the surgeon tell the patient?

"We made a mistake during the operation that may have harmed you."

"A mistake occurred during the operation, but there was no harm to you."

"The case took longer than we thought it would, but everything went well."

"A mistake occurred because this hospital has poor operating room protocols."

"The operation was successful and no complications occurred."

Recurrent laryngeal nerve protection for USMLE Step 1: High-Yield Surgery Lessons

🗺️ The Nerve's Journey

A branch of the Vagus Nerve (CN X), the RLN has an asymmetric thoracic course before ascending into the neck.
Right RLN: Loops inferior to the right subclavian artery. Has a shorter, more oblique path.
Left RLN: Loops inferior to the aortic arch (near the ligamentum arteriosum). Has a longer, more vertical path.
Both ascend in the tracheoesophageal groove, closely related to the Inferior Thyroid Artery (ITA), to enter the larynx.

⭐ A Non-Recurrent Laryngeal Nerve (NRLN) is a rare anomaly (~1%), almost always on the right, linked to an aberrant right subclavian artery (arteria lusoria). High risk of iatrogenic injury.

Recurrent Laryngeal Nerve Anatomy

🗣️ Anatomy: Functional relevance - The Voice Box Boss

Anatomy of the Neck: Nerves, Vessels, and Organs

Origin: Branch of the Vagus nerve (CN X).
Motor: Innervates all intrinsic laryngeal muscles except the cricothyroid (innervated by the superior laryngeal nerve).
- Posterior Cricoarytenoid (PCA): The only vocal cord abductor.
- 📌 Mnemonic: PCA = Pulls Cords Apart.
Sensory: Sensation to the larynx below the vocal cords.

⭐ Unilateral RLN injury causes hoarseness (paramedian vocal cord). Bilateral injury causes acute airway obstruction (median vocal cords).

🗺️ Anatomy: Clinical Correlations - Danger Zones

Recurrent Laryngeal Nerve Anatomy

Inferior Thyroid Artery (ITA) Crossing:
- RLN course is variable: posterior, anterior, or between ITA branches.
- ⚠️ Ligate ITA branches individually, close to the thyroid capsule, not the main trunk.
Ligament of Berry:
- Fibrovascular band attaching thyroid to trachea.
- RLN passes deep or through it; high risk of injury during final gland mobilization.
Tubercle of Zuckerkandl (ToZ):
- Posterolateral thyroid projection; often covers the RLN.
- 💡 A reliable landmark to identify the nerve.

⭐ Non-Recurrent Laryngeal Nerve (NRLN): A rare (~1%) anomaly, almost exclusively on the right, associated with an aberrant right subclavian artery (arteria lusoria).

🛡️ The Guardian's Playbook

Pre-op: Baseline laryngoscopy for patients with pre-existing hoarseness, dysphonia, or history of prior neck surgery.
Intra-op Gold Standard: Meticulous dissection and definitive visual identification ("see the nerve").
- Medial-to-lateral approach is common.
- Key landmarks: Inferior thyroid artery, Tracheoesophageal groove, Tubercle of Zuckerkandl, Ligament of Berry.
- Intraoperative Nerve Monitoring (IONM) aids localization and confirms functional integrity post-dissection.
- ⚠️ Avoid blind clamping, excessive traction, and thermal injury from electrocautery near the nerve.

⭐ Non-Recurrent Laryngeal Nerve (NRLN): A rare anomaly (~0.5-1%), almost exclusively on the right, associated with an aberrant right subclavian artery (arteria lusoria).

Recurrent Laryngeal Nerve Surgical Landmarks

⚠️ Complications - The Aftermath

Unilateral Injury:
- Presents with hoarseness, dysphonia, and a weak, breathy voice.
- Vocal cord assumes a paramedian position due to unopposed cricothyroid (SLN) action.
Bilateral Injury:
- A surgical emergency presenting with acute stridor and respiratory distress.
- Both vocal cords are adducted (median position), causing severe airway obstruction.
- Requires immediate airway intervention (intubation/tracheostomy).

⭐ The posterior cricoarytenoid is the only vocal cord abductor. Its paralysis in bilateral RLN injury leads to unopposed adduction and airway closure.

Unilateral vocal cord paralysis with anatomy

⚡ Biggest Takeaways

The recurrent laryngeal nerve (RLN), from the vagus nerve (CN X), is at risk during thyroidectomy; visual identification is key.

Unilateral RLN injury causes hoarseness and a breathy voice due to ipsilateral vocal cord paralysis.

Bilateral RLN injury is an emergency causing airway obstruction and stridor from paralyzed midline vocal cords.

Superior Laryngeal Nerve (SLN) injury affects the cricothyroid muscle, causing loss of high-pitched sounds.

A non-recurrent RLN is a rare anomaly, almost always on the right side.

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