vocal cord paralysis

**Anatomy/Innervation (high-yield):** - All intrinsic laryngeal muscles are innervated by the recurrent laryngeal nerve (RLN, branch of CN X) EXCEPT the cricothyroid, which is innervated by the external branch of the superior laryngeal nerve (SLN). The cricothyroid tenses the vocal cords (raises pitch). - Posterior cricoarytenoid (PCA) is the ONLY vocal cord abductor ("opens the cords"; mnemonic: "PCA = Pull Cords Apart"). Lateral cricoarytenoid, interarytenoids, and thyroarytenoid adduct. - Sensory: internal branch of SLN above the vocal folds; RLN below the folds. - Left RLN loops under the aortic arch (ligamentum arteriosum); right RLN loops under the right subclavian artery. The left RLN's longer course makes it more vulnerable to mediastinal pathology.

**Etiology:** - Iatrogenic (most common): thyroidectomy, parathyroidectomy, carotid endarterectomy, anterior cervical spine surgery, cardiothoracic surgery (e.g., PDA ligation, aortic arch/mitral valve surgery), prolonged intubation. - Neoplastic: lung cancer (apical/Pancoast tumors, left hilar/mediastinal nodes), thyroid cancer, esophageal cancer, lymphoma, skull base tumors. - Cardiovascular: thoracic aortic aneurysm, left atrial enlargement (e.g., mitral stenosis; Ortner syndrome = cardiovocal syndrome), - Neurologic: stroke (lateral medullary/Wallenberg—nucleus ambiguus), jugular foramen lesions, Guillain-Barré, ALS, bulbar palsy, myasthenia gravis (not a true nerve lesion). - Infectious/inflammatory: viral neuritis (idiopathic cases often presumed viral), Lyme disease, sarcoidosis, TB. - Trauma, and idiopathic.

**Clinical Features:** - Unilateral: hoarseness, breathy/weak voice, diplopia of pitch, aspiration/cough with liquids, ineffective cough. Airway usually adequate. The paralyzed cord often sits in a paramedian position and may partially compensate over time via contralateral cord compensation. - Bilateral: inspiratory stridor, dyspnea, and potentially respiratory distress (cords paralyzed in a median/paramedian position), voice may be relatively preserved. Often follows total thyroidectomy. This is an airway emergency, requiring possible intubation or tracheostomy. - Isolated SLN injury (external branch): voice fatigue, loss of high pitch (important in singers); risk during ligation of the superior thyroid artery. - Vagus lesion above nodose ganglion (high lesion): also palate weakness, dysphagia, uvula deviation away from the lesion.

**Diagnosis:** - Laryngoscopy (flexible fiberoptic) is the initial test to visualize cord mobility. - Laryngeal EMG helps prognosis. - Look for the underlying cause: CT neck/chest from the skull base to the aortic arch (follows the RLN course), plus chest X-ray; MRI brain if central cause suspected.

**Management:** - Unilateral: voice therapy and observation (many recover within 6–12 months); temporary injection medialization (e.g., hyaluronic acid, calcium hydroxylapatite) early; permanent options include thyroplasty (type I medialization laryngoplasty), arytenoid adduction, or reinnervation. - Bilateral: airway first (tracheostomy), then later procedures such as cordotomy, arytenoidectomy, or posterior cricoid split to widen the airway (at the cost of voice quality). - Treat the underlying cause.

**Board pearls:** - Post-thyroidectomy hoarseness → RLN injury; bilateral injury → stridor immediately after extubation. - Hoarseness + lung mass → think mediastinal/hilar involvement (left RLN) or Pancoast tumor. - Wallenberg syndrome: hoarseness, dysphagia, ipsilateral facial pain/temperature loss, contralateral body pain/temperature loss, Horner syndrome, ataxia. - Neonatal: congenital vocal cord paralysis may be associated with Arnold-Chiari malformation (bilateral stridor) and birth trauma. - Do not confuse with vocal cord dysfunction (paradoxical vocal fold motion), which is a functional disorder mimicking asthma.