## Most Common Cause of Unilateral Vocal Cord Paralysis **Key Point:** Idiopathic vocal cord paralysis is the most common cause of unilateral VCP in adults, accounting for 30–50% of cases. This is a diagnosis of exclusion made after structural and systemic causes have been ruled out. ### Why Idiopathic is Most Common Despite extensive investigation, no identifiable cause is found in a substantial proportion of patients. Proposed mechanisms include: - Viral infection (HSV, VZV, influenza) causing subclinical RLN inflammation - Autoimmune mechanisms - Microvascular ischemia of the RLN - Spontaneous recovery occurs in 30–60% of idiopathic cases within 3–6 months ### Differential Causes of Unilateral VCP | Cause | Frequency | Clinical Clue | |-------|-----------|---------------| | **Idiopathic** | 30–50% | No identifiable cause after full workup | | Thyroid surgery/malignancy | 20–30% | History of thyroid intervention or known thyroid disease | | Lung cancer (RLN involvement) | 10–15% | Smoking history, chest imaging findings | | Aortic aneurysm | 5–10% | Hypertension, atherosclerosis; rare | | Intubation trauma | 5–10% | Recent ICU admission or difficult intubation | | Skull base lesion | 2–5% | Jugular foramen syndrome | **High-Yield:** Idiopathic unilateral VCP is common and often self-limiting. Always perform a full diagnostic workup (thyroid imaging, chest X-ray, CT neck/chest) to exclude structural causes before labeling as idiopathic. **Mnemonic: CHOPS** — Causes of Unilateral VCP: - **C**ancer (lung, thyroid, mediastinal) - **H**eart (aortic aneurysm, cardiac surgery) - **O**ther surgery (thyroid, cardiac, esophageal) - **P**ost-intubation - **S**pontaneous (idiopathic) **Clinical Pearl:** A paramedian position of the vocal cord suggests RLN injury (as opposed to a lateral or intermediate position, which suggests superior laryngeal nerve injury or central causes).
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