CAUSES OF VOCAL CORD PALSY
Surgical anatomy: The vagus nerve arises from the lateral surface of the medulla.
It gives rise to two main branches in the larynx namely:
- Superior laryngeal nerve– It further gives two branches namely:
- Internal laryngeal nerve (sensory)- It supplies sensation to the mucosa from the epiglottis to just above the level of the vocal folds.
- External laryngeal nerve- It gives motor supply to Inferior constrictor muscle and cricothyroid muscle
- Recurrent laryngeal nerve– It gives motor fibres to all laryngeal muscles except cricothyroid (motor) and supplies sensation to the rest of the larynx below the level of the vocal folds.
Motor Paralysis:
a) Cortical paralysis: These lesions are rare as the larynx has bilateral motor innervation. May be seen in cases of:
- Congenital cerebral palsy.
- Encephalitis.
- Kernicterus.
- Diffuse cerebral arteriosclerosis.
b) Corticobulbar paralysis: These are extremely rare due to paralysis of the corticobulbar tracts.
c) Bulbar paralysis: This is a flaccid type of paralysis due to destruction of all or part of nucleus ambiguous in the medulla.
- Vascular insufficiencies such as vertebral or Postero-inferior cerebellar arteries.
- Multiple sclerosis.
- Intramedullary tumours like gliomas.
d) Peripheral causes: They are responsible for 90 percent of the vocal cord paralysis. The lesion involves the fibres of the laryngeal nerves from the surface of the medulla up-to the larynx. Usually combines with multiple cranial nerves.
Peripheral causes of vocal cord palsy:
Inflammatory:
- Neuritis.
- Meningitis.
- Diphtheria.
- Herpes zoster.
- Tuberculosis.
- Jugular bulb thrombophlebitis.
Neoplastic:
- Meningioma.
- Glomus jugulare.
- Thyroid Malignancy.
- Thymus tumours.
- Malignant lymphoma.
Trauma:
- Blunt neck trauma.
- Bullet wounds.
- Fracture clavicle.
- Surgical trauma.
- Thyroidectomy.
- Tracheostomy.
- Radical neck dissection.
- Pneumonectomy.
Neuropathy Secondary to:
- Diabetes mellitus.
- Rheumatoid arthritis.
- Polyarteritis nodosa.
- Lead poisoning.
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