Radiation as a treatment for malignant head and neck tumors can reduce the number of blood vessels in the treatment area and lead to scarring. In some cases, this can paralyze the vagus nerve, of which the RLNs are branches. Tumors of the vagus nerve, called vagal neurilemmomas, can also paralyze the vocal folds. Trauma
VF paresis can result from trauma to one of more laryngeal nerves during intubation, surgery (e.g. thyroidectomy, spine surgery, carotid endartectomy, vagal nerve stimulator implantation), injection of botulinum neurotoxin, or penetrating neck trauma. Thyroid disease
Causes of VF paresis also include diseases of the thyroid gland, such as hypothyroidism, goiter, and thyroiditis. Systemic neurologic diseases
Several neurological diseases can cause VF paresis including:

Myasthenia Gravis (MG), a rare neuromuscular autoimmune disease. MGs dominant characteristic is muscles weakness including facial, jaw, pharyngeal and laryngeal muscles. Charcot-Marie-Tooth (CMT), a neurological heredity disease that affects both motor and sensory functions. CMT affects the nerve cells and interrupts the transmission of nerve impulses as it concerns the axons and the myelination of the nerve cells. Multiple Sclerosis (MS), which is an autoimmune disease that damages the myelin sheet surrounding the axons of the cranial nerves and the spinal nerves. There are several types of MS depending on the course of the disease. Spinocerebellar Degeneration, a term that refers to a rare yet diverse chronic disease that affects the brain and the spinal cord.
Phenylephrine/ketorolac, sold under the brand name Omidria, is a combination drug used during cataract surgery or intraocular lens replacement to prevent intraoperative miosis and to reduce postoperative pain. It contains phenylephrine and ketorolac.Phenylephrine/ketorolac was approved for medical use in the United States in May 2014, and in the European Union in July 2015. References
External links
"Ketorolac mixture with phenylephrine". Drug Information Portal. U.S. National Library of Medicine.