Congenital
Congenital conditions that are implicated in VFP include neurological disorders like hydrocephalus and Arnold-Chiari malformation, dysmorphic neurological disorders such as Moebius syndrome or Goldenhar Syndrome, anatomical abnormalities such as a tracheoesophageal fistula, vascular anomalies (e.g. vascular ring) affecting the vocal mechanism, syndromes affecting brainstem function or atrophic diseases such as Charcot-Marie-Tooth.In the absence of imaging, either invasive (e.g. laryngoscopy) or non-invasive (e.g. computed tomography scan), congenital VFP can be detected in infants through the presence of stridor (i.e. a high-pitched wheezing resulting from a blockage in the larynx or trachea), difficulties feeding, an abnormal sounding cry or excessive hoarseness.Recovery from congenital VFP varies and is reliant on the severity of the condition. Some cases of VFP recover spontaneously, often within the first year. If the paresis is persistent, surgical options such as vocal fold injections or tracheotomy can be taken into consideration. Infection
Many viral infections have been reported as a cause for VF paresis, including herpes simplex virus, Epstein-Barr virus, Varicella-Zoster, cytomegalovirus, HIV, West Nile virus, and upper respiratory infection. Bacterial infections have also been reported to cause VF paresis, such as syphilis and Lyme disease. Tumors
When abnormal cells group together in the body, they are said to form a tumor. Tumors can be either malignant (cancerous) or benign (non-cancerous). Tumors may lead to paralysis of the vocal folds when they affect the recurrent laryngeal nerves (RLNs) either directly or indirectly:

RLN paralysis can be caused by tumors of the thyroid, lung, esophagus, and mediastinum.
Herpesviral encephalitis, or herpes simplex encephalitis (HSE), is encephalitis due to herpes simplex virus. It is estimated to affect at least 1 in 500,000 individuals per year, and some studies suggest an incidence rate of 5.9 cases per 100,000 live births.About 90% of cases of herpes encephalitis are caused by herpes simplex virus-1 (HSV-1), the same virus that causes cold sores. According to a 2006 estimate, 57% of American adults were infected with HSV-1, which is spread through droplets, casual contact and sometimes sexual contact, though most infected people never have cold sores. The rest of cases are due to HSV-2, which is typically spread through sexual contact and is the cause of genital herpes. Two-thirds of HSE cases occur in individuals already seropositive for HSV-1, few of whom (only 10%) have history of recurrent orofacial herpes, while about one third of cases results from an initial infection by HSV-1, predominantly occurring in individuals under the age of 18. Approximately half of individuals who develop HSE are over 50 years of age. Signs and symptoms
Most individuals with HSE show a decrease in their level of consciousness and an altered mental state presenting as confusion, and changes in personality. Increased numbers of white blood cells can be found in patients cerebrospinal fluid, without the presence of pathogenic bacteria and fungi. Patients typically have a fever and may have seizures.