Pseudobulbar palsy is a medical condition characterized by the inability to control facial movements (such as chewing and speaking) and caused by a variety of neurological disorders. Patients experience difficulty chewing and swallowing, have increased reflexes and spasticity in tongue and the bulbar region, and demonstrate slurred speech (which is often the initial presentation of the disorder), sometimes also demonstrating uncontrolled emotional outbursts.The condition is usually caused by the bilateral damage to corticobulbar pathways, which are upper motor neuron pathways that course from the cerebral cortex to nuclei of cranial nerves in the brain stem. Signs and symptoms
Signs and symptoms of pseudobulbar palsy include:

Slow and indistinct speech
Dysphagia (difficulty in swallowing)
Small, stiff and spastic tongue
Brisk jaw jerk
Dysarthria
Labile affect
Gag reflex may be normal, exaggerated or absent
Examination may reveal upper motor neuron lesion of the limbs

Causes
Pseudobulbar palsy is the result of damage of motor fibers traveling from the cerebral cortex to the lower brain stem. This damage might arise in the course of a variety of neurological conditions that involve demyelination and bilateral corticobulbar lesions.
The third symptom would be recovery, followed by a Parkinson-like syndrome. If patients of Stern followed this course of disease, he diagnosed them with encephalitis lethargica. Stern suspected encephalitis lethargica to be close to poliomyelitis, without evidence. Nevertheless, he experimented with the convalescent serum of survivors of the first acute syndrome. He vaccinated patients with early-stage symptoms, telling them that it might be successful. Stern is author of the definitive 1920s book, Die Epidemische Encephalitis.In 2010, in a substantial Oxford University Press compendium reviewing the historic and contemporary views on EL, its editor, Joel Vilensky, of the Indiana University School of Medicine, quotes another researcher, writing in 1930, who states, "we must confess that etiology is still obscure, the causative agent still unknown, the pathological riddle still unsolved…", and goes on to offer the following conclusion, as of that publication date:

Does the present volume solve the "riddle" of EL, which… has been referred to as the greatest medical mystery of the 20th century? Unfortunately, no: but inroads are certainly made here pertaining to diagnosis, pathology, and even treatment." Subsequent to publication of this compendium, an enterovirus was discovered in encephalitis lethargica cases from the epidemic. In 2012, Oliver Sacks, the author of the book Awakenings, about institutionalized survivors, acknowledged this virus as the probable cause of the disease. Other sources have suggested Streptococcus pneumoniae as a cause. Diagnosis
There have been several proposed diagnostic criteria for encephalitis lethargica.