Pathogenesis: uncertain. The role of influenza (since the epidemic occurred in association with the great pandemic) has been excluded. The current hypothesis is a postinfectious autoimmune disorder, possibly triggered by Streptococcus pyogenes.
Clinical features of the infection
(1) acute febrile infection
(2) headache
(3) malaise
(4) pharyngitis
Clinical features of encephalitis lethargica:
(1) sleep disorder
(1a) somnolence
(1b) sleep inversion
(1c) insomnia
(1d) vivid nightmares
(1e) sleep walking
(2) lethargy
(3) movement disorder
(3a) Parkinsonism
(3b) dyskinesias
(3c) chorea
(3d) myoclonus
(4) psychiatric disturbances
(4a) mutism
(4b) catatonia
(4c) anxiety
(4d) depression
(4e) obsessive-compulsive neurosis
(4f) apathy
(4g) mutism
(4h) paranoia
(5) ocular disorder
(5a) oculogyric crises
(5b) ophthalmoplegia
(5c) ptosis
(6) central cardiorespiratory problems
(6a) hiccups
(6b) respiratory depression requiring ventilation (variable)
Laboratory and pathologic findings in encephalitis lethargica:
(1) lesions in the midbrain and basal ganglia
(2) presence of oligoclonal bands in the CSF
(3) presence of serum autoantibodies to antigens in the basal ganglia
