Encephalitis lethargica and Phrenitis

Encephalitis lethargica noun - An encephalitis that was epidemic between 1915 and 1926; symptoms include paralysis of the extrinsic eye muscle and extreme muscular weakness.

Phrenitis and encephalitis lethargica are semantically related. In some cases you can use "Phrenitis" instead a noun phrase "Encephalitis lethargica".

Phrenitis noun - Inflammation of the brain usually caused by a virus; symptoms include headache and neck pain and drowsiness and nausea and fever (`phrenitis' is no longer in scientific use).

Encephalitis lethargica and phrenitis are semantically related. Sometimes you can replace phrase "Encephalitis lethargica" with "Phrenitis", this terms are similar.