What are typical neurodegenerative diseases without overt neuropathology? a. Creutzfeldt-Jakob disease b. Schizophrenia c. Essential tremor d. Torsion dystonia e. All but a

First, let's define the terms in the exercise. Neurodegenerative diseases are disorders characterized by the progressive loss of neurons, often resulting in cognitive decline or physical dysfunction. Overt neuropathology refers to the presence of visible or easily detectable brain abnormalities.

Now, let's analyze each option and determine which diseases are neurodegenerative and do not have overt neuropathology: a. Creutzfeldt-Jakob disease (CJD) is a rare and fatal neurodegenerative condition characterized by rapidly progressive dementia. It involves the accumulation of an abnormal protein in the brain called a prion, which leads to severe brain damage with overt neuropathology such as spongiform changes and neuronal cell death. b. Schizophrenia is a chronic psychiatric disorder that affects an individual's thoughts, perceptions, and behaviors. While the exact cause remains unknown, it is not considered a neurodegenerative disease. c. Essential tremor is one of the most common movement disorders, characteristically causing uncontrolled shaking in various parts of the body. It is considered a neurodegenerative disorder, and overt neuropathology is not typically observed in essential tremor. d. Torsion dystonia (also called primary dystonia) is another movement disorder that results from involuntary muscle contractions and abnormal twisting postures. The pathophysiology is not entirely understood, but it is not considered a classical neurodegenerative disease like Alzheimer's or Parkinson's.

Based on our analysis, the correct answer is: e. All but a That means essential tremor (c) and torsion dystonia (d) are considered neurodegenerative diseases without overt neuropathology, while Schizophrenia (b) is not classified as a neurodegenerative disease. Conversely, Creutzfeldt-Jakob (a) is a neurodegenerative disease but has overt neuropathology.