Neurodegenerative disorders, which are chronic and progressive, are characterized by selective and symmetric loss of neurons in motor, sensory, or cognitive systems.
[nejm.org]
Neurology A chronic progressive neuropathy characterized by selective and generally symmetrical loss of neurons in motor, sensory, or cognitive systems Types by area Cerebral
[medical-dictionary.thefreedictionary.com]
Neurodegenerative disorders are illnesses characterized by a loss of nervous system functioning that are usually caused by neuronal death.
[courses.lumenlearning.com]