Neurodegeneration

Abstract

Neurodegeneration is any pathological condition in which the nervous system or nerve cell (i.e. neuron) loses its function, structure, or both. On a medical point of view however, the term neurodegeneration is used in a more restricted sense. Typically, it represents a large group of heterogeneous disorders in which affected neurons belong to specific subtypes, within specific anatomofunctional territories of the nervous system. Often, but not always neurodegenerative diseases arise for unknown reasons and progress in a relentless manner. Within the context of this definition diseases of the nervous system can be catalogued into three board categories: (i) pathologies which are restricted to the nervous system and which are primary neuronal diseases (i.e. neurodegenerative diseases per se); (ii) pathologies which are restricted to the nervous system but are not primary neuronal diseases, such as brain neoplasm or cerebral edema and hemorrhage; and, (iii) pathologies provoked by systemic causes which damage the nervous system, such cardiovascular arrest, carbon monoxide poison, or infections due to herpes simplex. Based on this simple categorization, hundreds of disorders of the nervous system including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis clearly fulfill the criteria of neurodegenerative disorder and are unanimously regarded as such.