142 Neurodegenerative Diseases
written by Justin Field, Dalhousie University
Learning Objectives
By the end of this section, you will be able to:
- Define neurodegenerative disease
- Describe some of the techniques used to diagnose neurodegenerative diseases
- Define Alzheimer’s disease and describe the clinical features
- Compare and contrast the brains of those with Alzheimer’s disease to those without
What is a Neurodegenerative Disease?
Neurodegenerative diseases vary in their causes, pathology, clinical symptoms, and treatment, which leads us to ask: What is considered a neurodegenerative disease? They are commonly characterized by gradual neuronal loss that can result in cognitive and motor impairments (Gao & Hong, 2008). Neurodegenerative diseases most often affect older individuals, and with an aging population these diseases will likely become more common (Brookmeyer et al., 2007). This section will describe the causes, clinical symptoms, and treatments of common neurodegenerative diseases including Alzheimer’s, Parkinson’s, Huntington’s, multiple sclerosis (MS), and amyotrophic lateral sclerosis (ALS). But what specific evidence do we have that these neurodegenerative diseases even exist in the first place?
Evidence for Neurodegenerative Diseases
Early Evidence
Before the age of neuroimaging, physicians and researchers studied neurodegenerative diseases with a more ‘manual’ approach: post-mortem brain examinations. The basic idea was that if an individual showed pathological behaviour while they were living, observed abnormalities in their brain structure after they died could reveal Constantin Tretiakoff (PY.24) was a young researcher working in France who made an important contribution to the understanding of Parkinson’s disease using this strategy. Tretiakoff compared the brains of individuals with Parkinson’s to healthy age-matched individuals, focussing on an area called the substantia nigra. Tretiakoff found that those with Parkinson’s showed a loss of neurons in this area which he suspected to contribute to the observable symptoms of the disease (Parent & Parent, 2010). This finding paved the way for further research in Parkinson’s by drawing a connection between observable symptoms and a specific region of the brain.
Modern Techniques
While post-mortem examinations are valuable in in studying neurodegenerative diseases, neuroimaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) are less invasive alternatives that can be performed on living people. Like post-mortem examinations, neuroimaging allows us to examine specific brain areas, but also allows for measurement of behaviour from living and conscious participants. A major benefit of neuroimaging techniques is that they can be used to monitor brain physiology throughout the course of a neurodegenerative disease to better understand how it progresses. For example, researchers used MRI to scan the brains of patients with mu