Alzheimer Disease

Alzheimer Disease is a progressive neurodegenerative disease that causes death of nerve cells in the brain. The symptoms include loss of memory and reasoning as well as personality and behavioural changes. A 2001 study found that 364,000 Canadians over 65 have Alzheimer Disease and related dementias. By 2031, over ¾ of a million Canadians are expected to suffer from this debilitating disease. Although no exact cause has been identified, researchers have determined a number of risk factors. These include, being over the age of 65, and having a family history of Alzheimer's disease.(6)(12)

Two forms of Alzheimer disease have been identified- Sporadic Alzheimer Disease and Familial Autosomal Dominant Alzheimer Disease (FAD). The sporadic form is generally found in individuals over the age of 65, and accounts for 90-95% of all cases. Genetic mutations that cause excessive accumulation of amyloid protein are associated with this form. The familial form is caused by a gene mutation that is passed on from parent to offspring. If the child carries the gene, they have a 50% chance of inheriting Alzheimer disease.(6)(12)

There are a number of treatments both currently available, as well as under review for use in Canada. These include, cholinesterase inhibitors, precursor loaders, NMDA (N-methyl D-aspartate) receptor antagonists, and Vitamin E and other anti- oxidants. Cholinesterase inhibitors inhibit the activity of the enzyme that breaks down acetylcholine, so that more of this chemical is available for use in the brain. The result is improved brain function in non-cognitive areas of the brain. Precursor loaders sold under the band names choline and lecithin are similar to cholinesterase inhibitors; however, they increase the chemicals needed to produce more acetylcholine.. NMDA receptor antagonists are currently being reviewed for use in Canada, and work by blocking glutamate in the brain of patients in the later stages of the disease.(6)(12)

These treatment options do not stop the progression of the death of nerve cells that occurs with this disease. One method that researchers are currently studying that offers hope for individual's afflicted with this disease is the regeneration of nerve cells through neurogenesis.

Huntington's Disease

Huntington's is an incurable genetic neurodegenerative disorder that affects 1 out of every 10,000 Canadians. The symptoms of this disease include uncontrolled movements, impaired intellectual processing, and emotional problems. The basal ganglia, cortex and striatum are the specific areas in the brain that are affected. The disease usually occurs during middle age. However, there is also an early-onset form, which develops in individuals before the age of 20, and is usually inherited from their fathers. The genetic defect that is responsible for Huntington's has been located on chromosome 4. Approximately 50% of children that have a parent with Huntington's will develop the disease.(3)

There is no treatment currently available that can halt the devastating effects of Huntington's disease. However, there are medications that can be taken to help treat emotional and movement problems. Antipsychotic drugs can be used to help control symptoms including hallucinations and delusions. These medications have the unwanted effect of causing further stiffness in patients suffering from muscle contractions called dystonia. For depressive symptoms, selective seretonin reuptake inhibitors can be prescribed. Tranquilizers are often used to control anxiety, and mood stabilizers can be prescribed to control mood swings.(3)

Research is currently being done in many different areas in an effort to find a cure for the disease. One area of research includes fetal tissue and stem cell studies that attempt to restore neurons in the brain. Imaging techniques such as magnetic resonance imaging (MRI) have also been used to measure increases or decreases in brain chemicals thought to play a role in the disease, so that researchers can gain a better understanding of how Huntington's disease leads to neuron death.(3)

Parkinson's Disease

Parkinson's disease is a chronic and progressive neurodegenerative disease. It is the most common form of Parksinsonian syndromes, a group of disorders that are characterized by tremors and stiffness (rigidity), slowness of movement (bradykinesia) and difficulty keeping balance (postural instability). Parkinson's disease occurs when the neurons that are located in the brain stem's substantia nigra are destroyed. These neurons work by connecting with other neurons in the corpus striatum, which then send messages to the areas in the cortex which control motor functioning. Parkinson's patients have a decreased number of neurons in the substantia nigra, which causes a decrease in the amount of dopamine in the brain. This results in a decrease in the number of signals that are sent to the corpus striatum, which interferes with the normal functioning of the nervous system. (1)

Approximately 100,000 people in Canada are affected with Parkinson's. Current approaches for the treatment of Parkinson's disease include treating the symptoms of the disease with a combination of L-DOPA and carbidopa, which will increase the synthesis and release of dopamine. These medications are effective in the early stages at alleviating symptoms of tremor and stiffness and slowness of movement. A drawback of this treatment is side effects such as nausea, vomiting and hypertension. As the disease progresses, less dopamine neurons are available to synthesize dopamine and the effectiveness of the treatment decreases. Other approaches that can be used are, deep brain stimulation and fetal tissue transplantation. Deep brain stimulation uses stimulating electrodes to control tremors. Fetal tissue transplantation involves transplanting human embryonic brain tissue into patients. The hope with this treatment is that the neural stem cells will develop and produce dopamine in the patient.(1)