60. Basic etiology and pathogenesis of the diseases of the nervous system. – cerebral ischemia, cerebral edema, intracranial hypertension, neurodegenerative diseases.

BASIC ETIOLOGY AND PATHOGENESIS OF THE DISEASES OF THE NERVOUS SYSTEM

• The nervous system is divided into two parts:

1. Central nervous system = brain and spinal cord
2. Peripheral nervous system = connects CNS to the rest of the body

Etiology of disease of the nervous system

1. Vascular disorders e.g. stroke, aneurysm, vascular dementia
2. Trauma to the head and spinal cord
3. Congenital problems

• Chiari malformation type 1
• Congenital anomaly of the cerebellum
• The tissue in the lower part of the cerebellum protrudes into the spinal canal, which can obstruct CSF from flowing into the spinal canal
• This causes pressure on the surrounding tissues
• Can result in loss of coordination, difficulting swallowing/speaking
• Anencephaly
• Birth defect in which the brain and bones of the skull don’t form completely while the baby is in the womb
• As a result, the baby’s brain, particularly the cerebellum, develops minimally
• It is a neural tube defect → neural tube is a narrow shaft that normally closes during fetal development and forms the brain and spinal cord
• Spina Bifida
• A neural tube defect where the spinal column of the fetus doesn’t close completely during the first month of pregnancy resulting in the meninges or spinal cord or both protruding through the opening
• This can result in damage to the nerves and spinal cord

4. Exposure to toxins - carbon monoxide, arsenic, lead
5. Degenerative loss of function - e.g. Parkinson’s disease, multiple sclerosis, Alzheimer’s disease, Huntington’s disease
6. Infections

• May occur in the brain (encephalitis) or membrane surrounding the brain and spinal cord (meningitis)

7. Overuse of or withdrawal from prescription and nonprescription medication, illegal drugs, or alcohol
8. Brain tumour
9. Organ system failure - e.g. respiratory failure, heart failure, liver failure

Pathogenesis of diseases of the nervous system

Vascular disorders - stroke

• Stroke is an acute focal neurologic deficit from a vascular disorder that injures brain tissue
• There are two main types of strokes; ischemic stroke and hemorrhagic stroke
• Ischemic strokes are caused by local interruption of blood flow caused by thrombosis or emboli
• Hemorrhagic strokes are caused by rupture of a blood vessel and bleeding into the brain

Spinal cord injury

• Spinal cord injury (SCI) represents damage to the neural elements of the spinal cord
• The most common cause is motor vehicle accidents, falls, violence and sports injuries
• Injuries to the vertebral column include fractures, disolocations, and subluxations (partial dislocation)
• Primary neurologic injury occurs at the time of mechanical injury and is irreversible