mar 26

Class Overview

  • Lecture recaps from guest speakers discussed.

  • Importance of individual differences in treatment and outcomes presented.

Stroke Discussion

Types of Stroke

  1. Hemorrhagic Stroke    - Understanding individual differences in recovery.    - Incidence rates vary by race:      - Hemorrhagic strokes are more common in males than females.      - Incidence in Asian individuals is about twice that in Black and White individuals in the U.S.      - Hemorrhage occurs about 10 years earlier in Black and Hispanic persons in the U.S. than in White individuals.    - Causes for differences in incidence rates not fully understood.      

  2. Ischemic Stroke    - Defined as a blockage of a blood vessel, in contrast to hemorrhage, which is a breakage of a blood vessel.    - Effects of blockage vary based on the blood vessel's width.      - Microstrokes affect very small arterioles causing tiny infarcts.    - Significant strokes typically tend to be from profound blockages.    - Importance of restoring blood flow quickly to prevent cell death due to lack of oxygen.      - After an ischemic stroke, critical time frame is 2-3 hours before damage can become permanent.    

Types of Cerebral Ischemia

  • Three types of cerebral ischemia/dysfunction:   1. Thrombosis      - A thrombus: a plug that can consist of blood clots, fat, or air bubbles causing blockage in a blood vessel.   2. Embolism      - An embolus is a thrombus that has traveled through the bloodstream to lodge in a narrower vessel, causing blockage.   3. Arteriosclerosis      - A slow buildup of a coating in a blood vessel over years leading to narrowing, which can obstruct blood flow during other blockages.

Risk Factors for Stroke

  • Major risk factor: Smoking   - Risk decreases significantly when an individual quits smoking, returning close to baseline within 1-2 years.

  • Other risk factors include:   - Higher BMI   - Diabetes   - Hypertension

Differences between Hemorrhagic and Ischemic Stroke

  • Hemorrhagic Stroke: immediate cell death due to blood leakage.

  • Ischemic Stroke: Takes longer to develop; immediate treatment increases the chances of survival.    - Often linked to glutamatergic activity; excess glutamate can lead to excitotoxicity and cell death.

Brain Infections and Neurotoxins

Types of Brain Infections

  1. Bacterial Infections    - Can lead to cerebral abscesses, which are pockets of pus formed by white blood cells around an infection site.    - Meningitis is more common than infections of the brain tissue.    - Meningitis outbreaks can be severe and are seen regularly across populations (e.g., UK outbreak).

  2. Viral Infections    - Rabies virus specifically targets neural tissue and can lead to severe brain infection.    - COVID-19 virus can also affect the brain, leading to potential long-term neurodegenerative changes.    - Symptoms of rabies infection include fever followed by severe pain with swallowing, hydro- phobia, and then rapidly progressing to severe neurological deficits.

  3. Parasitic Infections
       - Example: Neurocysticercosis caused by tapeworms in the brain from ingesting undercooked pork.

Neurotoxins

  1. Heavy Metals:    - Mercury and Lead: Prolonged exposure leads to toxic psychosis.    - Mercury can be inhaled from amalgam fillings; lead exposure often occurs in older homes.

  2. Toxicology Principle
       - "The dose makes the poison" (Paracelsus). Toxicity is dose-dependent; substances can be harmful or beneficial based on quantity.

Epilepsy Overview

Definition and Seizures

  • Epilepsy: Condition characterized by recurrent, unprovoked seizures.

  • Seizures: Defined by excessive and disorderly nerve discharge, affecting consciousness, sensation, and behavior.    - Seizures may occur without motor symptoms, such as an absence seizure.

Seizure Classification

  • Types of Seizures: Focal (localized) and generalized (widespread across the brain).    - Ictal: during a seizure; Interictal: between seizures; Postictal: following a seizure (state of confusion or fatigue).

Diagnosis of Epilepsy

  • Primarily diagnosed through EEG; video EEG systems provide additional data by capturing the seizures as they happen.

  • Aura: A sensory experience before a seizure that provides clues about the seizure focus location in the brain. This can help in diagnosis and management.

Practical Considerations

Treatment and Emergency Response

  • Importance of immediate treatment for strokes to minimize damage.

  • Seizure first aid: Understanding what to do during a seizure is critical, including recognizing medical identification and determining when to call for emergency help (e.g., seizure lasting over 2-3 minutes).

  • Discussing misconceptions about seizures and the importance of understanding seizures in society to reduce stigma.