Acquired Brain Injury and Neuropsychological Disorders: Blood Supply, Stroke, and Neuropsychological Consequences

Acquired Brain Injury and Neuropsychological Disorders

Introduction

Acquired brain injury (ABI) and neuropsychological disorders are central topics in biological psychology and neuropsychology. These conditions impact cognition, emotion, and behavior by disrupting normal brain function. Understanding their causes, mechanisms, and consequences is essential for psychology students.

Main Divisions of Brain Disorders

1. Acquired Brain Injury (ABI)

• Definition: ABI refers to focal or acute events that cause sudden or localized damage to the brain, not due to hereditary, congenital, or degenerative causes.

• Common Examples:

  • Stroke (ischemic or hemorrhagic)

  • Traumatic brain injury (TBI): accidents, falls, violence

  • Anoxia/hypoxia: lack of oxygen

  • Brain tumor: space-occupying lesions

  • Infections: encephalitis, abscesses

  • Substance abuse/toxic damage: alcohol, solvents, drugs, heavy metals

• General Impact: Sudden, often focal deficits in cognition, motor, or emotional functions depending on location.

2. Neurodegenerative and Neurological Diseases

• Definition: Progressive conditions affecting the brain over time.

• Examples:

  • Neurodegenerative: Alzheimer’s, Parkinson’s, Huntington’s, Multiple Sclerosis, Frontotemporal dementia, Lewy body dementia, ALS

  • Neurological (non-degenerative): Epilepsy, Migraine, Sleep disorders

• General Impact: Gradual, chronic decline in neural tissue, leading to widespread or selective cognitive decline.

Acquired Brain Damage: Key Concepts

Why Study ABI in Neuropsychology?

• Lesion studies: Reveal how specific brain regions support cognitive, emotional, and behavioral functions.

• Localization: Patterns of deficits help localize brain function and guide rehabilitation.

• Neuroplasticity: The brain can adapt, but understanding lost functions is crucial for recovery planning.

Types of Acquired Brain Injury

• Non-Traumatic Brain Injury:

  • Caused by internal factors (e.g., stroke, anoxia, tumor, infection, toxic exposure).

  • Examples: Ischemic stroke (blocked blood flow), Hemorrhagic stroke (bleeding), Anoxia/hypoxia (lack of oxygen), Brain tumor, Infections, Toxic damage.

• Traumatic Brain Injury (TBI):

  • Caused by external force (e.g., blows to the head, accidents, assaults).

  • Can be closed (no penetration) or open (penetrating injury).

Classification Table: Types of Acquired Brain Injury

Type	Description	Typical Cause	Key Consequence
Ischemic Stroke	Blood flow to part of the brain is blocked.	Artery obstruction (thrombosis or embolism)	Localized tissue death (infarct) due to lack of oxygen
Hemorrhagic Stroke	A brain artery ruptures, causing bleeding inside or around the brain	Hypertension, aneurysm rupture, trauma	Pressure on nearby tissue and reduced blood flow beyond hemorrhage
Transient Ischemic Attack (TIA)	Brief, reversible blockage of blood flow (mini-stroke)	Temporary vessel occlusion	Symptoms resolve within 24 hours, but it warns of possible future stroke

Blood Supply to the Brain

Main Arteries and the Circle of Willis

• Four main arteries:

  • Two internal carotid arteries (front of neck)

  • Two vertebral arteries (back of neck)

• These arteries ascend each side of the neck and enter the skull.

• Circle of Willis: Circular network at the base of the brain formed by these arteries, ensuring constant blood flow even if one artery is blocked.

Branches Supplying the Brainstem and Cerebellum

Artery	Main Area Supplied
Posterior Inferior Cerebellar Artery (PICA)	Posterior/inferior cerebellum, medulla oblongata
Anterior Inferior Cerebellar Artery (AICA)	Anterior/inferior cerebellum, part of pons
Superior Cerebellar Artery (SCA)	Superior cerebellum, upper pons
Basilar Artery Branches	Pons, central brainstem structures
Vertebral Artery Branches	Medulla, spinal cord

Branches Supplying the Forebrain

Artery	Main Areas Supplied	Typical Symptoms if Blocked
Anterior Cerebral Artery (ACA)	Medial frontal and parietal lobes	Contralateral weakness (especially leg), personality or executive changes
Middle Cerebral Artery (MCA)	Lateral frontal, temporal, parietal lobes	Most common stroke site. Causes aphasia (left), hemineglect (right), visual field loss, focal weakness
Posterior Cerebral Artery (PCA)	Occipital lobe, inferior temporal lobe	Visual field loss, hemianopia, visual agnosia, memory disturbances

Stroke: Cerebrovascular Disorders

Definition and Medical Emergency

• Stroke (CVA): Sudden loss of blood flow to the brain or bleeding inside the head.

• Neurons begin to die within minutes without oxygen and glucose.

• Time is critical: Early treatment can reduce effects; clot-busting drugs are effective within 4.5 hours of symptom onset.

• Recognizing stroke signs and calling emergency services immediately can save brain tissue and function.

Types of Stroke

1. Ischemic Stroke:

   • Caused by blockage (blood clot or plaque) in a blood vessel.

   • Cells die within minutes due to lack of oxygen and nutrients.

   • Most common type of stroke.

   • Subtypes: Thrombotic (clot forms in brain vessel), Embolic (clot travels from elsewhere).

2. Hemorrhagic Stroke:

   • Caused by rupture of a cerebral blood vessel, leading to bleeding inside or around the brain.

   • Increases intracranial pressure, compresses brain tissue, disrupts normal blood flow.

   • Subtypes: Intracerebral hemorrhage (within brain tissue), Subarachnoid hemorrhage (between arachnoid and pia mater).

3. Transient Ischemic Attack (TIA):

   • Short-term blockage of blood flow, symptoms resolve within 24 hours.

   • Warning sign for future stroke.

Stroke Symptoms and Effects

• Paralysis, speech problems, loss of feeling, memory and reasoning problems, coma, death.

• Severity depends on type, location, hemisphere, size, and time to treatment.

Treatments

• Thrombolytic therapy: Injection of tissue plasminogen activator (tPA) to dissolve clots.

• Diagnosis via CT scan to confirm stroke type.

• tPA is only used for ischemic strokes, not hemorrhagic strokes.

Computed Tomography (CT) Scan

What is a CT Scan?

• Uses X-rays and computer processing to create detailed cross-sectional images of the brain.

• Quick, first-line tool for diagnosing acute brain injury (especially stroke and bleeding).

• Bone appears white, healthy brain tissue gray, damaged/ischemic areas dark, hemorrhage bright white.

Why Important in Neuropsychology?

• Detects brain injuries, strokes, tumors, hemorrhages.

• Widely available and fast, making it the first imaging tool in emergencies.

• Helps localize brain damage and guide treatment.

Summary Table: Main Types of Stroke

Type	Description	Typical Cause	Key Consequence
Ischemic Stroke	Blood flow to part of the brain is blocked.	Artery obstruction (thrombosis or embolism)	Localized tissue death (infarct) due to lack of oxygen
Hemorrhagic Stroke	A brain artery ruptures, causing bleeding inside or around the brain	Hypertension, aneurysm rupture, trauma	Pressure on nearby tissue and reduced blood flow beyond hemorrhage
Transient Ischemic Attack (TIA)	Brief, reversible blockage of blood flow (mini-stroke)	Temporary vessel occlusion	Symptoms resolve within 24 hours, but it warns of possible future stroke

Key Terms and Definitions

• Ischemia: Insufficient blood supply to tissue, leading to cell death.

• Hemorrhage: Bleeding from a ruptured blood vessel.

• Thrombosis: Formation of a blood clot within a vessel.

• Embolism: Obstruction of a vessel by a clot traveling from elsewhere.

• Aneurysm: Weakened area in a blood vessel wall that can rupture.

• Neuropsychological syndrome: Pattern of cognitive, emotional, or behavioral deficits resulting from brain injury.

Formulas and Equations

• Cerebral Perfusion Pressure (CPP): $CPP = MAP - ICP$ Where MAP is mean arterial pressure and ICP is intracranial pressure. Application: Used to assess blood flow to the brain, especially in cases of stroke or trauma.

Example

Case Study: A patient presents with sudden right-sided weakness and speech difficulties. CT scan reveals blockage in the left middle cerebral artery (MCA). Diagnosis: Ischemic stroke. Treatment: tPA administered within 3 hours of symptom onset.

Additional info:

• Neuropsychological deficits after stroke depend on the affected vascular territory and hemisphere.

• Early intervention is critical for minimizing long-term cognitive and behavioral consequences.