Module 7: Brain Damage and Neuroplasticity

Brain Damage

Damage to a part of the brain

Causes of Brain Damage

Tumors, Strokes, Physical Injury, External Agents: Infections & Neurotoxins, Neurodevelopmental Disorders

Tumor

Any form of cellular growth that develops and spreads in an uncontrolled manner

Benign Tumor

Noncancerous, slow-growing, and localized, rarely spreading to other body parts

Malignant Tumor

Cancerous, grow rapidly, and can invade nearby tissue or metastasize through blood/lymph systems

-oma

Suffix for describing which tumor

Neuroma

A normally benign tumor that grown from a PNS nerve

Meningioma

A tumor that grows on one of the meninges of the brain—dura mater, arachnoid mater or pia mater

Infiltrating Tumors

A malignant tumor that enters and replaces the healthy tissue of an organ

Metastatic Tumors

A tumor that originates from another location on the body and starts in other organs due to the circulatory system

Strokes

A cardiovascular disorder that causes death of the surrounding brain tissue

Cerebral Hemorrhage

A stroke caused by a ruptured blood vessel, leading to tissue damage

Cerebral Ischemia

A stroke caused by a blockage in the blood vessels, depriving the brain section of nutrients

Concussions

A disturbance of consciousness following a blow to the head

Punch-Drunk Syndrome

A dementia and cerebral scarring observed in boxers and other individuals who experience repeated concussions

Encephalitis

Infections in the brain

-itis

Suffix for infection

Meningitis

Inflammation of the meninges usually caused by bacterial infection

Rabies

An extremely deadly but preventable viral infection with a special affinity for attacking the nervous system and the brain

Mumps

A viral infection that manifests normally with lumps on the throat area, but may transfer and attack the brain in some causes

Toxic Psychosis

Chronic insanity or psychiatric disturbance that is caused by exposure to toxic chemicals

Tardive Dyskinesia

A motor disorder that results from chronic use of certain antipsychotic drugs.

Tardive Dyskinesia Symptoms

Its symptoms include involuntary smacking, sucking movements of the lips, thrusting and rolling of the tongue, lateral jaw movements and puffing of the cheeks

Neurodevelopmental Disorders

Down’s Syndrome, Parkinson’s Disease, Alzheimer’s Disease, Huntington’s Disease, Multiple Sclerosis

Down’s Syndrome

A developmental disorder caused by an extra copy of chromosome 21; intellectual disability, characteristic physical features (flat face, upward eyes), and potential health complications like congenital heart defects

Parkinson’s Disease

A movement disorder that is associated with degeneration to the substantia nigra (loss of dopamine), leading tremors and rigidity

Substantia Nigra

Produces dopamine that is essential for smooth movement, and plays a major role in Parkinson's disease, where neuron death causes motor symptoms

Alzheimer’s Disease

A progressive illness characterized by cognitive and memory decline caused by plaques in the neural fibers, neuron loss, and loss of myelin sheaths.

Huntington’s Disease

Fatal, inherited neurodegenerative terminal disorder that causes progressive breakdown of nerve cells in the brain, impacting movement, cognition, and mental health

Multiple Sclerosis

A progressive disease where the immune system mistakenly attacks and destroys myelin sheaths and associated axons. Neurons develop hard scar tissue and lose the ability to conduct signals properly.

Effects of Brain Damage

Seizures, Agnosia, Aphasia, Apraxia

Seizures

A symptom that often involves tremors, rigidity and loss of both balance and consciousness

Epilepsy

Chronic disorder of seizures

Generalized Seizure

Involve the entire brain. Some begin as focal discharges that gradually spread through the entire brain.

Types of Generalized Seizures

Grand mal and Petit mal

Grand mal seizure

Symptoms are loss of consciousness, loss of equilibrium and violent tonic-clonic convulsion, tongue-biting and cyanosis (bluish discoloration)

Petit mal seizure

Characterized by disturbances in consciousness like cessation of ongoing behavior, a vacant look, and sometimes fluttering eyes

Partial/Focal Seizure

Does not involve the entire brain and is not usually accompanied by a total loss of consciousness or equilibrium.

Agnosia

The inability to consciously recognize sensory stimuli of a particular class that is not attributable to a sensory deficit or to verbal or intellectual impairment. Brain cannot recognize or interpret sensory information (objects, faces, sounds, smells) despite intact senses

Aphasia

A disturbance in the ability to use or comprehend language

Types of Aphasia

Broca’s Aphasia and Wernicke’s Aphasia

Broca’s Aphasia

Difficulty in speech production caused by damage to the inferior prefrontal cortex/inferior frontal gyrus

Wernicke’s Aphasia

Difficulty in language comprehension caused by damage to the posterior end of the superior temporal gyrus

Broca’s Aphasia Damage

Damage in inferior prefrontal cortex/inferior frontal gyrus

Wernicke’s Aphasia Damage

Damage in posterior end of the superior temporal gyrus

Apraxia

Neurological motor planning disorder where the brain cannot properly sequence movements, despite the person having the desire and physical ability to perform them caused by damage to the posterior parietal cortex

Apraxia Cause of Damage

Damage in posterior parietal cortex

Specialized Parts of the Brain with Certain Functions (Lateralization)

Optic Chiasm & Wernicke's and Broca’s Area

Optic Chiasm

Left eye goes to right size of brain and vice-versa

Wernicke’s and Broca’s Area

Only of the left hemisphere that comprehends and produces speech and language

Right Hemisphere of the Brain

Seems to have a stronger spatial ability, but not totally exclusive

Effect of a Damaged Corpus Callosum

Inability of left hemispheres and right hemispheres to communicate.

Brain Function with a Damaged Corpus Callosum

With a damaged corpus callosum, sometimes the left hemisphere tries to “correct: the right hemisphere, and vice-versa.

Nerve damage without severing the Schwann cells (ex: crushing)

Individual axons regenerate to their correct targets

Severed ends of the Schwann cell sheaths are slightly separated

Individual axons often regenerate up incorrect sheaths and reach incorrect targets

Severed ends of the Schwann cells are widely separated

Typically no functional regeneration

New Studies on Neuron Regeneration

Areas in the temporal lobe show consistent generation of new brain cells

Neuroplasticity

The ability of the brain to repurpose and change by re-organizing how neurons are wired; “Nerves that fire together, wire together.”

Apoptosis

Planned cell death of unused nervous pathways

Apoptosis Process

Regular neural connection → Pathway sees less use due to lack of practice (connection gets weaker) → Pathways shut down. Full apoptosis may occur

Creation of Neural Pathways

Regular neural connection → Pathway shuts down due to damage or apoptosis. → Signal travels through alternate pathways due to re-acquisition or rehabilitation.

Neural Healing Through Rehab

Healing or regenerated neural connections must reinforce their connections in order to regain lost function