Chapter 10- Brain Damage and Neuroplasticity

Transgenic

Referring to animals into which genes of another species have been introduced.

Encephalitis

The inflammation from brain infection by microorganism invasion of the brain.

Oligodendroglia

These cells myelinate CNS axons. They do not clear debris or stimulate or guide regeneration. They release factors that actively block regeneration.

Meningiomas

These grow between the meninges that cover the CNS and constitute 20% of tumors found in the human brain. All of these are encapsulated tumors.

Collateral sprouts

These grow out from healthy axon terminal branches or the nodes of Ranvier on neurons adjacent to degenerating axons. They synapse at the sites vacated by the degenerating axon.

Programmed cell death

This describes the apoptotic programs of self-destruction caused by tumors, cerebrovascular disorders, closed-head injuries, infections, toxins, and genetic factors.

Lewy bodies

Clumps of proteins in surviving dopaminergic neurons of the substantia nigra.

Gliomas

Common and rapidly growing infiltrating brain tumors that develop from glial cells.

Closed head injuries

Damage to the brain from exterior trauma that does not penetrate the skull.

Endogenous

Produced by the patient's body. Some antibodies that have this quality can attack particular components of the nervous system.

Epileptogenesis

The development of epilepsy.

MPTP

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. An identified agent tentatively charged with inducing Parkinson's.

Contrecoup injuries

A blow to one side of the head that causes a contusion on the opposite side of the brain.

L-dopa

A chemical from which the body synthesizes dopamine that can be injected to alleviate Parkinson's symptoms. Only a temporary solution that the patient can build a tolerance to.

Contusion

A closed head injury that involves damage to the cerebral circulatory system. Causes internal hemorrhaging that results in a hematoma. Occurs when the brain slams against the inside of the skull.

Deep brain stimulation

A controversial treatment of Parkinson's where low-intensity electrical stimulation is continually applied to an area of the brain through a stereotaxically implanted electrode. Chronic bilateral eletrical stimulation of a nucleus just beneath the thalamus connected to the basal ganglia aka the sub-thalamic nucleus.

Epilepsy

A disorder whose primary symptom is repeated seizures triggered consistently by a chronic brain dysfunction. Diagnosis relies heavily on EEG evidence where bursts of high amplitude spikes occur alongside seizures.

Cerebral ischemia

A disruption of the blood supply to an area of the brain. Caused by thrombosis, embolism, and arteriosclerosis. Two critical properties: 1. Long development time. Usually little to no evidence of brain damage immediately after an episode. 2. Does not occur equally in all parts of the brain. Neurons in certain areas of the hippocampus are especially susceptible.

Concussion

A disturbance of consciousness following a blow to the head that causes no evidence of contusions or structural damage to the brain.

Tonic-clonic seizure

A generalized seizure whose primary symptoms are are loss of equilibrium, and a violent clonic-tonic convulsion (i.e., tongue biting, urinary incontinence, and cyanosis (turning blue from excessive oxygen use during convulsions). Can be accompanied by a brain damaging hypoxia.

Huntington's disease

A hereditary disorder with a simple genetic basis associated with severe dementia. Caused by a single mutated dominant gene called huntingtin that codes for the huntingtin protein.

Hematoma

A localized collection of clotted blood in an organ or tissue; an internal bruise.

Tumor (Neoplasm)

A mass of cells that grows independently of the rest of the body.

Tardive dyskinesia (TD)

A motor disorder originally induced by antipsychotic drugs whose symptoms involve involuntary smacking and sucking of the lips, thrusting and rolling of the tongue, lateral jaw movements, and puffing of the cheeks.

Parkinson's disease

A movement disorder of middle and old age. It is associated with widespread degeneration of particularly in the substantia nigra from a dopamine defecit.

Aneurysm

A pathological balloonlike dilation that forms in the wall of an artery at a point where the elasticity of the artery wall is defective. They are especially harmful in the brain but can occur in any part of the body. They can be congenital or from exposure to vascular poisons or infection.

Thrombosis

A plug is formed that blocks blood flow at the site of its formation. It can be composed of a blood clot, fat, oil, an air bubble, tumor cells, or any combination thereof.

Multiple sclerosis (MS)

A progressive autoimmune disorder that attacks the myelin of axons in the CNS until they become dysfunctional and degenerate. Causes ataxia.

Absence seizure

A seizure not associated with convulsions whose primary behavioral symptom is a disruption of consciousness associated with a cessation of ongoing behavior, a vacant look, and sometimes fluttering eyelids. EEG's of this are different from others in that they are bilaterally symmetrical 3-per-second spike-and-wave discharges. Most common in children and frequently cease at puberty.

Partial seizures

A seizure that does not involve the entire brain. Epileptic spiking visible in the EEG that does not spread to other areas of the brain. Behavioral symptoms are tied to where the seizure occurs.

Infiltrating tumors

Aside from meningiomas, these are the most frequent brain tumors. They grow diffusely through surrounding tissue and so they are most often malignant and difficult to destroy or remove completely.

Meningitis

Bacteria-caused inflammation of the meninges that is fatal in 25% of adults. I.e., Syphilis

Toxic psychosis

Chronic insanity produced by a neurotoxin from accumulations of harmful chemicals in the brain.

Metastatic tumors

Brain tumors that do not originate in the brain. These constitute 10% of brain tumors. Many originate as cancer of the lungs.

Arteriosclerosis

Describes a thickening of the walls of blood vessels as channels narrow usually due to buildups of fat deposits that can eventually lead to complete blockage of the blood vessel.

Congenital

Describing something present at birth.

Acoustic neuromas

Encapsulated tumors that grow on cranial nerves or tracts.

Dementia

General intellectual deterioration

Convulsions

Motor seizures that include tremors (clonus), rigidity (tonus), and loss of balance and consciousness.

3-per-second spike-and-wave discharge

Occurs during absence seizures

Simple partial seizures

One of two major categories of partial seizures. Describes seizures with primarily sensory and/or motor symptoms. Epileptic discharges spread through the sensory motor areas of the brain and then systematically through the body.

Complex partial seizures

One of two major categories of partial seizures. Often restricted to the temporal lobes, those who experience these are said to have temporal lobe epilepsy. During this, the patient engages in compulsive repetitive, simple behaviors commonly referred to as automatisms.

Cerebral hemorrhage

One of two major types of strokes that occurs when a cerebral blood vessel ruptures and blood seeps into the surrounding neural tissue damaging it. Bursting aneurysms are a common cause.

Epileptic aura

Peculiar psychological changes that epileptics may experience before a convulsion. Examples include bad smells, specific thoughts, vague feelings of familiarity, hallucinations, or tightness of the chest. It provides clues about the location of the epileptic focus and a warning of an incoming seizure.

Generalized seizures

Seizures that involve the entire brain. Can begin as focal discharges that spread, or simultaneous discharges occurring in all parts of the brain. Can result from diffuse pathology or can originate focally in a structure, such as the thalamus, that projects to many parts of the brain.

Hypoxia

Shortage of oxygen supply to tissue, for example, to the brain.

Embolism

Similar to a thrombosis, but carried by blood to the site where it becomes lodged. A thrombosis that did not originate where it is.

Strokes

Sudden-onset cerebrovascular disorders that cause brain damage. They often cause amnesia, aphasia (language difficulties), paralysis, and coma.

Penumbra

The area surrounding the dead/dying tissue caused by a stroke (infarct) that is at risk of dying soon after but also has the potential to recover.

Glutamate

The brain's most prevalent excitatory neurotransmitter. Plays a major role in stroke-induced brain damage. When a blood vessel become blocked, blood-deprived neurons become overactive and release excessive quantities of this. This causes a chain of events that spreads the damage and kills postsynaptic neurons.

Anterograde degeneration

The degeneration of the distal segment. Occurs first. This occurs quickly because the axotomy severs the axon from the cell body, which is the metabolic center of the neuron. Distal segment is swollen in a few hours and fragments in a few days.

Retrograde degeneration

The degeneration of the proximal segment. Occurs second. It progresses gradually back from the cut to the cell body. In 2 or 3 days, major regenerative or degenerative changes become apparent in the cell bodies. Regenerative changes indicate potential for massive protein synthesis that will allow the neuron to survive contingent on successful synaptic contact with the appropriate target. Degenerative changes indicate impending neuron death usually by apoptosis, but sometimes by necrosis or both.

Punch-drunk syndrome

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

Substantia nigra

The midbrain nucleus whose neurons project via the nigrostriatal pathway to the striatum of the basal ganglia.

Alzheimer's disease

The most common cause of dementia, a progressive genetic disorder marked by a selective decline in memory, deficits in attention, and personality changes. Definitive diagnosis of this must wait until autopsy. Brains of those suffering have small dot lesions called microbleeds from microhemorrhaging. 3 defining characteristics: 1. Neurofibrillary tangles, thread like tangles of protein in neural cytoplasm. 2. Amyloid plaques, clumps of scar tissue composed of degenerating neurons and a protein called amyloid. 3. Neuron loss These 3 are particularly prevalent in the entorhinal cortex, amygdala, and hippocampus all located in the medial temporal lobe and involved in memory.

NMDA (N-methyl-D-aspartate) receptors

The most involved glutamate receptors in the process of stroke induced brain damage.

Kindling phenomenon

The progressive development and intensification of convulsions elicited by a series of periodic brain stimulations and among the first neuroplastic phenomena to be widely studied.

Neural regeneration

The regrowth of damaged neurons. Not a very successful process in mammals. Virtually nonexistent in the CNS of adult mammals. Hit or miss in the PNS.

Proximal segment

The segment of a cut axon between the cut and the cell body.

Distal segment

The segment of a cut axon between the cut and the synaptic terminals.

Subdural space

The space between the dura mater and arachnoid membrane that accumulates blood from blunt trauma to the brain (i.e., contusions).

Transneuronal degeneration

The spread of degeneration from damaged neurons to neurons that are linked to them by synapses.

Epidemiology

The study of various factors that influence the distribution of a disease in the general population.

General paresis

The syndrome of insanity and dementia that results from a syphilitic infection.

Viral infections

There are two types of these: those with a particular affinity for neural tissue (i.e., rabies) and those that attack neural tissue with no particular affinity towards it (i.e., mumps and herpes).

Schwann cells

These cells clear debris and scar tissue, release neurotrophic factors that stimulate the growth of growth cones, new axons, and CAMs on their cell membranes. Success of neural regeneration is contingent on the state of their sheaths. Intact sheaths allow for axonal regeneration to correct targets. Slightly separated severed sheaths often misdirect axonal regeneration to incorrect targets. Widely separated severed sheaths prevent any functional regeneration.

Benign tumors

Tumors that are surgically removable with little risk of further growth in the body.

Encapsulated tumors

Tumors that grow within their own membrane and are therefore easy to identify on a CT scan. They can influence the function of the brain only by the pressure they exert on surrounding tissues and are almost always benign.

Down syndrome

When a child is born with an extra chromosome 21 created in the egg.