Chapter Fifteen Neurological Disorders Copyright © Houghton ...

Chapter Fifteen

Neurological Disorders

Copyright © Houghton Mifflin Company. All rights reserved. 15 - 2

Chapter Fifteen

Neurological DisordersS

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Vascular Disorders

• Ischemia: a condition of low oxygen levels due to interruption to the blood supply to the brain.

• Cerebral vascular accidents (CVA; strokes) result from blockage or hemorrhage.

© Crni/Photo Researchers, Inc.


Hemorrhages Result From:

• Aneurysms• Hypertension• Structural defects in blood vessels• Blood diseases• Exposure to toxins


Blockage Results From:

• A thrombosis, a plug of material that doesn’t move from its point of origin; or

• An embolism, a plug that passes to smaller vessels until it stops.

• The area of brain damage is known as an infarct.

© James Cavallini/Photo Researchers, Inc.


John Olney and “Excitotoxicity”

• Observed damage following stroke is not consistent with the idea that cells die due to oxygen and glucose deprivation.

• Olney suggested that excess glutamate following stroke is responsible for damage.– Neurons may swell and burst.– Calcium moves into neuron, possibly initiating

apoptosis.– Interactions with NO may damage neurons.


Vascular Malformations

• Arteriovenous malformations (AVMs) are abnormally formed collections of blood vessels in the brain.

• Cavernous malformations are similar to AVMs, but differ in that brain tissue generally does not develop within the abnormal area.


Characteristics of Vascular Malformations

• Symptoms include headache, seizures, hemorrhage.

• Probably genetic in origin.• Surgery may be used to remove affected

vessels.• Track star Florence Griffith Joyner died

following a seizure caused by a cavernous malformation.


Head Injury

• Open head injuries involve penetration of the skull, as through gunshot wounds.

• Closed head injuries (concussions, traumatic brain injuries) do not involve penetration of the skull.

© Thomas E. Witte/NewSport/CORBIS


Results of Closed Head Injury

• The site of a blow is known as a coup.

• The area on the opposite side of the head is the countercoup.

• Bleeding (hematoma), white matter damage, and swelling may occur.


Chronic Traumatic Brain Injury (CTBI)

• Repeated concussions may produce: – slurred speech.– memory and personality changes.– a Parkinson’s-like syndrome.

• The APOE4 gene, implicated in Alzheimer’s, may influence CTBI.

© Szenes Jason/CORBIS SYGMA


Brain Tumors

• Tumors do not arise from mature neurons, which do not typically replicate.

• Tumors do arise from glia and the tissues of the meninges.

• Infiltrating (malignant) tumors lack defined boundaries.– usually return after surgical removal– often shed cells or metastasize

• Encapsulated (benign) tumors rarely reoccur after surgery or metastasize.


Symptoms of Tumors

• General symptoms occur due to displacement and pressure.– headache, vomiting, seizures, double vision,

reduced heart rate, reduced alertness

• Specific symptoms relate to the location of the tumor (e.g. occipital tumors affect vision).


Types of Tumors

• Gliomas range in severity. – Astrocytomas– Medulloblastomas

• Meningiomas are usually benign.


Treatment for Tumors

• Surgical Removal• Chemotherapy• Thalidomide


Epilepsy

• Partial seizures originate in an identifiable part of the brain and then spread outward.

• Generalized seizures symmetrically affect both sides of the brain and do not appear to have a focus or clear point of origin.


Characteristics of Partial Seizures

• Accompanied by paroxysmal depolarizing shift (PDS).

• Simple partial seizures cause movements or sensations appropriate to the location of the starting point, or focus, of the seizure activity. – little change in consciousness– Jacksonian seizure

• Complex partial seizures normally begin in the temporal lobes and are associated with alterations in consciousness. – memory loss and confusion– sense that environment is either very familiar or foreign


Characteristics of Generalized Seizures

• Grand mal seizures– Cycling of tonic and

clonic phases followed by coma

• Petit mal seizures– Loss of consciousness,

but patient doesn’t fall over

– 3/sec spike and wave pattern


Treatments for Epilepsy

• Effective medications are usually GABA agonists.

• Surgery may be used to remove seizure focus or restrict seizures to one hemisphere.

• In children, ketogenic diets may be useful.


Neurocysticercosis (Brain Worms)

• Infection with the pork tapeworm.• When encysted worm dies, the immune

response initiates focal seizures.• Treatments include seizure medication,

surgery and antiworm medication.

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Brain Infections

• Encephalitis (e.g. West Nile virus) is an inflammation of the brain caused by viral infection.

• Meningitis is inflammation of the meninges, resulting from infection by bacteria, viruses or fungi.

• Lyme disease is caused by viruses transmitted by ticks.

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AIDS Dementia Complex (ADC)

• Causes:– Direct action of HIV virus– Indirect results of opportunistic infections

• Affects mood, cognition and movement• Treated with antiretroviral medications


Transmissible Spongiform Encephalopathies (TSEs)

• Psychological disturbances:– Paranoia– Anxiety– Depression

• Progressive loss of cognition• Motor disturbances• Death


Types of TSEs

• Scrapie (sheep)• Bovine spongiform

encephalopathy (BSE or “mad cow”; cattle)

• Creutzfeldt-Jakob disease (humans)

• Kuru (humans)• New variant Creutzfeldt-Jakob

disease (vCJD; humans)

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What Causes TSEs?

• TSE infectious agents differed from viruses:– long incubation period.– lack of inflammation.– immunity to hospital sterilization techniques.

• Prusiner isolated abnormal proteins called “prions.”


BSE and vCJD

• An outbreak of BSE in Great Britain coincided with human cases of vCJD.

• Prohibitions against using animal carcasses in feed appear to have reduced the incidence of both BSE and vCJD.


vCJD• vCJD patients are younger than classic CJD patients.• Prions responsible for vCJD are found in nervous

system tissue.• Muscle (steak) is probably safe, but mixed meats

(sausage, hamburger) carry more risk.


Migraine Headaches

• Symptoms include excruciating pain, an aura, nausea and vomiting.

• Initially believed to be a vascular disorder.• Brainstem “migraine generator” may be

responsible:– Possibly the Raphe nuclei.– Serotonin levels are low at the onset of a headache.– CGRP is released by the trigeminal nerve (V), leading to

dilation of blood vessels.– Triptans (serotonin agonists) may be helpful.


Assessing Neurological Disorders

• Neurological assessments combine examinations of:– a patient’s sensory and motor capabilities.– observations of cognitive function.

• Neuropsychological assessments focus on the cognitive outcomes of central nervous system damage.


Recovery From Brain Damage

• The Kennard Principle states that recovery from brain damage is a function of developmental stage.

• Language functions show more recovery than other cognitive processes.

• Most recovery occurs within the first 6 months following injury.

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Therapy for Brain Damage

• Rehabilitation should address:– cognitive changes.– emotional factors.– physical correlates, e.g. pain.

• “Mental muscle” approaches stress repeated practice of a general cognitive skill (e.g. attention).

• Specific-training focuses on a particular skill, such as driving a car.

• Specific-training appears more effective than the “mental muscle” approach.


Pharmacological Therapies for Brain Damage

• Support for using medications to reduce brain activity following damage is weak.

• Medications that reduce glutamate activity should reduce damage, but are hampered by severe side effects (e.g. psychosis).

• Vampire bat saliva may be used as a “clot buster” following stroke.


Neural Tissue Transplants

• Fetal cell transplants have been helpful in restoring motor function.

• Animal models of Alzheimer’s disease and ischemia have benefited from neural cell implants.

Courtesy Nuveen Investments and Christopher Reeve Paralysis Foundation


Virtual Reality and Rehabilitation

• The average patient receives only 30–60 minutes per day of formal rehabilitation therapy.

• Virtual reality technology allows the user to immerse himself or herself in a realistic artificial environment.

• VR activates the same brain areas as a real interaction with the environment.

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