NEUROPATHOPHYSIOLOGY IIITrauma, Stroke and Toxins

Nancy Long Sieber, Ph.D.

September 27, 2010

Disease and Trauma of the Peripheral Nerves

Dermatomes are the regions on the body that

correspond with specific cranial or spinal nerves.

Damage to a nerve will cause loss of sensation and motor function in that region of the body.

Guillain-Barre Syndrome involves demyelinization of peripheral nerves

http://www.monografias.com/trabajos37/sindrome-guillain-barre/Image8645.jpg

Adaptation to Sensory Loss:

Blindness

See link: http://www.the-scientist.com/blog/display/55315/

Anatomy of the Visual System

http://www.kellogg.umich.edu/theeyeshaveit/anatomy/visual-pathway.html

The Braille Alphabet

Governor Paterson of New York is legally blind. He does not read Braille, but he does have a tremendous memory.

To be legally blind, a person must have vision worse than 20/200 in their best eye, or a visual field of 20 degrees or less.

Injury and Trauma to the CNS

http://dailyme.com/gallery/medical-condition/head-injury.html

from http://www.cureparalysis.org/faq/spine.gif

Injury to the spinalcord causes loss offunction below the lesion site.

Causes:45% motor vehicle18% falls17% violence13% sports, esp. diving

Who:80% maleAvg age 31.5 yrs.

Sequence of events following spinal cord injury

• Spinal shock – transient (hours to days) loss of reflexes in area below lesion. Muscles become flaccid, motor function lost due to injury & inflammation. May lose sympathetic tone.

• Reflexes gradually return over the next few days to weeks. – Axons of surviving cells begin to recover

• Patient may experience hyperreflexia, as normal inhibitory signals that descend down the spinal cord are blocked by the injury. Gradually stabilizes.

Sensory pathways cross to the opposite side of the spinal cord or

medulla before ascending to the cortex.

http://thalamus.wustl.edu/course/bsen1.gif

From: McPhee, Lingappa, Ganong & Lange Pathophysiology of Disease 1995

Injury to one side of the spinal cord can cause loss of function on both sides of the body.

Concerns with spinal cord injury

• Loss of function below site of lesion – may be complete or partial, depending on the injury.

• Loss of thermoregulation

• Pressure wounds

• Autonomic dysreflexia

Stroke:Hemorrhagic and Ischemic

Adaptations to Maintain Brain Blood Flow

• Anastomoses – interconnections between blood vessels, compensate for blocked vessels.

• Autoregulation:– Myogenic autoregulion brain blood vessels dilate in

response to a fall in blood pressure, and constrict in response to an elevation in blood pressure

– Metabolic autoregulation – matches brain bloodflow to metabolic activity

– Helps maintain blood flow if vessel is partially occluded.

http://ww2.heartandstroke.ca/images/english/stroke_isc_web.jpg

http://ww2.heartandstroke.ca/images/english/stroke_hem_web.jpg

Neurotoxins

• Organophosphates

• Strychnine poisoning

• Tetanus toxin

• Heavy Metals– Lead– Mercury

http://www.environmentalhealthnews.org/ehs/newscience/depressed-about-pesticides/

Organophosphate pesticidesinhibit acetylcholinesterase.

http://www.drugstoremuseum.com/sections/level_info2.php?level=1&level_id=74

Strychnine

http://animalpetdoctor.homestead.com/PoisonRat.html

Strychnine blocks the activity of glycine, an inhibitory neurotransmitter.

Tetanus

A soldier dying from tetanus. Painting by Charles Bell in the Royal College of Surgeons, Edinburgh.

Heavy Metals

• Lead

• Mercury– Elemental mercury (quicksilver)– Methylmercury

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1247191/pdf/ehp0112-000987.pdf

Intelligence quotient as a function of lifetime average blood lead concentration.

Koller, et al. Recent Developments in Low-Level Lead Exposure and IntellectualImpairment in Children. Envtl. Health Persp. • VOLUME 112 | NUMBER 9 | June 2004

http://www.ghana-mining.org/ghweb/en/pmu-mssp/mer-abate.html

Elemental mercury is used in artisanal gold mining

http://www.worstpolluted.org/projects_reports/display/56

http://www.nimd.go.jp/archives/english/tenji/a_corner/a03.html

1. Gait disturbance, loss of balance (ataxia), speech disturbance (dysarthria)

2. Constriction of the visual fields

3. Stereo anesthesia

4. Muscle weakness, muscle cramp

5. Loss of hearing

6. Disturbance of sense of pain, touch or temperature.

Adverse effects to nervous system caused by methylmercury.

http://www.nimd.go.jp/archives/english/tenji/a_corner/a03.html

Lupus and the nervous system

• About 10-15% of people with lupus have CNS effects, typically fatigue, headaches, disorientation.

• More common: peripheral neuropathy, typically as a result of vasulitis. Pain, loss of function of extremities, esp. feet. Sometimes autonomic systems is affected as well.

Spi

nal

Cor

d

Organ

{

NT= acetylcholine receptor= nicotinic

Neurotransmitters and receptors of the autonomic nervous system

Parasympathetic (cholinergic)Sympathetic (adrenergic)

Preganglionic neuron

Organ

Preganglionic neuron

Postganglionic neuron

NT= acetylcholine receptor= nicotinic

Spi

nal

Cor

d NT = acetylcholine receptor = muscarinic

NT = norepinephrine receptor= or ß adrenergic

Postganglionic neuron