VASCULAR DISORDERS IN THE NERVOUS SYSTEM

Overview of Topics

Overview of Cerebrovascular Accidents
Ischemia and Infarction
Intracerebral Hemorrhage
Intracranial Aneurysm
Arterial System in the Brain: Carotid System
Arterial System in the Brain: Vertebral System
Stroke Prone Profile
Outline for evaluating a patinet with symptoms which suggest cerebrovascular disorder

Overview of Cerebrovascular Accidents

Basic Facts

Brain requires 150 gm glucose, 72L 02 every 24 hrs.
No storage capacity.
Internal carotid to each hemisphere.
Only the arterioles can regulate blood flow.

A. The acute onset of "apoplexy," "stroke" is usually associated with disease of the intracranial vascular tree, blood, or trauma. The most common causes of generalized/focal disturbance of brain function are cerebral vascular lesions.

The main types of spontaneous cerebrovascular accidents are:

1. Cerebral thrombosis
2. Cerebral hemorrhage
3. Cerebral embolism
4. Subarachnoid hemorrhage

B. Etiology: CVA's may occur at any age, but intracerebral hemorrhages and thromboses are rare before age 40.

1. Peak incidence for cerebral thrombosis 50-70 years.
2. Peak incidence for cerebral hemorrhage 40-70 years.
3. Cerebral thrombosis is most common cause of strokes (c. 60 %)
4. Cerebral hemorrhage and embolism " (c. 20%).

C. Incidence

1. Cerebrovascular disease - most common disorder in adults. 25% of autopsies.
2. Cerebral arteriosclerosis and associated neurological disorder account for 15%, of admissions to institutions for chronic care.

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Ischemia and Infarction

A. Basic facts

1. Area involved receives less than the required amount of blood (02, Glucose, etc.)
   1. Basic process is that of atherosclerosis. Involves large and medium sized arteries.
   2. Fat deposits produce stenosis (narrowing) of the lumen.
   3. Ischemia develops after 30 sec. of restriction.
   4. After 1 minute neural function may cease.
   5. After 5 minutes cerebral infarction develops.

B. Etiology:

1. General preciptors
   1. fall in arterial pressure falls below reg. level.
   2. blood too viscous.
   3. glucose or 02 too low a level.
   4. Neoplasms can compress arteries.
   5. cerebral arterial spasms can occur, with migraine syndromes and cause ischemia.
   6. occlusion of artery by thrombus or embolus.
      1. occlusive lesions may produce signs depending upon collateral circulation. (principal factor is the rate of development of the obstruction).
      2. There is no 1-1 relation between occlusion and tissue death (infarction or encephalomalacia).
      3. Total occlusion may occur without the development of focal symptoms.
      4. May only have transient ischemic attacks.

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2. Atherosclerosis: clotting at site of an ulcerated plaque in the vessel wall.
   1. clot propagates until it (1) occludes the lumen or (2) sheds microemboli which plug distal arteries.
   2. most common site -- carotid sinus.

3. Embolism: The occlusion of a cerebral vessel by a small piece of blood clot, tumor, fat, air, or even a clump of bacteria.
   1. Etiology
      1. Air embolism: lung injury, bends, etc.
      2. Fat embolism: associated with bone fracture.
      3. Children - commonly associated with valvular heart disease.
      4. Adults - commonly caused by atrial fibrillation or myocardial infarction.
      5. Most common cause of transient ischemic attacks is microembolism from atherosclerotic plaques locating in aortocranial arteries.
   2. Pathology
      1. Emboli may partially/totally occlude a cerebral vessel; result = infarct
      2. Emboli to the brain are frequently multiple.
      3. Tissue of embolized artery becomes ischemic.
      4. Pathology similar to those with atherothrombosis.
      5. Frequently multiple and associated with infarcts in lungs, spleen, kidneys, etc.

C. Pathology of Infarction

1. After 48 hours - soft & mushy (necrotic).
2. Swelling after 8 hours.
3. Swelling decreases over next 10 days.
4. Enzymatic liquefaction occurs resulting in a cavity.
5. Area of infarction - invaded by neutrophylic polymorphic leukocytes & macrophages.
6. Capillaries & astrocytes then engage in a repair process.
   1. Astrocytes - wall off damaged area.

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Intracerebral Hemorrhage

Basic Facts

1. Many diseases (e.g., Leukemia), infections and trauma may induce hemorrhage as well as a brain tumor.
2. Softening of brain tissue around a vessel probably facilitates rupturing.
3. Nature of ruptured vessel: (arterial, capillary, venous)-

A. Etiology

1. Major cause -- rupture of arteriolar aneurysms. (end result of longstanding arterial hypertension). May result from rupture of vessel anywhere in CNS
2. Other causes: rupture of tiny hematomas, large AV malformations, blood dyscrasias, systemic diseases, neoplasms, infections, toxins, and anticoagulants.
3. Classified according to location: (extradural, subdural, subarachnoid, parenchymatous, intraventricular).
4. Many subdural hematomas caused by traumatic rupture of the bridging veins that traverse the subdural space.
5. Intrancerebral arterioles - vessels most often ruptured in hypertensive patients.

B. Pathology

1. 80% are fatal.
2. Most common site - basal ganglia.

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Intracranial Aneurysms

1. Incidence
   1. 4% of all autopsies
   2. 50% of all CVA under 45.
   3. 14% in 45 - 64 years - 14% (most common)
   4. 2% in 65 + years

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2. Symptoms and signs
   1. arteriosclerosis and hypertension are common signs.
   2. septic foci may be observed.
   3. visual defects common also paralysis of muscles by 3 and 6 nerve.
   4. 90% of aneurysms are silent until they rupture (1/3 during sleep.)
   5. preceded by pain in occipital region.
   6. Kernig's sign - stiffness of neck occurs within a few hours.
   7. Hypertension present in 50%

3. Pathologic Considerations
   1. Majority due to congenital weakness.
   2. Often the result of maldevelopment of the media, particularly at bifurcation, allowing intima to bulge through.
   3. In some cases, weakness due to systemic abnormality affecting the connective tissue (Ehlers-Danlos Syndrome).
   4. May also be caused by septic emboli, syphilis and arteriosclerosis.
      1. mycotic and syphilitic - now uncommon
      2. arteriosclerotic changes most common in 40 yr. +
   5. Aneurysms range in size from microscopic to the size of an orange.
   6. 60% occur on internal carotid or middle cerebral artery.
   7. most on basal surface of skull.

4. Diagnosis
   1. suspect anytime patient has sudden onset of headache, followed by Kernig's sign and one or more additional signs.

5. Course and Prognosis
   1. rupture -- mortality greater.
   2. may recover.

6. Treatment
   1. Keep flat in bed with minimal disturbance.
   2. Angiography - serves to locate.
   3. clipping, etc.

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Arterial System in the Brain

Carotid System: Common and Internal Carotid Arteries

No neurologic deficit in persons with normal aortocranial circulation due to many anastomoses

Branches

1. ophthalmic
2. posterior communicating
3. anterior choroidal
4. anterior cerebral
5. middle cerebral

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A. Internal Carotid

1. Internal carotid supplies homolateral eye, frontal lobe and parts of temporal and parietal lobes

2. Problems resulting from disruption of internal carotid
   1. Transient attacks of homolateral blindness, contralateral hemiplegia or hemianesthesia and aphasia. (if LH)
   2. Episodes usually terminate within 30 minutes.
   3. If longer, may be due to emboli originating from a plaque in the neck lodging in intracranial arteries.
   4. Infarction evolves in a stepwise fashion leading to hemiplegia or hemiparesis with a cortical type of sensory loss.

3. Stenosis of internal carotid: Stenosis likely at origin at bifurcation of common carotid artery into internal and external carotid branches.
   1. episodes of monocular blindness (amaurosis fugox).
   2. later involves motor and sensory
   3. carotid border zone -- produces most common pattern.
   4. numbness of face and hand weakness.
   5. expressive aphasia if dominant hemisphere.
   6. symptoms indicate involvement of the middle cerebral area (most marked).

4. Syndrome of Lenticulostriate Penetrating branches.
   1. supply putamen & caudate.
   2. pure motor syndrome - spastic hemiplegia of face, arm & leg.

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B. Anterior Cerebral Artery

1. Supplies anterior internal capsule, head of caudate, and putamen, corpus callosum, and medial surface of frontal cortex.
2. includes are involving legs and subcortical white matter beneath Broca's speech area.
3. Occlusion of proximal portion uncommon.
4. Occlusion of branches common and followed by paralysis and sensory loss on contralateral side.
   1. Dominant Hemisphere - may produce mental confusion, clouding of consciousness, and aphasia.

C. Middle Cerebral Artery

1. Supplies lateral portions of cerebral hemisphere including parietal cortex and subcortical white matter of the insula, & lateral part of frontal, temporal & parietal lobes.
2. Also gives off lenticulo-optic and lenticulo-striate arteries, to basal ganglia.
3. Middle cerebral occluded more frequently than other cerebral vessel.
4. Damage produces contralateral hemiplegia, hemianesthesia, and homonymous hemianopsia (LH - aphasia).
5. Atherothrombosis or embolism occurs more frequently in branches rather than main trunk.
6. Paralysis of face and arm is often more complete than that of the leg.

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D. Posterior Cerebral Artery

1. Supplies inferior and medial portions of the posterior temporal and occipital lobes and to optic thalamus.
2. Main trunk blockage - both thalamus and the occipital lobe are damaged.
3. Signs will consist of the thalamic syndrome together with homonymous hemianopia.
4. Thalamic syndrome -- flaccid type of transient hemiparesis or hemiplegia;
   1. impairment of superficial sensation and loss of deep sensation.
   2. Agonizing, burning pain.
   3. Choreoathethoid movements, ataxia or tremor.
   4. All on contralateral side.

E. Bilateral Multiple Infarctions (Pseudobulbar Palsy)

1. Syndrome characterized by paralysis or weakness of the muscles supplied by the medulla oblongata.
2. Syndromes often includes loss of emotional control, unprovoked outbursts of laughing or crying.

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The Vertebral-Basilar System

A. Vertebral Arteries

1. Symptoms resulting from occlusion of a vertebral artery are indistinguishable from those caused by occlusion of a posterior inferior cerebellar artery.

B. Basilar Artery

1. Formed by the junction of the two vertebral arteries and supplies blood to the pons, midbrain and cerebellum.
2. Terminates by forming the two posterior cerebral arteries.
3. Occlusion (sudden) - sudden coma and disastrous neurological damage.
4. Transient ischemic attacks - vertigo, slurring of speech, confusion, transient loss of postural tone (drop attacks), hemiplegia or quadriplegia, and paresthesis on one side of the body.
5. Also disorders of eye movements, blindness and pupillary abnormalities.
6. Unilateral or bilateral paralysis of 3, 4, 6 nerves, disorders of gaze, involvement of SNS.
7. Deep reflexes are increased.
8. Sphinctor incontinence almost always present.

C. Various Syndromes

1. Paramedian Area - occlusion results in paralysis of the contralateral arm or leg.
   1. Midbrain - 3rd nerve nucleus and cerebral peduncle -- there is ophthalomoplegia (ptosis) on one side of lesion and paralysis of contralateral limb. (Webers Syndrome).
   2. Pons - 6th n. 7th n. (Millard-(Gubler syndrome)
      1. eye on side of lesion is deviated inward.
   3. Medulla Oblongata - 1/2 of tongue (ss).

2. Lateral area
   1. midbrain - pain and tpt red. - paralysis.
   2. pons - Horner's syndrome, facial paralysis
   3. bulb - Wallenberg's syndrome of dysphagia dysarthria

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3. Intracerebral Hemorrhage

4. Lacunar State - microinfarctions
   1. multiciplicity of lacunas called lacunar state.
   2. Four characteristic syndromes
      1. Homolateral cerebellar ataxia and pyramidal tract signs involving weakness of legs.
      2. Isolated hemiplegia
      3. "dysarthria - clumsy hand syndrome"
      4. Pure sensory stroke involving the face, arm and leg.

5. Hypertensive Enceplialopathy
   1. Common symptoms - headache, convulsions, amaurosis, transient periods of confusion, stupor or coma, and sometimes focal signs such as hemiplegia, aphasia, or hemlailopia.
   2. Also papilledema, hemorrhages, severe hypertension, and urinary abnormalities.
   3. Distinguished from uremia blood urea nitrogen is normal.

6. Brain Death
   1. Loss of all brain functions despite continued heart beat and detectable blood pressure.
   2. No EEG on two occasions 12 to 24 hours apart.

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The Stroke Prone Profile

A. Risk Factors. (Cerebral infarction - not an accident but the end result of a chain of events.)

1. Prior cerebral infarction
2. transient ischemic attacks
3. hypertension
4. Cardiac abnormalities
   1. EKG - indicating left ventricular hypertrophy.
   2. myocardial infarction
   3. cardiac dysrhythmia (atrial fibrillation)
   4. X-ray evidence of cardiac enlargement.
   5. congestive heart failure.
5. Clinical evidence of atherosclerosis.
   1. angina pectoris
   2. intermittent claudication of legs.
   3. arterial bruits
6. Diabetes Mellitus or evidence of impaired glucose tolerance.
7. Elevated blood lipids.
   1. cholesterol (below 50 years)
   2. Beta lipoprotein, endogenous triglyccride

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B. Premonitory and Initial Symptoms

1. Patients usually asymptoniatic until the disorder reaches a late stage.
2. Premonitary symptoms are infrequent occur as headache, dizziness, drowsiness, & mental confusion.
3. Focal premonitory symptoms - represent onset of infarction other than the hemorrhage.
   1. an aneurysm, by compressing one of the cranial nerves, may cause focal signs for several weeks or months before it ruptures.
      1. Seizures - if present, detailed history and description of attacks must be obtained.
      2. Cardiac irregularities - does heart beat irregularly or slowly during attacks (suggests Stokes-Adams syndrome).
      3. Headaches - duration, frequency, type severity, site, radiation.
      4. Visual Disturbances - unilateral or bilateral, transient or persistent, etc.

C. Onset

1. In majority of cases -- sudden onset and reach maximum onset within minutes or hours.
2. Symptoms may be focal or generalized.
   1. Premonitary ("Warning") symptoms: headache, dizziness, drowsiness, mental confusion.
   2. The onset of CVA may be sudden, involving falling and coma or may occur without loss of consciousness -- symptoms vary may last seconds, minutes, longer.
   3. Focal-signs: (paralysis; sensory loss; speech defects)
   4. Generalized: headache, vomiting, convulsions, coma - esp. with cerebral hemorrhage. Cannot touch chin to chest: common in intracerebral or subarachnoid hemorrhage.

D. Recovery

1. Typical; sometimes seems complete, usually partial -- depends on locus and extent of brain tissue destroyed/end.
2. Generalized - more common in patients with intracerebral or subarachnoid hemorrhiagic.

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Outline for evaluating a patinet with symptoms which suggest cerebrovascular disorder

Vascular etiology

A. Parenchymatous

1. Primary hypertension
2. A-V malformation
3. Hemorrhagic infarction

1. Primary subarachnoid hemorrhage
2. Pituitary hemorrhage
3. Subdural hematoma
4. Extradural hematoma

1. Primary intracerebral hemorrhage with rupture into subarachnoid space
2. Intraventricular hemorrhage

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Obstruction to Flow
A. Embolus

1. Thrombus
   1. Sterile
   2. Septic
2. Neoplasm
   1. Benign
   2. Malignant
3. Air
4. Fat
5. Fibrin-platelet
6. Cholesterol
7. Foreign body

1. Stenosis
2. Occlusion

1. Autoinimune diseases
2. Phlebitis

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Change in Blood Constituents
A. Hemoglobinopathies
B. Dysproteinemias
C. Consumption coagulopathies
D. Myeloproliferative disorders
E. Hypercoagulable states

Vasospasm
A. Migraine
B. Postemolic
C. Hypertensive encephalopathy?
D. Ruptured aneurysm

Nonvascular etiology

A. Neoplasm

1. Benign
2. Malignant

1. Akinetic
2. Focal with Todd's paralysis
3. Grand mal with postictal coma