Unit 3 CNS Flashcards
Descrive CVA (cerebrovascular accidents)/stroke.
- a clinical syndrome characterized by a focal neurological deficit, due to an abnormality of the cerebral circulation
Describe the blood supply to the brain.
- Two internal carotid arteries anteriorly
- Ophthalmic, posterior communicating, anterior choroidal, anterior cerebral, and middle cerebral
- Vertebral arteries posteriorly
- Internal carotid and vertebral arteries communicate at the base of the brain through the circle of Willis.
Describe the cerebral vascular arteries.
Lateral View
http://en.wikipedia.org/wiki/File:Cerebral_vascular_territories.jpg
Medial View
http://en.wikipedia.org/wiki/File:Cerebral_vascular_territories_midline.jpg
Middle cerebral artery (upper body)
Anterior cerebral artery (lower body)
Occiptial (visual, etc.)
What are the etiologies (risk factors) of a stroke?
- Age
- Gender
- Race
- High cholesterol levels
- Cigarette smoking
- Diabetes mellitus
- Other risk factors
- Heart diseases
- Blood diseases
- Alcohol, cocaine and illicit drug use (Chlamydia pneumoniae)
- Sedentary life style
What are the two types of stroke?
Ischemic strokes
- Caused by an interruption of blood flow in a cerebral vessel and are the most common type of stroke, accounting for 70–80% of all strokes.
Hemorrhagic strokes
- Caused by bleeding into brain tissue, usually from a blood vessel rupture caused by hypertension, aneurysms, arteriovenous malformations, head injury, or blood dyscrasias
What is a thrombosis?
- a solid mass of blood constituents (blood clot) formed within the vascular system in a living being
Predisposing Factors
- Changes in the intimal surface of the blood vessel
- Changes in the pattern of blood flow
- Changes in the blood constituents
What is an emobolism?
- is a mass of material in the vascular system able to become dislodged within a vessel and block its lumen
- a piece of thrombus
- foreign bodies
- fat tissue
- bacterial organism
What are the risk factors for a hemorrhagic stroke?
Hemorrhage
- severe hypertension
- aneurysm
- congenital berry aneurysm
- arteriovenous malformation
- bleeding disorders
What are signs and symptoms of a Cerebral Aneurysm?
- Most small aneurysms are asymptomatic.
- Large aneurysms may cause chronic headache, neurologic deficits, or both.
- Other manifestations include signs of meningeal irritation, cranial nerve deficits,
What are arterious malformations?
- blood is shunted from the high-pressure arterial system to the low-pressure venous system without the buffering advantage of the capillary network.
- The draining venous channels are exposed to high levels of pressure, predisposing them to rupture and hemorrhage
What are the classes of stroke?
- TIA
- presents with neurological deficit but will full recover within 24hr, warning sign of higher risk stroke in the future
- embolism most likely
- Evolving stroke (stroke in evolution)
- progressing, begins with warm then moves to legs, most likely a thrombus (ischemia or small hemorrhage)
- Completed stroke
- paralysis of R or L side
- R side stoke = language difficulties
- hemorrhagic or big thrmobus
Descrive the pathophysiology of a stroke.
- destruction of brain substance
- edema of surrounding brain tissue
- increased intracranial pressure
Ischemic
- Cerebrovascular obstructions by an embolism or thrombus
- central core of dead or dying cells surrounded by a penumbra (halo of cells recieving marginal bloodflow)
- Cell in penumbra have marginal bloodflow and their metabolic activities are impaired. although areas undergoes an electrical failure, the structural integrity of the cells is maintained
- Function of cells in penumbra depends on return of circulation, volume of toxic products produced by dying cells, degree of cerebral edema, and alterations in local blood flow.
Hemorrhagic
- rupture of blood vessel
- hemorrhage into brain tissue
- focal hematoma
- infarction
- increased ICP by hematoma
- edema
What are the clinical manifestations of a stroke?
Clinical Manifestations are Determined:
- by the cerebral artery that is affected
- Size of the vessel – Lacunar infarct
- by the area of brain tissue that is supplied by that vessel
- By the adequacy of the collateral circulation
- Presence or absence of cerebral edema and increased ICP
- Ischemic (more focal) and hemorrhagic (more global)
See figure below for arteries (effects listed according to list below) (see page 1266 for more details), http://postimg.org/image/9mg9g3k8d/
- anterior cerebral artery
- middle cerebral artery
- posterior cerebral artery
- basilar and vertebral artery
What is brain herniation?
There are four main types of brain herniation syndromes. These include the cingulate, central, uncal, and cerebellar tonsillar herniations described below:
Subfalcine (or cingulate) herniation:
- A section of brain herniates under the falx cerebri. This can cause compression of the anterior cerebral artery.
Downward Transtentorial (or central) herniation:
- The thalamic area herniates down over the tentorial notch. This can lead to decorticate posturing during which the individual’s body is in an extended position but the arms and wrists flex in response to pain.
Temporal Transtentorial (or uncal) herniation:
- The medial part of the temporal lobe herniates down over the tentorial notch. This can lead to pressure on the brainstem and decerebrate posturing, often beginning unilaterally and progressing to involve both sides. Decerebrate posturing is full extension of the arms, legs, and back.
- The paramedian arteries that branch off of the basilar artery may rupture due to excessive stretching. This will cause a characteristic brain bleed known as Duret hemorrhages. The result is usually fatal.
- Uncal herniation can also create dilated pupils on the same side as the lesion. This is due to stretching of cranial nerve III.
- Paresis (slight or partial paralysis) may also be present on the ipsilateral side (same side as the lesion). However, this is known as a false localizing sign because it is actually due to compression damage on the side opposite the lesion to an area known as the crux cerebri. This area is where the bulbar and corticospinal tracts run on their way to the spinal cord.
Cerebellar Tonsillar herniation:
- Part of the cerebellum herniates through the foramen magnum. Neck stiffness, known as nuchal rigidity, is a common finding. Irregular respiration can quickly lead to cessation of breathing due to direct pressure on the medulla.
What is conciousness and how is it measured (TQ)?
- is a state of awareness of self and the environment and of being able to become oriented to new stimuli
- rely on RAS (ascending fibers) for being alert
- the content and cognitive aspects of consciousness are determined by a functioning cerebral cortex
Levels of Conciousness
- Confusion – conscious but disorientated
- Delirium - restless, delusions
- Obtundation – decreased alertness with psychomotor retardation
- Stupor – not unconscious, but no spontaneous activity
- Coma - unarousable, unresponsive
http://www.smartdraw.com/examples/view/traumatic+brain+injury+-+glasgow+coma+scale/
