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Tutoría 8: Introducción al ACV, Irrigación del SNC y síndromes asociados (Parte I)
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Tutoría 8: Introducción al ACV, Irrigación del SNC y síndromes asociados (Parte I)

Tutorial Overview

The tutorial is divided into two main parts. Part 1 focuses on the basics of anterior circulation in the central nervous system, while Part 2 delves into posterior circulation and associated syndromes.

Introduction to Tutorial Content

  • Epidemiology, classification, risk factors, and anamnesis are discussed.
  • Emphasis on understanding cerebral irrigation for better comprehension of ACB.
  • Recommended neuroanatomy resources for clear understanding of arterial pathways.

Clinical Relevance and Syndromes

  • Clinical aspects covered in Adams' neurology book or a Toro for easier comprehension.
  • Importance of quick action due to brain tissue sensitivity to oxygen deprivation.

Epidemiology Insights

Detailed insights into the epidemiology of ACB, emphasizing gender prevalence, risk factors, and global incidence rates.

Gender Prevalence and Risk Factors

  • Brain tissue vulnerability to oxygen deprivation highlighted with staggering neuron loss statistics.
  • Gender differences in ACB incidence until menopause; post-menopause estrogen loss equalizes risks.

Global Incidence and Impact

Global incidence rates, prevalence in Colombia, types of ACB (ischemic vs. hemorrhagic), and associated risk factors are discussed.

Incidence Rates and Risk Factors

  • ACB as a leading cause of disability in Colombia after trauma; high new case numbers annually.
  • Distinction between terms "stroke," "accident," or "disease" cerebrovascular clarified based on preventability.

Classification of ACB

Classification breakdown between hemorrhagic and ischemic strokes with a focus on causes, symptoms, and intracranial effects.

Types of Strokes

  • Hemorrhagic stroke rarity compared to common ischemic stroke occurrence.

Empathy and Habits Impact on Brain Hemorrhage

The discussion delves into how habits, such as substance use like cocaine and amphetamines, along with conditions like aneurysm rupture, can lead to brain hemorrhage. Symptoms vary based on the location and extent of the hemorrhage.

Impact of Hemorrhage Location

  • Hemorrhages near specific brain regions can result in distinct symptoms:
  • Cerebellum proximity may cause ataxia.
  • Left temporal lobe lateral region involvement may lead to aphasia and motor or sensory signs.

Causes and Characteristics of Subarachnoid Hemorrhage

  • Subarachnoid hemorrhage occurs due to aneurysm rupture or vascular malformations.
  • It differs from intraparenchymal hemorrhage by being confined to cerebrospinal fluid spaces.

Distinctive Features of Subarachnoid Hemorrhage

  • Characterized by a thunderclap headache reaching maximum intensity abruptly.
  • Presents with increased intracranial pressure symptoms like vomiting and blurred vision.

Types of Brain Ischemia

Brain ischemia encompasses thrombotic, embolic, and systemic hypoperfusion types, each with unique etiologies and implications.

Thrombotic Ischemia Variants

  • Large vessel disease involves artery blockages due to conditions like arteriosclerosis.
  • Small vessel disease affects smaller arteries like those in the carotid or vertebral systems.

Embolic Ischemia Classification

  • Embolism origins include venous clots traveling to the brain, cardioembolism from heart issues, or arterial embolism between vessels.

Systemic Hypoperfusion Implications

  • Results from systemic failures like heart issues or pulmonary embolism affecting cerebral perfusion.

Other Brain Vascular Conditions

Venous thrombosis and hematological disorders contribute to diverse brain vascular pathologies requiring genetic predisposition consideration during differential diagnosis.

Venous Thrombosis & Hematological Disorders

  • Venous thrombosis links to genetic factors impacting coagulation cascades.

Understanding Hematomas in Neuroimaging

In this section, the speaker discusses the differences between epidural and subdural hematomas in terms of anatomy, etiology, morphology, and clinical implications.

Epidural vs. Subdural Hematomas

  • The epidural hematoma is located above the dura mater and is typically arterial, while the subdural hematoma is below the dura mater and associated with venous bleeding.
  • Epidural hematomas often result from arterial bleeds due to trauma like a rupture of the middle meningeal artery, whereas subdural hematomas are more commonly caused by cortical vein ruptures.
  • Epidural hematomas evolve rapidly causing compression, while subdural hematomas progress slowly, making them more dangerous as symptoms may not manifest early.

Clinical Implications and Detection Challenges

  • Subdural hematomas pose challenges due to their slow evolution, leading to delayed symptom presentation in older adults who may not seek immediate medical attention.
  • Differentiating between epidural and subdural hematomas during treatment is crucial; mnemonic "viejito atontado" aids in remembering that confused elderly patients might have a subdural hematoma.
  • Symptoms like nonsensical speech or cognitive impairments in an elderly patient post-fall could indicate a subdural hematoma necessitating prompt evaluation.

Factors Influencing Intracranial Bleeding Risk

This part delves into modifiable and non-modifiable risk factors for intracranial hemorrhage focusing on hypertension, hyperlipidemia, and their management strategies.

Non-modifiable Risk Factors

  • Non-modifiable risks include age over 65 years, male gender predominance, genetic predispositions (polygenic inheritance), and certain ethnicities like Latinos or African descent individuals.

Modifiable Risk Factors: Hypertension & Hyperlipidemia

  • Hypertension stands out as a significant individual risk factor for intracranial bleeds; controlling blood pressure can reduce the risk substantially.
  • Lowering blood pressure by 10 mmHg can decrease intracranial bleed risk by 33%, emphasizing the importance of managing hypertension effectively through medications like hydrochlorothiazide.

Risk Factors for Cardiovascular Disease

In this section, the speaker discusses various modifiable risk factors for cardiovascular disease, including obesity, alcohol consumption, physical inactivity, smoking, diabetes mellitus, and arrhythmias.

Obesity as a Risk Factor

  • : Obesity exceeding 30% of body weight is a significant risk factor for cardiovascular disease.
  • : Maintaining normal BMI values (18 to 25) and waist circumference below 87.5 cm for women and 100 cm for men is crucial to mitigate risks associated with obesity.

Alcohol Consumption and Physical Activity

  • : Alcohol consumption is linked to increased blood viscosity and cardiovascular risk; moderation is advised.
  • : Regular aerobic exercises (moderate to vigorous intensity) for about 30 minutes three to four days a week are recommended to reduce the risk of cardiovascular events.

Smoking and Diabetes Mellitus

  • : Active smoking nearly doubles the risk of cardiovascular disease; quitting smoking can normalize risks after five years.
  • : Diabetes mellitus significantly increases the risk of ischemic heart disease due to its association with atherosclerosis.

Diabetes Mellitus and Other Risk Factors

  • : Monitoring hemoglobin A1c levels below 7% helps prevent microvascular complications but does not directly reduce the risk of cardiovascular events.
  • : Atrial fibrillation poses a sixfold increase in stroke risk; anticoagulants like warfarin are prescribed to manage this condition effectively.

Circulation Anatomy: Anterior Circulation

The speaker delves into the anatomy of anterior circulation in relation to cerebral irrigation patterns and arterial systems involved in brain perfusion.

Cerebral Irrigation Systems

  • : The brain's irrigation comprises anterior and posterior circulations connected by the Circle of Willis, allowing compensation during arterial occlusions.
  • : The Circle of Willis features multiple anastomoses that ensure collateral circulation between arteries, preventing disturbances upon occlusion.

Importance of Understanding Arterial Variations

  • : Anatomical variations in cerebral arteries are common; comprehensive knowledge aids in identifying potential issues early on.

Understanding the Anatomy of Carotid Arteries

In this section, the speaker delves into the detailed anatomy of carotid arteries, discussing their segments and branches.

Carotid Artery Segments and Branches

  • The common carotid artery bifurcates at the level of the fourth cervical vertebra into the external and internal carotid arteries. -
  • The internal carotid artery is focused on due to its significance in supplying blood to intracranial structures. -
  • The common carotid artery has four surgical segments, with the first segment extending from the bifurcation to the thyroid cartilage level. -

Internal Carotid Artery Segments

  • The C1 or cervical portion of the internal carotid artery does not give off branches in the neck region. -
  • The C2 or petrous segment travels within the carotid canal, leading to smaller branches like the tympanic artery. -

Intracranial Segments and Branches

  • The cavernous segment (C3) within the cavernous sinus gives rise to important branches that supply structures like the pituitary gland. -
  • Issues in this area can affect cranial nerves, such as trigeminal nerve dysfunction due to compression by surrounding structures. -

Terminal Segments and Divisions

  • The terminal segment (C4) known as supraclinoid extends from above sella turcica to terminal bifurcation into anterior and middle cerebral arteries. -
  • Apart from these divisions, additional arteries branch off during this course, contributing to specific brain regions' perfusion. -

Perforating Arteries and Their Roles

Overview

In this section, the speaker discusses the anatomy and manifestations related to the internal carotid artery.

Internal Carotid Artery Manifestations

  • The internal carotid artery gives rise to many important arteries, leading to collateral flow that often masks symptoms.
  • Symptomatic occlusion of the internal carotid artery can present with transient monocular blindness and other clinical signs like iris atrophy.
  • Bilateral infarction from internal carotid artery occlusion can result in coma and quadriplegia due to anterior circulation compromise.

Ischemic Presentations

  • Infarctions from hypoperfusion typically affect cortical or deep watershed regions, leading to shoulder weakness and facial droop.
  • Terminal infarctions at bifurcation points may mimic middle or anterior cerebral artery syndromes based on location.

Arterial Occlusion Symptoms

This part delves into characteristic symptoms of ischemia resulting from internal carotid artery occlusion.

Characteristic Symptoms

  • Ischemia due to internal carotid artery occlusion primarily manifests as monocular blindness, distinguishing it from transient visual disturbances like migraines.
  • Optic neuritis may be present proximally, affecting vision; however, its absence on physical exam does not rule out posterior involvement.

Hypoperfusion Effects

The discussion shifts towards hypoperfusion effects in specific brain regions.

Hypoperfusion Consequences

Detailed Surgical Segments Overview

In this section, the speaker discusses various surgical segments related to the cerebral arteries, emphasizing the importance of specific arterial branches and their functions.

Internal Segments of Cerebral Arteries

  • The speaker identifies four main surgical segments, marking them as M1 for the initial portion originating from the middle cerebral artery bifurcation.
  • These segments give rise to crucial arteries like ventricular striate arteries and perforating arteries of the cerebral artery, known for traversing distinct regions.
  • Focus shifts to M2 segment, highlighting its location over the insula and its role in irrigating this area before reaching a circular sulcus where it terminates.
  • Further details on M2 segment are provided, including its path along the insula and subsequent branching towards unnamed branches and pecular segment leading out of the insula.

Clinical Significance of Cerebral Arteries

This part delves into clinical implications associated with different segments of cerebral arteries and their impact on brain function.

Arterial Functions and Clinical Relevance

  • Discussion extends to cortical branches originating from these arterial segments, influencing various brain regions and functions.
  • Visual representation showcases how different segments (M1-M4) contribute to arterial distribution within the brain's structures.
  • Emphasis is placed on understanding M1-M4 pathways through illustrations depicting their course along the insula and cortical surfaces.
  • Detailed insights into M1 segment highlight its significance in supplying critical brain areas such as caudate nucleus while interacting with other key arteries.

Tract Pathways in Internal Capsule

Exploring tract pathways within the internal capsule sheds light on how different tracts navigate through distinct regions impacting motor and sensory functions.

Tract Navigation in Internal Capsule

  • The internal capsule serves as a vital route for both ascending and descending tracts essential for motor control, sensory processing, and cranial nerve functions.
  • Distinction between corticospinal tract (extremities-related movements) and corticobulbar tract (facial movements), elucidating their separate trajectories within the internal capsule.

New Section

In this section, the speaker discusses the anatomy related to sensitivity pathways in the brain.

Sensitivity Pathways in the Brain

  • The cerebellum and pontine tracts are crucial for ascending sensitivity pathways.
  • Sensory information must pass through the thalamus to reach the cortex via the internal capsule.
  • Sensory pathways for face, arm, and leg ascend in a specific order towards the brain.

New Section

This part focuses on manifestations of occlusions in cerebral arteries.

Manifestations of Arterial Occlusions

  • Occlusion in specific cerebral arteries can lead to infarctions affecting different brain regions.
  • Understanding differences between striatocapsular and lacunar infarctions is essential for diagnosis and treatment planning.

New Section

The discussion delves into characteristics of different types of infarctions and their implications.

Types of Infarctions

  • Striatocapsular infarctions can result in contralateral motor deficits affecting face, hands, and legs.
  • Lacunar infarctions are smaller and may lead to incomplete motor syndromes due to more localized damage.

New Section

Exploring the impact of striatocapsular infarctions on motor functions.

Motor Implications of Striatocapsular Infarctions

  • Striatocapsular infarctions can cause complete contralateral motor syndromes due to involvement of corticospinal tracts.

Understanding the Impact of Cerebral Artery Occlusion

In this section, the speaker discusses the impact of occlusion in the cerebral artery, focusing on specific areas affected and resulting symptoms.

Areas Affected by Cerebral Artery Occlusion

  • The occlusion affects the white matter directly, impacting mainly the face and upper extremities up to the shoulder. This corresponds to the middle cerebral artery's cortical portion.

Broca's Area and Motor Functions

  • Broca's area (areas 44 and 45) is affected by occlusion, leading to issues in speech production.
  • Supplementary motor area and other prefrontal motor areas are also impacted.
  • Manifestations include hemiplegia contralateral of face, arm, and leg.
  • Leg may be affected due to collateral circulation connections.
  • Sensory deficits contralaterally can occur along with visual field defects.
  • Ocular movements can be impaired due to involvement of optic radiations.
  • Lesions on one side affect vision fields on both eyes contralaterally.

Clinical Presentations of Middle Cerebral Artery Occlusion

  • Complete territory infarction results in classic syndrome with contralateral hemiplegia of face, arm, and leg.
  • Specific muscle groups may be affected based on arterial supply variations.
  • Motor syndromes present alongside sensory deficits and neglect phenomena.
  • Right hemisphere lesions lead to spatial awareness issues like neglect or anosognosia.
  • Left hemisphere lesions result in language-related impairments such as Broca's aphasia or dyscalculia.

Detailed Analysis of Cortical Lesions

This section delves into global cortical lesions' implications based on lesion location within the brain.

Global Cortical Lesions: Hemispheric Differences

  • Left hemisphere lesions primarily affect dominant hemisphere functions related to language processing and calculation abilities.
  • Right hemisphere lesions impact non-dominant functions like spatial awareness and recognition tasks.
  • Detailed analysis involves understanding how different regions within each hemisphere contribute to various cognitive processes.

Visual Cortex and Arterial Segments

In this section, the discussion revolves around the visual cortex and arterial segments in the brain.

Visual Cortex Alterations

  • : Patients may exhibit neglect of the left visual field due to cortical alterations, leading to conditions like homonymous hemianopia.

Arterial Segments and Visual Fields

  • : The inferior cortical part relates to optic radiations, where upper radiations correspond to the lower visual field. This arrangement can be opposite to what is expected.

Arterial Pathways Discussion

  • : The segment on the middle cerebral artery concludes. It highlights how afflictions in different segments lead to distinct clinical manifestations like quadrantopsia.

Anterior Cerebral Artery Pathway

  • : Moving on to the anterior cerebral artery, detailing its course from the internal carotid artery and its branches towards deeper brain regions.

Arterial Segments: A1-A5

This section delves into specific arterial segments (A1-A5) and their anatomical pathways.

A1 Segment Description

  • : A1 segment spans from internal carotid artery bifurcation to contralateral connection via anterior communicating artery, crucial for interhemispheric blood flow.

A2 Segment Transition

  • : Transitioning from A1 to A2 segment marks a change in nomenclature, now termed as pericallosal artery, serving superior brain regions.

Pre-Callosal Segment (A3)

  • : The pre-callosal segment extends till corpus callosum genu, giving rise to marginal artery supplying superior brain areas above corpus callosum.

Supra-Callosal vs. Infra-Callosal (A4 & A5)

Anatomy of Cerebral Arteries

In this section, the speaker delves into the anatomy of cerebral arteries, discussing various branches and their implications on different brain regions.

Understanding Cerebral Artery Anatomy

  • The theory peri callosa gives rise to arteries in blue, green, and red regions.
  • Ramas callosas play a crucial role in frontal-polar artery distribution.

Implications of Arterial Occlusions

  • Unique tronco bifurcation can lead to severe consequences like paraplegia.
  • Oclusión distan de lo results in lower limb motor deficits and personality changes due to frontal lobe alterations.

Effects of Anterior Cerebral Artery Occlusion

  • Anterior cerebral artery occlusion causes contralateral sensorimotor deficits and urinary incontinence.
  • Presentation of contra lateral grasp reflex highlights specific impairments post-infarction.

Impact on Behavior and Personality

  • Frontal lobe lesions manifest as complex behavioral changes like abulia and altered task performance.
  • Alterations in perforating arteries can result in emotional changes, personality disorders, and intellectual deficits.

Role of Hypothalamic Arteries

  • Hypothalamic artery occlusion leads to emotional disturbances and intellectual deficits.
  • Recurrent artery occlusion may cause transient hemiparesis with facial involvement.

Cerebral Arterial Circulation Overview

This section delves into the cerebral arterial circulation, discussing key structures and their implications in various syndromes.

Cerebrospinal Circulation Pathway

  • The internal carotid artery irrigates structures such as the internal capsule's posterior arm, shared with the middle cerebral artery.
  • Implicated structures include the optic tract, amygdala, hippocampus, and anterior limb of the internal capsule.

Triple H Syndrome

  • Lesions affecting thalamic nuclei anterior to the midline may lead to classic symptoms like contralateral hemiplegia.
  • The syndrome presents with total contralateral hemiplegia involving arms, legs, and face due to involvement of homonymous sectorial optic radiation.

Arterial Supply Summary

This part summarizes the arterial supply pattern within the brain's vasculature.

Arterial Pathways

  • The Willis circle comprises arteries like the internal carotid artery transforming into middle and anterior cerebral arteries.
  • Branches include perforating arteries supplying crucial regions like thalamus and corpus callosum.

Nuclei and Arterial Irrigation

Focuses on specific brain nuclei and their corresponding arterial irrigation patterns.

Nuclei Irrigation

  • The caudate nucleus receives anterior cerebral artery supply while putamen is mainly from middle cerebral artery.
  • Detailed coverage of how different parts of these nuclei are irrigated by specific branches of major cerebral arteries.

Corona Radiata and Capsule Interna

Explores white matter tracts' vascular supply in critical brain regions.

Vascular Territories

  • Corona radiata primarily supplied by middle cerebral artery; lower portions by anterior cerebral artery.