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Case 18: Anatomical Pathology (Strokes) - Coggle Diagram
Case 18: Anatomical Pathology (Strokes)
Computed Tomography (CT Scan)
Define the process of Computed Tomography (CT Scan)
Computed Tomography (CT Scan) refers to the rotation of several x-ray beams and electronic X-ray detectors around the patient, these instruments measure the amount of radiation being absorbed through the patient's body
Outline the purpose of a Computed Tomography (CT Scan)
Computed Tomography (CT Scan) is used a tool used to observe Haemorrhage, Trauma, Fracture to the Skull and Hydrocephalus
Computed Tomography (CT Scan) uses radiation to produce an image
On the CT Scan:
Bone is White
Skull is White
Soft Tissue is Shades of Grey
Brain is Shades of Grey
Air is Black
Cerebrospinal Fluid is Black
Vessels with contrast appear White
Outline how to view a Computed Tomography (CT Scan)
CT Scan and MRI is viewed as if you are standing a the patient's feet looking at them
Magnetic Resonance Imaging (MRI)
Describe the process of Magnetic Resonance Imaging (MRI)
In Magnetic Resonance Imaging (MRI), the Radio Waves realign Hydrogen Atoms that exist within the Body
As the Hydrogen Atoms return to their usual alignment, they emit different amounts of energy depending on the type of body tissue they are located in.
Scanner captures this energy and creates an image using this information
Magnetic Resonance Imaging (MRI) does NOT use Radiation
Magnetic Resonance Imaging (MRI) can detect a Stroke at a very early stage ( as early as 30 minutes) by mapping the motion of the Water Molecules in the Tissue
Types of MRI Images
T1-Weighted and T2-Weighted are different types of MRI Images
Tissues, Fats and Fluids appear differently in these MRI Images because of the different pulse sequence used
Outline how the different types of MRI Images differ
In T1-Weighted MRI images:
Water appears Dark
In T2-Weigthed MRI Images:
Water appears Light
MRI Images show a high level of detail compared to CT Scans
Image on the Left is a T1 MRI showing a "butterfly" glioblastoma multiforma
The Image on the right shows Acute Bacterial meningitis
Outline the Arterial Supply to the Brain
Anterior Circulation of the Brain is supplied by the Internal Carotid Artery
Internal carotid Artery continues as the Middle Cerebral Artery (MCA)
Internal Carotid Artery then gives rise to the Anterior Cerebral Artery (ACA)
Left and Right Anterior Cerebral Arteries are connected by the Anterior Communicating Artery
Anterior Communicating Artery is a branch of the Internal Carotid Artery
Posterior Circulation of the Brain is supplied by the Basilar Artery
Basilar Artery is formed by fusion the Left and Right Vertebral Artery
Basilar Artery gives rise to the Posterior Cerebral Artery (PCA)
List the Arteries which make up the Circle of Willis
Circle of Willis is formed by the:
Anterior Cerebral Artery
Anterior Communicating Artery
Posterior Communicating Artery
Posterior Cerebral Artery
Internal Carotid Artery
Vascular Territories of the Brain
Outline the Vascular Territories of the Brain
Vascular Territories of the Brain are the specific region of the Brain supplied by a specific Artery
Outline the vascular territories of the Anterior, Middle and Posterior Cerebral Artery
Anterior Cerebral Artery supplies the:
Medial Portion of the Frontal Lobe
Superior Medial Part of the Parietal Lobes
Anterior Part of the Corpus Callosum
Middle Cerebral Artery supplies the:
Lateral Surfaces of the Hemispheres
Except for the Medial Portion of the Frontal Lobe, Superior Medial Portion of the Parietal Lobes which are supplied by the Anterior Cerebral Artery
Except for the Inferior Part of the Temporal Lobe which are supplied by the Posterior Cerebral Artery
Posterior Cerebral Artery supplies the:
Infero-Medial Part of the Temporal Lobe
Occipital Lobe
Primary Visual Cortex
Splenium of the Corpus Callosum
Watershed Zones
Define the term Watershed Zones
Watershed Zones are areas of the Brain which are supplied by the Distal most Ends of the overlapping Arterial Territories
Outline the characteristics of Watershed Zones
Watershed Zones are reliant on sustained Blood Pressure
They are susceptible to Hypotensive Episodes
List the types of Watershed Zones and their Overlapping Arterial Territories
Cortical Border Zone
Cortical Border Zone is supplied by the Arterial Cerebral Artery and Middle Cerebral Artery
Internal Border Zone
Internal Border Zone is supplied by LCA and Middle Cerebral Artery
Cortical Border Zone:
Cortical Border Zone is supplied by the Posterior Cerebral Artery and Middle Cerebral Artery
Stroke
Define the term Stroke
Stroke refers to a Neurological Disability presumed to be cerebrovascular, lasting longer than 24 hours
Define the term Transient Ischaemic Attacks
Transient Ischaemic Attacks (TIA) are reversible and last less than 24 hours
Aetiology of Strokes
Outline the Aetiology of Strokes
75% of Strokes are due to Atherosclerosis and Thromboembolism
15% of Strokes are due to spontaneous Intra-cranial Haemorrhage (Sub-arachnoid or Parenchymal)
Risk Factors of Strokes
List the Risk Factors of Strokes
Hypertension
Atherosclerosis
Diabetes Mellitus, Heart Disease
Smoking
Age, Gender, Race
Personal or Family History of Stroke or Transient Ischaemic Attacks
Brain aneurysms or Arteriovenous Malformations
Stroke Patterns
Outline how Stroke Patterns are grouped according to Blood Pressure
Macroscopic Appearance of Stroke patterns is grouped according to whether there is High Blood Pressure or Low Blood Pressure
With High Blood Pressure a person will see:
Pale infarcts
Haemorrhagic Infarcts
With Low Blood Pressure a person will see:
Laminar Necrosis
Watershed Infarcts
Pale Infarcts
Outline the characteristics of Pale Infarcts
Pale Infarcts usually happen at the End of an Arterial Territory
Pale Infarcts are seen in Increased Blood Pressure
In the Image below:
Left Hemisphere and Left Basal Ganglia is larger than the Right Hand Side
Subcortical White Matter on the LHS is expanded
There is a Pale Homogenous Firm appearance to the Swelling
This is compatible with a Left Middle Cerebral Artery (MCA) Territory Infarct
Haemorrhagic Infarcts
Describe the characteristics of Haemorrhagic Infarcts
Haemorrhagic Infarcts are caused by:
Reperfusion of Pale Infarcts
Superior Sagittal Sinus thrombosis
Haemorrhagic Infarcts are seen in Increased Blood Pressure
In the Image below:
Left Convexity shows surface and superficial cortical haemorrhage
The White Matter below it is subtly expanded
This is consist with the Reperfusion Injury of the Middle Cerebral Artery(MCA) Territory Infarct
Laminar Necrosis
Describe the characteristics of a Laminar Necrosis
Laminar Necrosis occurs as a result of poor perfusion over an area of Arterial Territory
Due to Selective Vulnerability of Cortical Neurons there is a loss of Neurons with thinning of the Cortex
Although, there is a loss of Neurons, the Glia and Vessels are still viable
Laminar Necrosis is NOT a true infarction
Laminar Necrosis is seen in Decreased Blood Pressure (Hypotensive Episodes)
In the Image, there is subtle thinning of the Cortical Grey Matter
In this image, there is a Band of Cortex which shows clear spaces
This is consist with Necrosis or Ischaemia
Watershed Infarcts
Describe the characteristics of Watershed Infarcts
Watershed Infarcts are wedge-shaped areas of infarction that occur in the regions of the Brain and Spinal Cord that lie at the most Distal Fields of Arterial Perfusion
Anterior Cortical Border Zone between the Anterior Cerebral Artery (ACA) and Middle Cerebral Artery (MCA) is of highest risk
During Watershed Infarcts, Global Ischaemia due to Hypotension leads to cell death
NOTE: Watershed infarcts are often Bilateral (occur in Left and Right Side)
Watershed Infarcts are seen in decreased blood pressure (Hypotensive Episodes)
Example: Shock
Intra-Cranial Haemorrhage
Outline the Patterns of Intra-Cranial Bleeding
There are 4 types of Intra-Cranial Bleeding:
Epidural Haematoma
Subdural Haematoma
Intra-Parenchymal Haemorrhage
Sub-Arachnoid Haemorrhage
Epidural Haematoma is usually associated with Trauma and Damage to the Middle Meningeal Artery
Subdural Haematoma is usually due to Trauma
Typically in old patients with atrophic brains who fall and tear the Bridging Meningeal Veins
Intra-Parenchymal Haemorrhage and Sub-Arachnoid Haemorrhage are usually medical patterns we see
They are NOT due to Trauma
Intra-Cerebral (Intra-Parenchymal) Haemorrhage
Describe the characteristics of Intra-Cerebral (Intra-Parenchymal) Haemorrhage
Intra-Cerebral Haemorrhage is also known as an Intra-Parenchymal Haemorrhage
Spontaneous cases of Intra-Parenchymal Haemorrhage can occur in patient in their 60s
Most cases of Intra-Parenchymal Haemorrhage occur in the rupture of small intra-parenchymal vessels
Causes of intra-Parenchymal Haemorrhage include:
Hypertension
Hypertension affects the Basal Ganglia, Thalamus, Pons and Cerebellum
Cerebral Amyloid Angiopathy (CAA)
In Cerebral Amyloid Angiopathy (CAA) amyloidogenic peptides are deposited in the walls of the medium and small meningeal and cortical vessels - with resultant Lobar Haemorrhages
This image shows a Hypertensive Basal Ganglia Bleed
This image shows a Pontine Bleed
Typically the Small Lenticulostriate Vessels of the Basal Ganglia and Pons are affected
NOTE: a tiny bleed in the Brainstem can be rapidly fatal
This image shows Lobar Haemorrhage as a result of Cerebral Amyloid Angiopathy (CAA) with CT Scan
This image shows Immuno-beta Amyloid
Charcot-Bouchard Micro-aneurysms
Outline the characteristic of Charcot-Bouchard Micro-aneurysms
In Charcot-Bouchard Micro-aneurysms:
Hypertension affects deep penetrating arteries and arterioles
It may also affect the Basal Ganglia, Hemispheric White Matter, Brain Stem
The Vessels may develop Hyaline Arteriolar Sclerosis
Small Aneurysms of less than 300 microns can also develop (Charcot Bouchard)
Major Complication of Charcot Bouchard micro-aneurysms is Rupture (haemorrhage) in the Territories supplied by the Lenticulostriate Vessels
Perforating Branches off the Middle Cerebral Artery (MCA) will supply the Basal Ganglia and Deep White Matter
Sustained Hypertension causes tiny aneurysms in these small vessels
Lenticulostriate Vessels of the Basal Ganglia and Pons are the most affected
In this image the True Micro-aneurysms have a Fusiform Shape
The altered flow leads to Fibrin and Platelet Aggregation with subsequent remodelling of the vessel wall and further weakening
Sub-Arachnoid Haemorrhages
List the causes of Sub-Arachnoid Haemorrhages
Sub-arachnoid Haemorrhages are caused by:
Rupture of Saccular (Berry) Aneurysm
Vascular Malformation
Trauma
Extension of Intracerebral haemorrhage
Haematological Disturbances
Tumours
Pathological Features of Sub-Arachnoid Haemorrhages
Outline the Pathological Features of Sub-Arachnoid Haemorrhages
1/3 of Sub-Arachnoid Haemorrhages are associated with Increased Intra-Cranial Pressure
This is described as the "worst headache ever
25-50% of patients will die with the First Rupture
Recurrent bleeding is common in survivors
Multiple aneurysms may be present in less than 1/3 of patients
Sub-Arachnoid Haemorrhages are associated with Autosomal Dominant polycystic kidney disease
There is a 1.3% per year rate of bleeding which is related to the size
Blood is present in the Sub-arachnoid space at the Base of the Brain
NOTE: In the Sub-arachnoid Haemorrhage, Blood tracks down the Sulci
As opposed to a Subdural Haemorrhage where Blood would not track down the Sulci
CT Scan with a Blood in a Sub-Arachnoid Space in a "star pattern"
