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Oncology-Brachytherapy
I. Definition and Indications:
  • Brachytherapy: Radiation therapy where sources are placed within or near the tumor. Crucially, precise tumor extent is vital because treatment targets a small volume, and missing the tumor (geographic miss) significantly increases recurrence risk. Accessibility for source insertion and removal, along with accurate source positioning, is also crucial.
II. Advantages:
  • High Localized Dose: Delivers a high dose to a small area, maximizing local tumor control while minimizing damage to surrounding normal tissue due to the sharp fall-off of radiation dose.
  • Short Treatment Duration (2-7 days): Uses low-dose-rate irradiation, leveraging the differing repair/repopulation rates of normal and malignant cells for enhanced therapeutic ratio. This also allows for reoxygenation of initially resistant hypoxic cells, increasing their radiosensitivity.
  • Compensation for Hypoxic Cells: Higher doses in the tumor center (near sources) help overcome the radioresistance of hypoxic cells often found in avascular/necrotic areas.
  • Irregular Tumor Treatment: Allows for treatment of irregularly shaped tumors by precise source placement, avoiding critical normal tissues.
III. Disadvantages:
  • Staff Radiation Exposure: γ-emitting sources expose staff to low but significant radiation. Afterloading techniques and low-energy radionuclides mitigate this risk.
  • Unsuitable for Large Tumors: Typically not suitable for large tumors; may be used as a boost after external beam radiotherapy (EBRT) and/or chemotherapy.
  • Accurate Source Positioning Crucial: Dose falls off rapidly (inverse square law), requiring precise source placement. This demands specialized skill and is not universally available.
  • Limited Treatment Volume: Surrounding structures (e.g., lymph nodes) are not irradiated.
IV. Types of Brachytherapy:
  • Intracavity: Radioactive material placed within body cavities (e.g., cervix, bronchus, esophagus, bile duct).
  • Interstitial: Radioactive material inserted into tissues (e.g., prostate, breast, head & neck, anal).
  • Surface: Radioactive material placed on the tumor surface (e.g., skin, eye).
V. Implant Types:
  • Manual Insertion: Should be avoided due to radiation hazards to staff.
  • Afterloading: Radioactive material loaded into pre-inserted applicators (needles, catheters). Reduces staff exposure significantly, allowing for optimal source placement.
    • Manual Afterloading: Radioactive material manually loaded into applicators.
    • Remote Afterloading: Machines (e.g., Selectron, Microselectron, Cathetron) control source placement, eliminating staff exposure. High-dose-rate remote afterloading often involves multiple outpatient fractions.
VI. Radionuclides:
  • γ Emitters:
    • Radium: Obsolete; radon gas is a hazard.
    • Cesium-137: Replaces radium; longer half-life (30 years), less penetrating γ rays.
    • Iridium-192: Used in wires or seeds; flexible, advantages in interstitial brachytherapy; shorter half-life (74 days).
    • Iodine-125: Used for permanent prostate implants; short half-life (59.6 days), low-energy γ rays allow for early discharge.
  • β Emitters: Primarily used in eye tumor treatment (strontium-90, ruthenium-106/rhodium-106 plaques).
VII. Dosimetry:
  • Treatment Planning Systems: Various systems (Paris system, Parker-Paterson, Quimby) are used to plan source distribution. The Paris system, common for iridium wire implants, uses parallel, equidistant wires. Computer calculations and graphs (Oxford cross-line curves) assist in dose calculation.
  • Dose Prescription: The basal dose rate (mean of minimum values between sources) is calculated. Treatment dose is prescribed to a reference dose line (often 85% of basal dose). Prescription points vary depending on the treatment type (e.g., Manchester A point for gynecological treatments). The ICRU Report 38 recommends reporting dose based on the volume enclosed by a 60Gy isodose line in gynecological treatments.
VIII. Future Developments:
  • 3D Planning: Sophisticated 3D planning using CT or MRI scans for precise dose calculations.
  • Biological Effective Dose: Incorporating biological effects in dose calculations.
  • High-Dose-Rate Remote Afterloading: Continues to reduce staff exposure and improve treatment outcomes. High-dose-rate pulsed insertions are increasingly replacing continuous low-dose-rate implants for greater homogeneity.
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Pathology- Dementia with Lewy Bodies (DLB)

I. Definition & Epidemiology

  • Definition: DLB is a neurodegenerative disease. Clinically, it presents as dementia. Histopathologically (microscopically), it's characterized by the presence of Lewy bodies in brain neurons (both cortical and subcortical).
  • Epidemiology:
    • Second most common cause of dementia.
    • Prevalence: ~5% in individuals >85 years old.
    • Slightly more prevalent in men.

II. Etiology & Pathogenesis

  • Etiology (Cause): Unknown.
  • Pathogenesis (Mechanism): The accumulation of Lewy bodies within neurons is believed to cause neuronal damage and subsequent cell loss, leading to the clinical manifestations of DLB.

III. Clinical Presentation & Differentiation from Alzheimer's Disease (AD)

  • Presentation: Progressively worsening dementia, similar to Alzheimer's Disease (AD).
  • Key Distinguishing Features from AD: This is crucial for diagnosis! DLB presents with:
    • Fluctuating cognition: Mental clarity varies significantly throughout the day or week.
    • Recurrent visual hallucinations: Patients experience vivid, often repetitive, visual hallucinations.
    • Parkinsonism: Features of Parkinson's disease, such as tremors, rigidity, and slow movement, may be present.

IV. Macroscopic & Microscopic Findings (Pathology)

  • Macroscopy (Gross Examination):
    • Cerebral atrophy (brain shrinkage), particularly in the temporal and parietal lobes.
    • Loss of pigment in the substantia nigra (a brain region crucial for movement control).
  • Histopathology (Microscopic Examination):
    • Lewy bodies: Intracytoplasmic (within the cell's cytoplasm) inclusions composed of α-synuclein, ubiquitin, and parkin. These are the hallmark of DLB.
    • AD-like changes: Amyloid plaques and neurofibrillary tangles (characteristic of Alzheimer's) are often present but areas typically severely affected in AD (like the hippocampus) are usually spared in DLB. This is a critical differentiator.

V. Prognosis

  • Highly variable, but the average survival after diagnosis is 5-7 years.

VI. Summary Table for Comparison with Alzheimer's Disease

Feature

Dementia with Lewy Bodies (DLB)

Alzheimer's Disease (AD)

Hallmark Feature

Lewy bodies (α-synuclein, ubiquitin, parkin)

Amyloid plaques and neurofibrillary tangles (tau protein)

Cognition

Fluctuating

Progressive decline, typically more gradual

Visual Hallucinations

Frequent, recurrent

Less common

Parkinsonism

Often present

Usually absent

Hippocampus

Usually spared

Severely affected
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Pathology-Central Nervous System (CNS) Neoplasms

I. Astrocytic Tumors

  • Most common primary intracranial neoplasms in adults. Unknown etiology. Typically arise in cerebral hemispheres.
  • Presentation: Headaches, seizures, focal neurological signs.
  • Histological Spectrum & Grading (WHO): Differentiation dictates grade and prognosis. Higher grade = worse outcome. Key genetic alterations drive progression.

Grade

Tumor Type

Histological Features

Genetic Alterations

Average Survival

II

Diffuse Astrocytoma

Slightly increased glial cellularity, mild atypia

P53 mutation, PDGFR-A overexpression

~5 years

III

Anaplastic Astrocytoma

Increased cellularity, greater atypia, mitotic figures

RB and P16 mutations added

~3 years

IV

Glioblastoma

Highly aggressive; atypical astrocytes, necrosis, vascular proliferation

(Above + more aggressive changes)

<1 year

II. Oligodendroglial Tumors

  • Usually arise in cerebral hemispheres.
  • Presentation: Neurological signs or seizures.
  • Genetic Alterations: Loss of heterozygosity at chromosomes 1p and 19q is common. Progression to anaplastic histology involves loss of 9p and 10q, and CDKN2A mutations.

Grade

Tumor Type

Histological Features

Genetic Alterations

Average Survival

II

Oligodendroglioma

Well-differentiated; round nuclei, clear cytoplasm, calcification common

1p/19q loss

~10 years

III

Anaplastic Oligodendroglioma

Increased cellularity, atypia, increased mitotic activity

1p/19q loss, 9p/10q loss, CDKN2A mutations

2-3 years

III. Ependymal Tumors

  • Originate from ependymal-lined ventricular system.
  • Location: Adults – mostly spinal cord; Children – mostly around fourth ventricle.
  • Histology: Mostly well-differentiated (WHO grade II); regular round nuclei, fibrillary background, glandular structures, perivascular rosettes.
  • Prognosis: Children (posterior fossa) ~50% 5-year survival; Adult spinal tumors have better outcomes.

IV. Meningiomas

  • Composed of neoplastic meningothelial cells.
  • Location & Appearance: Usually smooth, well-circumscribed, adherent to dura mater; can infiltrate skull.
  • Grading (WHO) & Prognosis: Most are low-grade (I), low recurrence risk post-surgical excision.

Grade

Tumor Type

Histological Features

Prognosis

I

Meningioma

Low mitotic activity, minimal atypia

Low recurrence risk post-surgical excision

II

Atypical Meningioma

Increased mitotic activity, cytological atypia or necrosis

Higher recurrence rate; may require radiotherapy

III

Anaplastic Meningioma

Markedly atypical cells, very high mitotic activity

Aggressive, malignant

V. Medulloblastoma

  • Predominantly in children. Primitive embryonal tumor, exclusively in cerebellum.
  • Presentation: Rapid growth, hydrocephalus. Can disseminate via CSF.
  • Histology: Very cellular; mitotically active small cells, hyperchromatic nuclei, scant cytoplasm.
  • Prognosis: Rapid growth; fatal without treatment; ~75% 5-year survival with treatment.

VI. Primary CNS Lymphomas

  • Lymphomas arising in CNS without extra-CNS disease.
  • Association: Strong association with immunosuppression.
  • Most common type: Diffuse large B-cell lymphoma; sheets of large atypical B-lymphoid cells.

VII. CNS Metastases

  • Occur at grey-white matter junction.
  • Common Primary Cancers: Breast, lung, renal, melanoma.
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Pathology - Intracerebral Haemorrhage (ICH)
I. Definition:
  • Spontaneous (non-traumatic) bleeding into the brain tissue. Crucially, this differentiates it from other types of strokes.
II. Epidemiology:
  • Accounts for approximately 20% of all strokes.
  • Predominantly affects individuals in late middle age. Note the age range for highest risk.
III. Aetiology (Causes):
  • Hypertension (High Blood Pressure): This is the most frequent cause. Understand the strong link between uncontrolled hypertension and ICH.
  • Less Common Causes: These are important to remember for differential diagnosis:
    • Cerebral amyloid angiopathy (CAA)
    • Ruptured arteriovenous malformation (AVM)
    • Coagulation disorders (problems with blood clotting)
IV. Pathogenesis (Mechanism):
  • Hypertension-related ICH: Mostly caused by the rupture of Charcot-Bouchard microaneurysms (small, weakened areas in blood vessels). Focus on understanding this key mechanism.
  • Haematoma Formation: The resulting blood clot (hematoma) destroys brain tissue and rapidly increases intracranial pressure (ICP). This pressure increase is the primary cause of morbidity and mortality.
V. Clinical Presentation:
  • Sudden Onset: The symptoms appear abruptly.
  • Focal Neurological Deficits: Symptoms depend on the location of the bleed. Remember that the location dictates the specific neurological symptoms.
  • Raised Intracranial Pressure (ICP) Symptoms: These are common and can include headache, vomiting, altered consciousness.
  • Mortality Risk:
    • Large hemorrhages can cause death rapidly due to high ICP and herniation (brain tissue displacement).
    • Even small hemorrhages in vital brainstem areas (controlling breathing and heart rate) can be fatal.
VI. Macroscopic Findings (Gross Examination):
  • Haematoma: Visible blood clot replacing brain tissue.
  • Mass Effect: The hematoma pushes on surrounding brain structures, causing midline shift and potentially herniation.
  • Location:
    • Hypertensive bleeds: Usually in basal ganglia, internal capsule, pons, or cerebellum.
    • Other cause bleeds: More likely to be in the lobes (lobar). This helps in differential diagnosis.
VII. Histopathological Findings (Microscopic Examination):
  • Early Stages: Blood clot surrounded by brain tissue with hypoxia (lack of oxygen) and edema (swelling).
  • Later Stages: Reactive astrocytes (glial cells) proliferate, and the damaged area organizes similarly to an infarct (area of dead tissue from lack of blood supply).
VIII. Prognosis:
  • High Mortality Rate: >40% mortality due to the devastating effects of raised intracranial pressure. This highlights the seriousness of ICH.
Key Concepts to Master:
  • Relationship between hypertension and ICH: This is the cornerstone of understanding this condition.
  • Pathophysiology of haematoma formation and its consequences: Understand the chain of events leading to increased ICP and potential death.
  • Clinical presentation variations based on location: Different areas of the brain will cause different symptoms.
  • Differential diagnosis based on location and etiology: Knowing the likely cause based on the location of the hemorrhage.​
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Pathology- Creutzfeldt-Jakob Disease (CJD)
I. Definition & Epidemiology:
  • Definition: CJD is a rare, fatal spongiform encephalopathy caused by the accumulation of misfolded prion protein (PrP) resistant to normal cellular breakdown. It's the most common human prion disease.
  • Epidemiology: Extremely rare, with an annual incidence of approximately 1 per 1,000,000.
II. Etiology (Causes):
  • Sporadic CJD: Spontaneous, random misfolding of normal PrP into the abnormal PrP form. The exact mechanism remains unclear.
  • Familial CJD: Inherited mutations in the PRNP gene increase the likelihood of PrP misfolding.
  • Variant CJD (vCJD): Believed to be transmitted via consumption of beef contaminated with PrPSc from cattle with bovine spongiform encephalopathy (BSE, "mad cow disease").
III. Pathogenesis (Disease Mechanism):
  • Misfolded Protein Propagation: The presence of abnormal PrPSc acts as a template, causing normal PrPC to misfold into the abnormal form.
  • Exponential Growth & Cell Death: This process leads to an exponential increase in PrPSc, ultimately causing neuronal cell death and the characteristic brain damage.
IV. Clinical Presentation:
  • Sporadic CJD: Typically affects middle-aged and elderly individuals. Onset is marked by rapidly progressing neurological symptoms.
  • Variant CJD (vCJD): Affects younger individuals (<30 years old). initially presents with psychiatric symptoms, followed by cerebellar ataxia (problems coordination and balance) dementia. < />pan>Key difference from sporadic CJD.
V. Histopathology (Microscopic Findings):
  • Sporadic CJD & vCJD: Both show spongiform changes (vacuolation of grey matter), neuronal loss (death of nerve cells), and gliosis (scarring in the brain).
  • Variant CJD (vCJD only): The presence of numerous "florid plaques" composed of amyloid forms of PrPSc is a key distinguishing neuropathological feature. These are absent in other CJD forms.
VI. Prognosis:
  • Currently, no effective treatment exists for CJD. The disease is invariably fatal.​

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Pathology-Motor Neurone Disease (MND)
I. Definition & Epidemiology:
  • Definition: MND is a group of neurodegenerative diseases causing selective loss of motor neurons. This means the nerve cells that control voluntary muscle movement are progressively destroyed.
  • Epidemiology:
    • Rare disease: Annual incidence 1-5 per 100,000.
    • Slight male predominance.
    • Typical onset: 50-70 years old.
II. Aetiology (Causes):
  • Mostly Idiopathic: In most cases (90%), the cause is unknown.
  • Familial (Inherited): Approximately 10% of cases are inherited, showing a genetic component.
  • Genetic Links: Several genes associated with familial MND have been identified, including SOD1, TDP-43, and FUS.
III. Pathogenesis (Disease Mechanisms):
  • Poorly Understood: The precise mechanisms driving MND remain largely unclear, even with insights from familial cases.
  • RNA Metabolism Dysfunction: A leading hypothesis points to defects in RNA metabolism as a crucial factor in motor neuron degeneration. This is based on the properties of TDP-43 and FUS proteins.
  • TDP-43 & FUS: Both are RNA/DNA-binding proteins with similar structures. Their dysfunction is strongly implicated in MND development.
IV. Clinical Presentation:
  • Muscular Symptoms: Asymmetrical muscle weakness and wasting (atrophy), muscle twitching (fasciculations), and muscle stiffness (spasticity) in limbs are common early signs.
  • Bulbar Symptoms: Difficulty with swallowing (dysphagia), chewing, speaking (dysarthria), coughing, and breathing (dyspnea) are characteristic as the disease progresses and affects the muscles controlling these functions.
  • Cognitive Changes: Cognitive impairment can also occur in some cases.
V. Macroscopic & Microscopic Findings:
  • Macroscopy (Gross Examination): The anterior roots of the spinal cord (which carry motor neuron axons) are atrophied (shrunken).
  • Histopathology (Microscopic Examination):
    • Selective loss of motor neurons in the motor cortex (brain) and anterior horns of the spinal cord is the defining feature.
    • In sporadic (non-inherited) MND, remaining motor neurons often contain abnormal protein inclusions that include ubiquitin and TDP-43.
VI. Prognosis:
  • Progressive & Fatal: MND is typically progressive, leading to death within a few years.
  • Cause of Death: Aspiration pneumonia (lung infection from inhaling food or saliva due to swallowing difficulties) is a frequent cause of death.




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Pathology- Huntington's Disease
I. Definition & Epidemiology:
  • Definition: HD is an inherited, neurodegenerative disorder resulting from a mutation in the HTT gene. This mutation leads to the production of a dysfunctional huntingtin protein.​
  • Epidemiology:
    • Prevalence: 5-10 per 100,000 globally, with geographical variation.
    • Onset: Typically 35-45 years, but can occur at any age.
    • Sex: Affects men and women equally.
    • Inheritance: Autosomal dominant (only one affected copy of the gene is needed to develop the disease).
II. Genetics:
  • HTT Gene: Contains a CAG trinucleotide repeat sequence.
    • Normal HTT: Less than 36 CAG repeats.
    • Mutant HTT: More than 36 CAG repeats. The number of repeats directly correlates with disease severity and age of onset (more repeats = earlier onset, greater severity).
  • Anticipation: The number of CAG repeats tends to increase in subsequent generations, leading to earlier onset and more severe disease in offspring. This phenomenon is known as anticipation.
III. Pathogenesis:
  • Huntingtin Protein (HTT): The protein encoded by the HTT gene has various cellular functions and is expressed throughout the body, but is most concentrated in the brain and testes.
  • Mechanism of Disease: Mutated huntingtin protein is cytotoxic (toxic to cells), particularly affecting neurons in the caudate nucleus and putamen (basal ganglia structures crucial for movement control).
IV. Clinical Presentation:
  • Early Symptoms: Uncontrolled, jerky, involuntary movements (chorea).
  • Progressive Disease: Over time, HD leads to progressive motor, neuropsychiatric (mood disorders, cognitive issues), and cognitive decline, ultimately culminating in dementia.
V. Macroscopic & Microscopic Findings:
  • Macroscopy: Significant atrophy (shrinking) of the caudate nucleus and putamen. Cortical atrophy may also be present.
  • Histopathology: Marked neuronal loss in the caudate nucleus. Surviving neurons contain excessive amounts of the mutated huntingtin protein.
VI. Prognosis:
  • Survival: Average survival is approximately 20 years from symptom onset, but varies depending on the number of CAG repeats (more repeats = shorter survival).
  • Cause of Death: Often pneumonia or cardiac failure due to mutated huntingtin expression in cardiac muscle.
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Pathology-Parkinson's Disease
I. Definition & Epidemiology:
  • Definition: Parkinson's disease is a neurodegenerative disorder. Clinically, it's characterized by parkinsonism (a group of motor symptoms); histologically (microscopically), it's defined by neuronal loss in the brain and the presence of Lewy bodies (abnormal protein aggregates) concentrated in the substantia nigra. Crucially, parkinsonism itself is not diagnostic of Parkinson's Disease.
  • Epidemiology: Primarily affects the elderly. Prevalence is approximately 1% in individuals over 60 years old.
II. Aetiology (Causes):
  • Mostly Unknown: The cause of most Parkinson's cases remains unclear.
  • Genetic Factors (Rare Cases): Rarely, inherited mutations in the PARK1 gene (chromosome 4), which codes for α-synuclein (a protein component of Lewy bodies), are implicated.
III. Pathogenesis (Disease Mechanism):
  • Dopamine Deficiency: Neurons in the substantia nigra project to the putamen and globus pallidus (basal ganglia structures crucial for movement). These neurons release dopamine, a neurotransmitter essential for controlling movement. In Parkinson's, dopamine release is significantly reduced.
  • Movement Disorder: The lack of dopamine leads to the characteristic movement disorders.
IV. Presentation (Symptoms):
  • Parkinsonism: The classic triad of symptoms includes:
    • Tremor: Involuntary shaking.
    • Rigidity: Stiffness and resistance to movement.
    • Bradykinesia: Slowness of movement.
  • Important Note: Parkinsonism can result from various causes (drugs, toxins, infections, trauma) and isn't solely indicative of Parkinson's disease.
V. Macroscopic & Microscopic Findings:
  • Macroscopy (Gross Examination): Shows pallor (loss of color) in the substantia nigra and locus ceruleus (brain regions).
  • Histopathology (Microscopic Examination): Reveals:
    • Loss of pigmented neurons in the substantia nigra.
    • Presence of Lewy bodies within remaining neurons.
VI. Prognosis & Treatment:
  • Treatment: Dopamine-replacement therapies can alleviate parkinsonism symptoms. However, these treatments do not slow or stop the disease's progression.
  • Variable Progression: The rate of disease progression varies significantly between individuals.
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Pathology - Cerebral Infarction
I. Definition & Epidemiology
  • Definition: Cerebral infarction is ischemic (lack of blood flow) necrosis (tissue death) of a brain region. This is crucial to understand
  • the fundamental nature of the condition.
  • Epidemiology: It's the most common type of stroke (~80%), predominantly affecting the elderly. Remember this high prevalence and its association with age.
II. Aetiology (Causes)
  • Thromboembolism: The majority of cases result from blood clots (thromboemboli) originating in the internal carotid artery or the left side of the heart. These clots travel to and block a cerebral artery. Understand the source of the emboli is key here.
  • In situ thrombosis: A smaller percentage arises from clots forming directly within a cerebral artery, often due to atherosclerosis (hardening of the arteries). Distinguish between emboli and in situ thrombosis.
III. Pathogenesis (Mechanism)
  • Artery Occlusion: Sustained blockage of a cerebral artery leads to ischemia and subsequent necrosis in the brain area supplied by that artery. The longer the occlusion, the greater the damage.
IV. Presentation (Symptoms)
  • Rapid Onset: Cerebral infarction presents with a sudden onset of neurological symptoms specific to the affected artery's distribution. This is a hallmark of stroke.
  • Middle Cerebral Artery Involvement: Most infarctions affect the middle cerebral artery, resulting in contralateral (opposite side) hemiplegia (paralysis) or hemiparesis (weakness), homonymous hemianopia (loss of half of the visual field in both eyes), and dysphasia (language impairment). Memorize these common symptoms and their locations.
  • Transient Ischemic Attacks (TIAs): TIAs are brief episodes of focal neurological symptoms (less than 24 hours) that serve as significant warning signs for future infarction. Recognize TIAs as crucial predictors.
V. Macroscopic Changes (Visible with the Naked Eye)
  • 24 hours: The infarcted area softens, and the grey-white matter boundary becomes indistinct. Cerebral edema (brain swelling) and midline shift may occur.
  • 48 hours - 10 days: The infarct becomes gelatinous, and the distinction between infarct and normal tissue clarifies.
  • 10 days - 3 weeks: Liquefaction (conversion to liquid) and cystic changes (cavity formation) develop.
  • Hemorrhagic Infarct: Reperfusion (restoration of blood flow) can sometimes lead to bleeding into the infarcted area.
Remember the temporal progression of macroscopic changes.
VI. Histopathology (Microscopic Changes)
  • First 48 hours: Ischemic neuronal changes (shrunken, eosinophilic neurons) and neutrophil (white blood cell) infiltration are observed.
  • Later Stages: Mononuclear cells (other white blood cells) remove myelin debris, and astrocytes (glial cells) proliferate as the infarct heals.
VII. Prognosis & Complications
  • Mortality: High initial mortality (20% at 1 month), followed by a 10% annual mortality rate.
  • Complications: Pneumonia, depression, contractures (muscle shortening), constipation, bedsores, and significant emotional impact on the family are common. Remember the range of potential complications.
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Pathology - Subarachnoid Hemorrhage (SAH)
I. Definition & Epidemiology:
  • Definition: Bleeding into the subarachnoid space (the space between the arachnoid mater and pia mater surrounding the brain).
  • Incidence: Approximately 8 cases per 100,000 people annually.
  • Age of Onset: Most common in adults aged 35-65.
II. Etiology & Pathogenesis:
  • Primary Cause: Rupture of a berry aneurysm (a small, saccular aneurysm, usually at arterial bifurcations).
  • Aneurysm Formation: Hypothesized to result from a congenital defect in the tunica media (middle layer) of cerebral vessels, exacerbated by later-life atherosclerosis and hypertension. Crucially, most berry aneurysms do not rupture.
  • Location of Aneurysms: Most commonly found at the base of the brain, specifically:
    • Anterior communicating artery (40%)
    • Middle cerebral artery (34%)
    • Internal carotid artery (20%)
    • Posterior cerebral artery (4%)
  • Rupture Mechanism: Rupture leads to extensive subarachnoid hemorrhage, potentially extending into the brain parenchyma (brain tissue itself).
III. Clinical Presentation:
  • Cardinal Symptom: Sudden, severe headache, often described as a "thunderclap" headache or feeling like being hit on the back of the head.
  • Precipitating Factors: Exertion or straining can trigger rupture.
  • Severity: Can range from unconsciousness to immediate death in severe cases.
IV. Macroscopic & Microscopic Findings:
  • Macroscopy: Blood is found in the subarachnoid space, frequently accumulating around the circle of Willis at the brain's base. The ruptured berry aneurysm may be visible after clot removal.
  • Histopathology: The aneurysm wall lacks a muscular media layer; it consists of a thick fibrous intima (inner layer) and an outer adventitia (outer layer).
V. Prognosis:
  • Tripartite Outcome: Prognosis is generally categorized into thirds:
    • ⅓ Immediate Death: Due to tonsillar herniation (brain stem compression) from massive intracranial pressure increase.
    • ⅓ Unconscious with High Risk: High risk of mortality or permanent neurological deficits.
    • ⅓ Good Outcome: Provided there is no re-bleeding.
VI. Key Concepts for Understanding:
  • Congenital Weakness: The underlying congenital defect in the arterial wall is crucial to understanding aneurysm formation.
  • Atherosclerosis & Hypertension: These conditions exacerbate the congenital weakness, increasing rupture risk.
  • Location Matters: The specific location of aneurysms dictates potential neurological consequences based on affected arteries.
  • Rapid Onset: The sudden, severe headache is a hallmark symptom reflecting the acute nature of the hemorrhage.
  • Variable Outcome: The significant variability in outcomes highlights the severity and unpredictable nature of SAH.​
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Facts about medicine and its subtopic such as anatomy, physiology, biochemistry, pharmacology, medicine, pediatrics, psychiatry, obstetrics and gynecology and surgery.