Morphology Saccular Fusiform Dissecting Size



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Intracranial Aneurysms:
An Overview

Surgical Classification of Intracranial Arterial Aneurysms



  • Morphology

    1. Saccular

    2. Fusiform

    3. Dissecting

  • Size

    1. <3 mm

    2. 3-6 mm

    3. 7-10 mm

    4. 11-25 mm

    5. >25 mm (giant)

  • Location

    1. Anterior circulation arteries

      • Internal carotid

      • Anterior cerebral

      • Middle cerebral

    2. Posterior circulation arteries

      • Vertebral

      • Basilar

      • Posterior cerebral

Etiology of Saccular Intracranial Arterial Aneurysms

  • Hemodynamic

  • Structural

  • Genetic

  • Traumatic

  • Infectious

  • Neoplastic

  • Other disorders affecting blood vessels

  • Radiation-induced

Etiology of Fusiform Intracranial Arterial Aneurysms

  • Atherosclerosis

  • Structural

  • Genetic

  • Infectious (syphilis)

  • Other disorders of blood vessels

  • Hemodynamic

  • Radiation-induced

Anatomic Sites of Aneurysms

  • 95% of aneurysms occur close to the circle of Willis.

  • Aneurysms usually arise from the distal carina of a bifurcation.

  • They are usually on the convexity of a curve and point in the direction that the proximal axial bloodstream would have taken if the curve were not there.

Size of Aneurysms


  • The size at which aneurysms usually begin to rupture is about 3 to 4 mm, and the size at which they begin to produce symptoms by means other than rupture is around 7mm.

  • The mean size of ruptured aneurysms is 8.6 mm.

  • Aneurysms of ≤10 mm 16% ruptured.

  • Aneurysms of ≥11 mm 91% ruptured.

Multiple Aneurysms

  • They constitute about 15% of all intracranial aneurysms.

  • “Mirror” aneurysms!

  • Which aneurysm has ruptured?

    • The largest one

    • The proximal one (if they are on the same vessel)

    • Angiographic signs:

      • Local mass

      • Local vasospasm

      • Irregular aneurysm shape

      • Intra-aneurysmal clot

    • Localized subarachnoid blood on CT

    • Use clinical signs

    • Consider an EEG

Aneurysms and Sex





  • There is a clear female predominance overall.




  • Female: male = 1.6: 1




  • Above age 40, there is an increasingly strong predominance of females.

Incidence of Aneurysm Rupture


  • 2% is the incidence of aneurysms in entire population. It will rupture in less than 1% of the population, and will be the cause of death in 0.5%.

  • Aneurysmal SAH accounts for 5 to10 percent of strokes.

  • The incidence of aneurysms as a cause of unexpected sudden death is around 4%.

  • Aneurysms constituted 77% of cases of SAH.

  • The annual incidence of aneurysmal SAH is 9 to 28 per 100,000.

Familial Occurrence of Aneurysms

  • There may be autosomal dominant inheritance in some families.

  • Familial aneurysms tend to rupture at a smaller size and in younger age.

  • Screening is recommended for family members aged 35 to 65 years. MRA is a useful screening tool.

  • Associated genetic syndromes are: Ehlers-Danlos, Marfan’s, and Weber syndromes. Angiography and surgery are extremely hazardous in such patients.

  • There is increased risk of aneurysms in patients with polycystic kidney disease.

Aneurysms of Infancy and Childhood

  • 2% of all intracranial aneurysms are discovered under 20 years of age.

  • 60% of pediatric aneurysms occur in boys.

  • 45% occur in the vertebrobasilar circulation.

  • 30% are giant.

  • Traumatic and bacterial aneurysms are more common.

Hemodynamics of Aneurysms

  • The impingement of an axial blood stream on a distal carina can generate forces that cause local destruction of the internal elastic membrane and initiate aneurysm formation.

  • Aneurysms are less elastic, stiffer and of thinner wall.

  • The distal apex is the actual site of rupture.

Pathology and Pathogenesis of Aneurysms

  • Damage to the internal elastic lamina by hemodynamic factors is the critical pathologic change.

  • All aneurysms show absence of media, it ends abruptly at neck of aneurysm.

  • Ruptured site is usually the thinnest area of the dome of the sac.

  • Lumen may contain thrombus.

  • Parent arteries usually shows atherosclerotic changes.

  • Factors that alter the blood flow (such as vessel occlusions, AVMs and hypertension) may accelerate the degenerative process.

Association of Aneurysms with Other Vascular Lesions

  1. Anatomic Variants

    • Primitive trigeminal artery

    • Hyperplasia of one anterior cerebral artery

2. Arteriovenous Malformations (AVMs)

    • 1% of patients with intracranial aneurysms had intracranial AVMs.

    • 10% of patients with AVMs have associated aneurysms.

    • Aneurysms occur on arteries feeding the AVM in 37 to77% of cases.

    • There is equal rates of hemorrhage from each lesion. In general, the symptomatic lesion should be treated first.

. Infundibular Widening of The Posterior Communicating Artery

4. Hypertension



    • It is not a major factor in the etiology of saccular aneurysms, although it may cause more aneurysms in susceptible individuals and may promote aneurysmal rupture.

5. Arterial Occlusions and Stenoses

    • Relation of aneurysms to carotid ligation and carotid endarterectomy.

Predisposing Factors to Aneurysm Rupture

. Activities at Time of Rupture



    • Lifting or bending (12%)

    • Emotional strain (4%)

    • Defecation (4%)

    • Coitus (4%)

    • Trauma (3%)

    • Coughing (2%)

    • Urination (2%)

    • Parturition (0.35%)

    • During sleep (1/3)

2. Smoking

3. Alcohol Consumption

4. During Angiography

Diagnosis of Aneurysmal Rupture



    • Usually attributed to aneurysm expansion or minor SAHs.

    • Features are:

      • Headache (48%)

      • Dizziness (10%)

      • Orbital pain (7%)

      • Diplopia (4%)

      • Loss of vision (4%)

      • Motor and sensory disturbances (6%)

      • Seizures (4%)

      • Ptosis (3%)

      • Bruits (3%)

      • Dysphasia (2%).

    • The average interval between the warning signs and major hemorrhage is about 3 weeks.

  • Clinical Presentation of Aneurysmal Rupture

    • 89% of patients with aneurysms present with SAH; 7% with tumor symptoms; and 4% found incidentally.

    • Features occur as follows:

      • Meningism (64%)

      • Coma (52%)

      • Nausia and vomiting (45%)

      • Generalized headache (32%)

      • Classic occipital headache (21%)

      • Reflex changes (19%)

      • Motor deficits (17%)

      • Dysphasia (13%)

      • Confusion (12%)

      • Intraocular hemorrhage (12%)

      • Anisocoria (11%)

      • Papilledema (9%)

    • The cardinal diagnostic feature remains a headache that is unusually severe for the patient and has a very sudden onset.

Symptoms and Signs Not due to Rupture

  • Distal Embolization from Partially Thrombosed Aneurysms

  • Neurological Signs from Giant Aneurysms (>25 mm)

    • Features are related to location, and may include: seizures, focal neurological deficits, and pain.

    • Giant aneurysms form about 9% of all intracranial aneurysms.

  • Cranial Nerve Signs from Nongiant Aneurysms

    • Posterior communicating-internal carotid artery aneurysms third cranial nerve involvement (87%)

    • Ophthalmic- internal carotid artery aneurysms loss of vision (29%); third cranial verve symptoms (19%); fifth (13%); fourth (10%); and sixth (6%).

Causes of Sudden Severe Headache

  • Intracranial

    • SAH

      • Aneurysm

      • AVM (cerebral, dural, spinal)

    • Pituitary apoplexy

    • Arterial dissection

    • Cerebral venous thrombosis

    • Other intracranial hemorrhages

    • Acute hydrocephalus

    • Other intracranial mass (neoplasm, abscess)

    • Meningitis, encephalitis




  • Extracranial

    • Dental disease

    • Sinusitis

    • Ocular disease (glaucoma)

  • Systemic

    • Hypertensive encephalopathy

    • Temporal arteritis

  • Benign

    • Migraine (common, classic)

    • Cluster

    • Tension

    • Benign exertional headache

    • Benign coital headache



Clinical Grading of SAH



  • Grading is important in treatment decisions and outcome prediction.

  • The most important factors predicting outcome are level of consciousness and presence of hemiparesis and/or aphasia.

  • World Federation of Neurological Surgeons Scale

Grade

Description

1

GCS 15, no motor deficit

2

GCS 13 to 14, no motor deficit

3

GCS 13 to 14, with motor deficit

4

GCS 7 to 12, with or without motor deficit

5

GCS 3 to 6, with or without motor deficit

Natural History of Aneurysms

  • Asymptomatic aneurysms bleed at a rate of 1 to 2% per year.

  • The highest mortality rate occurs immediately following the hemorrhage and diminishes rapidly thereafter.

  • Rebleeding is estimated to occur in 50% of cases of ruptured aneurysms within 6 months of the first hemorrhage, and thereafter at a rate of 3% per year.

  • 60% of patients die after rebleeding, and 25% are left disabled.

  • It is recommended that asymptomatic aneurysms be clipped in most patients

Medical Complications of Aneurysmal Rupture as Percentage

Cardiovascular

 

Hypertension

16.4

Arrhythmia

3

Hypotension

2.3

Cardiac failure

1.6

Thrombophlebitis

1.4

Respiratory

 

Pneumonia

5.7

Atelectasis

2.3

Adult RDS

1.8

Pulmonary edema

1.2




Endocrine

 

SIADH

2.7

Metabolic

 

Diabetes mellitus

1.8

Gastrointestinal

 

Hemorrhage

3.2

Hepatic failure

1.6

Renal

 

Failure

1.2

Hematologic

 

Anemia

4.9




Neurological Complications of Aneurysmal Rupture

  • Intracranial Pressure (ICP) Elevation

    • Patients in clinical grades I and II have a mean ICP of 10 mmHg; and in grades III and IV, 29 mmHg.

    • Patients with no vasospasm have a mean ICP of 16 mmHg; where as those with severe vasospasm have a mean level of 27 mmHg.

    • Increased ICP is usually due to an increase in CSF outflow resistance and block of the arachnoid villi.

    • Higher ICP is associated with higher mortality.

  • Hydrocephalus

    • Acute or chronic

  • Epilepsy

    • It seams reasonable in most young patients with middle cerebral hematomas should be treated with anticonvulsants for at least 2 years.

Causes of SAH Excluding Aneurysms and AVMs

  • Angiopathy

  • Venous thrombosis

  • Blood diseases

  • Allergic diseases

  • Infections

  • Intoxications

  • Tumors

  • Trauma


partially thrombosed mca aneurysmpartially thrombosed periophthalmic ica aneurysmperianeurysmal hemorrhage (left pca)perianeurysmal hemorrhagegiant cavernous aneurysm



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