Amyloid angiopathy

Vascular Neurology

1.1 Amyloid angiopathy

■ Most common.

■ The etiology is assumed that the arteries affected by amyloidosis are so fragile that minor injury may cause a hemorrhage.

1.2 Cerebral vasculitis

■ Can be very diffi cult to diagnose as most tests are often negative.

■ Biopsy may be needed to confi rm the diagnosis.

■ Patients do not have to manifest systemic vasculitis.

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Multiple hemorrhages are rare. Patients with intracerebral hemorrhage and a history of hypertension rarely have multiple bleeds, as the etiology is thought to be lipohyalinosis and microaneurysms.

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Multiple hemorrhages, either at the same time or separated by days, are suggestive of amyloid angiopathy.

1.3 Hemorrhages from tumors

■ The hemorrhages may be multiple sites from a primary intracerebral tumor or from multiple locations of metastatic tumors.

1.4 Head injury

2 Systemic conditions: usually as a result of a defect in homeostasis 2.1 Disseminated intravascular coagulation (DIC)

2.2 Thrombocytopenia

2.3 Clotting disorders, e.g. hemophilia

Primary intraventricular hemorrhage

1 Occult arteriovenous malformations

◆ Idiopathic intraventricular hemorrhage is often speculatively attributed to oc-cult AVMs in the ependymal wall or choroid plexus.

◆ Rupture of the dural fi stula of the superior sagittal sinus can also result in intraventricular hemorrhage.

2 Uncommon aneurysms

◆ Aneurysms of the posterior inferior cerebellar artery and anterior inferior cere-bellar artery.

3 Tumors

◆ Pituitary tumors

◆ Ependymoma

◆ Meningioma 4 Others

◆ Brain abscess

◆ Moyamoya syndrome

◆ Lacunar infarction

◆ Cocaine, amphetamine

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Intraventricular hemorrhage is usually associated with either subarachnoid hemorrhage from a ruptured aneurysm (most often in the anterior communicating artery) or intracerebral hemorrhage.

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In both conditions, the outcome is worse with intraventricular rupture than without, and an intraventricular blood volume of more than 20 ml is almost invariably fatal.

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The outcome of primary intraventricular hemorrhage without a detectable cause is much better than if it is associated with SAH or intraparenchymal hemorrhage.

Intracranial aneurysms: description and types

1 Saccular or Berry aneurysm

◆ The most common type of aneurysm

◆ Forms as a result of congenital weakness in the media and elastica of the arte-rial wall. Common locations are at branching points where the parent vessel is curving including:

■ Anterior cerebral/anterior communicating artery

■ Internal carotid/posterior communicating artery

■ Middle cerebral artery

■ Posterior inferior cerebellar artery

◆ Arterial stress (age and hypertension) are important risk factors in the growth of aneurysms.

2 Fusiform aneurysm

◆ Atherosclerotic dilatations, usually of the vertebral and basilar artery.

3 Mycotic aneurysm

◆ Results from endocarditis with septic emboli to the vasa vasorum with second-ary destruction of the vessel wall so that all is left is the intima.

◆ Tends to be peripheral in the middle cerebral artery distribution, and multiple peripheral aneurysms should suggest the diagnosis.

4 Neoplastic aneurysm

◆ Results from tumor emboli and subsequent growth of tumor through the ves-sel wall.

◆ Occurs in atrial myxoma and choriocarcinoma.

5 Dissecting or traumatic aneurysm

◆ May occur after the trauma or spontaneously.

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An aneurysm is a focal dilatation of an artery. There are many different types of aneurysm, as listed below. The most frequent aneurysm in the CNS is the berry aneurysm.

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At present, the defi nite diagnosis of aneurysm is made on conventional angiography.

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An organized hematoma from a vessel that has bled is called a

pseudoaneurysm. There are no vessel walls, and the hematoma is confi ned by the adventitia.

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The diagnosis of aneurysm should not be missed. Subarachnoid hemorrhage (SAH), a complication of ruptured aneurysm, carries a signifi cant mortality and morbidity. 15% of patients with SAH die before reaching the hospital.

Rebleeding occurs in 20% of patients within 2 weeks, in 30% by 1 month, and in 40% by 6 months. Rebleeding is associated with an increased mortality of more than 40%.

Intracranial aneurysms: locations and associations

The most common locations are:

1 The anterior communicating artery (30%)

2 The junction of posterior communicating with internal carotid artery (25–30%) 3 The bifurcation of internal carotid and middle cerebral artery (20–25%) 4 The tip of the basilar artery (5–10%)

5 Infratentorial – posterior inferior cerebellar artery, body of the basilar, anterior inferior cerebellar artery (1–3%)

Associations:

1 Polycystic kidney disease (PKD)

◆ Autosomal dominant.

◆ 10–30% of patients with PKD have intracerebral aneurysms.

2 Fibromuscular dysplasia

◆ 25% of patients have aneurysms.

3 Family history

◆ Aneurysms found in 9.5% of patients with a family history of intracranial aneurysms.

4 Coarctation of aorta; anomalies of the circle of Willis 5 Moyamoya disease

6 Ehler-Danlos syndrome 7 Neurofi bromatosis type 1

8 Other possible associations: sickle cell disease, Marfan syndrome, vasculitis, tumors, infections.

Risk of hemorrhage:

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0.5% annual risk of aneurysmal rupture – no prior history and aneurysm <10 mm

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up to 6% annual risk of aneurysmal rupture – aneurysm >25mm

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Overall prevalence of saccular aneurysm in the general population is 9.6 per 100,000.

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Peak incidence is in the 6th decade of life. Rare in children and adolescents.

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Multiple in 15–20% of cases, especially in mirror locations.

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Aneurysms that rupture are usually more than 7–8 mm.

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Aneurysms that are larger than 25 mm (giant aneurysms) more often behave like space-occupying lesions.

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85–95% of aneurysms involve the circle of Willis and 5–15% are located in the vertebrobasilar circulation.

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Factors predisposing to rupture:

◆ Increasing age

◆ Female gender

◆ Hypertension

◆ Alcohol

◆ Smoking

◆ History of spontaneous dissections

Intracranial aneurysms: patterns of hemorrhage from a ruptured aneurysm

The following patterns of hemorrhage can occur in combinations.

1 Brain parenchyma

◆ Intracerebral hematomas usually give a good indication of the site of the rup-tured aneurysm.

◆ Aneurysms from the posterior circulation rarely give rise to intraparenchymal hematomas.

Location of hematoma Location of aneurysm

Midline or paramedian frontal areas Anterior cerebral or anterior communicating artery Frontal lobe, not close to the midline Ophthalmic artery

Between the frontal horns Anterior communicating artery Medial part of the temporal lobe Posterior communicating artery

Lateral fi ssure Middle cerebral artery

2 Subarachnoid cisterns

◆ The pattern of hemorrhage is less specifi c for the site of the aneurysm, especially if the hemorrhage is diffuse. However, the source can sometimes be inferred if the hemorrhage remains confi ned to one or is most dense in a single cistern.

3 Intraventricular hemorrhage

◆ Intraventricular hemorrhage occurs mostly with aneurysms of the anterior communicating artery, which can bleed through the lamina terminalis to fi ll the third and lateral ventricles.

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The distribution of extravasated blood on brain CT is an invaluable guide in determining the presence and the site of an offending aneurysm, and therefore in planning the order and the extent of angiography, especially in elderly patients in whom surgical repair is not always indicated.

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Identifying the source of hemorrhage from the scan is very helpful if more than one aneurysm is found, because there is a signifi cant difference in management between a ruptured and an unruptured aneurysm.

◆ Rupture of an aneurysm at the posterior inferior cerebellar artery may prefer-entially fi ll the fourth and the third ventricle from the back.

4 Subdural hematomas

◆ Subdural hematomas develop with aneurysmal rupture in 2–3%, most often associated with subarachnoid blood, but sometimes as the only manifesta-tion.

Abrupt severe headache: ‘worst headache of my life’

1 Sudden onset of severe headache WITH neck rigidity 1.1 Subarachnoid hemorrhage

■ Headache is the cardinal feature in SAH, classically occurring in a split second, ‘like a blow on the head’ or ‘an explosion inside the head’, reach-ing a maximum within seconds. The headache is generally diffuse and poorly localized but tends to spread within minutes or hours to the back of the head, neck, and back as blood tracks down the spinal subarach-noid space.

■ Consider subarachnoid hemorrhage whenever a patient complains of the sudden onset of ‘the worst headache of my life’.