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For further information, see CMDT Part 24-09: Stroke

Key Features

Essentials of Diagnosis

  • Sudden onset of subarachnoid or intracerebral hemorrhage

  • Distinctive neurologic signs reflect the region of the brain involved

  • Signs of meningeal irritation in patients presenting with subarachnoid hemorrhage

  • Seizures or focal deficits may occur

General Considerations

  • Result from a localized maldevelopment of part of the primitive vascular plexus

  • Consist of abnormal arteriovenous communications without intervening capillaries

  • Vary in size, ranging from massive lesions that are fed by multiple vessels and involve a large part of the brain to lesions so small that they are hard to identify at arteriography, surgery, or autopsy

  • In approximately 10% of cases, there is an associated arterial aneurysm, while 1–2% of patients presenting with aneurysms have associated arteriovenous malformations (AVMs)

  • Clinical presentation may relate

    • To hemorrhage from the malformation or an associated aneurysm

    • To cerebral ischemia due to diversion of blood by the anomalous arteriovenous shunt or due to venous stagnation

  • Regional maldevelopment of the brain, compression or distortion of adjacent cerebral tissue by enlarged anomalous vessels, and progressive gliosis due to mechanical and ischemic factors may also be contributory


  • Up to 70% of AVMs bleed, most commonly before the age of 40

  • Approximately 10% of cases are associated with arterial aneurysms, while 1–2% of patients with aneurysms have AVMs

Clinical Findings

Symptoms and Signs

  • Initial symptoms consist of

    • Hemorrhage in 30–60% of cases

      • Commonly intracerebral as well as into the subarachnoid space

      • Fatal in about 10% of cases

    • Recurrent seizures in 20–40%: more likely with frontal or parietal AVMs

    • Headaches in 5–25%

      • Especially likely when the external carotid arteries are involved in the malformation

      • Sometimes simulate migraine but more commonly are nonspecific in character, with nothing about them to suggest an underlying structural lesion

    • Miscellaneous complaints (including focal deficits) in 10–15%

  • Brainstem and cerebellar AVMs may cause obstructive hydrocephalus

  • Abnormal mental status and signs of meningeal irritation in patients with subarachnoid hemorrhage

  • Additional findings may help localize the lesion and sometimes indicate that intracranial pressure is increased

  • Cranial bruit

    • Always suggests the possibility of a cerebral AVM

    • May also be found with aneurysms, meningiomas, acquired arteriovenous fistulas, and arteriovenous malformations involving the scalp, calvarium, or orbit

    • Best heard over the ipsilateral eye or mastoid region

    • May be some help in lateralization but no help in localization

    • Absence of a bruit does not exclude the possibility of AVM

Differential Diagnosis

  • Aneurysmal hemorrhage

  • Intracerebral hemorrhage from other causes

  • Space-occupying lesion, eg, brain tumor


Imaging Studies

  • CT scanning

    • Indicates whether subarachnoid or intracerebral bleeding has recently occurred

    • Helps localize source of bleeding

    • May reveal the AVM

  • Arteriography


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