Intracerebral hemorrhage

An intracerebral hemorrhage, or intraparenchymal cerebral hemorrhage, is a subset of an intracranial hemorrhage as well as of stroke defined by the acute accumulation of blood within the brain parenchyma. This article concerns non-traumatic intracerebral hemorrhages; traumatic hemorrhagic cerebral contusions are discussed separately.

Terminology

By convention, intracerebral hemorrhage refers to macroscopically visible, recent hemorrhages. In contrast, cerebral microbleeds are discussed separately.

Pathology

Intracerebral hemorrhages arise from rupture of a small blood vessel within the brain parenchyma or, less commonly, of a blood vessel adjacent to the parenchyma (jet hematoma).

Etiology

Non-traumatic intracerebral hemorrhages were historically etiologically divided according to whether or not they have an underlying structural lesion or bleeding diathesis.

1. spontaneous intracerebral hemorrhage presumed due to small vessel disease (formerly primary intracerebral hemorrhage ¹⁰)

   • hypertensive microangiopathy

   • cerebral amyloid angiopathy

2. secondary intracerebral hemorrhage: hemorrhage complicating some underlying structural lesion or bleeding diathesis

   • hemorrhagic transformation of infarct (ischemic stroke)

   • vascular malformation (e.g., brain arteriovenous malformation, cerebral cavernous malformation)

   • tumor (e.g., metastases, glioblastoma)

   • cerebral venous thrombosis

   • bleeding diathesis (e.g., anticoagulation therapy)

Location

Non-traumatic intracerebral hemorrhages are classified by location, which vary by etiologic association ⁹.

1. lobar intracerebral hemorrhage: in any lobe(s) of the cerebral hemispheres in a cortical and/or subcortical location (excluding deep hemispheric and infratentorial regions)

2. non-lobar intracerebral hemorrhage: in deep hemispheric or infratentorial location

   1. deep hemispheric (basal ganglia, thalamus, internal capsule)

   2. brainstem (pons, midbrain, medulla)

   3. cerebellum

Radiographic features

CT

CT is usually the modality first obtained and demonstrates a hyperdense collection of blood, often with surrounding hypodense edema. A number of complications may be present, such as extension of the hemorrhage into other intracranial compartments, hydrocephalus, herniation, etc.

A number of CT features can predict the likelihood of hemorrhage expansion and are therefore useful in decision-making and prognosis.

• non-contrast CT

  • hemorrhage size

    • the volume of an intracerebral hemorrhage can be measured using ABC/2 formula or 3D volumetric software

    • hemorrhage size is considered to be the most reliable independent predictor of ICH expansion

    • hematoma expansion is measured as an increased growth >12.5 mL or volume >33% from the initial CT scan

    • hematomas with a volume of more than 30 mL are more prone to expansion

  • hemorrhage shape

    • intracerebral hemorrhage irregularity is thought to be due to multiple leaking vessels feeding the hematoma

    • hemorrhages with irregular shapes are more prone to expansion

  • hemorrhage density

    • the presence of hypodense or isodense regions within the hyperdense intracerebral hemorrhage represents active bleeding and is called swirl sign

    • when the swirl sign is encapsulated it is termed black hole sign

    • the presence of a relatively hypodense area adjacent to a hyperdense area is termed the blend sign

    • heterogeneous hemorrhage with hypodense foci is more prone to expansion

  • intraventricular hemorrhagic extension​

    • intraventricular hemorrhagic extension occurs due to decompression of the hemorrhage into the low resistance ventricular system, thus; hematomas located in the thalamus, caudate nucleus or pons are more prone to intraventricular extension than lobar hematomas

    • a study has shown that lenticular and lobar hematomas with accompanying intraventricular extension displayed a higher proportion of hematoma expansion ⁵​

• contrast-enhanced CT

  • active contrast extravasation within hematoma predicts future hemorrhage expansion, this can be observed on CT angiography (CTA) as spot sign and pooling of contrast within the hematoma

MRI

Findings depend on the size and age of the bleed (see aging blood on MRI).

Practical points

With any intracerebral hemorrhage the following points should be included in a report as they have prognostic implications ³:

• location

• size/volume

  • the ABC/2 formula is widely used, but there may be more accurate formulas (e.g. 2.5ABC/6, SH/2) and analyzes available, some of which, however, may require the addition of specific software to the standard PACS tools

• shape (irregular vs regular)

• density (homogeneous vs heterogeneous)

• presence/absence of substantial surrounding edema that may indicate an underlying tumor

• presence/absence of intraventricular hemorrhage

• presence/absence of hydrocephalus

• when CT angiography is performed, the presence/absence of the CTA spot sign or a vascular malformation

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