The brain lies within the cranial cavity – the large hollow area in the upper part of the skull. The bone of the skull protects the delicate brain tissue. Only narrow passages in the bottom of the cranial cavity allows the nerves, blood vessels and lymphatic vessels to travel to and from the brain. Therefore the brain lies in its own enclose space. Sometimes there may be bleeding either within the brain tissue or in the cranial cavity. This is broadly referred to as bleeding in the brain.
What is Bleeding in the Brain?
Bleeding in the brain is a common term that is used to describe many vascular conditions within the cranial cavity or brain tissue itself. All instances are considered as medical emergencies and require professional assessment and monitoring. Bleeding occurs when a blood vessel ruptures at some point. When this occurs blood cannot reach the parts that lie after the site of the blood loss. Therefore portions of the brain can be starved of oxygen and nutrients. Brain tissue is highly sensitive to such changes. Within seconds a person can become dizzy and faint. After a few minutes there will be brain damage. Death will ensue shortly thereafter. Therefore any bleeding in the brain is a cause for concern.
Types of Bleeding in the Brain
The various terms used to describe different types of bleeding within the brain or cranial cavity can often beconfusing to a patient. The word hemorrhage refers to bleeding while hematoma is an accumulation of blood. Intracranial means within the cranial cavity, the part of the skull that houses the brain and related structures. Intracerebal means within the brain. It is important to note that since the cranial cavity is closed and due to the limited space within it, most hemorrhages (bleeding) will lead to a hematoma (collection of blood).
A hematoma is a collection of blood similar to a red to blue bruise that occurs on the skin with injury. Here a blood vessel ruptures and blood pools at the spot. This hematoma can be within the cranial cavity or brain tissue, hence the term intracranial and intracerebral respectively.
Intracranial hematoma therefore means an accumulation of blood within the cranial cavity, and not necessarily within the brain. It can occur between the brain and the skull bone. An intracerebral hematoma is a collection of blood within the brain and is also known as a cerebral hematoma.
The different types of hematomas include :
- Epidural hematoma where blood collects between the brain and outer meningeal layer (dura mater).
- Subdural hematoma where blood collects between the outer and middle layers of the meninges (dura and arachnoid mater)
- Intracerebral hematoma where blood collects within the brain tissue. It is often associated with cerebral edema (swelling of the brain). Cerebellar hematoma or brain-stem hematoma is an accumulation of blood within the cerebellum or brain stem respectively and are separate entities although often related.
A hemorrhage means bleeding, or sometimes commonly called free bleeding. Here the blood is leaking throughout the are and is not confined to one spot as with a hematoma. Since the cranial cavity where the brain sits is an enclose space, eventually the hemorrhage will reach a point where it cannot fill any additional space. This excess blood presses against the brain.
Intracerebral hemorrhage means bleeding within the brain tissue, while an intracranial hemorrhage is bleeding within the cranial cavity and not necessarily within the brain itself.
- Subarachnoid hemorrhage is bleeding into the subarachnoid space which lies between the arachnoid and pia mater of the brain meninges.
- Intracerebral hemorrhageis bleeding within the brain tissue and can be either an :
- Intraparenchymal hemorrhage where there is bleeding within the brain parenchyma
- Intraventricular hemorrhage where there is bleeding into the brain’s ventricular system, which is responsible for cerebrospinal fluid formation and circulation.
Causes of Bleeding in the Brain and Skull
An intracerebral hemorrhage or hematoma is considered as a sub-type of an intracranial hemorrhage or intracranial hematoma since the brain sits in the cranial cavity. Many of the same causes may contribute to either an intracranial hemorrhage or intracerebral hemorrhage. This includes :
- Trauma to the head – laceration or contusion due to blunt or sharp force that may be seen with assault, accidents and falls.
- Hypertension (high blood pressure) can cause plaques in the wall of the blood vessel to rupture over time.
- Ruptured aneurysm is where a ballooning of the vessel wall eventually tears and blood can leak out.
- Arteriovenous (AV) malformations are points where the blood vessel is defective. This tends to be present from birth and can easily rupture.
- Vasculitis where the blood vessel is inflamed and becomes weaker. With time it can rupture.
- Infection of the brain and its linings causes affected blood vessels to become leaky and may eventually lead to a rupture.
Irrespective of the cause, the break in the blood vessel allows blood to either collect at one spot (hematoma) or bleed freely (hemorrhage).