Sometimes a breach can occur, such as physical trauma or a lumbar puncture resulting in leakage of the CSF.
This can change the pressure and allow the brain to not be as buoyant, which squishes on nerves and causes a variety of symptoms. In addition, in other cases a condition called hydrocephalus can occur. This can also result in pressure changes and if it occurs in the fetus it can result in an enlarged head. Hydrocephalus in an adult must be immediately corrected.
There are different types of hemorrhages that can occur in the central nervous system. We will discuss the four major types: epidural, subdural, subarachnoid and intracerebral hemorrhages. Epidural hemorrhages occur between the dura mater and the skull and are usually very rapid because the hemorrhage comes from damage to the arteries along the inside of the skull. Recall looking at the skulls in lab and seeing the grooves where the arteries of the skull once ran.
These arteries are under high pressure vessels bleed rapidly when damaged. This bleeding results in a hematoma, which strips the dura membrane off the skull as it expands, causing intense headaches.
More seriously is the compression of the nervous system as the hematoma expands against the skull. The most common cause of epidural bleeds is a skull fracture which lacerates these arteries.
Epidural hemorrhages can be fatal if left untreated. Treatment is done by surgically draining or removing the hematoma to relieve pressure on the brain. Subdural hemorrhages occur between the dura mater and the brain. These result from tears in the veins that cross the subdural space in response to a head injury, especially rotational or linear forces. Subdural hemorrhages are classic injuries found in shaken baby syndrome and severe whiplash.
They are also more common in people on aspirin, since aspirin inhibits blood clotting. They can be subdivided into acute, subacute and chronic subdural hematomas depending on the severity of the hemorrhage. Subacute hematomas fall into the same category although slightly less severe. Chronic subdural hematomas develop over a period of days to weeks and often result from minor head trauma like a concussion.
Symptoms of subdual hemorrhage typically have a slower onset than epidural bleeds because the bleeding comes from veins instead of arteries. License: Creative Commons Attribution 3. Grays Anatomy: Public Domain. To understand subdural hemorrhages better, it helps to examine the anatomy. In fact, a brain taken out of the head and not properly suspended e.
While the bone of the skull and spine provide most of the safeguarding and structural support for the central nervous system CNS , alone it isn't quite enough to fully protect the CNS. The meninges help to anchor the CNS in place to keep, for example, the brain from moving around within the skull.
They also contain cerebrospinal fluid CSF , which acts as a cushion for the brain and provides a solution in which the brain is suspended, allowing it to preserve its shape.
The outermost layer of the meninges is the dura mater, which literally means "hard mother. The dura provides the brain and spinal cord with an extra protective layer, helps to keep the CNS from being jostled around by fastening it to the skull or vertebral column, and supplies a complex system of veinous drainage through which blood can leave the brain.
The arachnoid gets its name because it has the consistency and appearance of a spider web. It is much less substantial than the dura, and stretches like a cobweb between the dura and pia mater. By connecting the pia to the dura, the arachnoid helps to keep the brain in place in the skull. Between the arachnoid and the pia there is also an area known as the subarachnoid space , which is filled with CSF.
The arachnoid serves as an additional barrier to isolate the CNS from the rest of the body, acting in a manner similar to the blood-brain barrier by keeping fluids, toxins, etc.
The pia mater is another thin layer, but unlike the arachnoid it closely follows all of the contours e. Thus, instead of a cobweb, it forms a tight membrane around the brain and spinal cord. The pia acts as a barrier and also aids in the production of CSF. Anatomy Flashcard Collection. The Inguinal Canal. A man with penile swelling. A man with blood in his urine. PSA Question Bank. Medical Student Finals Question Bank. ABG Quiz. Reading Meninges. Share Tweet. Last updated: October 22, Suggest an improvement.
You don't need to tell us which article this feedback relates to, as we automatically capture that information for you. This allows us to get in touch for more details if required. Please write a single word answer in lowercase this is an anti-spam measure. This field is for validation purposes and should be left unchanged. Dura mater This is the outermost layer that is directly underneath the skull. Arachnoid mater This is the middle layer that lies directly beneath the dura mater.
Pia mater This is the innermost layer of the meninges. It is relatively very thin and fragile. Some interesting etymology! Key neurosurgical knowledge Layers of the SCALP a mnemonic S kin C onnective tissue dense A poneurotic layer L oose connective tissue P ericranium When observing or assisting in theatre, your supervising doctor may ask you questions as they proceed with the operation.
You might also be interested in our Anatomy Flashcard Collection which contains over anatomy flashcards in addition to advanced features such as spaced repetition. Clinical relevance: Extradural haematoma Extradural haematoma is typically caused by an intracranial arterial bleed.
Blood accumulates outside the dura, between the periosteal dura and the inner skull surface. Blood is confined by dural investments in cranial sutures. A typical presentation of a patient with an extradural haematoma includes: Trauma to the pterion the junction of the frontal, temporal, parietal and sphenoid bones, which is the weakest area of the skull, making it vulnerable to fracture. This, in turn, causes a rupture of the middle meningeal artery which traverses the pterion.
This is where, following the initial neurological insult, there is a short period of complete resolution before symptoms resume and the patient deteriorates. Figure 4. An epidural haematoma on a CT scan compared with the shape of a lemon due to its convex shape. Clinical relevance: Subdural haematoma A subdural haematoma is typically caused by an intracranial venous bleed , due to rupture of the dural bridging veins.
The haemorrhage occurs beneath the dura and above the arachnoid mater. The haemorrhage is not contained by dural investments and therefore can flow freely over the arachnoid surface. It appears as a crescent-shaped opacity on a CT head scan somewhat resembling a banana. A typical presentation of a patient with an extradural haematoma includes: There may be a history of head trauma, often it is minor, sometimes there is no trauma reported.
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