SDH is a common acronym in medicine, most frequently representing Subdural Hematoma, a serious neurological condition involving bleeding around the brain. In the context of neurological health, SDH refers to an intracranial hemorrhage that requires prompt medical attention. This condition has the potential to cause severe brain compression and injury. This information focuses exclusively on the anatomy, causes, symptoms, and management of Subdural Hematoma.
Defining Subdural Hematoma
A subdural hematoma is a collection of blood that forms within the subdural space, located between the dura mater and the arachnoid mater. The dura mater is the outermost membrane lining the skull. This accumulation of blood places pressure on the underlying brain tissue, which can lead to significant neurological impairment or death.
SDH is classified based on the speed of onset: acute and chronic. Acute SDH develops rapidly, with symptoms appearing within minutes to hours, or up to two days. It is associated with high-impact trauma, such as a serious fall, and is considered a life-threatening emergency.
Chronic SDH develops slowly, with blood accumulating over weeks or months, often becoming symptomatic more than three weeks after an injury. This form is often caused by minor head trauma the patient may not recall. A subacute classification exists for hematomas that become symptomatic between two and twenty-one days after injury.
Causes and Contributing Risk Factors
The underlying mechanism for SDH is the tearing of bridging veins, small blood vessels stretching from the brain’s surface to the dural venous sinuses. These veins are vulnerable to tearing when the brain moves suddenly within the skull. Rapid acceleration or deceleration forces create a shearing stress that leads to rupture and bleeding.
Severe head trauma is the major cause of acute SDH. Several risk factors make a person susceptible to developing SDH, even from minor trauma. Advanced age is a factor because brain atrophy stretches the bridging veins, increasing the likelihood of rupture.
The use of blood-thinning medications, such as anticoagulants and antiplatelet drugs, increases the risk and severity of bleeding. Chronic alcohol use is another factor, as it can lead to brain atrophy and frequently results in falls. Clotting disorders also predispose individuals to subdural hematomas.
Recognizing the Signs of SDH
The clinical presentation of SDH varies widely, depending on whether it is acute or chronic. Acute SDH symptoms are typically severe and reflect rapidly increasing pressure on the brain. These include a sudden, severe headache, decreased consciousness, or complete loss of consciousness.
Other signs may involve focal neurological deficits, such as weakness or numbness on one side of the body, difficulty with speech, dizziness, or vomiting. Immediate medical intervention is necessary for acute cases to prevent brain herniation and death.
Chronic SDH symptoms are often subtle and develop gradually, sometimes mimicking conditions like dementia. Symptoms may fluctuate and include persistent, mild headaches, memory problems, confusion, or changes in personality. Gait changes or mild weakness on one side of the body can also be signs.
Since the initial injury for chronic SDH may have been minor or forgotten, the delayed symptoms can make diagnosis challenging. Any person who experiences a head injury and subsequently develops neurological signs, especially persistent headache or confusion, should seek prompt medical evaluation.
Diagnosis and Treatment Pathways
Diagnosis of SDH is primarily confirmed through medical imaging to visualize the location and size of the blood collection. A non-contrast Computed Tomography (CT) scan is the initial investigation of choice due to its speed and availability. On a CT scan, SDH usually appears as a characteristic crescent-shaped collection of blood lying over the surface of the brain.
The scan appearance helps distinguish the hematoma’s age: acute hematomas appear bright (hyperdense) due to fresh, clotted blood. Chronic hematomas appear dark (hypodense) as blood components break down. Magnetic Resonance Imaging (MRI) is sometimes used for smaller or subacute hematomas that are difficult to see on CT.
Treatment depends on the hematoma’s size, the patient’s symptoms, and the age of the collection. Small, asymptomatic hematomas, especially chronic ones, may be managed through careful observation with serial imaging. This conservative approach is suitable when the hematoma is not causing pressure on the brain.
For symptomatic or large hematomas causing neurological decline, surgical intervention is necessary to relieve pressure. Common procedures include burr hole trephination, where small holes are drilled into the skull to drain liquefied blood, often used for chronic hematomas. For large, acute hematomas where the blood is clotted, a craniotomy is performed, involving temporary removal of skull bone for clot evacuation.