Image of subdural hematoma on CT scan of the brain without contrast injection

This is an automatically translated article.

The article is expertly consulted by Master, Doctor Nguyen Thi Mai Anh - Doctor of Radiology - Department of Diagnostic Imaging and Nuclear Medicine - Vinmec Times City International General Hospital. Doctor Nguyen Thi Mai Anh has nearly 10 years of experience in the field of diagnostic imaging, especially in imaging breast and thyroid cancer.
A subdural hematoma is bleeding in the space around the brain. The subdural hematoma on unenhanced CT scan of the brain revealed the presence and size of the hematoma that formed between the dura mater and the arachnoid.

1. Pathophysiology

In closed traumatic brain injury, vibrational movements along the diameter of the skull can damage veins, arteries, or brain parenchyma, causing a subdural hematoma. Specifically:
The bridging veins that drain blood from the cerebral cortex to the dural sinuses are torn, causing blood to flow into the space between the arachnoid and dura. Usually, increased intracranial pressure or blood clots directly stop venous bleeding. Subdural hematomas due to a laceration of the vein tend to be in the fronto-parietal region. Arterial lacerations can also cause subdural hematomas, which account for about 20-30% of cases, mainly affecting small cortical arteries <1mm in diameter. A subdural hematoma due to an arterial tear tends to be located in the temporal-parietal region. Both arterial and venous causes carry a high risk of death. Another mechanism that causes subdural hematomas is low CSF pressure, also known as decreased intracranial pressure. The cause of this condition is spontaneous or idiopathic CSF leakage, which sometimes also occurs after lumbar puncture. As cerebrospinal fluid pressure decreases, cerebral tension decreases, causing stretching of dependent structures. Dilatation of the glomerulus veins can cause lacerations and ruptures of blood vessels, while a decrease in autologous intracranial pressure leads to cerebral venous stasis. The result is drainage into the subarachnoid space.

2. Symptoms and classification

Initially, the presentation of subdural hematoma is very diverse. Severe head trauma can cause coma, while milder injuries lead to acute hematoma, causing short-term loss of consciousness. Subacute or chronic subdural hematomas present insidiously, typically with cognitive impairment.
Classification of subdural hematoma is determined based on the time from the time of injury, specifically as follows:
Acute: From 1 to 2 days after injury Subacute: From 3 to 14 days after injury Chronic injury: From the 15th day after the injury. This definition is useful only when there is a clear history of trauma or provoking events until the onset of clinical symptoms.
2.1. Acute subdural hematoma Approximately 50% of trauma patients with a subdural hematoma will be comatose immediately after the injury. However, only about 12-38% of these acute patients experience a gradual decline in consciousness afterward. Posterior fossa subdural hematoma often presents with symptoms of increased intracranial pressure, including:
Headache Vomiting Pussy Dilated pupils Mute voice Cranial nerve paralysis Stiff neck Ataxia.

In some cases, decreased cerebral perfusion pressure can lead to cerebral infarction. After an acute subdural hematoma and complications of incarceration, the patient will have typical manifestations of Kluver-Bucy syndrome:
Apathy Loss of common sense of fear and anger Strange sexual behavior Increased appetite mouth Talk a lot. 2.2. Chronic subdural hematoma may insidious manifestations include:
Headache Light agitation Consciousness disturbance Apathy Lethargy Sometimes convulsions. These symptoms become more pronounced after several weeks of trauma, and may be transient or fluctuating. In chronic subdural hematomas, systemic defects (eg, altered mental status) are more common than focal neurologic findings. Possible focal neurological signs are:
Ipsilateral hemiparesis: Due to the displacement effect of the hematoma, it causes lateral displacement of the brain stem. Hemiplegia on the opposite side: May be the result of a hematoma pressing directly on the cerebral cortex. Chronic bilateral temporal subdural hematomas may present with transient mild paralysis at the extremities and with little pain.

3. Image of subdural hematoma on CT film of the brain

The most widely used diagnostic imaging test for acute head trauma is a head CT scan. The reason is because of its speed, high performance and availability of equipment in most centers. Patients admitted to the hospital after a head injury are sometimes also diagnosed with a subdural hematoma through magnetic resonance imaging (MRI). MRI is more likely to detect subdural hematomas than CT, but CT is faster and more convenient.
Subdural hematomas can run across joints, but are limited by adhesions of the meninges. So the typical manifestation of this condition is a crescent-shaped lesion.
The subdural hematoma can be clearly observed on acute non-injectable CT cranialography as a crescent-shaped, hyperattenuated mass surrounding the cerebral cortex (Figure 1).

Subacute and chronic subdural hematomas on CT brain imaging are crescent-shaped, mixed or hypodense, and surface deformed (Figure 2). The sheath may be enhanced in the subdural hematoma images on injectable brain CT.

Distinctions can be made between the subdural hematoma on unenhanced CT brain scans or on anatomical slides with an epidural hematoma. The epidural hematoma does not run through the joints, but separates the dura in the central virtual space and the skull. The result is an epidural hematoma characterized by a double-lens image (Figure 3).

The image of a subdural hematoma on CT of the brain on one side has a space-occupying effect and causes anatomical changes, but the two sides can be easily missed. The reason is that the brain parenchyma appears uniform, while the blood clot itself has the same density as the surrounding brain tissue. Thanks to the improvement in resolution, new generations of cranial CT scans can provide greater sensitivity in detecting subdural hematomas.
In acute head trauma, imaging of a subdural hematoma on cranial CT plays a key role in both diagnosing the lesion and determining appropriate initial treatments. In addition, any head injury may be present with a subdural hematoma, the clinical manifestations of which are difficult to distinguish. Therefore, determining the natural progression of each lesion is important, helping to have a specific treatment.
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