Uncal herniation

Uncal herniation is a type of brain herniation that occurs when the uncus, a part of the temporal lobe of the brain, is displaced from its usual position and moves past the structures that usually contain it. This displacement can compress adjacent structures, such as the brainstem and the third cranial nerve, leading to potentially life-threatening conditions. Uncal herniation is often a result of increased intracranial pressure which can be due to various causes including head injury, brain tumor, stroke, or inflammation of the brain tissue.

Causes

The primary cause of uncal herniation is an increase in intracranial pressure (ICP). This increase can be due to a variety of factors, including:

• Head injury
• Brain tumor
• Stroke
• Hemorrhage within the brain
• Inflammation of the brain tissue, such as encephalitis or meningitis

Symptoms

Symptoms of uncal herniation can vary depending on the extent of the herniation and the structures compressed. Common symptoms include:

• Headache
• Pupil dilation on the side of the herniation
• Changes in consciousness, including coma
• Paralysis on the opposite side of the body (due to compression of the cerebral peduncle)
• Respiratory arrest and other signs of brainstem compression

Diagnosis

Diagnosis of uncal herniation typically involves neuroimaging techniques such as:

• Computed tomography (CT) scan
• Magnetic resonance imaging (MRI)

These imaging methods can reveal the displacement of brain structures and help in assessing the extent of the herniation.

Treatment

Treatment of uncal herniation is aimed at reducing the intracranial pressure and preventing further displacement of brain structures. Treatment options include:

• Medication to reduce brain swelling, such as mannitol or hypertonic saline
• Surgical intervention to remove the cause of increased pressure, such as draining a hematoma or removing a tumor
• In some cases, a decompressive craniectomy may be performed to allow the swollen brain tissue more space

Prognosis

The prognosis for individuals with uncal herniation varies widely and depends on the cause, the speed of diagnosis and treatment, and the extent of brain damage. Early intervention can significantly improve outcomes, but delays in treatment can lead to permanent neurological damage or death.

See Also

• Brain herniation
• Intracranial pressure
• Temporal lobe