Computed tomography of the trapped fourth ventricle.

Area of Science:

• Neurology
• Radiology
• Neurosurgery

Background:

• A dilated fourth ventricle can mimic posterior fossa space-occupying lesions.
• Outlet obstruction is the primary cause of a trapped fourth ventricle.

Observation:

• Computed tomography (CT) reveals cystic dilatation of the fourth ventricle and supratentorial hydrocephalus.
• Symptoms often resolve with lateral ventricular shunting, normalizing the fourth ventricle.
• Direct shunting of the fourth ventricle is necessary if the aqueduct is obliterated.

Findings:

• Outlet obstruction, frequently linked to meningitis or subarachnoid hemorrhage, causes fourth ventricle trapping.
• In a CT review of 48 enlarged fourth ventricles, six cases of trapped fourth ventricle were identified.
• CT imaging characteristics aid in differentiating trapped fourth ventricle from cystic tumors and cysts.

Implications:

• Prompt diagnosis and appropriate shunting can lead to complete symptom resolution.
• Understanding CT findings is crucial for accurate diagnosis and treatment planning.
• Further research into the exact mechanisms of fourth ventricle trapping is warranted.