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Postulating the concept of compensated trapped fourth ventricle: a case-based demonstration with long-term
Suhas Udayakumaran1, Dilip Panikar
1Division of Pediatric Neurosurgery, Department of Neurosurgery, Amrita Institute of Medical Sciences & Research Center, Kochi, Kerala, India. dr.suhas@gmail.com
Insights
We introduce the concept of compensated trapped fourth ventricle (TFV), a nonprogressive state of hydrocephalus. This case study highlights long-term clinical and radiological findings in a patient with a compensated TFV.
Area of Science:
- Neurology
- Neurosurgery
- Pediatric Neurology
Background:
- A trapped fourth ventricle (TFV) is defined by obstructed inflow and outflow of the fourth ventricle, leading to its dilation.
- Hydrocephalus management often involves shunts, but complications like shunt malfunction can occur.
Observation:
- A pediatric patient with post-infectious hydrocephalus initially received a ventriculoperitoneal shunt.
- At age 9, the patient presented with altered sensorium and imaging confirmed enlarged ventricles and aqueductal obstruction, suggestive of TFV.
- Despite a diagnosis of TFV, the shunt was revised for suspected malfunction; the TFV remained untreated.
Findings:
- Long-term follow-up at age 25 revealed well-decompressed lateral ventricles but a persistent large fourth ventricle.
- Clinical examination showed truncal ataxia, and MR flow studies indicated aqueductal obstruction with bidirectional flow at the foramen of Magendie.
- These findings suggest a compensated state of the trapped fourth ventricle, where it is clinically and radiologically nonprogressive.
Implications:
- The concept of a "compensated" trapped fourth ventricle is proposed, representing a stable, nonprogressive hydrocephalus state.
- This challenges the purely radiological definition of TFV, emphasizing its functional and clinical aspects.
- Imaging findings should be interpreted in conjunction with clinical presentation for accurate diagnosis and management of TFV.
Background:
A trapped fourth ventricle (TFV) is diagnosed when the inlet and outlets of the fourth ventricle are obstructed with a resultant dilated fourth ventricle.
Case Report:
A 3-month-old male child had a ventriculoperitoneal shunt for post-infectious hydrocephalus. At the age of 9 years, he became symptomatic with altered sensorium. He had a CT head which showed enlarged ventricles with a large fourth ventricle. A subsequent ventriculogram revealed dilated lateral ventricles with an aqueductal obstruction in association with an enlarged fourth ventricle. Although diagnosed as a TFV radiologically, his lateral ventricle shunt was revised with a diagnosis of shunt malfunction as there was a simultaneous dilatation of the lateral ventricle. He was never treated for the TFV. At his latest follow-up at 25 years of age, his MRI brain showed well-decompressed lateral ventricles with a large fourth ventricle. On clinical examination, he had truncal ataxia noticed only during turning which, according to the mother, "was always there". His MR flow study showed obstruction at the level of the aqueduct with some evidence of bidirectional flow at the foramen of Magendie.
Discussion:
The concept of compensated hydrocephalus represents a stage where a previously active hydrocephalus attains a nonprogressive state clinically and radiologically. We postulate the concept of a "compensated" TFV with a long-term clinical and radiological follow-up.
Conclusion:
We demonstrate and describe a compensated TFV and reiterate that a TFV is a functional concept with imaging being at most only corroboratory.
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