Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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May 26, 2014
Trapped Ventricle Secondary to CNS Tuberculosis
- Involvement of the ventricular inlet and outlet pathways creates a “trapped ventricle” as continued secretion of CSF causes
the involved ventricle to behave as a mass lesion.
- In cases where there is trigone involvement of one of the lateral ventrices, the temporal horn is isolated, resulting in its subsequent cystic dilatation, called "trapped temporal horn".
- For the fourth ventricle to be "trapped" there must be both proximal (cerebral aqueduct of Sylvius) as well as distal (foramina of Luschka and Magendie) obstruction.
- Causes for trapped ventricle include previous meningitis with choroid plexitis and ventriculitis, intracranial neoplasms, intraventricular cysts, or hemorrhage within or in close proximity to the outlet pathways.
- Clinical manifestations include features of increased intracranial pressure due to mass effect.
- When there is a trapped temporal horn, a characteristic triad may be seen: hemiparesis, homonymous hemianopsia, and memory disturbance, which originate respectively due to compression over the internal capsule, Meyer loop, and hippocampus.
- Patients with a trapped fourth ventricle may present with posterior fossa signs and symptoms including ataxia, nystagmus, torticollis, and diplopia.
- Key Diagnostic Features: Focal disproportionate dilatation of the trapped structure associated with signs of transependymal CSF leakage (periventricular hypodensity (CT) or T2WI hyperintensity). Rest of the ventricular system appears normal or near normal. One of the primary causes like choroid plexitis or cyst may be evident.
- Rx: External drainage followed by shunt placement and treatment of the primary cause when treatable. Of note, some of these patients may have a shunt catheter functioning normally; however, the trapped structure is not communicated with the ventricular system, and therefore, the shunt must be placed in the trapped segment itself.
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