Presentation
One week history of global headaches. Past medical history of craniotomy and excision of colloid cyst more that a decade ago.
Patient Data
A 6 x 7mm colloid cyst is identified in the midline at the level of the foraminae of Munro, sharply circumscribed measuring 6mm in diameter, hyperintense on t1 weighted scans, hypointense on t2 weighted scans, and without significant contrast enhancement. No hydrocephalus is evident. The septum pellucidum is dehiscent or perforated adjacent to distortion and gliosis indicating the right transventricular pericallosal surgical approach. Some gliosis is seen on either side of midline in the white matter.
CONCLUSION:
Recurrent colloid cyst.
Histopathology:
MACROSCOPIC DESCRIPTION: "Unlabelled as to site": Two shiny grayish fragments 4 & 7mm across, A1. (SP/bm)
MICROSCOPIC DESCRIPTION: The section shows two fragments of acellular amorphous eosinophilic material consistent with the contents of a cyst. No epithelial component is identified.
DIAGNOSIS: "Unlabelled as to site": Material with features consistent with contents of a cyst.
The patient underwent a redo-craniotomy and excision of the colloid cyst. He remained stable for four years until he represented with month-long history of worsening global headaches and decreased hearing in the left ear.
A defect in the anterior part of the body of the corpus callosum, and some gliosis in the right frontal lobe indicates the surgical path taken for resection of the Colloid cyst. There is no evidence of residual recurrent Colloid cyst, and no evidence of hydrocephalus. In particular the third ventricular recesses are not distended, and there is no distension of the temporal horns of the lateral ventricles. Apart from the gliosis from the surgical site of the medial portion of the right frontal lobe, only a few white matter hyperintensities are seen in the left cerebral hemisphere and in the posterior fossa. Normal flow voids are seen from the major intracranial arteries. No extraaxial collection.
A left acoustic schwannoma expands the internal acoustic canal extending to the cerebellar pontine angle, measuring 21 mm in length, the maximum diameter within the cerebellar pontine angle cistern of 11 mm.
Conclusion:
No evidence residual recurrent third ventricular Colloid cyst. Left acoustic schwannoma projecting into the cerebellar pontine angle cistern, without brainstem compression/displacement.
The patient remained under radiological surveillance.
Case Discussion
This case illustrates recurrence of a colloid cyst.
Colloid cysts are benign intracranial lesions comprising of 0.5%–1% of primary brain neoplasms and 15%–20% of intraventricular masses 1-3. They commonly occur in the third to fifth decades of life 4. They originate from the primitive neuroepithelium (which gives rise to the choroid plexus and ependyma) and studies have shown that their contents include secretory and breakdown products of the epithelial lining of the cyst, including old blood, foamy cells, fat, hemosiderin-laden macrophages, cholesterol crystals, and CSF 5.
More than 99% are found wedged in the foramen of Monro 1. The cysts are typically attached to the anterosuperior portion of the third ventricular roof, with the fornix pillars straddling the cyst and lateral splaying of the frontal horns (posterior aspect of) 1.
Clinical presentation is variable, as most colloid cysts are found incidentally and are thereby asymptomatic. The most common presenting symptom is headache associated with nausea and/or vomiting, and relieved/diminished by reclining 4. Gait disturbance, temporary loss of consciousness, sudden weakness in extremities, blurred vision, and dizziness are among the less-frequent symptoms 4.
Both CT and MRI can be used in the radiologic diagnosis of colloid cysts. On CT, colloid cysts appear 2,4,5:
- hyperdense to brain parenchyma (although rarely may be hypo/isodense)
- well-delineated, oval or rounded hyperattenuated mass on non-enhanced CT scan
- following administration of iodinated contrast material, a thin rim of enhancement may be present and may represent the cyst capsule
- periventricular hypodensity or enlarged temporal horns could be seen on a CT view due to increased intraventricular pressure and transependymal CSF leak
Using MR imaging, colloid cysts have a variable appearance 2,4,5:
- approximately half of the cysts are hyperintense when compared with brain parenchyma on T1-weighted images; the remaining cysts are iso- or hypointense
- on T2-weighted images, most colloid cysts are hypointense to the brain
- usually, there is no diffusion restriction in colloid cysts on diffusion-weighted images
- cysts that are hypointense on T2-weighted sequences may be difficult to visualize using FLAIR
- MR imaging may occasionally show intracystic fluid levels or central and peripheral components in the lesion
Where surgical treatment is indicated (based on clinical history, examination, size and anatomical location of colloid cyst), this can be performed via a transcallosal approach, endoscopic aspiration or stereotactic excision 3. Post-surgery, it is very important to monitor for recurrence.
Case courtesy of Associate Professor Pramit Phal.
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