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Neuroradiology Case of the Week

Case 71

Ravinder Sidhu MD, Lawrence Buadu MD, PhD and Henry Wang MD, PhD

Clinical Presentation: A 60-year-old male with history of left nephrectomy for renal cell carcinoma presented with mental status changes.

Radiological Findings:  Non-contrast enhanced head CT showed a spherical hypodense mass of 1.5x1 cm in the left lateral ventricle near the foramen of Monro causing ipsilateral obstruction of the lateral ventricle (Fig. 1A). The mass showed homogeneous enhancement (Fig. 1B). There was a well-defined lytic lesion involving the clivus towards its right side (Fig. 1C).
    CECT of the abdomen revealed a hypodense lesion in the liver along with a sub-pleural nodule on the right side. A lytic expansile lesion was seen involving the left 6th rib (Fig.2).

Diagnosis: Metastatic renal cell carcinoma with intraventricular metastases

Discussion:  Most intraventricular lesions are due to primary tumors arising from epithelial and mesenchymal elements of the choroid plexus. The precise anatomical location of the tumor within the ventricles along with imaging features, patient age and associated clinical findings often provide important clues to the nature of the lesion [1].
    The differential diagnosis of lateral ventricular masses in older patients includes meningioma, subependymoma, lymphoma and metastases. Meningioma is the commonest cause of a mass in the trigone of lateral ventricle and is seen as an iso to hypodense homogeneous mass with marked enhancement. Subependymoma most often arise from the lower medulla and project into the caudal fourth ventricle. Rarely, it may be seen in lateral ventricle and appear as a hypo to isodense mass with no significant enhancement. Multiple centrally located lesions are frequent, the most common sites being the deep basal ganglia, the periventricular region, and the corpus callosum. They are seen as iso to hypodense lesions and show strong homogeneous enhancement [2].
    Intraventricular masses in adults include colloid cyst, central neurocytoma whereas choroid plexus papillomas/carcinomas and ependymomas are commonly seen in children. Colloid cyst occur in adults and is seen as a hyperdense mass located in the anterior third ventricle, typically positioned between the columns of the fornix and tends to cause obstructing hydrocephalus. Central neurocytoma occurs in anterior portion of the third ventricle and shows heterogeneous cystic appearance. Choroid plexus papillomas are seen as an iso to hyperdense lobulated mass with punctate calcification and heterogeneous enhancement. Choroid plexus carcinomas are rare, highly malignant tumors that invade the adjacent brain parenchyma to a greater degree. Approximately 90% of ependymomas are located in the fourth ventricle and cerebropontine angle cisterns [3,4].
     Intraventricular metastases are usually in the lateral ventricle, ependyma and choroid plexus but may be in the third or fourth ventricle and commonly seen in 6th /7th decade. Intraventricular metastases on non-contrast enhanced CT may be hyperdense, hypodense or isodense relative to the normal brain parenchyma depending on their cell type. They usually show marked enhancement on contrast administration based on their vascularity. Calcification is unusual. Hydrocephalus is usually not present unless the tumor blocks the normal cerebrospinal fluid pathway. MR imaging is superior to CT because of its multiplanar capabilities and detection of small lesions. In adults, metastases originate from carcinoma lung in more than half the cases, followed by breast and digestive tract malignancy, and renal cell carcinoma. However, in children, Wilm’s tumor, retinoblastoma and neuroblastoma are the common primary sites to metastasize to brain [5].
    Intraventricular metastases to the choroid plexus should be suspected in a patient with a known extracranial malignancy with a moderately to markedly enhancing mass demonstrated on CT. This lesion should be considered even more likely when metastatic disease is known to exist elsewhere within the patient. A definite diagnosis can be made by CT-guided stereotactic guided biopsy.

References:

1. Nakabayashi H, Murata K, Sakaguchi M, et al. Choroid plexus metastases from gastric cancer - case report. Neurol Med Chir (Tokyo) 1994; 34:183-6.
2. Osborn A. Brain tumors and tumor like masses: Classification and differential diagnosis. Diagnostic Neuroradiology. St. Louis, Mosby, 1994, pp 422.
3. Grianger RG, Allison DJ, Adam A, Dixon AK. Cranial and intracranial pathology (1): intracranial tumors in adults. Diagnostic Radiology, 3rd ed., pp 2334-35.
4. Kart BH, Reddy SC, Rao GR, Poveda H. Choroid plexus metastases: CT appearance. J Comput Assist Tomogr. 1986; 10:537-40.
5. Raila FA, Bottoms WT Jr, Fratkin JD. Solitary choroid plexus metastasis from a renal cell carcinoma. South Med J. 1998; 91:1159-62.