7 replies
    • neuropetvet
      neuropetvet says:

      For “zero MRI training,” you’re doing great! Those are several of the differentials. Check back in next Tuesday for the definitive diagnosis!

  3. John
    John says:

    Cats rarely get something good if they are sick. DDx: FIP > lymphoma > Glioma. The location is not where we normally see meningioma though it is the most common intracranial tumor in cats.

  4. neuropetvet
    neuropetvet says:

    This scan highlights the importance of determining the lesion location first as extraparenchyma (“extra-axial”) or intraparenchymal (“intra-axial”). I went back and forth on it, but ultimately thought it was more likely intraparenchymal (subependymal) than extraparenchymal (in this case, ventricular). Differentials for ring enhancement can be remembered by the mnemonic MAGIC-DR, which stands for Metastasis, Abscess, Glioma, Infarction (subacute phase), Contusion, Demyelinating disease, and Radiation necrosis. There were no other obvious neoplasms found on routine workup (CXR, AUS), he was quite young to have an infarction, and there was no history of head trauma or radiation therapy. This leaves glioma, abscess, and demyelinating disease. Since there was a clear mass effect, a glioma or abscess become the two most likely differentials. The dog’s owner elected to humanely euthanize and a limited necropsy of the brain was performed. Gross and histologic examination revealed the mass to be a “right lateral ventricle choroid plexus carcinoma (CPC) with marked anisokaryosis, multinucleation, intralesional necrosis and suppurative inflammation; regional parenchymal infiltration, edema, and gliosis.” Choroid plexus tumors are typically homogeneously enhancing. The largest retrospective on choroid plexus tumors to date (Westworth et al, JVIM, Sept/Oct 2008) found heterogeneous contrast enhancement in only 22% of dogs with CPC. Ring enhancement has been reported in people with CPC, but to my knowledge, this has not been reported in veterinary medicine.
    Gross and histologic images from this case.
    Gross and histologic images from this case.
    Left: Fixed brain, sectioned. Intraventricular mass with midbrain compression.
    Right:Ventricular mass, high magnification.
    Images courtesy of Taryn Donovan, DVM, DACVP.

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