When neoplasia is high on your differential list for your neurologic patient but an MRI isn’t an option, it can feel like your hands are tied! It’s hard to narrow down what the cancer is, how to treat it palliatively, and where we go from here prognostically. Here are a few tips for you to take with you each step of the way when you don’t have a definitive diagnosis.

What kind of cancer is it?

• When it comes to brain tumors, the most common primary tumor in dogs and cats is a meningioma, so this is often the top differential amongst cancers. Meningiomas are “benign” in that they don’t metastasize or invade through bone, so unfortunately short of an MRI, there aren’t other places to look in the body to try and affirm this presumptive diagnosis.
• Consider CNS lymphoma as well – you may not have peripheral lymphadenopathy or a lymphocytosis (the CNS is so good at keeping things out, but it’s good at keeping things in, too), but it’s worth looking for!
• The most common type of cancer that will metastasize to the brain? Melanoma. Make sure to evaluate your patients for a primary melanoma (don’t forget to check the mouth, especially!)
  
  

How can we treat it?

• Fortunately or unfortunately, CNS neoplasms are notoriously unresponsive to chemotherapies, so we’re left with palliative options for primary CNS tumors. You guessed it…prednisone (or prednisolone in cats!)
• My protocol? Start with 1 mg/kg/day for one week, then start to slowly taper to the lowest effective dose.
• Make sure to address other symptoms depending on presumed tumor locaiton (aka – if the presenting complaint is seizures, make sure to also treat the seizures with an anti-epileptic or if the presenting complaint was a myelopathy with spinal pain, make sure to address the pain too)
  
  

Where do we go from here prognostically?

As you know, prognosis really depends on what the primary neoplasm is, but let’s assume it’s the most commonly seen ones – meningioma or lymphoma

• Meningiomas have a median survival time of 6 months with palliative care alone, this is going to be your best case scenario as meningomas are the slowest growing, least aggressive neoplasms affecting the central nervous system
• Lymphoma or other primary CNS tumors have a worse prognosis
• BONUS: sometimes it’s not actually neoplasia! If you’re able to taper them down to a low dose of steroids or get them off steroids at all and they’re stable past that best case scenario of 6 month survival, then very possibly it was some other etiology with a better prognosis! This is also why it’s important to let clients know there are other differentials besides neoplasia, and if they want to give palliative care a try, it’s not entirely without hope!

There’s a lot more to CNS neoplasia, but hopefully this helps you feel a little more confident talking to your clients about palliative care if referral for imaging +/- radiation isn’t available to you!

#practicepearls

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 About the Author: Lara Curtis, DVM, DACVIM (Neurology)

Dr. Lara Curtis is a graduate of Washington State University and residency trained in a private practice setting in Seattle, WA. Her professional interests include immune-mediated disease, medical management of spinal cord injury, and education creation for the general practitioner and emergency clinicians. She loves working WITH clients and their primary care practitioners to manage neurologic issues that would otherwise be overwhelming and scary, and helping to restore some quality of life and hope!