What is Caudal Occiptal Malformation Syndrome (COMS)?
As the name suggests, this disease arises from malformation of the caudal aspect of the skull (occiptal bone). The resulting effect is overcrowding of the caudal fossa (the bit skull in the very back). Who cares? Well.. it turns out dogs (and us) need every bit of space in there otherwise the brainstem gets bent (called kinking), cerebellum is smashed (yikes) and the CSF doesn't flow well which then results in hydrocephalus and central spinal canal dilation
What is the clinical presentation for dogs with COMS?
Cavalier King Charles Spaniels are the most commonly affected breed however it has been documented in numerous other breeds.
Neck pain, hyperesthesia, allodynia, phantom neck scratching, postural reaction deficits, ataxia, paresis and seizures with hydrocephalus. There are a wide range of signs because clinical signs are driven by disease anywhere from the forebrain to the thoracolumbar spinal cord. Multifocal neuroanatomic lesion localization is common too.
How can COMS be diagnosed?
MRI. Sorry folks, it's the only way. We can see hydrocephalus with an ultrasound or CT but the other factors involved in COMS aren't easily diagnosed without an MRI.
How can I help my patient with COMS?
Surgical intervention - I can open up the caudal aspect of the skull to give things more "room". This is a temporary fix, sadly and signs often recur as the dog develops post surgical scars.
Medical intervention - Pain management is critical. Often combination therapy with anti-inflammatory treatment (steroids or NSAIDs) and gabapentin is my starting point for patients. I also use omeprazole because it decreases CSF production (yes, really!) and can improve clinical signs quite nicely. Finally, consider reducing stimulation to the shoulder/neck area because this area is the most common location for hyperpathia. This means that you should keep harness/collars off the dog as much as possible.
This weeks' TidBit Tuesday was inspired by a case from Madison. Thanks for the questions!!
Please let me know if you have any suggestions for TidBit Tuesday topics and keep those consults coming!