We've all been there, right? An elderly small breed patient with a grade II or III heart murmur presents to you with a history of "passing out". Clients aren't more descriptive than that, and they didn't catch a video. Is this syncope or was this a seizure?
You have several things to ask and look for (see prior TidBit Tuesday on syncope) but recent research has given us one more tool in our belt to help differentiate between these two diseases.
Human patients with generalized tonic-clonic seizures demonstrate a reduced phosphate level within several hours of the event and patients with syncope do not. A study from Israel published data in January that strongly suggested a link between hypophosphatemia and seizures in dogs, as well. According to this study, 87 dogs with seizures and 26 dogs with syncope were included. Phosphate was evaluated within 3 hours of the "event" in question and noted to be decreased in 28 (32%) of dogs with seizures. None of the dogs with syncope had a low phosphate level. Dogs were excluded from the study if their creatinine was above the normal range to eliminate those cases with hypophosphatemia from renal causes. Median phosphate levels were significantly different between the two groups!
Key point: With an optimum cutoff value of 0.97 mmol/L (about equal to 3.0 mg/dl), evidence of hypophosphatemia has a 100% specificity and 44% sensitivity to diagnose seizures.
Importantly, this tool should not be used as a stand alone finding to differentiate between seizures and syncope! However, identification of hypophosphatemia, within 3 hours of the witnessed event, could suggest a generalized seizure was more likely than a syncopal event if all other historical, physical examination and biochemical findings are concurrently evaluated. Important note: This has not been verified in dogs with focal seizures or complex partial seizures OR cats!
This week's TidBit Tuesday is short and sweet. I hope you have a wonderful start to March 2023!
Reference: https://doi.org/10.1016/j.tvjl.2022.105914