Age, the Neurologic Examination and Prediction of Disease

Age isn't a disease, right? But, disease is associated with age. The older pet, is more likely to have structural disease (i.e. idiopathic epilepsy vs CNS neoplasia), compared to the younger pet. But, none of us want to diagnose a terminal disease in an older patient simply because the patient is older!

How can the Neurologic Examination Help Vets with Old Patients?

Can we look at two of the most commonly performed tests on the neurologic examination and determine the sensitivity and specificity for the detection of a forebrain lesion? Actually, yes we can. The menace response and paw replacement (previously called conscious proprioception) testing both assess the forebrain and are some of the most commonly performed parts of the neurologic examination. Here is what a recent group from Australia found:

Menace response
Sensitivity: 72%
Specificity: 47%
Odds ratio: 2.26

Proprioception
Sensitivity: 54%
Specificity: 72%
Odds ratio: 3.08
If age is then factored into the analysis, dogs greater than or equal to 6 years of age are more likely to have a forebrain disease detected if they have a menace or proprioceptive deficit.

As a "field" neurologist (without a pocket MRI...yet) this tells me that I should encourage diagnostic imaging in patients with menace deficits and proprioceptive deficits. The chances (or Odds) of a patient having underlying forebrain disease is higher if they have these deficits than if they don't. Seems intuitive, but proprioceptive testing isn't as sensitive as assessing the menace response so by all means don't forget to do that on an older patient! :)

Hope this little study was insightful for you too.
Chan MK, Jull P. Accuracy of selected neurological clinical tests in diagnosing MRI-detectable forebrain lesion in dogs [published online ahead of print, 2020 Jul 15]. Aust Vet J. 2020;10.

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