Dear Pet Owner:
It sounds to me that your dog is having episodes of neuropathy. Neuropathy is a general term that refers to disease of the central nervous system CNS, which would encompass the brain, spinal cord, and nerves of the body.
Disease of the CNS may occur primarily, that is the CNS tissue is diseased, or may occur as a secondary consequence of disease elsewhere in the body that has neurological effects. We would call this secondary neuropathy.
Primary and secondary neuropathy are often clinically indistinguishable even with a thorough examination. hen first approaching a case, I tend to try to lump all clinical signs together into one disease process, as one disease versus multiple concurrent diseases manifesting all at once carries the higher probability. However, at your dog's age, multiple concurrent conditions certainly are possible.
Putting the catatonia that you described in conjunction with the wetting, the disease that first comes to mind is diabetes mellitus. For more on this disease, please refer to the link to this article I wrote on the disease:
With diabetes, the blood glucose can spike so high that the patient begins to have neurological effects i in the manner in which you are describing. In conjunction with that, they tend to drink excess water and can be prone to having accidents in the home when before that was an unusual event. This would be a secondary neuropathy, as diabetes is a metabolic disturbance that has adverse effects to the CNS among other systems.
Another possibility is a disease that may lead to seizures. While your dog is not displaying hallmark seizure behavior (the convulsive activity most associate with seizures), dogs can present with atypical seizures that presents as blank stares, catatonic states, loss of motor control, and voiding their urine or bowels. Causes for seizures include liver disease, kidney disease, and epilepsy. Less commonly, brain tumors can also cause seizures - I state less commonly, because primary brain tumors are not very common in canines. Below is an article I wrote on epilepsy for more information:
My approach to cases like this always begin with a thorough examination to see if there is more consistent neurological signs than the episodes you see. Physical examination can tells us allot and helps us to fine tune out diagnostic approach. Diagnostically, I would always begin with a basic data base that consists of general blood work (complete blood count, blood chemistry, and thyroid level) and urinalysis. Depending on the results, you may get a diagnosis if you are dealing with a secondary neuropathy, or your veterinarian may recommend chest and abdominal x-rays to further complete the diagnostic profile. If nothing turns up from this general approach, then the next step would be to consider imaging of the brain via CT or MRI, as well as having an analysis of the cerebrospinal fluid obtained through spinal tap.
There are a few different possibilities for what is occuring to your dog, some that are quite treatable, others less treatable, some not treatable. The first step should be to begin the pro cess with a physical examination by a veterinarian and proceed with some basic diagnostics, only moving no to more invasive (and expensive) techniques if the cases dictates it.