They often can coexist together, or be exclusive. It depends on which vessels are affected.
Neuropathy will typically pertain to the periphreal nervous system, that is everything outside the central nervous system which is (the brain and spinal cord). There are many different causes of neuropathy just as there are many different causes of dementia.
The term vascular neuropathy is most typically associated with diabetes, more specifically an autonomic neuropathy.
Usualy diabetes has to be out of control for ahwile before a periphreal or an autonomic neuropathy will show up or a vascular dementia..
a person can have vasular dementia without a neuopathy and vice versa, it just depends on which vessels are affected.
Remember diabetes affects the blood vessels and all organs need blood supply including the brain but also, including nerve cells and nerve fibers all over the body, nerve pain recpetors can be affected, leading to chronic neuropahtic pain seen in diabetics, but the autonomic nervous system, (automatic) like digestion, heart rate, blood pressure etc need nerve supply and those nerves need blood supply.
So the link is where there is smoke there is fire, it is not an automatic link, but it is something that a doctor should be suspicious of and aware off.
The common ways to control vasular disease, whether it is in the perihpreal nervous system, rxample (diabtetic pain in the foot) or in the brain (dementia) TIA's strokes etc, is to control blood glucose, blood pressure or hypertension, cholesterol etc.
Keeping the circulation and vessels nice and clean and flowing blood as openly as possible.
When there is a question of dementia, be it vascular or Alzheimer's, part of the diagnosis is a neurological exam, a thorough one. The rest of the nervous system has to be checked. Sometimes the doctor may find other "focal signs" on the neuro exam which would increase the possibility of dementia, if the history and MRI are ultimately consistent with this. Remember an MRI or CT can get a fairly good picture of blood vessel disease of it is there. Sometimes small strokes or infarcts are present, that the person did not know they had, with a consistent history of dementia, these fidnings on neuroimaging increase the possibility of vascular dementia.
The main differeence between vascular dementia and Alzheimer's is that vasular dementia is typically a 'stepwise' deterioration, that is the dementia gets worse, levels off and seems to stop progressing, then there is another step down again, and a leveling off etc, it is progressive but stepwise. Alzhiemer's is a slow progressvie disease that is a ocnsistent downhill curve, without stepwise downward progression.
The other reality and this is important, is that we like to sometimes artificially say it is Alzheimer's or it is vascular dementia. Very often, more than we like to consider sometimes, is that these two causes of dementia often co-exist.