Thanks for the additional infomration. It sounds like he's had a rough lot in life. I've owned a dog who lost her sight at around 8 years of age. She lived another 3 years perfectly fine. INitially she could hear and smell, then at around 9.5 she lost her hearing too. She could still smell and as a result was still able to get around pretty well. But then she lost her sense of smell and became much like you describe. She didn't want to move. On a leash she would move a short distance and then freeze unsure. Sometimes if I touched her, she would move a few more feet. At this point, her quality of life was severely compromised and we decided it was in her best interest not be scared to even move and we let her pass peacefully.
So the first thing I would recommend is having his hearing checked. He may have been taking verbal cues from either the sound of your footsteps or your voice and now has lost that and hasn't adjusted to using his nose. Or like my dog has lost the sense of smell as well. He might also be starting to experience some problems with his spine. Large dog breeds sometimes suffer from a condition called degenerative myelopathy which can also cause problems with the rear legs and paralyses. You can read about this here:
Buffered aspirin can be given to a dog with a dosage of up to 5-10 mg per pound every 12 hours. Keep in mind that a dog's body does not metabolize aspirin in the same way as a human and thus should not be given more than a day or two without contacting your Vet. The aspirin may need to clear your dog’s system before other medications can be given, so keep that in mind if you decide to give aspirin and be sure and tell your vet when your dog is seen. Read side effects and precautions here.
Given his age, I'd definitely get him in to have his hearing and other testing done since he is elderly. You might try the touch method to see if he responds to that. Often just a stick or can that you can lay against his shoulder might remind him you are still there and want him to move forward if indeed he is losing his other senses.
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Since there have been recalls on certain foods, please check the following site to be sure the food your animals eat is not affected. If it is affected, contact your vet as soon as possible. Have your dog seen if they have any symptoms.