I don't know if you understand this term "subacute combined degeneration of spinal cord"?
This is caused by lack of Vitamin B12.
The doctor gives you the Vitamin B Complex, because he did not see any symptom of rheumatoid arthritis from X-ray.
I think he is trying to give you supplement of Vitamin B Complex first.
If this is not working, the next step is to do the blood test.