Tingling hands and feeling of cramps can be explained on the basis of herniated disc in cervical (neck) spine. The tingling feet also can be due to degenerative disc in the lower back. The other common causes are;
1) Vitamin B 12 deficiency
2) Diabetic neuropathy
3) Peripheral neuropathy due to other causes like connective tissue disorders / immune mediated arthritis etc.
Following investigations would be essential to ascertain the cause;
1) Electromyography/nerve conduction studies (EMG/NCS)
2) MRI of the spine and brain
3) blood glucose, glucose tolerance test and glycosylated hemoglobin
4) serum B12 level with methylmalonic acid (with or without homocysteine),
5) serum protein electrophoresis
6) Anti-nuclear antibody
7) Lyme testing
8) Rheumatoid factor
9) Sjogren's syndrome testing (Anti-Ro, Anti-La Antibodies)
This should give the diagnosis and guidelines for the management.
Please feel free for your follow up questions.