@photographer: You didn't mention any pre-existing medical conditions. I realize that, due to privacy issues, you may not want to divulge this kind of info on an Internet board. That's OK. Given your history, you (and your doctor) should be trying to rule out any non-diving causes of the tingling/numbness sensation. The etiology of your symptoms could be cardiovascular or neurologic in nature...but certainly aren't limited to those causes. Only a full diagnostic work-up will shed some light on the situation. Tingling/numbness (paresthesia/anesthesia) in the arm/hands can be caused by any number of things: various medications, vitamin B6 toxicity, diabetes, brachial plexus neuropathies, thoracic outlet syndrome, cervical spondylosis, herniated cervical disc, Raynaud's disease, polyarteritis nodosa, pernicious anemia, hypoparathyroidism, low potassium, low calcium, low magnesium, metabolic alkalosis, infection, tumor, multiple sclerosis, ALS, headache/migraine, hyperventilation/anxiety, etc. It's a really long list of potential causes!
If it is true that you are only experiencing your symptoms after diving, then several of these possibilities may be excluded. The fact that your symptoms are asymmetric (specific to left side), peripheral, non-inclusive of the cranial nerves, and lingering (yet not permanent) is also useful diagnostic information.
Along the lines of what TSandM suggested, you may want to try to dissociate DCS from your symptomatology. For instance, you could gear up in your drysuit and execute a 15 foot dive (safety stop depth) in local waters during which you attempt to replicate the most recent dive that gave you the tingling/numbness sensations. Try to reproduce the same pre-/post-dive routine, level of activity, and total bottom time (only at a much shallower depth). If you experience the same kind of tingling/numbness, then I would be more inclined to say that it is not DCS-related. The hypothesis of a degenerative spine condition leading to nerve compression would definitely be one to consider. Then you can work with a physician (internist/neurologist/cardiologist) to figure out what's causing your symptoms. An internist will be requesting bloodwork. A neurologist may request an MRI or do electromyography. A cardiologist would probably be doing an EKG and some sort of echocardiography (transthoracic, transesophageal, transcranial). All of the specialists should be taking a thorough patient history and conducting various physical exams. As always, consultation with DAN might prove helpful.
Be patient. It may take some time to work through this issue.
Good luck with everything...and, if you ever figure out the cause(s) of your symptoms (and you feel comfortable sharing the info), please leave a follow-up post here so that others can learn from it, too.