Brief Answer:
Left L5 nerve root compression.

Detailed Answer:
Hello again! Sorry that you're seemingly having so many health issues.

If you have had a fall with disc protrusions at L4-L5 level then I think that is also the origin of your symptoms. These disc protrusions may lead to compression of nerve root at that level, in this case the left L5 root. Since the nerve root carries information on sensation its compression typically causes the unpleasant sensations you describe. Apart from the protrusion itself other factors may further contribute to narrowing of the canal where the nerve passes such as inflammation, arthritis changes to the facets (the small joints between the vertebral arches), vertebral body displacement. All these can add to the compression.

As for management initially it consists in anti-inflammatory pain killers like Ibuprofen and physical therapy (to strengthen back muscles and better support the spine). Most patients as the initial acute inflammation subsides improve over the course of 4-6 weeks. If not medication for neuropathic pain is used. Lyrica is a good such choice, if causing side effects duloxetine or amitriptyline, also a 1st choice for neuropathic pain but belonging to different class may be tried.

If medication and physiotherapy doesn't work then more invasive approaches may be tried such as steroid injections or as a last resort surgery to relieve nerve compression.

Let me know if I can further assist you.

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Brief Answer:
Read below.

Detailed Answer:
As I said those nerve roots which are compressed and damaged carry nerve fibers responsible for sensation. As a result they misfire, malfunction. That can lead to several types of sensation changes, there may be hypoesthesia which means lowered sensation, paresthesias (abnormal sensations in the absence of a stimulus), allodynia (perception of pain in response to a normally nonpainful stimulus) or dysesthesia such as in your case.
Dysesthesia is the perception of an unpleasant sensation either spontaneous or in the presence of a normally non-painful stimuli (such as your burning in response to touch).
Usually paresthesias and dysesthesias present together and are more common precisely in peripheral nerve damage like in your case.

I hope to have been of help.

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Brief Answer:
Read below.

Detailed Answer:
Nerve root compression is not the only cause of pain, there may be other causes such as the sciatic compression by piriformis muscle you mentioned or lumbar plexus trauma.
If the distribution is strictly in L5 territory though that is unlikely, because compression of the plexus or sciatic muscle involve more than the L5. You see after nerve roots come out of the spine they do not go unchanged downward to the limbs, they divide and the resulting branches form form the plexus, a sort of network, from which come out other nerves which are mixed, contain fibers from different levels (the main one the sciatic nerve has fibers from L4, L5, S1 for example). So is not a pure L5 compression anymore.
Other symptoms which orient more towards a nerve root compression is the positive Lassegue and increase of back pain by coughing or sneezing (increased intraabdominal pressure).

Now as to the differing opinions....I wonder what explanation did the surgeon give to your symptoms if he though there was no nerve root compression, did he suggest any other cause. If he examined you any neurological finding apart from the unpleasant sensations you report (abnormal reflexes, muscle weakness).
One explanation for this discrepancy between symptoms and MRI (assuming surgeon is right about no compression) may be the time factor. As I said if you go back to my first answer, nerve compression may be not only due to the disc protrusion but to several factors at the same time, including local inflammation, swelling. Since issue is present since October, it is possible for there to have been compression due to the added inflammation, but over the months inflammation has subsided and compression has been relieved but has left some residual damage, hence the persistent unpleasant sensations.
The other explanation may be simply that the neurosurgeon is wrong. Another exam which may help in evaluating nerve damage and give some additional information regarding damage site may be nerve conduction studies, a test evaluating electrical nerve conduction at different points along the nerve trajectory.

Hope you'll feel better soon.

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Brief Answer:
You're welcome.

Detailed Answer:
Looking forward to hearing from you again.

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