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Hello and thank you for your question.
It is unlikely to be MS as you would have symptoms like weakness, constant tingling in your limbs, blurred vision, bladder problems.
I think it can be related to your pinched nerve in your lower back leading to such symptoms.
Lhermitte's sign is an electrical sensation that shoots down the spine from the head towards the feet. It is often brought on by flexing the neck so that the chin moves towards the chest. The sign is thought to indicate dysfunction of the dorsal columns of the cervical spinal cord, which are responsible for transmitting information about light touch and vibration to the brain.
Sometimes Lhermitte's can also be caused by vitamin B12 deficiency.
Moreover in Lhermitte's you would experience symptoms running till legs and not only till thighs.
Sometimes cervical spondylosis can also be one reason. I would suggest to see a neurologist who can order MRI of your brain and cervical spine to evaluate further and order blood test for vitamin B12 deficiency.
Please get back to me if you have any further questions. Thank you.