My numbness is different...what is causing it?

Question:
I've had numb legs for almost 2 months now. But it's not at all like what I've been reading with other MS numbness. My numbness is totally symmetrical, starting just below both knees and stops just above both ankles. The sensation is also more in the front part of The legs and not in The calf area so much. The sensation is also slightly stronger in my right leg for some reason. The other weird thing is the sensation virtually disappears when I'm wearing shorts or no pants. If there's no material touching my legs, they almost feel totally normal. But the second i put pants back on. They're numb again. It's so weird and it's making me insane. My anxiety is at an all time high. I've had 2 MRIs with and without contrast on my brain and c-spine. I also had an EMG done. Blood work. Neurological physical. Everything came back completely normal and my neurologist says my symptoms are confusing and astounding but he seemed 100% confident it was not MS. But no one can give me a straight answer about my symptoms. I'm desperate.

Answer:
Numbness is an imprecise term. It is not synonymous with a lack of sensation or diminished sensation to some modality such as temperature, painful needle pricks or touch.  When most people tell you they are experiencing numbness they are referring to a spontaneously generated sensation not a lack of sensation. This spontaneously generated sensation could take the form of pins and needles such as when your limb, “falls asleep”, electrical shocks or even burning sensation. Sometimes people are referring to a normal sensation that is distorted when they tell you they are numb. For instance, light touch could feel prickly or burning. This could explain your abnormal sensations when you touch your leg below the knee or you wear pants.
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Generally speaking, we are most concerned when an individual has decreased sensation to a testing modality in a particular area. For instance, the person may not feel a pin prick or even light touch in an area. Spontaneously generated sensations (e.g. burning, electrical, pins and needles, pain to light touch) without abnormalities on examination are less specific and often occur due to nerve irritation or during the chronic/recovery phase of injury.
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You refer to abnormal sensations (“numbness” ) between the knee and your ankle but mostly on the front of the leg. The only nerve with a distribution in this region would be the saphenous nerve, a sensory branch of the femoral nerve. The sensations could also be coming from the central nervous system but it would be unusual for the sensation to stop at the ankle.
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A good neurologist should be able to figure our the problem given time.


Revere (Rip) Kinkel MD
Professor of Clinical Neurosciences
Director of the Multiple Sclerosis Program
Clinical Neurosciences Director
University of California San Diego