I was sitting in the couch for about 2 hours. I woke up and felt numbness on my right inner shin. Its been 24 hours now, and am still feeling the numbness. What would be a cause of this? What should I do?
The cause of numbness is a peripheral sensory nerve not working. contrary to what everyone's mother has told them, when you sit on your foot and it goes to sleep, it is not due to the circulation being cut off. It is due to the sustained pressure on the nerves that supply the foot.
After a period of sustained compression, the nerve will go "to sleep" or become numb. This is called neuropraxia. Depending upon how long the compression was applied, the nerve will usually start to "wake up" in a short period of time. However, in some cases, in can take hours to days.
In very rare cases, such as when a patient has had too much to drink the night before (for example) and sleeps on his/her arm wrong, the numbness can be associated with weakness, and it can last for months (or forever). This is known as a Saturday night palsy.
Also, in some cases, numbness in a specific dermatome (area of skin) can be caused by a nerve root being compressed in the spine. This is usually associated with pain, but not always. So, this also has to kept in the back of your mind.
But, somehow, you most likely have applied pressure to the sensory nerve that supplies the medial side of the leg (which is the medial crural nerve off of the saphenous nerve, which arises from the L3 and L4 lumbar nerve roots). It should start to wake up soon, which will be the sensation of pins and needles. However, it can sometime takes a few days to get the sensation back.
Once you develop the pins and needles feeling, it is known that at least the nerve is still working. However, if the numbness is associated with weakness or the numbness just doesn't not begin to resolve in a few days, then you might want to see someone about it. There is usually not much that can be done about it in the acute stages, but a firm diagnosis can be made (if it is peripheral or in the spine).