From the "Hypochondriac's Guide to Life. And Death."

try this simple diagnostic test:

Reach into your pocket or purse. Feel for a coin. Don't take it out,
just explore its surfaces with your fingertips. Can you tell which side is
heads and which is tails? You should be able to. This is called "stereognosis,"
and it is a basic test of the functioning of the parietal lobes of the brain.
Failure to distinguish heads from tails can sometimes herald the presence
of a parietal lobe tumour or an oncoming stroke.

Note: This is taken from a humour book.. don't take it too seriously... :p