Re: Cold Sensation on top of head
An unusual neurological sensation for the top of your head is almost certainly going to be related to the occipital nerve or one of the lesser branches of C2. Trauma or compression of nerve fibers anywhere along the C2 tract can account for such symptoms. Unless there is a clear injury to the nerve or structural anomaly that may be pinching or compressing the nerve, the cause may not be visible on CT, regular X-Rays, or even MRIs. Most neurologists and pain physicians will rely on other diagnostic tools, including nerve blocks, nerve stimulation (such as TENS units,) and a detailed neurological exam.
Your doctor may want to try other things to both treat your sensation and using your response to these treatments, hopefully home in on a diagnosis. Off hand, I'd suspect a compressed nerve, neuritis, or occipital neuralgia (something I'm all too familiar with.) Some of these diagnostic and therapeutic approaches may include long-acting nerve blocks, epidural steroid injections, and drug therapy with anti-depressants, anti-spasmodics, anti-anxiety, or other neurological meds that have been shown to help reduce nerve pain and discomfort. The list of these meds is VERY long, but a few of the currently popular medications for nerve discomfort are Lyrica, Tegretol (very commonly used for trigeminal neuralgia,) Neurontin, Elavil, and Pamelor. Most of these drugs work by reducing the effect of certain sensory neurotransmitters (notably acetylcholine and substance-P) as well as increasing the effects of "feeling good" neurotransmitters such as serotonin and norepinepherine, both of which affect the levels of dopamine in the brain, which in turn increases the release of the body's natural pain killers known as endorphins.
There really is no telling what the cause is or whether the situation will either get worse or resolve by itself, but it is best to see a neurologist or pain physician to treat and monitor you. I wish you all the best.