The situation of hollow sound when you hit your head with your hand is caused by the following reasons: 1, caused by the collision of the skull and hand bones. Because there is no muscle and fat tissue in the brain, most of it is water, if there are no symptoms of discomfort in general, this situation is normal without treatment. 2, fever. If there is a fever, the above-mentioned symptoms, it is best to take the temperature, such as temperature increase, you can drink more water, check the blood routine to find out the cause of fever, and actively treat. 3, intracranial lesions. Such as intracranial occupational lesions, encephalitis, etc. will also appear the above symptoms, but also can cause headache, blurred vision and other pressure symptoms, it is best to further examination to confirm the diagnosis, such as cranial nuclear magnetic, intracranial lesions early treatment effect is better, as soon as possible to find out the cause, symptomatic treatment. The cause of intracranial lesions is better treated early.