[durgaa]

This website (Waldo Vieira who has been do astral projection most of his life) describes a chakra at the back of the head (they have their own terms) - nucal chakra (by the nucal ligament). They say this about it:

http://www.iacworld.org/english/research/chakras

Nucalchakra: positioned at the back of the head in the cerebellum region, the nucal chakra is related to communication with non-physical consciousnesses (individuals who have passed away). Sometimes we experience various sensations in this chakra when such consciousnesses are present. People who exhibit greater energetic sensitivity and who have an aptitude for mediumship usually have a more activated or sensitive nucal chakra. Synonyms: cerebellum chakra, umeral chakra.

They also say:

Nonetheless, even though the chakras are interconnected and affect one another, each chakra carries out a specific function, working in harmony with the physical body. For this reason, energetic equilibrium is a vital component of physical health and well-being. An imbalance in one's chakras can have physical repercussions. Some of the repercussions most commonly noticed in everyday life are those related to emotions, energetic blockages or the activation of one's energies. For example, an accumulation of energy that is emotional in nature in the heartchakra may cause a person to feel pressure in the chest, tachycardia or shortness of breath. Obviously, we should always verify first if our sensations have physical causes. Once this is done and when we can be sure that the sensations do not originate from the physical body, we should consider the possibility of there being an energetic or chakral cause. Another example is when individuals experience an uncomfortable block in their throat (usually followed by pressure, heat or an aching sensation) even though no physical cause is known for this condition. This may be the result of an energetic blockage in their laringochakra, a condition sometimes caused by intense shock.
The trials and traumas of past lives can also cause blockages in the chakras which may result in physical problems. Conversely, the individual's physical condition influences his or her energetic condition.