It can be also the sexual energy raising through your spine and finding a blockage in the crown chakra (then it will feel like a knot in the chakra extension below). Similar can happen to your astral hearing spots, but this is temporary and nothing to be worried about.
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Given the experiences of many, it appears that the three granthis [knots where the chakra concerned has a powerful energy block that prevents the serpent from ascending] are not at the base, heart, and sixth chakras as popularly taught, but are at the second [sacral] chakra, the throat chakra, and the crown chakra. There have been many accounts of one's heart chakra feeling a burning sensation; as the serpent cannot ascend any further due to a blocked throat chakra.
Now, if the heart chakra were blocked and contained one of the three granthis, the burning sensation would manifest in the solar chakra, not the heart. Going further, the sensation of the crawlies near the crown chakra strongly indicates that chakra is blocked. If it were the 6th chakra as most sources of information available inform us, the sensation would be at the throat or BENEATH the 6th chakra. From direct experience, it appears that seventh is the most difficult chakra to fully open. The sensation of the crawlies, compared by some to ants crawling, indicates that the serpentine energy is going *around* the seventh chakra and not *through* it as it should when this chakra has been fully opened. Other symptoms include pain and discomfort, especially when one's serpentine energy is fully activated.