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No head trauma or brain injury will not have an external manifestation as white patch of hair.
The brain which is enclosed in the skill has no direct relation to the scalp or hair. The colour of the hair is determined by the melanocytes (the colouring cells) which can be affected by something superficial rather than something like a head trauma.
It could be due a simple aberration following an injury or a fungal infection or even congenital.
Eitherway this does not signify any past or ongoing head injury or trauma.
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