Question: I have found it in this [video](https://youtu.be/MZkFDnDoIf4). It is at 4 minute and 51 second. Here is the context:

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> The brain doesn't atrophy because the brain is the most important organ **as far as we are concerned with** survival.
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I am aware that the phrase *as far as someone is concerned* means to in someone's opinion. But the preposition *with*. It seems to me it has a diffetent meaning I cannot find in dictionaries.

Answer: 
It's an odd, overly wordy, and possibly redundant phrase that makes more sense when you recognize it's a narrator speaking off the top of his head, not from a prepared script. It's a compound of two ideas:

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> The brain is the most important organ
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> The brain is required for survival (in terms of hunting ability, etc.)
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The speaker awkwardly combined these with the phrase "as far as we are concerned with" when he could have just used "for".

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> The brain is the most important organ **for** survival [because of ...]
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Or simply:

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> The brain is the most important organ [because of ...]
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Consider the statement "The brain is the most important organ" and the phrase "as far as we are concerned". Combine the two and you get the sentence "The brain is the most important organ as far as we are concerned." This sentence is correct, but it is also very general.

The word "with" is used to connect the word "survival" to this sentence. Doing so adds a detail that makes the sentence more specific: it is not just that the brain is the most important, but that the brain is specifically the most important with survival.

Other words such as "for", "to", "regarding", or even phrases like "in regards to" can be used to do the same thing as "with".