As a user on this homebrew issue utter's like a savant "package managers managing package managers rarely works out well."
First clean up your homebrew crap:
brew uninstall --force node rm -rf ~/.npm rm -rf ~/.node
Install NPM with the NVM install script
curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.29.0/install.sh | bash
The inital version installed with homebrew is ok, but updating node after installing via homebrew is impossible due to how homebrew handles linking. Using NPM makes upgrades and managing versions simpler.