Today I read the description of Maggie Packet @my home
and they have written in black "No added MSG"
There are many many forms of MSG so they usually get away with it.
Just to clarify things here is how glutamate operates -
Your brain consist of neurons which are basically cells with dendrites and axons attached to them. Dendrites take the input from other neurons and pass it to the cell region and then that is passed to the output region of the cell - Axons. Most of the neurons have a potential of ~-60 mv and some of them in amygdala are more negatively charged at -80 mv.
Neurons communicate via neurotransmitters namely glutamate and GABA ( Gamma AminoButyric Acid). Glutamate increases the potential of the neurons and helps in firing information from one neuron to another whereas GABA decreases the potential and decreases the chance of firing. Basically the firing is controlled by the GABA which itself is supported with things like Modulators(Amines, Peptides,Hormones).
If there is too much firing and its not controlled with GABA then neurons will eventually die.
So if you mess up with the amount of glutamate or similar compounds in your diet then the firing will be uncontrolled and will kill your neurons.
This explanation is a simplified version of how glutamate works and may not be very accurate.