Here is why you should supplement with creatine
 

Potential for use of creatine supplementation following mild traumatic brain injury

Few studies have looked at creatine supplementation after traumatic brain injury (TBI) with none investigating mTBI.
However, the article above makes a case for supplementing with creatine following mTBI.

Here is a summary of the article with arguments for taking creatine following an mTBI (or if you have PCS):

- There is considerable overlap between the neuropathology of mild traumatic brain injury (mTBI) and the role of creatine in the brain.

- Neural creatine concentrations are altered after mTBI and subconcussive injury, with a reduction (or no change) in gray matter areas and an increase in white matter areas.

- The post-concussion syndrome symptoms reported after mTBI share some similarity to those reported in individuals with impairments in creatine metabolism, and may both be due to a shared underlying cellular energy deficit.

- TBI studies demonstrate that creatine supplementation can have both neuroprotective effects in animal models (e.g., protect mitochondrial function, antioxidant effects and increased ATP) and in clinical cohorts (e.g., improve recovery, reduce headache, dizziness, fatigue, improved cognition).

- Creatine supplementation also improves cognition in nonclinical populations, outcome in anxiety and depression-related mood disorders, and has a protective effect in situations that impair cell energy status.

Dosage:

"In general, traditional supplementation protocols include a short (3–7 days) ‘loading phase’ with high-dose creatine (15–20 g/day) and/or a longer duration ‘maintenance phase’ of 1–3 months (3–10 g/day)"

I want to add that creatine supplementation has a lot of scientific backing regarding increased muscle performance and faster strength gain. This can be an additional bonus if you don't have a lot of capacity to excercise, as you will gain more muscle for less work/using less energy.

Creatine can also make people more resistant to fatigue from physical exertion as your muscles, like the brain, can use the creatine as an additional energy source for when there is a large energy demand.

Forget what I said about the dosing. You should have around 20 g per day; with multiple doses of 5 g spread throughout the day (so 4x 5g/day). This is a better dosing regimen for increasing neural creatine levels and to make it more bioavailable.

Or honestly, there isn't enough research to know the optimal dosage. So you can decide for yourself what dose you want to take long-term. One thing is certain though: it's best to take multiple small doses (according to what I've read: not more than 10 g, preferably under 5) spread throughout the day to increase the uptake.