The LED's you require are made by Pacer international in England.

You need 840 for an effective helmet, so thats 12 boards of 70.
They get hot, yes so fan cooled shrouds are needed. They may also supply these. Also required - a power supply that will power both the led's and fans on seperate circuts.
The helmet should have eight around the skull, two on top and two hanging down on adjustable brackets (light bendable soft metal) for the eyes sockets which are the most important part.
Dose is 6 to 8 mins per time, you can use once or twice daily.
Results typically start after 10 to 14 days, however it can take two to three months to get a decent result.

This is EXPENSIVE to built due to the LED cost.

Do not use on people with epilepsy.

May have postivive effects on many other neuro conditions also, but i have no personal exerience of anything but Dementia/Alzheimers. Typical results in an 84 year old who was scoring 12 on the MMSE before 10 weeks treatment.
Faster response to questions, happier mental state, asking a lot more questions, short term memory recall improvement. Now scoring 19 on MMSE, and easy to converse with.

Results on younger patients especially those under 70 happen much quicker.

Hope this helps.