I am not so certain that serrapeptase would be effective in the brain as the blood brain barrier MIGHT affect it's usage. I do not know whether this would be an issue but it might be. I am a fan of serrapeptase but do not know for certain that it would be effective in the brain.
It might be worth you looking at the expanded/enhanced Linus Pauling therapy which uses nutrients to address circulatory disorders. These are things like high dose Vitamin C or better still liposomal vitamin C, Magnesium, L-Proline, L-Lysine and associated nutrients. Magnesium carbonate is fairly inexpensive and reacts in an acid/base reaction with acids such as ascorbic acid to form highly absorbable magnesium salts. Tri Methyl Glycine can also be helpful as it lowers homocysteine levels. Vitamin C is the key though as it is with all circulatory disorders in including heart disease.