Whisk flour, flaxseed meal, walnuts, baking powder, baking soda, and salt in medium bowl to blend.
Whisk buttermilk, 1/4 cup maple syrup, and egg in another medium bowl.
Add buttermilk mixture to dry ingredients and whisk just until incorporated.
Brush large nonstick skillet lightly with vegetable oil and heat over medium heat. Working in batches, add batter to skillet by scant 1/4 cupfuls. Cook until bubbles appear on surface of pancakes and undersides are golden brown, about 2 minutes. Turn pancakes over and cook until golden on bottom, about 2 minutes.
Transfer pancakes to plates. Serve with additional maple syrup.