Can l1-l2 herniated disk cause foot drop?

Not typically: Typically due to compressive pathology of the L4 nerve root or L5 -- most commonly at the l4-5 level. Not just a small herniated disc. There are other causes: neuromuscular, peripheral sciatic or peroneal nerve palsies or injuries. See your spine surgeon.

Usually not: A few important points here: a centrally located, massive disc herniation at l1-2 can cause foot drop plus leg weakness. Foot drop alone is commonly associated with l5-s1 disc herniation.