Final answer:
A patient might sue for lack of informed consent if a lumbar puncture was performed without a signed consent form.
Step-by-step explanation:
A lumbar puncture was performed on a patient without a signed informed consent form. In this scenario, the patient might sue for Lack of informed consent. Informed consent is a legal and ethical requirement in medical practice that ensures patients have the right to make decisions about their own healthcare. Without a signed informed consent form, the patient's right to be fully informed and involved in their own medical care was violated.