What he wasn't entirely clear about was the lingering effects over the subsequent days. He mentioned that I'd be in some pain and by Saturday I was pleasantly surprised that I felt (and still feel) no pain around the spot where the procedure was done. Some time later on Saturday, it occurred to me that since the headaches and neck aches I was experiencing weren't identical to the initial nasty headache, maybe it was related to the extraction of cerebrospinal fluid. Discussions ensued and a google search for "lumbar puncture neck pain" found this description of the procedure with these notes about side effects:
You may experience side effects caused by the removal of some of your cerebrospinal fluid. The most common side effect is a headache that persists for several hours or up to several days. Symptoms that may accompany a headache include nausea, vomiting, dizziness, or tightness in the shoulders, base of the neck, or lower back.(emphasis added) A doctor in my neighborhood confirmed that this sort of headache can last four days (or more!). As of Monday morning, I can remain upright for about an hour and a half before I need to rest my neck again. I see my doctor later today. We'll see what he recommends.