**Core Concept**
Post spinal headache, also known as postdural puncture headache (PDPH), is a type of headache that occurs after a lumbar puncture or spinal anesthesia. It is caused by the leakage of cerebrospinal fluid (CSF) through the dural puncture site, leading to a decrease in CSF volume and pressure.

**Why the Correct Answer is Right**
The duration of PDPH can vary from person to person, but it usually lasts for several days to a week. The exact mechanism of PDPH is not fully understood, but it is thought to be related to the decrease in CSF volume and pressure, which can lead to traction on the pain-sensitive structures of the brain and spinal cord. This can cause a dull, aching, or throbbing headache that is often worse when standing or sitting upright.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because PDPH typically lasts longer than a few hours. The exact duration can vary, but it is often several days to a week.
**Option B:** This option is incorrect because PDPH can last for several days to a week, not just a day or two.
**Option C:** This option is incorrect because while some cases of PDPH may resolve within a few days, it is not uncommon for them to last longer.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the risk of PDPH can be reduced by using smaller-gauge needles and avoiding lumbar punctures in patients with a history of headache or other neurological conditions.

**Correct Answer: D.**