**Core Concept**
Ophthalmoplegic migraine is a rare neurological condition characterized by recurrent episodes of headache accompanied by ipsilateral (same side) paralysis of one or more cranial nerves controlling eye movements. This condition is often associated with vasculogenic or demyelinating pathology.

**Why the Correct Answer is Right**
The correct answer describes the typical presentation of ophthalmoplegic migraine, where headache is followed by complete paralysis of the IIIrd (oculomotor) and VIth (abducens) cranial nerves on the same side as the hemicrania. This occurs due to inflammation or demyelination of the nerves, leading to impaired nerve conduction. The IIIrd cranial nerve controls most of the extraocular muscles responsible for eye movements, while the VIth cranial nerve controls the lateral rectus muscle, which is responsible for outward gaze.

**Why Each Wrong Option is Incorrect**
**Option B:** This option is incorrect because ophthalmoplegic migraine typically involves complete paralysis of the IIIrd and VIth cranial nerves, not partial paralysis. Additionally, the condition is often associated with scotoma (blind spots) due to involvement of the optic nerve.

**Option C:** This option is incorrect because ophthalmoplegic migraine primarily involves the IIIrd and VIth cranial nerves, not the IVth (trochlear) nerve. The IVth cranial nerve controls the superior oblique muscle, which is responsible for downward and inward eye movement.

**Option D:** This option is incorrect because ophthalmoplegic migraine is not directly associated with optic neuritis, which is an inflammation of the optic nerve leading to vision loss.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that ophthalmoplegic migraine is a rare condition, but it can mimic other more common neurological disorders, such as stroke or multiple sclerosis. A high index of suspicion and thorough neurological examination are necessary for diagnosis.

**✓ Correct Answer: A. When headache is followed by complete paralysis of the III rd and VI nerve on the same side as the hemicrania.**

✓ Correct Answer: A. When headache is followed by complete paralysis of the III rd and VI nerve on the same side as the hemicrania.