**Question:** A 33-year-old woman experiences visions of flashing lights followed by throbbing left-sided temporal pain and nausea. The most likely diagnosis is:

A. Migraine
B. Subarachnoid haemorrhage
C. Bacterial meningitis
D. Tension headache

**Correct Answer:** A. Migraine

**Core Concept:** Migraine is a type of primary headache disorder characterized by recurrent, severe headaches, typically unilateral (one-sided) and pulsating in nature. The headache is often accompanied by nausea, vomiting, and sensitivity to light and sound (photophobia and phonophobia).

**Why the Correct Answer is Right:** In this case, the patient presents with a combination of symptoms including unilateral temporal pain, flashing lights, and nausea. Migraine fits these symptoms best. Migraine is known to cause unilateral headaches, often aggravated by specific triggers (e.g., food, stress), and is commonly associated with photophobia and phonophobia.

**Why Each Wrong Option is Incorrect:**

A. Subarachnoid haemorrhage: This refers to a rupture of an abnormal cerebral aneurysm, leading to bleeding in the subarachnoid space. The clinical presentation of subarachnoid haemorrhage is acute onset severe headache, often described as a thunderclap headache, along with focal neurological deficits and sometimes aphasia.

B. Tension headache: This refers to a headache caused by muscle contraction in the neck and head, typically bilateral and non-pulsatile. Tension headaches are usually associated with muscle tenderness in the head and neck muscles.

C. Bacterial meningitis: This refers to inflammation of the meninges (protective membranes) due to bacterial infection. Bacterial meningitis presents with fever, lethargy, neck stiffness, and sometimes a 'flu-like' illness.

**Clinical Pearl:**

Migraine is a common primary headache disorder that can be challenging to differentiate from other conditions like subarachnoid haemorrhage, tension headache, and bacterial meningitis. However, careful clinical examination, history, and appropriate investigations can help in making the correct diagnosis. A thorough understanding of headache types and associated symptoms is essential for accurate diagnosis and management of these conditions.