**Question:** A young female presented with halo's, abdominal pain and amnesia she is likely to be suffering from-

A. Encephalitis
B. Traumatic brain injury
C. Subarachnoid haemorrhage
D. Meningitis

**Correct Answer:** C. Subarachnoid haemorrhage

**Core Concept:** Subarachnoid haemorrhage (SAH) is a life-threatening neurological emergency resulting from bleeding into the subarachnoid space around the brain. The subarachnoid space is the space containing cerebrospinal fluid (CSF) that surrounds the brain and spinal cord.

**Why the Correct Answer is Right:** The correct answer is Subarachnoid haemorrhage (SAH) because the patient exhibits symptoms related to this condition:

1. Halo's: This refers to the characteristic "ring enhancing" pattern on computed tomography (CT) scan or magnetic resonance imaging (MRI) scans. The halo represents the area of increased blood breakdown products surrounding the bleeding spot, which is an essential diagnostic clue for SAH.
2. Abdominal pain: This is a non-specific symptom, which can occur due to various causes, including SAH. However, abdominal pain is not the primary symptom in SAH cases.
3. Amnesia: Memory impairment is a common feature of SAH, but the patient's presentation also includes halo signs and abdominal pain, which narrows down the diagnosis to SAH.

**Why Each Wrong Option is Incorrect:**

A. Encephalitis: Encephalitis is an inflammation of the brain, which can present with neurological symptoms but lacks the characteristic halo sign on imaging studies.
B. Traumatic brain injury: This term covers a wide range of injuries and does not specifically explain the halo sign or abdominal pain.
D. Meningitis: Meningitis is an inflammation of the meninges, which covers the brain and spinal cord, not a bleeding disorder like SAH.

**Clinical Pearl:** The halo sign on imaging studies is a crucial diagnostic clue for Subarachnoid haemorrhage (SAH). The halo sign is a radiological feature observed on computed tomography (CT) or magnetic resonance imaging (MRI) scans, characterized by a ring-like pattern created by increased blood breakdown products surrounding the bleeding spot. This feature helps differentiate SAH from other disorders presenting with similar symptoms.