**Question:** Which of the following will manifest as "pachymeningitis heamorrhagica interna"?

A. Encephalitis
B. Subarachnoid haemorrhage
C. Subdural haematoma
D. Brain abscess

**Core Concept:** Pachymeningitis haemorrhagica interna (PHI) is a rare clinical entity characterized by subacute inflammation of the thick layer (pachya) of the meninges. This condition is typically associated with a bleeding diathesis, suggesting an underlying cause.

**Why the Correct Answer is Right:** Bleeding diathesis is the key feature of PHI, which refers to an increased tendency to bleed due to impaired hemostasis. PHI can be caused by various factors, including autoimmune diseases, infections, or medications. In this case, choice B (subarachnoid haemorrhage) is the correct answer as it represents a type of bleeding within the subarachnoid space, which can lead to inflammation of the meninges and PHI.

**Why Each Wrong Option is Incorrect:**

A. Encephalitis: Encephalitis is inflammation of the brain tissue, not the meninges. PHI is characterized by inflammation of the meninges, which are separate from the brain tissue.

C. Subdural haematoma: Subdural haematoma is an accumulation of blood between the dura mater and the arachnoid mater, not within the meninges. Subarachnoid haemorrhage (choice B) is more closely related to PHI than subdural haematoma.

D. Brain abscess: Brain abscess is an infection within the brain tissue, not the meninges. PHI is characterized by inflammation of the meninges, which are separate from the brain tissue.

**Clinical Pearl:** In cases where patients present with symptoms of PHI, a thorough workup is essential to identify the underlying cause of the bleeding diathesis. This may involve blood tests (e.g., coagulation profile), imaging studies (e.g., computed tomography, magnetic resonance imaging), and sometimes cerebrospinal fluid analysis. Once the cause is identified, appropriate management can be initiated, which may include anti-coagulant therapy or treatment of the underlying condition.