**Core Concept**
The sphenoid sinus is a paranasal sinus that can exhibit varying degrees of pneumatisation, which is the process of air-filled cavities developing within the sinus. The pneumatisation pattern of the sphenoid sinus is an important anatomical consideration in otolaryngology and neurosurgery.

**Why the Correct Answer is Right**
Pneumatisation patterns of the sphenoid sinus include conchal, prelabyrinthine, presellar, and post-sellar types. The presellar and post-sellar types are further sub-classified into various subtypes based on the presence and extent of pneumatization. The correct answer will not be one of these pneumatisation patterns.

**Why Each Wrong Option is Incorrect**
**Option A:** Conchal pneumatisation is a normal variant and is not an exception.
**Option C:** Post-sellar pneumatisation is a valid pneumatisation pattern.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the pneumatisation pattern of the sphenoid sinus can vary significantly among individuals, and the surgeon or radiologist must be aware of these variations to avoid complications during surgical procedures.

**Correct Answer: B.**