## **Core Concept**
Sarcoidosis is a systemic granulomatous disease that can affect multiple organs, including the nervous system. Neurosarcoidosis occurs in a small percentage of patients with sarcoidosis and can manifest in various ways, including cranial neuropathy. The facial nerve (cranial nerve VII) is particularly susceptible to involvement.

## **Why the Correct Answer is Right**
The facial nerve is the most commonly involved cranial nerve in patients with sarcoidosis. This is due to its long and complex course through the temporal bone and the high concentration of immune cells in this area, making it more susceptible to granulomatous infiltration. The involvement of the facial nerve can result in facial weakness or paralysis, which can be mistaken for Bell's palsy. The presence of bilateral facial nerve involvement or facial nerve involvement in conjunction with other systemic symptoms should raise suspicion for neurosarcoidosis.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While cranial nerve VI (abducens nerve) can be involved in various conditions, including sarcoidosis, it is not the most commonly affected nerve in this context.
- **Option B:** Cranial nerve VIII (vestibulocochlear nerve) can be involved in sarcoidosis, leading to hearing loss or vertigo, but it is less commonly affected compared to the facial nerve.
- **Option C:** Although other cranial nerves can be involved in sarcoidosis, they are less frequently affected compared to the facial nerve.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that patients with sarcoidosis can present with facial nerve palsy that mimics Bell's palsy. The presence of other systemic symptoms such as lung involvement, lymphadenopathy, or skin lesions, or the failure of facial nerve palsy to resolve as expected with corticosteroids, should prompt consideration of neurosarcoidosis.

## **Correct Answer:** . Facial nerve (VII)