Bell's Palsy: This is the most common cause of acute facial nerve weakness, characterized by a sudden onset of unilateral facial weakness or paralysis. It is often idiopathic but can be associated with viral infections.

Stroke or Transient Ischemic Attack (TIA): Facial weakness can be a presenting symptom of a stroke or TIA, especially if accompanied by other neurological deficits such as limb weakness, speech difficulties, or visual disturbances.
Lyme Disease: Neuroborreliosis, a manifestation of Lyme disease, can cause facial nerve palsy, often bilateral.
Ramsay Hunt Syndrome: Caused by the varicella-zoster virus, this condition leads to facial nerve paralysis and a rash in the ear or mouth.

Cerebellopontine Angle Tumors (e.g., Acoustic Neuroma): Although rare, these tumors can compress the facial nerve, leading to progressive facial weakness. Early diagnosis is crucial for effective treatment.
Multiple Sclerosis: This demyelinating disease can present with facial nerve weakness among other neurological symptoms. It's crucial to consider in patients with a history of relapsing neurological symptoms.
Sarcoidosis: This systemic disease can affect the facial nerve, causing weakness or paralysis, and is often accompanied by other systemic symptoms.

Melkersson-Rosenthal Syndrome: A rare neurological disorder characterized by recurrent, often bilateral, facial paralysis or weakness, along with swelling of the face and lips, and the development of folds and furrows in the tongue (fissured tongue).
Mobius Syndrome: A rare congenital neurological disorder characterized by facial paralysis and impaired eye movements.
Tolosa-Hunt Syndrome: A rare disorder characterized by headache, facial pain, and weakness or paralysis of the muscles supplied by the cranial nerves, including the facial nerve, due to nonspecific inflammation of the cavernous sinus or superior orbital fissure.