Fourth Cranial Nerve (Trochlear Nerve) Palsy: This condition is a common cause of double vision, especially if it's abrupt in onset. The trochlear nerve controls the superior oblique muscle, which is responsible for rotating the eye. Damage to this nerve can lead to diplopia (double vision).

Third Cranial Nerve (Oculomotor Nerve) Palsy: Similar to the fourth cranial nerve palsy, damage to the third cranial nerve can cause double vision due to its control over several eye muscles. This condition can present with ptosis (drooping eyelid) and pupil dilation on the affected side.
Sixth Cranial Nerve (Abducens Nerve) Palsy: The sixth cranial nerve controls the lateral rectus muscle, which abducts the eye. Damage to this nerve can cause horizontal diplopia.
Myasthenia Gravis: An autoimmune disorder that affects the neuromuscular junction, leading to fluctuating muscle weakness. Ocular symptoms, including double vision, are common presentations.
Thyroid Ophthalmopathy: Inflammation and swelling of the tissues around the eye, including the extraocular muscles, can cause double vision. This condition is often associated with Graves' disease.

Aneurysm (e.g., Posterior Communicating Artery Aneurysm): Although less common, an aneurysm pressing on the third cranial nerve can cause sudden onset of double vision, often accompanied by other symptoms like headache or pupillary dilation. Missing this diagnosis can be catastrophic.
Stroke or Transient Ischemic Attack (TIA): Vascular events in the brainstem or cerebral cortex can cause double vision. It's crucial to rule out these conditions due to their potential for severe consequences.
Multiple Sclerosis: An autoimmune disease that affects the central nervous system. Optic neuritis and double vision can be presenting symptoms, and early diagnosis is important for management.

Wernicke's Encephalopathy: A condition caused by thiamine deficiency, often seen in alcoholics, which can present with ophthalmoplegia (paralysis of the eye muscles) and double vision.
Tolosa-Hunt Syndrome: A rare condition characterized by inflammation of the cavernous sinus or superior orbital fissure, leading to painful ophthalmoplegia and double vision.
Orbital Myositis: Inflammation of the extraocular muscles, which can cause double vision, pain, and swelling around the eye.