Differential Diagnosis for Ptosis with Non-Reactive Pupil
Single Most Likely Diagnosis
- Third Cranial Nerve (Oculomotor Nerve) Palsy: This condition is the most likely cause because the oculomotor nerve controls both eyelid elevation (through the levator palpebrae superioris muscle) and pupil constriction. A lesion affecting this nerve can result in ptosis (drooping eyelid) and a non-reactive, dilated pupil.
Other Likely Diagnoses
- Horner's Syndrome: Although typically associated with a reactive pupil, in some cases, especially if there's significant sympathetic disruption, the pupil reaction can be diminished. Ptosis in Horner's syndrome is usually mild.
- Myasthenia Gravis: This autoimmune disorder can cause fluctuating ptosis and, in some instances, may affect the pupil's reactivity, especially during periods of increased muscle fatigue.
Do Not Miss Diagnoses
- Aneurysm of the Posterior Communicating Artery: This is a critical diagnosis to consider because an aneurysm can compress the oculomotor nerve, leading to ptosis and a non-reactive pupil. Missing this diagnosis can have severe consequences, including subarachnoid hemorrhage.
- Pituitary Apoplexy: Although less common, pituitary apoplexy can cause sudden expansion of the pituitary gland, compressing nearby structures, including the oculomotor nerve, leading to acute ptosis and pupil dysfunction.
Rare Diagnoses
- Botulism: A rare condition caused by the toxin of Clostridium botulinum, which can lead to bilateral ptosis and non-reactive pupils due to its effect on neuromuscular transmission.
- Miller Fisher Syndrome: A variant of Guillain-Barré syndrome, characterized by ophthalmoplegia (paralysis of the eye muscles), ataxia, and areflexia. Ptosis and non-reactive pupils can be part of the presentation.
- Cavernous Sinus Thrombosis: A rare but serious condition that can lead to multiple cranial nerve palsies, including the oculomotor nerve, resulting in ptosis and pupil abnormalities.