Differential Diagnosis for Left Eye Unable to Adduct
- Single most likely diagnosis
- Medial Rectus Muscle Palsy or Third Cranial Nerve (Oculomotor) Palsy: This is the most common cause of inability to adduct the eye, as the medial rectus muscle is responsible for adduction, and the third cranial nerve controls this muscle among others. Conditions affecting this nerve, such as an aneurysm, stroke, or trauma, can lead to this symptom.
- Other Likely diagnoses
- Thyroid Eye Disease: Inflammation and swelling of the tissues around the eye, including the muscles, can cause restriction of eye movements. While more commonly associated with proptosis and other symptoms, significant inflammation can restrict adduction.
- Orbital Fracture: Trauma to the orbit can cause entrapment of the medial rectus muscle, limiting its ability to contract and thus preventing adduction.
- Myasthenia Gravis: An autoimmune disease that affects the neuromuscular junction, leading to fluctuating muscle weakness. Ocular symptoms can include diplopia and weakness of extraocular muscles, potentially affecting adduction.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Aneurysm of the Posterior Communicating Artery: Although less common, an aneurysm compressing the third cranial nerve can cause palsy, leading to inability to adduct the eye. This is a medical emergency due to the risk of rupture and subarachnoid hemorrhage.
- Cavernous Sinus Thrombosis: A rare but potentially life-threatening condition that can cause multiple cranial nerve palsies, including the third nerve, due to thrombosis in the cavernous sinus.
- Rare diagnoses
- Gradenigo’s Syndrome: A rare condition caused by inflammation of the petrous apex, leading to a combination of symptoms including sixth cranial nerve palsy (which affects abduction, not adduction, but can be considered in the differential for ocular motility disorders).
- Moebius Syndrome: A rare neurological disorder characterized by facial paralysis and impaired eye movements, including inability to adduct the eye, due to underdevelopment of the sixth and seventh cranial nerves.
- Congenital Fibrosis of the Extraocular Muscles: A rare condition where there is fibrosis of the extraocular muscles, leading to restrictive eye movements. While congenital, symptoms may become more apparent over time.