Differential Diagnosis for Convergent Strabismus, Sixth Cranial Nerve Paresis, and Latent Hemiparesis
Single Most Likely Diagnosis
- Left posterior cerebral artery (PCA) or posterior communicating artery (PCoA) ischemia: This diagnosis is most likely because the combination of convergent strabismus (due to sixth cranial nerve paresis) and latent hemiparesis suggests a lesion affecting both the sixth cranial nerve and the motor pathways, which could be located in the brainstem or at the base of the brain where these arteries supply.
Other Likely Diagnoses
- Left midbrain or pontine ischemia: Ischemia in these areas could explain the sixth nerve paresis and the hemiparesis due to the involvement of the corticospinal tract and the sixth cranial nerve nucleus or its outflow.
- Left cerebellar ischemia: Although less common, cerebellar strokes can present with crossed cerebellar diaschisis, affecting the opposite hemisphere and potentially causing hemiparesis, and could also involve the sixth cranial nerve if the lesion is large enough.
Do Not Miss Diagnoses
- Vertebrobasilar insufficiency or occlusion: Given the patient's risky cardiovascular background, missing a vertebrobasilar occlusion could be catastrophic. This condition can present with a variety of symptoms including those described, due to its supply to the brainstem and posterior cerebral circulation.
- Carotid artery dissection or stenosis: Although the symptoms might not perfectly align with a typical carotid distribution, carotid disease can lead to embolic events causing a wide range of neurological deficits, including those described.
Rare Diagnoses
- Moyamoya disease: A rare condition causing stenosis or occlusion of the internal carotid artery and its branches, leading to ischemic symptoms. It could potentially cause the described symptoms if there's involvement of the posterior circulation or if there are embolic events.
- Primary central nervous system vasculitis: A rare inflammatory condition affecting the blood vessels of the brain, which could potentially cause the described symptoms by affecting the appropriate areas of the brain.