Differential Diagnosis for 80M with Bilateral Cataracts and Sudden Unilateral Double Vision
Single Most Likely Diagnosis
- Abducens nerve (CN VI) palsy: This is the most likely diagnosis given the sudden onset of unilateral double vision that is only elicited on right lateral gaze, suggesting a problem with the nerve responsible for lateral rectus muscle function, which controls outward gaze. The absence of other neurological deficits or eye findings supports this localized issue.
Other Likely Diagnoses
- Thyroid ophthalmopathy: Although the eye exam is otherwise normal, thyroid eye disease can cause restrictive myopathy leading to diplopia, especially on gaze in the direction of the affected muscle. The presence of bilateral cataracts might not directly relate, but the condition could be a separate issue in an elderly patient.
- Myasthenia gravis: This autoimmune disorder can cause fluctuating weakness of the extraocular muscles, leading to diplopia. However, symptoms typically worsen with fatigue and improve with rest, which is not specified in the scenario.
- Orbital myositis or other inflammatory conditions: Inflammation of the extraocular muscles can cause diplopia, especially if the inflammation affects the muscle's function on one side. The lack of pain or other symptoms makes this less likely but still a consideration.
Do Not Miss Diagnoses
- Aneurysm or vascular malformation compressing CN VI: Although less common, an aneurysm or vascular malformation compressing the abducens nerve can cause isolated sixth nerve palsy. Given the potential for serious complications, including subarachnoid hemorrhage, this diagnosis must be considered and ruled out, especially in the absence of other clear causes.
- Diabetic neuropathy: Diabetes can cause a third, fourth, or sixth cranial nerve palsy. While the patient's diabetic status is not mentioned, given the prevalence of diabetes and its potential to cause isolated nerve palsies, it's crucial to consider and investigate, especially if there are other signs of diabetes.
- Giant cell arteritis: This condition can cause visual symptoms, including diplopia, due to involvement of the cranial nerves or the vessels supplying the eye. Given the patient's age, giant cell arteritis is a critical diagnosis not to miss due to its potential for causing irreversible vision loss if not promptly treated.
Rare Diagnoses
- Tolosa-Hunt syndrome: A rare condition characterized by painful ophthalmoplegia due to nonspecific inflammation of the cavernous sinus or superior orbital fissure. The absence of pain makes this less likely, but it remains a rare consideration.
- Wernicke's encephalopathy: This condition, caused by thiamine deficiency, can lead to ophthalmoplegia among other symptoms. It's rare and usually associated with more systemic signs of malnutrition or alcohol abuse, but it's a diagnosis that could be considered in a differential for unexplained ophthalmoplegia.
- Skew deviation: A vertical misalignment of the eyes due to a lesion in the brainstem or its connections, which could cause diplopia. This would be an unusual presentation without other neurological signs but remains a rare possibility.