Differential Diagnosis for Right Eye Deviation and Limited Adduction of the Left Eye
Single Most Likely Diagnosis
- Medial Longitudinal Fasciculus (MLF) Lesion: This is the most likely diagnosis given the patient's presentation of right eye deviation medially in primary gaze and limited adduction of the left eye. The MLF is a nerve tract that connects the nuclei of the cranial nerves responsible for eye movements, and a lesion here can cause internuclear ophthalmoplegia (INO), characterized by impaired adduction of the eye on the same side as the lesion and nystagmus of the contralateral eye.
Other Likely Diagnoses
- Partial Third Cranial Nerve Palsy: This could cause limited adduction of the left eye if the palsy affects the medial rectus muscle. However, it would not typically cause medial deviation of the contralateral eye in primary gaze.
- Thyroid Ophthalmopathy: Can cause restrictive strabismus leading to limited eye movements, but the presentation would typically be more complex and include other signs such as exophthalmos, eyelid retraction, and potential optic neuropathy.
Do Not Miss Diagnoses
- Multiple Sclerosis (MS): A demyelinating lesion in the MLF can cause INO, and MS is a common cause of such lesions in young adults. Missing this diagnosis could lead to delayed treatment of MS.
- Stroke or Brainstem Infarct: A stroke affecting the brainstem can cause a variety of ocular motor disturbances, including those mimicking MLF syndrome. Prompt recognition is crucial for timely intervention.
- Tumor (e.g., Glioma, Metastasis): A tumor in the brainstem or affecting the MLF can cause similar symptoms and requires early detection for appropriate management.
Rare Diagnoses
- Wernicke's Encephalopathy: This condition, caused by thiamine deficiency, can lead to ophthalmoplegia, among other symptoms. It's rare but important to consider, especially in malnourished or alcoholic patients, as it is treatable with thiamine supplementation.
- Progressive Supranuclear Palsy (PSP): A neurodegenerative disorder that can cause vertical gaze palsy and other ocular motor disturbances. While it's a rare condition, its distinctive features and poor prognosis make it worth considering in the differential diagnosis.