Differential Diagnosis for 6th Nerve Palsy with Partial 3rd Nerve and Eyelid Palsy

Single Most Likely Diagnosis

• Cavernous Sinus Syndrome: This condition is characterized by the involvement of multiple cranial nerves (III, IV, V, and VI) due to a lesion in the cavernous sinus. The presentation of 6th nerve palsy along with partial 3rd nerve palsy and eyelid involvement (ptosis, which could be due to 3rd nerve involvement) fits well with this diagnosis, as the cavernous sinus is a location where these nerves are in close proximity.

Other Likely Diagnoses

• Diabetic Neuropathy: Diabetes can cause multiple cranial neuropathies, including 3rd and 6th nerve palsies. While less common than microvascular ischemia causing a single nerve palsy, the combination of nerves involved could suggest a more widespread process like diabetes affecting nerve function.
• Tolosa-Hunt Syndrome: This is an inflammatory condition affecting the cavernous sinus or superior orbital fissure, leading to painful ophthalmoplegia. It could present with a combination of 3rd and 6th nerve palsies, among other symptoms.

Do Not Miss Diagnoses

• Aneurysm (Especially Posterior Communicating Artery Aneurysm): An aneurysm, particularly one arising from the posterior communicating artery, can compress the 3rd cranial nerve, leading to palsy. If large enough, it could also affect the 6th nerve, especially if it expands into the cavernous sinus or affects the nerve's passage near the brainstem. Missing this diagnosis could be catastrophic due to the risk of aneurysmal rupture.
• Pituitary Apoplexy: Sudden hemorrhage or infarction of a pituitary adenoma can lead to acute expansion and compression of surrounding structures, including the cavernous sinus and its contents (cranial nerves III, IV, V, and VI). This is a medical emergency requiring prompt intervention.

Rare Diagnoses

• Gradenigo’s Syndrome: This syndrome involves the 5th (trigeminal) and 6th cranial nerves due to an inflammatory process (often petrous apicitis) at the petrous apex. While it primarily affects the 5th and 6th nerves, rare cases could potentially involve the 3rd nerve if the inflammatory process spreads.
• Neoplastic Involvement (e.g., Lymphoma, Metastasis): Various neoplasms can infiltrate the cavernous sinus or brainstem, leading to multiple cranial nerve palsies. These are less common but important to consider, especially in patients with a known history of cancer or those who do not respond to initial treatments for more common conditions.