Differential Diagnosis

The patient's symptoms of 3rd and 6th nerve palsy with pupil sparing, decreased vision in the left eye, diplopia, and sensory involvement of the ophthalmic and maxillary branches of the trigeminal nerve suggest a complex neurological condition. Here's a categorized differential diagnosis:

• 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 sparing of pupils and the specific involvement of the ophthalmic and maxillary branches of the trigeminal nerve, along with the 3rd and 6th nerve palsy, make this a strong consideration. The decreased vision could be due to compression of the optic nerve or its branches.

• Other Likely diagnoses

  • Tolosa-Hunt Syndrome: An inflammatory condition affecting the cavernous sinus or superior orbital fissure, leading to painful ophthalmoplegia. While it typically involves the 3rd, 4th, and 6th nerves, the involvement of the trigeminal nerve branches could be part of the syndrome's variable presentation.
  • Diabetic Cranial Neuropathy: Though less common, diabetes can cause multiple cranial neuropathies, including 3rd and 6th nerve palsy. However, the involvement of specific trigeminal branches and decreased vision might be less typical.

• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)

  • Giant Cell Arteritis: This condition can cause visual loss and cranial neuropathies, including those affecting the 3rd and 6th nerves, especially in older adults. Prompt diagnosis and treatment are crucial to prevent further visual loss.
  • Meningioma: A tumor arising from the meninges, which could compress multiple cranial nerves and cause the described symptoms. Early detection is vital for effective management.

• Rare diagnoses

  • Neurosyphilis: Can cause a wide range of neurological symptoms, including cranial neuropathies. The specific pattern of nerve involvement could be consistent with neurosyphilis, though it would be less common.
  • Sarcoidosis: A systemic granulomatous disease that can affect any part of the nervous system, including cranial nerves. While rare, it should be considered in the differential diagnosis due to its potential for widespread neurological involvement.