What is the most likely diagnosis for a 72-year-old woman with photophobia, inability to keep her eyes open, difficulty looking upward, a benign pituitary adenoma, MRI showing parenchymal enhancement and a small fusiform aneurysm of the upper right middle cerebral artery, and a negative lumbar puncture?

Blepharospasm or Apraxia of Eyelid Opening Secondary to Chiasmal Compression

This patient most likely has photophobia and difficulty opening her eyes (blepharospasm or apraxia of eyelid opening) caused by chiasmal compression from her pituitary adenoma, and she requires urgent neuro-ophthalmologic evaluation and likely surgical decompression.

Clinical Reasoning

The constellation of photophobia, inability to keep eyes open, and difficulty with upward gaze in a patient with a known pituitary mass strongly suggests chiasmal compression with atypical neuro-ophthalmologic manifestations. While photophobia is commonly attributed to anterior segment pathology, compressive lesions of the optic chiasm can present with photophobia as the primary or sole visual symptom 1. In a case series, all five patients with chiasmal compression presenting primarily with photophobia had resolution after tumor treatment 1.

Key Diagnostic Considerations

The difficulty looking upward combined with photophobia and eye closure problems suggests:

• Chiasmal compression affecting visual pathways (explaining photophobia)
• Possible suprasellar extension affecting midbrain structures or causing dorsal midbrain syndrome
• The "inability to keep eyes open" may represent either:
  • Blepharospasm secondary to photophobia
  • Apraxia of eyelid opening from suprasellar mass effect
  • Cranial neuropathy from cavernous sinus involvement

The Aneurysm and Parenchymal Enhancement

The small fusiform MCA aneurysm is likely incidental—the coexistence of pituitary adenomas and intracranial aneurysms occurs in 2.3-5.4% of cases 2. The parenchymal enhancement on MRI could represent:

• Pituitary apoplexy (hemorrhage into the adenoma)
• Inflammatory changes
• Mass effect-related edema

The negative lumbar puncture effectively rules out infectious or inflammatory meningitis but does not exclude chiasmal compression or apoplexy.

Immediate Management Algorithm

Step 1: Urgent Neuro-ophthalmologic Evaluation

• Formal visual field testing (looking for bitemporal hemianopsia or other defects)
• Visual acuity assessment
• Pupillary examination
• Extraocular movement testing
• Patients with abnormal visual field test results must be evaluated by a neuro-ophthalmologist 3

Step 2: Determine Surgical Candidacy According to 2025 Pituitary Society guidelines 3:

• Surgery is recommended for visual compromise, cranial neuropathy, or neurological deficit related to the adenoma 3
• At age 72, if the adenoma abuts the optic chiasm, surgery is recommended after evaluation at a pituitary center, though observation can be considered if visual function is intact and functional status is poor 3
• For severe and/or progressive vision loss, surgery is suggested for most patients 3

Step 3: Address the Aneurysm

• The fusiform MCA aneurysm requires neurovascular consultation
• If surgery is planned, consider preoperative aneurysm treatment (coiling or flow diversion) to prevent catastrophic rupture during transsphenoidal surgery 2, 4
• Unrecognized aneurysms pose rare but potentially fatal risk during pituitary surgery 4

Critical Pitfalls to Avoid

1. Don't dismiss photophobia as a minor symptom—it can be the presenting sign of chiasmal compression requiring urgent intervention 1, 5

2. Don't assume the aneurysm is causing symptoms—while it requires management, the symptom complex points to the pituitary mass as the primary culprit

3. Don't delay surgical evaluation in a 72-year-old—while age >65 allows for observation in some cases, the presence of neurological symptoms (photophobia, eye opening difficulty, upgaze limitation) mandates surgical consideration 3

4. Don't proceed to pituitary surgery without addressing the aneurysm—preoperative aneurysm treatment prevents intraoperative rupture 2, 4

Recommended Diagnostic Workup

• Formal visual field testing (perimetry)
• Complete ophthalmologic examination by neuro-ophthalmologist
• Pituitary hormone panel (to assess for hypersecretion or hypopituitarism)
• Neurovascular imaging review to characterize the aneurysm and determine treatment necessity
• Review MRI for signs of apoplexy (intralesional hemorrhage) which could explain acute symptom onset 6, 7

The patient requires multidisciplinary evaluation at a pituitary tumor center of excellence with coordinated neurosurgery, neuro-ophthalmology, and endovascular neurosurgery input 3.