No, a prominent pituitary gland cannot explain right-sided homonymous hemianopsia
The pituitary enlargement is anatomically incapable of causing this patient's visual symptoms, and urgent MRI brain imaging is required to identify the true retrochiasmatic pathology that is likely causing her deficit.
Why the Anatomy Doesn't Match
The visual field defect described—right-sided homonymous hemianopsia—indicates a retrochiasmatic lesion affecting structures posterior to the optic chiasm (optic tracts, lateral geniculate nucleus, optic radiations, or occipital cortex) 1. The pituitary gland sits anterior to the optic chiasm and can only compress the chiasm or optic nerves when enlarged.
Pituitary lesions cause bitemporal hemianopsia, not homonymous defects 1. When pituitary macroadenomas grow into the suprasellar cistern and compress the optic chiasm, they produce characteristic bitemporal visual field defects or junctional scotomas 1. The anatomical relationship makes it impossible for a pituitary lesion to cause a homonymous hemianopsia.
Critical Next Steps
Immediate Imaging Required
This patient needs an urgent MRI brain without and with contrast 1, 2. The CTA head and neck was inadequate imaging for this presentation. According to the 2025 ACR Appropriateness Criteria, patients presenting with homonymous hemianopsia require MRI to identify retrochiasmal pathology 1.
Most Likely Diagnoses to Consider
The most common cause of homonymous hemianopsia is ischemic stroke 1:
- Posterior cerebral artery (PCA) stroke if the lesion is in the occipital lobe
- Middle cerebral artery (MCA) stroke if affecting the optic radiations
- Venous infarction from dural venous sinus or cerebral vein thrombosis (can be hemorrhagic)
Other important causes include 1:
- Parenchymal hematoma
- Brain tumor
- Trauma (though not reported here)
- Demyelinating disease
- Neurosurgical complications
Common Pitfall to Avoid
Do not be distracted by incidental findings. The prominent pituitary gland is likely an incidental finding (pituitary incidentaloma) that is unrelated to her presenting symptoms 3. Pituitary incidentalomas are common and found in approximately 1 in 1100 persons 4. While the pituitary prominence warrants eventual endocrine evaluation 3, it is not causing her current visual deficit.
Clinical Urgency
The acuity of symptoms should alert you to the possibility of stroke 1. Even though patients may not immediately be aware of a hemianopsia 1, a 48-year-old woman with acute-onset homonymous hemianopsia requires urgent stroke workup. Time is critical if this represents an acute vascular event.
Stroke Protocol Considerations
If MRI confirms acute ischemic stroke, refer to stroke protocols for management. If vascular imaging (MRA or additional CTA) shows aneurysm or vascular malformation, neurosurgical consultation may be needed 1, 2.
Regarding the Pituitary Finding
While not causing her current symptoms, the prominent pituitary should be followed up separately:
- Endocrinology consultation for hormonal evaluation 3
- Dedicated pituitary MRI protocol if macroadenoma suspected 1
- This can be addressed after the acute visual deficit is evaluated and managed
The bottom line: Look posterior to the chiasm for the true pathology causing her homonymous hemianopsia, not at the pituitary gland.