chiasmal syndrome
Pattern of visual field defects caused by lesions at the optic chiasm, typically producing bitemporal hemianopia.
Full Definition
Chiasmal syndrome refers to the constellation of visual field defects and clinical findings resulting from lesions affecting the optic chiasm, where the optic nerves from both eyes partially cross. The hallmark visual field defect is bitemporal hemianopia, where the temporal (outer) visual fields of both eyes are lost, creating a characteristic pattern that respects the vertical meridian. This occurs because crossing fibers from the nasal retinae are preferentially affected at the chiasm. Common causes include pituitary adenomas, craniopharyngiomas, meningiomas, and other sellar or suprasellar masses. The syndrome may also include decreased visual acuity, reduced color vision, and optic disc pallor. Early detection is crucial as chiasmal compression can lead to irreversible visual loss, but timely intervention may restore or preserve visual function.
Usage
Usage note: Use 'chiasmal' rather than 'chiasmatic' when referring to the syndrome; specify visual field pattern.
In Context
- "The patient's bitemporal visual field defects were consistent with chiasmal syndrome." — Neuro-ophthalmology report
- "MRI revealed a pituitary macroadenoma causing chiasmal syndrome with bilateral temporal field cuts." — Radiology correlation