A homonymous hemianopia that respects the vertical meridian and is denser superiorly is classically associated with a lesion in which anatomical location?

Explanation

## Anatomical Basis of Superior Quadrantanopia **Key Point:** Meyer's loop is the inferior temporal portion of the optic radiations that loops anteriorly into the temporal lobe before projecting posteriorly to the inferior visual cortex. A lesion here produces a contralateral superior quadrantanopia (also called "pie-in-the-sky" defect). ### Meyer's Loop Anatomy - Located in the **temporal lobe**, anterior to the lateral geniculate nucleus (LGN) - Carries fibres from the **inferior retina** (which represent the **superior visual field**) - Loops forward into the temporal lobe before curving back to reach area 17 - Lesions produce a **superior homonymous quadrantanopia** that respects the vertical meridian ### Why Superior and Not Inferior? - The inferior retina (inferior nasal and inferior temporal) represents the **superior visual field** (inverted image on retina) - Meyer's loop damage → loss of superior field fibres → superior quadrantanopia ### Differential: Other Radiations | Location | Defect | Characteristics | |----------|--------|------------------| | **Meyer's loop (inferior temporal)** | **Superior quadrantanopia** | Denser superiorly; temporal lobe lesion | | Superior parietal radiations | Inferior quadrantanopia | Denser inferiorly; parietal lobe lesion | | Optic tract | Complete homonymous hemianopia | No quadrantanopia; respects vertical meridian | | Optic chiasm | Bitemporal hemianopia | Respects horizontal meridian | **High-Yield:** "Pie-in-the-sky" = Meyer's loop lesion. The superior field loss looks like a slice of pie removed from the top of the visual field. **Clinical Pearl:** Meyer's loop lesions are commonly seen in anterior temporal lobe strokes, temporal lobe tumours, and temporal lobe surgery (e.g., anterior temporal lobectomy for epilepsy).