Wernicke’s hemianopic pupillary response is seen in lesions at –
**Core Concept**
Wernicke's hemianopic pupillary response is a clinical phenomenon where a unilateral pupillary light reflex abnormality is observed in the presence of a contralateral visual field defect. This occurs due to the interruption of the afferent pupillary pathway, which involves the optic nerve and optic tract.
**Why the Correct Answer is Right**
Wernicke's hemianopic pupillary response is typically seen in lesions affecting the optic tract, which is responsible for transmitting visual information from the contralateral visual field to the brain. The interruption of this pathway leads to a relative afferent pupillary defect (RAPD), where the pupils of the affected eye dilate when light is shone in the affected visual field. This is because the afferent input from the affected visual field is impaired, leading to an imbalance in the pupillary light reflex.
**Why Each Wrong Option is Incorrect**
* **Option A:** Lesions affecting the optic nerve would result in a unilateral visual field defect, but Wernicke's hemianopic pupillary response is not typically seen in this scenario.
* **Option B:** Lesions affecting the optic chiasm might result in bitemporal hemianopia, but Wernicke's hemianopic pupillary response is not characteristically associated with this type of lesion.
* **Option D:** Lesions affecting the lateral geniculate body or visual cortex would not typically result in Wernicke's hemianopic pupillary response, as these structures are involved in higher-order visual processing.
**Clinical Pearl / High-Yield Fact**
Wernicke's hemianopic pupillary response is a useful clinical sign that can help localize lesions affecting the optic tract, which is an important structure in the visual pathway.
**Correct Answer:** C.