Understanding Pupillary Reflex Responses in CN II and CN III Damage
This analysis explores the effects of damage to the right optic nerve (CN II) and oculomotor nerve (CN III) on pupillary reflexes. In cases of CN II damage, the right eye exhibits an absent direct response to light but maintains consensual response, indicating light perception loss. Conversely, CN III damage results in the inability to constrict the pupil on the affected side while maintaining light sensitivity. Clinical correlations, including the Argyll-Robertson pupil observed in tertiary neuro syphilis, highlight the complexity of pupillary reflex mechanisms.
Understanding Pupillary Reflex Responses in CN II and CN III Damage
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Presentation Transcript
Constrictor pupillae muscle • Damage to Right CNII: • Right direct response • Left consensual response • Left direct response • Right consensual response • Damage to Right CNIII: • Right direct response • Left consensual response • Left direct response • Left consensual response
Damage to Right CNII: • Right direct response: Absent • Left consensual response: Absent • Left direct response: Present • Right consensual response: Present • This occurs as the right eye cannot sense any light but still has CNIII innervation. • Damage to Right CNIII: • Right direct response: Absent • Left consensual response: Present • Left direct response: Present • Left consensual response: Absent • Here the side that is damaged lacks the ability to activate constrictor pupillae but can still sense light.
Clinical Point: Argyll-Robertson Pupil • Seen in tertiary neuro syphilis • Get no pupillary light reflex but still have accommodation. • Mechanism to produce it is unclear.
