A 60-year-old man with longstanding type 2 diabetes mellitus (HbA1c 8.2%) presents with sudden-onset diplopia. Vital signs: BP 148/92, HR 82, RR 16, Temp 37°C, SpO2 98%. Examination reveals the left eye positioned down and out with ptosis; importantly, the pupil remains equal and reactive to light bilaterally. MRI brain shows no acute infarction. He denies headache or neck stiffness. Which mechanism best explains the preserved pupillary function?
- A)The lesion is in the Edinger Westphal nucleus only
- B)The trochlear nerve is compensating for the deficit
- C)The optic nerve is intact
- D)Parasympathetic fibers run superficially and are spared in ischemic injuryGABARITO
- E)The sympathetic chain is also damaged
Explicação
Parasympathetic fibers run superficially and are spared in ischemic injury is correct. Microvascular ischemia in diabetes affects the centrally located somatic fibers of cranial nerve III, causing ophthalmoplegia and ptosis while sparing the superficial parasy... Ver explicação completa e trilha adaptativa →