PCNSL – HD-MTX Not Resection — SCE Neurology MCQ
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Correct answer: C — One-and-a-half syndrome from a pontine gaze-centre lesion
The best answer is “One-and-a-half syndrome from a pontine gaze-centre lesion”. A dorsal midbrain lesion produces vertical-gaze palsy, convergence-retraction nystagmus and light-near dissociation; pineal masses are a classic structural cause and may also obstruct the aqueduct. “Internuclear ophthalmoplegia from a medial longitudinal fasciculus lesion” is less appropriate because internuclear ophthalmoplegia impairs adduction with abducting nystagmus during horizontal gaze “Parinaud syndrome from a dorsal midbrain lesion” is less appropriate because cavernous disease combines ocular motor palsies with trigeminal sensory loss “Cavernous-sinus syndrome involving ocular motor nerves” is less appropriate because one-and-a-half syndrome is a pontine horizontal-gaze disorder “Ocular myasthenia causing fatigable ophthalmoplegia” is less appropriate because myasthenia causes fatigable weakness without pupillary or convergence-retraction signs
Reference: NICE NG99: Brain tumours and brain metastases in adults. https://www.nice.org.uk/guidance/ng99/chapter/Recommendations