Chiasmal syndromes present mostly with visual problems, such as changes in visual fields, decreased visual acuity, or dyschromatopsia (and classically without pupillary reflex defects). The prototypical bitemporal hemianopia upon visual field testing can easily suggest chiasmal compression due to sellar/suprasellar involvement. However, because of the complexity of the decussation of fibres at the optic chiasm and the presence of anatomical variants, unpredictable visual fields defects can be detected in chiasmal diseases. In some patients, especially in those who have undergone neurosurgical procedures, visual field examination and neuroimaging may not completely reflect the classical pattern of chiasmal visual loss. We describe a novel semiological sign, reporting a patient in which a pupillary bitemporal hemihypokinesia was not accompanied by hemianopia, with the phenomenon being abolished by surgical resection of the causative pituitary macroadenoma. In addition, this finding was an important tool in making the diagnosis.
Keywords: Bitemporal hemihypokinetic pupil; Wernicke’s hemianopic phenomenon; chiasmal sign; hemiretina stimulation; pituitary macroadenoma; pupillary hemihypokinesia.
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