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Fanny Tréchot, Marc Braun, Veronique Cloche, Karine Angioi; Prospective study on the contribution of MRI in the analysis of isolated mydriasis: a new kind of neurovascular conflict. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4378.
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To study the contribution of MRI (sequence FIESTA) in analysis of isolated, persistant and idiopathic mydriasis and to describe a new type of neurovascular conflict between Cranial Nerve III (CN III) and adjacent structures.
Prospective single center study (November 2010 to March 2012) including patients with unilateral mydriasis (pure intrinsic CN III palsy) without life-threatening pathology. Complete ophthalmological, systemic and neurological examinations were performed. All patients with any symptoms of extrinsic CN III palsy (diplopia, ptosis or ophthalmoplegia), with tonic pupil (pilocarpine diluted test positive), use of toxic or drug taking, sign of focus at neurological examination have been excluded. Our patients underwent cerebral MRI: images acquisitions were performed on a GE 3T MRI, protocol included FIESTA and 3D TOF sequences.
Five patients were included (20 to 41 years), 2 women. They presented with a single non reactive, isolated and persistent mydriasis with a negative pilocarpine diluted-test. In patients MRI revealed a neurovascular conflict by clamping between a prevailing Posterior Communicating Artery (PCoA), CN III and posterior clinoid process at entrance of osteodural channel. No cases occurred in the Root Entry Zone. There was no controlateral conflict. Isolated achievement of intrinsic component of CN III can be explained by the presence of parasympathetic fibers walking dorsally and medially on the CN III, corresponding to the location of the neurovascular conflict.
Contribution of MRI in the study of anisocoria must be considered, and could help us for etiological diagnosis in a case of a pathology tagged idiopathic. FIESTA and 3D TOF reveal a new neurovascular conflict between CN III, PCoA and posterior clinoid process in patients with isolated CN III intrinsic palsy.
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