Unilateral mydriasis can represent a diagnostic challenge and it may carry ominous significance when associated with other signs or symptoms. Third cranial nerve compression should be excluded in cases of unilateral mydriasis with no light response [1, 2]. Very rarely, focal seizures may cause unilateral fixed mydriasis [3–6]. A 47-year-old woman had transient loss of consciousness. She denied previous medical problems. At admission, physical examination showed mild left hemiparesis. Brain computed tomography (CT) scan showed right fronto-basal hypodensity (Fig. 1a). The day after, she suddenly developed headache worsening, nausea and dizziness. Physical examination confirmed mild left hemiparesis and showed the appearance of right unilateral mydriasis which was unresponsive to light and waxed and waned, in that longlasting periods of right fixed mydriasis alternated with periods of symmetric pupils and normal bilateral response to light. Mydriasis was associated with some excessive sweating and facial flushing. Eye exposure to drugs and intraocular diseases were excluded by a neuro-ophthalmologist. Brain CT angiography, digital angiography and lumbar puncture ruled out intracranial aneurysm and subarachnoid haemorrhage. The following night, she developed seizures which started with fixed right mydriasis and left-sided clonic jerks followed by secondary generalization; seizures recurred on the following three days and sodium valproate was started. In this period, she presented some episodes of right unilateral mydriasis unresponsive to light. Mydriasis and left hemiparesis disappeared when seizures stopped. Brain magnetic resonance imaging (MRI) confirmed the right fronto-basal lesion with normal diffusion-weighted sequences, suggesting encephalomalacia (Fig. 1b). Ictal electroencephalography (EEG) was not recorded. Interictal EEG was normal on two occasions, during an episode of right fixed mydriasis, and after sleep deprivation. She underwent 256-channel densearray EEG (dEEG, Electrical Geodesics Inc., Eugene, Oregon, USA), which showed spikes on zygomatic-temporal electrodes and localized the spike focus in the right inferior temporal gyrus (Fig. 1c, d). At eight-month followup, seizures and mydriasis disappeared and the patient was well. The patient gave informed consent for case report. Unilateral fixed mydriasis without extraocular motility deficit is rare. The parasympathetic fibers, which cause pupil constriction, lie in the most peripheral part of the third cranial nerve and, because of their superficial location, are the most susceptible to compression [1]. Because of its close position to the superior cerebellar and the posterior cerebral arteries, the third cranial nerve may be compressed by intracranial aneurysms, especially those arising from the posterior communicating to internal carotid artery junction [2]. In our patient, right fixed mydriasis, hemiparesis and headache suggested subarachnoid haemorrhage due to ruptured intracranial aneurysm compressing the right third cranial nerve, but investigations excluded this hypothesis. Tonic Adie pupil [1, 2] was excluded because light-near dissociation and segmental sphincter palsy were absent and deep tendon reflexes were preserved. Opthalmoplegia associated with migraine or cluster headache [2] was excluded because of no previous S. Tamburin (&) G. Turri P. Kuhdari A. Fiaschi P. Manganotti Department of Neurological, Neuropsychological, Morphological and Movement Sciences, G.B. Rossi Hospital, University of Verona, Piazzale Scuro 10, 37134 Verona, Italy e-mail: stefano.tamburin@univr.it
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Mar 11, 2013
Allison C Waters + 1
Open Access