Perceptual Decisions in the Presence of Relevant and Irrelevant Sensory Evidence.

Perceptual decisions in the presence of decision-irrelevant sensory information require a selection of decision-relevant sensory evidence. To characterize the mechanism that is responsible for separating decision-relevant from irrelevant sensory information we asked human subjects to make judgments about one of two simultaneously present motion components in a random dot stimulus. Subjects were able to ignore the decision-irrelevant component to a large degree, but their decisions were still influenced by the irrelevant sensory information. Computational modeling revealed that this influence was not simply the consequence of subjects forgetting at times which stimulus component they had been instructed to base their decision on. Instead, residual irrelevant information always seems to be leaking through, and the decision process is captured by a net sensory evidence signal being accumulated to a decision threshold. This net sensory evidence is a linear combination of decision-relevant and irrelevant sensory information. The selection process is therefore well-described by a strong linear gain modulation, which, in our experiment, resulted in the relevant sensory evidence having at least 10 times more impact on the decision than the irrelevant evidence.

Pseudo-Orbital Apex Syndrome in the Acute Trauma Setting Due to Ipsilateral Dissection of Internal Carotid Artery.

Traumatic causes of orbital apex and superior orbital fissure syndrome are uncommon. The authors present the first case of a traumatic superior orbital fissure syndrome simulating orbital apex syndrome, with loss of vision from posterior ischemic optic neuropathy. A 35-year-old man was initially felt to have a right orbital apex syndrome with left craniofacial and orbital trauma. CT revealed left orbital fractures, a right superior orbital fissure fracture, a retained metallic foreign body in the right sphenoid sinus, and a right frontoparietal subdural hematoma. CT angiography showed a secondary dissection and occlusion of the right internal carotid artery from osseous erosion of the posterolateral wall of the sphenoid sinus. Internal carotid artery dissection is a possible, though rare, cause of ischemic optic neuropathy. The right pseudo-orbital apex syndrome resulted from a mechanical superior orbital fissure syndrome and posterior ischemic optic neuropathy from an internal carotid artery dissection.

Acute orbital apex syndrome and rhino-orbito-cerebral mucormycosis.

PURPOSE: To demonstrate the successful clinical identification and management of rhino-orbital mucormycosis, a fungal infection with a high mortality rate. PATIENTS AND METHODS: A diabetic male patient with a headache and orbital apex syndrome in the right eye was examined using computed tomography (CT) and magnetic resonance imaging (MRI) for a possible fungal infection. Endoscopic surgical resection was performed and a pathology sample was taken. Specimens were prepared with Gömöri methenamine silver and hematoxylin and eosin staining. The patient was treated with liposomal amphotericin B 400 mg daily, followed by posaconazole 400 mg twice daily. RESULTS: CT and MRI revealed a mass of the right sphenoid spreading into the orbit, indicative of a fungal infection. The biopsy confirmed the diagnosis of mucormycosis. Complete recovery of eyelid and oculomotor function was achieved after 10 months of treatment, although the patient continues to suffer from irreversible blindness in the right eye due to optic nerve atrophy. He has been without signs or symptoms of recurrence. CONCLUSION: Patients with rhino-orbito-cerebral mucormycosis need extensive surgical and medical treatment to maximize outcomes. Success requires multidisciplinary management.

Tolosa-Hunt syndrome masquerading as a carotid artery dissection.

PURPOSE: To demonstrate the difficulties of diagnosing a patient with Tolosa-Hunt syndrome (THS) due to its complicated presentation and extensive diagnostic testing, and how to manage the treatment of a patient in an emergent setting. PATIENTS AND METHODS: A female patient with THS affecting the left eye was examined using two magnetic resonance imaging (MRI) scans. The patient was treated with high-dose methylprednisolone (Solu-Medrol(®)) and prednisone. A follow-up MRI and magnetic resonance angiogram (MRA) was also performed 4 months later. RESULTS: The second MRI scan disclosed a 5×9×10 mm lesion in the left superior orbital fissure/cavernous sinus. After administration of methylprednisolone and prednisone, the patient's pain completely resolved, and the left eye regained full duction and eyelid mobility. The MRI and MRA obtained after the treatment showed no abnormalities. CONCLUSION: The rarity of THS makes it difficult to diagnose, especially when there is a question of accuracy and reproducibility of the testing performed. An ophthalmologic consultation in such cases is crucial.