Assessment of Cortical Dysfunction in Patients with Intermittent Exotropia: An fMRI Study.
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ABSTRACT:
SUBMITTER: Li Q
PROVIDER: S-EPMC4976854 | biostudies-literature | 2016
REPOSITORIES: biostudies-literature
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Assessment of Cortical Dysfunction in Patients with Intermittent Exotropia: An fMRI Study.
Li Qian Q Bai Junxing J Zhang Junran J Gong Qiyong Q Liu Longqian L
PloS one 20160808 8
Neural imaging studies have found the connection between strabismus and brain cortex. However, the pathological mechanisms of intermittent exotropia are still not fully understood. In the present study, changes of binocular fusion related cortices in intermittent exotropia were investigated with blood oxygen level dependent functional magnetic resonance imaging. Activated cortices induced by fusion stimulus were found to be distributed in several regions such as bilateral middle occipital gyrus, ...[more]
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Project description:Intermittent exotropia (IXT) is characterized by intermittently outward deviation of the eye and involved with vergence dysfunction. This study aimed to investigate the brain areas related to voluntary convergence and cortical activation changes between IXT patients and normal subjects. A total of 21 subjects, including 11 IXT patients and 10 age- and sex-matched normal subjects, were recruited for this study. A voluntary convergence task was employed, with changes in brain function measured by functional magnetic resonance imaging (fMRI). Correlations between cortical activation and clinical measurements were conducted by Pearson's correlation analysis. fMRI results showed that during voluntary convergence, the medial frontal gyrus (MFG) and bilateral occipital cortex were activated in the normal group, whereas only activation of the occipital cortex in IXT patients. Compared with the normal, IXT patients showed hypo-activation of both the MFG and cuneus during the task. The activation of MFG was negatively correlated to the duration of IXT. This study demonstrates that both MFG and occipital cortex may participate in voluntary convergence in normal subjects, while IXT patients have an aberrant cortical function of the MFG and cuneus, and the duration of IXT likely influences the severity of MFG. These findings may provide valuable insights for understanding the relationship between convergence and IXT.
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Project description:BackgroundThe clinical management of intermittent exotropia has been discussed extensively in the literature, yet there remains a lack of clarity regarding indications for intervention, the most effective form of treatment and whether or not there is an optimal time in the evolution of the disease at which any treatment should be carried out.ObjectivesThe objective of this review was to analyse the effects of various surgical and non-surgical treatments in randomised trials of participants with intermittent exotropia, and to report intervention criteria and determine the significance of factors such as age with respect to outcome.Search methodsWe searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library, Issue 4, 2012), MEDLINE (January 1966 to May 2012), EMBASE (January 1980 to May 2012), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to May 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 4 May 2012. We are no longer searching the UK Clinical Trials Gateway (UKCTG) for this review. We manually searched the British Orthoptic Journal up to 2002, and the proceedings of the European Strabismological Association (ESA), International Strabismological Association (ISA) and American Academy of Paediatric Ophthalmology and Strabismus meeting (AAPOS) up to 2001. We contacted researchers who are active in the field for information about further published or unpublished studies.Selection criteriaWe included randomised controlled trials of any surgical or non-surgical treatment for intermittent exotropia.Data collection and analysisEach review author independently assessed study abstracts identified from the electronic and manual searches. Author analysis was then compared and full papers for appropriate studies were obtained.Main resultsWe found one randomised trial that was eligible for inclusion. This trial showed that unilateral surgery was more effective than bilateral surgery for correcting the basic type of intermittent exotropia.Authors' conclusionsThe available literature consists mainly of retrospective case reviews, which are difficult to reliably interpret and analyse. The one randomised trial included found unilateral surgery more effective than bilateral surgery for basic intermittent exotropia. However, across all identified studies, measures of severity and thus criteria for intervention are poorly validated, and there appear to be no reliable natural history data. There is therefore a pressing need for improved measures of severity, a better understanding of the natural history and carefully planned clinical trials of treatment to improve the evidence base for the management of this condition.
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Project description:Surgical treatment of childhood intermittent exotropia (XT) is associated with high recurrence rates. In addition, the natural history of intermittent XT has not been rigorously studied and, anecdotally, some cases resolve without surgery. We compared long-term cure rates in children with surgically and non-surgically managed intermittent XT. Children undergoing surgery for intermittent XT who had 5 years follow-up were retrospectively identified. A non-surgical cohort of comparable children was selected by matching each surgical patient for age at onset and age at the 5-year examination. Cure was defined as no manifest tropia on examination or by history, no new monofixation (stereoacuity subnormal for age), and no additional surgery. Each group had 33 children (total follow-up from presentation 7.2±2.6 years in the surgical group vs 6.8±2.3 years). There were no significant differences between groups for age at onset, age at presentation, or distance or near angle of deviation at presentation (all P≥0.4). The cure rate at 5 years was 30% in the surgical group and 12% in the non-surgical group (P=0.1; difference 18%, 95% CI -1 to 37%). Only a small proportion of surgical and non-surgical patients met our definition of cure, with the vast majority demonstrating a constant or intermittent manifest deviation after an average of 7 years follow-up. In childhood intermittent XT, long-term cure is difficult to achieve with surgical intervention, and in some patients managed non-surgically the intermittent XT will spontaneously resolve.
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Project description:A test of suppression was developed to provide a standardized approach to detecting and grading density of suppression in children with intermittent exotropia when manifestly exotropic. This new Office Suppression Test is a three-step procedure to grade suppression on a 4-point scale (from 0 for "negligible suppression" to 3 for "dense suppression"). The test was performed in 57 children 3-13 years of age with intermittent exotropia (distance angle of 16Δ-35Δ, with spontaneous tropia) during enrollment in a randomized trial. Of the 57 children, 51 could complete testing: 28 (55%) had dense suppression, 12 (24%) had moderate suppression, 5 (10%) had mild suppression, and 6 (12%) had negligible suppression. In a subgroup of 20 untreated children, suppression was evaluated again at 8 weeks. There was moderate agreement between suppression scores at baseline and at 8 weeks (weighted κ = 0.65 [95% CI, 0.45-0.84]).
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