Summary:Purpose: Clinically silent lesions localized in the splenium of the corpus callosum (SCC) are a rare finding in the magnetic resonance imaging (MRI) of patients receiving antiepileptic drugs (AEDs). They are usually of benign character but may induce unnecessary complementary examinations if their nature is unrecognized. So far, 22 cases have been described in the literature, for which different etiologies have been proposed. We describe two further cases and discuss the probable lesion etiology.Methods: We report two cases including a 25-year-old male patient and a 12-year-old female patient with a transient SCC lesion discovered in the context of a presurgical epilepsy evaluation.Results: Comprehensive MRIs, including diffusion tensor imaging-based fiber tracking of the lesion, revealed a cytotoxic edema not disrupting neuronal fibers. Serum arginine vasopressin (AVP) measurements revealed an altered secretion during the acute phase in one patient.Conclusions: On the basis of our results, we hypothesize that the lesion consists of a cytotoxic edema, possibly induced by abrupt AED concentration changes and associated to alterations of AVP secretion. key Words: Epilepsy-MRISplenium-Corpus callosum-Antiepileptic drugs-Arginine vasopressin-Cytotoxic edema.Several reports of clinically silent lesions in the splenium of the corpus callosum (SCC) of patients receiving antiepileptic treatment have been recently published (Table 1). Different pathophysiologic hypotheses have been put forward as possible etiologic explanations, such as vasogenic edema secondary to blood-brain barrier breakdown (1), cytotoxic edema secondary to seizure spread (2-4), or antiepileptic drugs (AED) toxicity (5,6), demyelinating disease secondary to vitamin B deficiency, as well as edema secondary to arginine vasopressin (AVP) imbalance induced by rapid AED changes (7). Here we report two cases of epilepsy patients with splenial lesions discovered in the context of presurgical epilepsy evaluation. CASE REPORT Patient 1A 25-year-old male patient with an anxiety disorder and pharmacoresistant epilepsy since age 12 years was , combined with repeated sleep deprivation, no seizure occurred during our evaluation. Six days after the beginning of AED discontinuation, CBZ was reintroduced, and a control brain MRI was carried out. Aside from the postsurgical status in the right temporal lobe, a circumscribed lesion in the SCC, hypointense on T 1 and hyperintense on T 2 -weighted sequences, was noted. A diffusion-weighted acquisition showed a hyperintense lesion corresponding to a decreased apparent diffusion coefficient, which suggested the presence of a cytotoxic edema (Fig. 1). The patient's neurologic status was normal. Neuropsychological evaluation ruled out a disconnection syndrome. Routine laboratory tests, including hematologic analysis, were normal as were vitamin B 1 , B 2 , and B 6 levels. A repeated brain MRI 10 days after the first imaging showed an almost resolved lesion that completely disappeared on a MRI control 1 year later. A ...

Both TPN and DMN are affected in OSA patients, with nocturnal desaturation affecting both networks; whereas BMI appears to be the major negative factor influencing the TPN and has a significant negative correlation with behavioral performance.

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Introduction: Obstructive sleep apnea syndrome (OSAS) is a frequent breathing disorder occurring during sleep that is characterized by recurrent hypoxic episodes and sleep fragmentation. It remains unclear whether OSAS leads to structural brain changes, and if so, in which brain regions. Brain region-specific gray and white matter volume (GMV and WMV) changes can be measured with voxel-based morphometry (VBM). The aims of this study were to use VBM to analyze GMV and WMV in untreated OSAS patients compared to healthy controls (HC); examine the impact of OSAS-related variables (nocturnal hypoxemia duration and sleep fragmentation index) on GMV and WMV; and assess the effects of therapeutic vs. sham continuous positive airway pressure (CPAP) treatment. We discuss our results in light of previous findings and provide a comprehensive literature review.Methods: Twenty-seven treatment-naïve male patients with moderate to severe OSAS and seven healthy age- and education-matched HC were recruited. After a baseline fMRI scan, patients randomly received either active (therapeutic, n = 14) or sham (subtherapeutic, n = 13) nasal CPAP treatment for 2 months.Results: Significant negative correlations were observed between nocturnal hypoxemia duration and GMV in bilateral lateral temporal regions. No differences in GMV or WMV were found between OSAS patients and HC, and no differences between CPAP vs. sham CPAP treatment effects in OSAS patients.Conclusion: It appears that considering VBM GMV changes there is little difference between OSAS patients and HC. The largest VBM study to date indicates structural changes in the lateral aspect of the temporal lobe, which also showed a significant negative correlation with nocturnal hypoxemia duration in our study. This finding suggests an association between the effect of nocturnal hypoxemia and decreased GMV in OSAS patients.

IntroductionFunctional magnetic resonance imaging studies enable the investigation of neural correlates underlying behavioral performance. We investigate the effect of active and sham Continuous Positive Airway Pressure (CPAP) treatment on working memory function of patients with Obstructive Sleep Apnea Syndrome (OSAS) considering Task Positive and Default Mode networks (TPN and DMN).MethodsAn experiment with 4 levels of visuospatial n-back task was used to investigate the pattern of cortical activation in 17 men with moderate or severe OSAS before and after 2 months of therapeutic (active) or sub-therapeutic (sham) CPAP treatment.ResultsPatients with untreated OSAS had significantly less deactivation in the temporal regions of the DMN as compared to healthy controls, but activation within TPN regions was comparatively relatively preserved. After 2 months of treatment, active and sham CPAP groups exhibited opposite trends of cerebral activation and deactivation. After treatment, the active CPAP group demonstrated an increase of cerebral activation in the TPN at all task levels and of task-related cerebral deactivation in the anterior midline and medial temporal regions of the DMN at the 3-back level, associated with a significant improvement of behavioral performance, whereas the sham CPAP group exhibited less deactivation in the temporal regions of Default Mode Network and less Task Positive Network activation associated to longer response times at the 3-back.ConclusionOSAS has a significant negative impact primarily on task-related DMN deactivation, particularly in the medial temporal regions, possibly due to nocturnal hypoxemia, as well as TPN activation, particularly in the right ventral fronto-parietal network. After 2 months of active nasal CPAP treatment a positive response was noted in both TPN and DMN but without compete recovery of existing behavioral and neuronal deficits. Initiation of CPAP treatment early in the course of the disease may prevent or slow down the occurrence of irreversible impairment.