Investigating cortical excitability and inhibition in patients with schizophrenia: A TMS-EEG study.

BACKGROUND: Transcranial magnetic stimulation (TMS) combined with electromyography (EMG) has widely been used as a non-invasive brain stimulation tool to assess excitation/inhibition (E/I) balance. E/I imbalance is a putative mechanism underlying symptoms in patients with schizophrenia. Combined TMS-electroencephalography (TMS-EEG) provides a detailed examination of cortical excitability to assess the pathophysiology of schizophrenia. This study aimed to investigate differences in TMS-evoked potentials (TEPs), TMS-related spectral perturbations (TRSP) and intertrial coherence (ITC) between patients with schizophrenia and healthy controls. MATERIALS AND METHODS: TMS was applied over the motor cortex during EEG recording. Differences in TEPs, TRSP and ITC between the patient and healthy subjects were analysed for all electrodes at each time point, by applying multiple independent sample t-tests with a cluster-based permutation analysis to correct for multiple comparisons. RESULTS: Patients demonstrated significantly reduced amplitudes of early and late TEP components compared to healthy controls. Patients also showed a significant reduction of early delta (50-160 ms) and theta TRSP (30-250ms),followed by a reduction in alpha and beta suppression (220-560 ms; 190-420 ms). Patients showed a reduction of both early (50-110 ms) gamma increase and later (180-230 ms) gamma suppression. Finally, the ITC was significantly lower in patients in the alpha band, from 30 to 260 ms. CONCLUSION: Our findings support the putative role of impaired GABA-receptor mediated inhibition in schizophrenia impacting excitatory neurotransmission. Further studies can usefully elucidate mechanisms underlying specific symptoms clusters using TMS-EEG biometrics.

Visual snow syndrome: a comparison between an Italian and British population.

BACKGROUND AND PURPOSE: Visual snow manifests as a pan-field, dynamic visual disturbance described as continuous television static-like tiny flickering dots. Current diagnostic criteria further require at least two additional symptoms for visual snow syndrome (VSS) from: palinopsia (afterimages and trailing); entoptic phenomena (floaters, blue field entoptic phenomenon, photopsia, self-light of the eye); photophobia and nyctalopia. Our objective was to compare the phenotype of VSS in an Italian and British population. METHODS: Patients with VSS were characterized clinically using the current criteria. An online survey was prepared in collaboration with the patient group Eye-on-Vision. Patients were directed to the site if they contacted us by email asking to be involved in research. After data collection, we compared the phenotypic characteristics of a subgroup of British versus Italian patients taking part in the survey. As we expected more responses from the UK, we matched 100 UK patients for gender and age with our Italian cohort. RESULTS: Patients were enrolled from the UK (n = 100) and Italy (n = 100). The populations had similar demography. After multiple correction testing there were no differences in VSS features between the two groups. The same was true for the prevalence of migraine and previous use of recreational drugs. CONCLUSION: This is the first study comparing the phenotype of VSS between two distinct populations. Our findings suggest that the visual snow phenotype, as well as migraine comorbidity, is similar across the two groups.

Sapienza Global Bedside Evaluation of Swallowing after Stroke: the GLOBE-3S study.

BACKGROUND AND PURPOSE: Dysphagia occurs in up to 50% of all patients with acute stroke. There is debate regarding which is the most effective screening tool in identifying aspiration in patients with acute stroke. We assessed the accuracy of the Sapienza Global Bedside Evaluation of Swallowing after Stroke (GLOBE-3S), which combines the Toronto Bedside Swallowing Screening Test (TOR-BSST©) with oxygen desaturation and laryngeal elevation measurement during swallowing. METHODS: We prospectively enrolled consecutive patients with stroke within 72 h of symptom onset. All patients with stroke firstly underwent a standard neurological examination, then the GLOBE-3S evaluation and finally the fiberoptic endoscopic evaluation of swallowing (FEES). Two different assessors, a neurologist and a speech pathologist, blind to both the clinical data and each other's evaluation, administered the GLOBE-3S and FEES examination. We assessed the accuracy of the GLOBE-3S in detecting post-stroke swallow impairment with aspiration using the FEES as the standard. RESULTS: We enrolled 50 patients with acute stroke, 28 of whom (56%) had swallowing impairment with aspiration at FEES evaluation. A total of 33 patients (66%) failed the GLOBE-3S evaluation. The GLOBE-3S reached a sensitivity of 100% and a specificity of 77.3% (negative predictive value, 100%; positive likelihood ratio, 4.34). The median time required for the GLOBE-3S to be performed was 297 s. CONCLUSIONS: GLOBE-3S is quick to perform at the bedside and can accurately identify aspiration in patients with acute stroke. By including the measurement of laryngeal elevation and monitoring of oxygen desaturation, it could represent a highly sensitive instrument to avoid the misdiagnosis of silent aspirators.

Lack of habituation of evoked visual potentials in analytic information processing style: evidence in healthy subjects.

Habituation is considered one of the most basic mechanisms of learning. Habituation deficit to several sensory stimulations has been defined as a trait of migraine brain and also observed in other disorders. On the other hand, analytic information processing style is characterized by the habit of continually evaluating stimuli and it has been associated with migraine. We investigated a possible correlation between lack of habituation of evoked visual potentials and analytic cognitive style in healthy subjects. According to Sternberg-Wagner self-assessment inventory, 15 healthy volunteers (HV) with high analytic score and 15 HV with high global score were recruited. Both groups underwent visual evoked potentials recordings after psychological evaluation. We observed significant lack of habituation in analytical individuals compared to global group. In conclusion, a reduced habituation of visual evoked potentials has been observed in analytic subjects. Our results suggest that further research should be undertaken regarding the relationship between analytic cognitive style and lack of habituation in both physiological and pathophysiological conditions.

Cardioembolic stroke: Protective effect of a severe internal carotid artery stenosis in a patient with cardiac embolism.

Cardioembolic stroke is generally caused by intracranial artery occlusion. Clots may be identified in the intracranial vessels by means of conventional neuroimaging in the acute phase. High-resolution ultrasonography may show some features suggestive of cardiac emboli when occluding extracranial carotid arteries. We describe a patient with cardioembolic ischemic stroke in the right hemisphere in whom a left internal carotid artery stenosis paradoxically protected the ipsilateral hemisphere from distal intracranial embolism. The patient also presented multiple acute ischemic embolic lesions in the right middle cerebral artery territory and in the right occipital lobe, which was fed by the posterior cerebral artery, anomally originating from the right carotid siphon. Interestingly, the left internal carotid artery--which showed a severe preexisting stenosis--was occluded by the cardiac clot, whereas the right internal carotid artery only presented a moderate stenosis that had probably allowed the clots to pass. Therefore, the severe left internal carotid artery stenosis may have blocked the cardiac embolus, preventing it from reaching the ipsilateral hemisphere.