No abstract

The aim of the present study was to explore further the effects of light deprivation (LD) on visual cortex excitability. Healthy subjects reporting reliable induction of phosphenes by occipital transcranial magnetic stimulation (TMS) underwent 60 min of complete LD. Phosphene threshold (PT) was measured before (T 0 ), after 45 min (T 1 ) and 60 min (T 2 ) of LD, and then every 10 min after light re-exposure until recovery to T 0 values. Repetitive TMS (rTMS) (at 1 or 10 Hz) was applied in separate sessions during the last 15 min of LD. PTs significantly decreased after 45 min of LD. rTMS differentially modified the effects of 60 min LD on PTs depending on stimulation frequency. One hertz rTMS did not change the decreasing of PT values as observed in baseline condition, but significantly prolonged the time to recover T 0 PT values after light re-exposure. By contrast, 10 Hz rTMS significantly increased PT and the time to recover T 0 PT values after light re-exposure was shortened. The results of this study show that the modulatory effects of different rTMS frequencies on visual cortex critically depend on the pre-existing excitability state of inhibitory and facilitatory circuits, and provide novel insights into the neurophysiological changes that take place in the visual cortex following functional visual deafferentation.

Cognitive decline was present even when physical disability was not yet severe, but it was mild and did not limit patients' ability to work. The cognitive impairment outlined was of the subcortical type and correlated with illness duration. This study emphasizes the importance of cognitive examination in clinical practice. It is suggested that a complete neurological examination include tests on memory and abstract reasoning.

Background: Epidemiological studies conducted in Sicily and Sardinia, the two major Mediterranean islands, showed elevated incidence and prevalence of multiple sclerosis (MS)and a recent increase in disease frequency. Objective: To confirm the central highlands of Sicily as areas of increasing MS prevalence and elevated incidence, we performed a follow-up study based on the town of Caltanissetta (Sicily), southern Italy. Methods: We made a formal diagnostic reappraisal of all living patients found in the previous study performed in 1981. All possible information sources were used to search for patients affected by MS diagnosed according to the Poser criteria. We calculated prevalence ratios, for patients affected by MS who were living and resident in the study area on December 31, 2002. Crude and age- and sex-specific incidence ratios were computed for the period from January 1, 1993, to December 31, 2002. Results: The prevalence of definite MS rose in 20 years from 69.2 (retrospective prevalence rate) to 165.8/100,000 population. We calculated the incidence of definite MS for the period 1970–2000. These rates calculated for 5-year periods increased from 2.3 to 9.2/100,000/year. Conclusion: This survey shows the highest prevalence and incidence figures of MS in the Mediterranean area and confirms central Sicily as a very-high-risk area for MS.

We recently reported a paradoxical facilitatory effect of 1 Hz repetitive TMS (rTMS) on the primary visual cortex in migraine possibly due to the failure of inhibitory circuits, unable to be upregulated by low frequency rTMS. To investigate if inhibitory circuit dysfunction extends beyond striate cortex in migraine with aura, we studied the effects of 1 Hz rTMS over the right extrastriate cortex on perception of illusory contours in these patients. Low-frequency rTMS enhanced activity of extrastriate cortex in migraineurs, speeding up reaction times on illusory contour perception. This finding supports the view of a failure of inhibitory circuits also involving the extrastriate cortex in migraine with aura.