G. Reale

Small-World Characteristics of Cortical Connectivity Changes in Acute Stroke

Background. After cerebral ischemia, disruption and subsequent reorganization of functional connections occur both locally and remote to the lesion. Recently, complexity of brain connectivity has been described using graph theory, a mathematical approach that depicts important properties of complex systems by quantifying topologies of network representations. Functional and dynamic changes of brain connectivity can be reliably analyzed via electroencephalography (EEG) recordings even when they are not yet reflected in structural changes of connections. Objective. We tested whether and how ischemic stroke in the acute stage may determine changes in small-worldness of cortical networks as measured by cortical sources of EEG. Methods. Graph characteristics of EEG of 30 consecutive stroke patients in acute stage (no more than 5 days after the event) were examined. Connectivity analysis was performed using eLORETA in both hemispheres. Results. Network rearrangements were mainly detected in delta, theta, and alpha bands when patients were compared with healthy subjects. In delta and alpha bands similar findings were observed in both hemispheres regardless of the side of ischemic lesion: bilaterally decreased small-worldness in the delta band and bilaterally increased small-worldness in the alpha2 band. In the theta band, bilaterally decreased small-worldness was observed only in patients with stroke in the left hemisphere. Conclusions. After an acute stroke, brain cortex rearranges its network connections diffusely, in a frequency-dependent modality probably in order to face the new anatomical and functional frame.

Trunk-lower limb coordination pattern during gait in patients with ataxia.

OBJECTIVE Although deficit of coordination between the upper and lower body segments might play an important role in impairing gait and stability in ataxic patients, this deficit has not been investigated in subjects with ataxia so far. To evaluate the coordination between trunk and thigh in a sample of patients with ataxia compared with healthy controls and to correlate the coordination measures with the clinical severity. DESIGN Prospective observational study. SUBJECTS Sixteen patients with degenerative cerebellar ataxia and sixteen age- and sex-matched controls were studied. METHODS We assessed the coordination on the sagittal plane between trunk and thigh, considered as rigid segments, by the continuous relative phase (CRP) method. We used the coefficient of multiple correlation (CMC) to measure the within-subject (CMCWS) variability, and the SARA scale to assess clinical severity. RESULTS CRP curves are dissimilar between ataxic patients and controls, the former showing a chaotic behavior compared to the well-shaped CRP curves observed in the latter. Trunk-thigh coordination has a higher within-subject variability in ataxic patients (median CMCWS: 0.53 for patients, 0.89 for controls, p<0.001). We also found that the CMCWS of the CRP curves negatively correlates with the gait (ρ: -0.565, p: 0.023) and stance (ρ: -0.567, p: 0.022) sub-scores and the total score of the SARA scale (ρ: -0.711, p: 0.002). CONCLUSIONS Ataxia shows a deficit of spatio-temporal coordination between trunk and thigh. Such a deficit is correlated with the degree of the clinical impairment indicating an important role of inter-segmental coordination in determining the severity of ataxia.

Rinsing after spinning: plasmapheresis in EBV-related post-infectious cerebellitis

Dear Sirs, A previously healthy 19-year-old male was evaluated for acute onset of speech disturbances and imbalance after an episode of fever and sore throat occurred 2 weeks before. Neurological examination showed cerebellar dysarthria, postural instability, ataxic gait with negative Romberg sign and normal sensory examination, including pallaesthesia. A gadolinium-enhanced brain MRI resulted unremarkable. Serological tests showed the presence of circulating anti-VCA IgM antibodies (10.50, normal index \1.1), indicating a recent Epstein Barr Virus (EBV) infection. Cerebrospinal fluid (CSF) analysis revealed normal protein (29 mg/dl, range 20–40) and glucose (58 mg/dl, blood glucose 98 mg/dl) concentrations, mild pleocytosis (25 cells/mm, normal \5), normal anti-onconeural antibody testing (including anti-Hu, anti-Yo, antiCV2, anti-Ri and anti-amphiphysin), negative results of real-time PCR for EBV DNA and of EBV antibody testing (anti-VCA and EBNA). Post-infectious cerebellitis was diagnosed and treatment with high-dose intravenous methylprednisolone (1 g per day for 5 days) and intravenous acyclovir (750 mg three times per day for 15 days) was started, without benefit. Based on previous evidences in two cases [1] and the persistence of symptoms 20 days after onset, five plasmaphereses were performed, obtaining rapid recovery (Supplementary video). The score of SARA (Scale for the Assessment and Rating of Ataxia), a validated tool used to assess ataxia [2], was 10.5 before plasmaphereses, 4 after plasmaphereses (day 30 after onset of symptoms) and 0 (normal) at follow-up (day 60 after onset of symptoms). While EBV infection can directly cause an acute meningoencephalitis, EBV-related post-infectious cerebellitis is characterized by a generally benign, selflimiting ataxic syndrome attributed to an immune-mediated response triggered by the viral infection. Laboratory analyses usually show negative CSF EBV antibody titers despite the serological positivity for acute EBV infection. Occasionally, the ataxic syndrome can be severely disabling and symptoms can be longlasting, especially in adults [3, 4]. The lack of improvement in our patient prompted us to treat him with plasmaphereses, and the favorable response to plasma exchange supports the possible immune mediated nature of this disease. To the best of our knowledge, the use of plasmapheresis in EBV-related postinfectious cerebellitis has been reported in only two patients so far, with excellent results [2], and few other patients have been successfully treated with intravenous immunoglobulins [5]. Our experience confirms that plasmapheresis can accelerate recovery and rapidly ameliorate neurological outcome in patients with EBVrelated post-infectious cerebellitis that do not show improvement in the first weeks.

82. Prefrontal cortex as a compensatory functional substrate during ataxic overground gait: A correlation study between cortical activity and gait parameters

To investigate whether prefrontal cortex (PFC) activation is linked to compensatory mechanisms (time–distance parameters) or to gait features (kinematic parameters) specifically related to the functional role of the cerebellum in ataxic patients. We performed a correlation analysis between the PFC metabolic profile during gait and time–distance and kinematic parameters in a sample of 19 patients affected by neurodegenerative gait ataxia and 15 age/sex matched healthy subjects. PFC metabolism was evaluated by a 2-channel functional near-infrared imaging system while gait analysis was performed using a stereophotogrammetric system. We found a positive correlation between the PFC metabolism and the step width (the correlation coefficient was r : 0.54, p =0.02 for the right PFC, and r : 0.50, p =0.03 for the left PFC). No correlation was found between PFC activity, the other time–distance parameters and the intra-subject variability of gait. PFC activation during ataxic gait correlates with step width and therefore it seems involved in maintaining compensatory strategies rather than due to primary cerebellar deficits. To our knowledge this is the first study correlating cortical activity and gait characteristics in order to assess how cerebral cortex is modulated during a pathological gait.