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Biomedical subjects

Norbert Nighoghossian

Publications and source records attributed to Norbert Nighoghossian.

23 records · Page 2Linked to original sources
PubMed2003

Altered awareness of voluntary action after damage to the parietal cortex.

A central question in the study of human behavior is the origin of willed action. EEG recordings of surface brain activity from human subjects performing a self-initiated movement show that the subjective experience of wanting to move follows, rather than precedes, the 'readiness potential'--an electrophysiological mark of motor preparation. This raises the issue of how conscious experience of willed action is generated. Here we show that patients with parietal lesions can report when they started moving, but not when they first became aware of their intention to move. This stands in contrast with the performance of cerebellar patients who behaved as normal subjects. We thus propose that when a movement is planned, activity in the parietal cortex, as part of a cortico-cortical sensorimotor processing loop, generates a predictive internal model of the upcoming movement. This model might form the neural correlate of motor awareness.

Adult↗
PubMed2003

Early magnetic resonance imaging prediction of arterial recanalization and late infarct volume in acute carotid artery stroke.

In patients with acute ischemic stroke, early recanalization may save tissue at risk for ischemic infarction, thus resulting in smaller infarcts and better clinical outcome. The hypothesis that clinical and diffusion- and perfusion-weighted imaging (DWI, PWI) parameters may have a predictive value for early recanalization and final infarct size was assessed. Twenty-nine patients were prospectively enrolled and underwent sequential magnetic resonance imaging (1) within 6 hours from hemispheric stroke onset, before thrombolytic therapy; (2) at day 1; and (3) at day 60. Late infarct volume was assessed by T2 -weighted imaging. At each time, clinical status was assessed by the National Institutes of Health Stroke Scale (NIHSS). Twenty-eight patients had arterial occlusion at day 0 magnetic resonance angiography (MRA). They were classified into two groups according to day 1 MRA: recanalization (n = 18) versus persistent occlusion (n = 10). Any significant differences between these groups were assessed regarding (1) PWI and DWI abnormality volumes, (2) relative and absolute time-to-peak (TTP) and apparent diffusion coefficient within the lesion on DWI; and (3) day 60 lesion volume on T2 -weighted imaging. Univariate and multivariate logistic regression analysis showed that the most powerful predictive factors for recanalization were lower baseline NIHSS score and lower baseline absolute TTP within the lesion on DWI. The best predictors of late infarct size were day 0 lesion volume on DWI and day 1 recanalization. Early PWI and DWI studies and day 1 MRA provide relevant predictive information on stroke outcome.

Acute Disease↗
PubMed2003

Hypointense transcerebral veins at T2*-weighted MRI: a marker of hemorrhagic transformation risk in patients treated with intravenous tissue plasminogen activator.

Prediction of hemorrhagic transformation (HT) in patients treated by intravenous recombinant tissue-type plasminogen activator (rt-PA) is a challenging issue in acute stroke management. HT may be correlated with severe hypoperfusion. Signal changes may be observed at susceptibility-weighted magnetic resonance imaging (MRI) within large perfusion defects. A signal drop within cerebral veins at T2*-weighted gradient-echo MRI may be expected in severe ischemia, and may indicate subsequent risk of HT. The authors prospectively searched for an abnormal visibility of transcerebral veins (AVV) within the ischemic area in patients with hemispheric ischemic stroke, before they were treated with intravenous rt-PA therapy. Any correlation between AVV and baseline clinical or MRI findings, or further HT, was noted. An AVV was present in 23 of 49 patients (obvious, n = 8; moderate, n = 15), and was supported by severe hemodynamic changes at baseline MRI. The AVV was correlated with the occurrence of parenchymal hematoma type 2 at computed tomography during the first week (r = 0.44, P = 0.002). Five of six type 2 parenchymal hematomas occurred in association with obvious AVV. At multiple regression analysis, two baseline MRI factors had an independent predictive value for HT risk during the first week: the AVV and the cerebral blood volume ratio (Nagelkerke R2 = 0.48).

Adult↗
PubMed2002

Factors influencing early admission in a French stroke unit.

BACKGROUND AND PURPOSE: Intravenous tissue plasminogen activator improves outcome after ischemic stroke when given within 3 hours of symptoms onset in carefully selected patients. However, only a small proportion of acute stroke patients are currently eligible for thrombolysis, mainly because of excessive delay to hospital presentation. We sought to determine the factors associated with early admission in a French stroke unit. METHODS: We prospectively studied the admission delay of acute stroke patients in a French stroke unit during a 12-month period ending July 1999. Univariate and multivariate regression analyses were performed to evaluate the factors influencing early stroke unit admission and transport by the Emergency Medical Services (EMS) or Fire Department (FD) ambulances. RESULTS: One hundred sixty-six patients were primarily admitted to the stroke unit, with a median admission time of 4 hours 5 minutes. Twenty-nine percent presented within 3 hours of symptoms onset and 75% within 6 hours. Univariate analysis showed that early stroke unit arrival was significantly associated with the following factors: female sex, stroke severity assessed by the National Institutes of Health Stroke Scale score, lowered consciousness, sudden onset of stroke, not living alone, recognition of symptoms by bystanders, and transport by EMS or FD ambulances. Age, ethnicity, level of education, employment status, nocturnal onset, distance from place of stroke to the stroke unit, stroke lesion location, presence of brain hemorrhage, and awareness about the symptoms and risk factors of stroke had no measurable effect on early admission. A multivariate regression model demonstrated that the most significant factors associated with early stroke unit arrival were transport by EMS or FD ambulances and sudden onset of stroke. Female sex and not living alone were also significantly associated with early admission in the multivariate model. Multivariate analysis of the mode of transport showed that transport by EMS or FD ambulances was significantly more frequent among female patients, when stroke symptoms were recognized by bystanders, and when the general practitioner was not the first medical contact. CONCLUSIONS: The present study shows that hospital arrival within the first hours of stroke is feasible in a French stroke unit. As many as 75% of the patients are admitted within the first 6 hours of stroke. This is the first study demonstrating that stroke unit admission in France is fastest in patients brought to the hospital by EMS or FD ambulances. However, only 35% of stroke patients activate the emergency telephone system and are currently transported by EMS or FD ambulances. French stroke patients should be encouraged to seek immediate medical attention by using the emergency telephone system, and stroke management should be reprioritized in the French EMS as a time-dependent medical emergency, with the same level of organization and expertise currently applied to myocardial infarction.

Aged↗