Interhemispheric communication following unilateral cerebrovascular lesions

39 patients with a single small cerebrovascular lesion (20 in the right, 19 in the left hemisphere) were subjected to a simple reaction time (RT) task with visual stimuli flashed to the visual field either ipsilateral or contralateral to the cerebral lesion. The subject responded always with the ipsilateral hand. The crossed-uncrossed difference (CUD), i.e. the RT when both stimulus and response occur on the same side minus the RT when stimulus and response occur on opposite sides, is assumed to assess the transit time of information through callosal fibers, and in normal people is about 3–5 msec. In our patients the mean CUD, expressed as the difference between contralateral and ipsilateral responses, was 20 msec. Patients with parietal lesions had still longer CUDs, 37 msec on the average. There was no statistical difference in CUDs between right and left brain-damaged patients. The CUD in brain-damaged patients was of the same order of magnitude as that found in acallosal or split-brain patients. Nonetheless, the present findings are interpreted as reflecting the intrahemispheric rather than the interhemispheric delay in information transmission, with the possible additive effect of an asymmetrical orienting of attention.

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Sommario In 39 pazienti portatori di una singola lesione cerebrovascolare emisferica (in 20 all'emisfero destro, in 19 all'emisfero sinistro), è stato effettuato un test di tempi di reazione semplici a uno stimolo visivo non strutturato presentato nel campo visivo ipsilaterale o controlaterale alla lesione. Le risposte erano effettuate sempre con la mano ipsilaterale. La differenza fra tempi di reazione crociati (cioè stimolo e risposta su lati opposti) e tempi di reazione non-crociati (cioè stimolo e risposta dallo stesso lato) rappresenta il tempo di transito callosale dell'informazione e nei soggetti normali è dell'ordine di 3–5 msec. Nei pazienti con lesione cerebrale tale valore era allungato a 20 msec di media, con un ulteriore ritardo a 37 msec. nei pazienti con lesione parietale. Non vi era nessuna differenza, significativa fra pazienti con lesione dell'emisfero destro e pazienti con lesione dell'emisfero sinistro. La differenza fra risposte crociate e risposte dirette da noi trovata nei cerebrolesi è dello stesso ordine di grandezza di quella che presentano i soggetti con agenesia del calloso o i pazienti sottoposti a callosotomia. Tuttavia, è verosimile che nei nostri pazienti il ritardo trovato rifletta piuttosto la somma di un'anomala conduzione intraemisferica e di possibili disturbi attenzionali.

     

Vertebrobasilar ischemia after neck motion.

BACKGROUND. Vertebrobasilar ischemic strokes may occur after chiropractic manipulation of the cervical spine or, less often, after spontaneous and abrupt head movement. SUMMARY OF REVIEW. We describe three such cases of vertebrobasilar ischemic strokes and review 36 other reported cases. CONCLUSIONS. We give evidence that 1) the population at risk cannot be identified a priori in the vast majority of cases; 2) symptoms may develop after many uneventful manipulations; 3) clinical syndromes consist of occipital lobe (5%), cerebellar (8%), locked-in (8%), Wallenberg's (28%), other brain stem (49%), and unclassifiable (2%); 4) mortality or very severe long-term impairment occurs in 28% of cases; 5) the development of transient neurological symptoms during previous manipulations, the presence of known or suspected ligament laxity, and, if known, the presence of a vertebral artery terminating in posterior inferior cerebellar artery should always contraindicate any chiropractic neck maneuver; and 6) the pathogenetic mechanism involves vertebral artery dissection at the atlantoaxial joint with intimal tear, intramural bleeding, or pseudoaneurysm that can lead to thrombosis or embolism.     

Lower cranial nerve palsy produced by internal carotid artery dilatation. Report of two cases

We report two cases of lower cranial nerve palsies (XII in case 1, IX–X–XII in case 2) associated with abnormalities of the internal carotid artery at the base of the skull. In case 1 a limited dissection of the carotid wall produced both paresis of the hypoglossal nerve and Horners syndrome by compression of the nerve trunk against the base of the skull and stretching of the periarterial sympathetic fibres respectively. In case 2 we speculate that a narrow angled kinking of the internal carotid artery may have damaged cranial nerves IX, X and XII by interfering with the blood supply to the nerve trunks. In both cases the outcome was favorable with almost complete regression of the initial symptoms. We conclude that the association between lower cranial nerve disturbances and internal carotid artery abnormalities is probably more common than was thought. We suggest that the pathogenesis of the damage to the cranial nerves may differ from one case to the next.

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Riassunto Gli Autori riportano due casi di paralisi dei nervi cranici bulbari (XII nel caso 1, IX–X–XII nel caso 2) causate da anomalie dell'arteria carotide interna alla base cranica. Nel caso 1 la paresi del XII nervo cranico, associato con sindrome di Claude Bernard Horner ipsilaterale, è state determinata da un anuerisma dissecante della carotide con conseguente compressione del tronco nervoso contro la base cranica e stiramento delle fibre simpatiche periarteriose. Nel caso 2 viene ipotizzato che la lesione del IX, X e XII nervo cranico sia stata di origine ischemica per la presenza di un'ansa ad angolo acuto dell'arteria carotide interna. In entrambi i casi il decorso è stato favorevole, con regressione pressochè completa dei sintomi iniziali. L'associazione fra anomalie della carotide interna e disturbi dei nervi cranici bulbari è probabilmente più frequente di quanto si ritenesse in precedenza e la patogenesi della lesione nervosa può essere variabile da caso a caso.

     

Gene promoter hypermethylation in oral rinses of leukoplakia patients--a diagnostic and/or prognostic tool?

Leukoplakia is the most frequent oral precancerous lesion and shows a variable rate of malignant transformation. We hypothesised that the detection of molecular alterations, like the promoter hypermethylation of DNA, in oral cytological samples from patients at risk of developing primary or recurrent tumours could be a valuable diagnostic and prognostic tool in the management of these lesions. Two groups of patients with differing risks of developing oral squamous cell carcinoma (OSCC) were analysed. DNA was extracted from the oral rinse of each patient. The methylation status of the p16, p14 and MGMT gene promoters was determined using a methylation-specific polymerase chain reaction (MSP). Methylation of p16 and MGMT was observed in 44 and 56% of the oral samples, respectively. Only 12% of the cases showed p14 methylation. DNA hypermethylation was more frequent in patients with previous OSCC. DNA promoter hypermethylation is frequent during early oral carcinogenesis and even more so in the later stages. MSP using oral rinses is a non-invasive and highly sensitive technique which could be used to monitor patients with precancerous and cancerous oral lesions.     

SAR and mode of action of novel non-nucleoside inhibitors of hepatitis C NS5b RNA polymerase

Novel non-nucleoside inhibitors of the HCV RNA polymerase (NS5b) with sub-micromolar biochemical potency have been identified which are selective for the inhibition of HCV NS5b over other polymerases. The structures of the complexes formed between several of these inhibitors and HCV NS5b were determined by X-ray crystallography, and the inhibitors were found to bind in an allosteric binding site separate from the active site. Structure-activity relationships and structural studies have identified the mechanism of action for compounds in this series, several of which possess drug-like properties, as unique, reversible, covalent inhibitors of HCV NS5b.     

Spatial compatibility and anatomical factors in simple and choice reaction time

Simple reaction time to a lateralized unstructured visual stimulus was studied in subjects with hands crossed or uncrossed. Regardless of the hand position, the right hand was faster than the left hand when the stimulus was to the right of fixation, and vice versa. In both conditions there was a left visual field superiority. In a second experiment the same lateralized stimuli were presented to subjects with hands crossed or uncrossed who had to decide which hand to use depending on the position of the stimulus. In this experiment the faster hand was the one in the same visual space as the stimulus (spatial compatibility). We conclude that in simple reaction time experiments the difference between ipsilateral and contralateral reactions is due to the elementary anatomical connectivity, and that spatial compatibility becomes important only in choice situations.