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The generation of regular and irregular inflected verb-forms has been taken as a crucial test between models of inflection in the mental lexicon, namely approaches which invoke different mechanisms for regular and irregular forms (rule-based procedures vs. recovery of whole forms stored in an associative network) and accounts which postulate a single procedure for all forms. An alternative hypothesis suggests that inflectional processes are explained by membership of words to clusters, for instance, Italian inflectional classes (conjugations). In a behavioural and a rapid event-related fMRI experiment, participants overtly generated the past participle of verbs from the three Italian conjugations. Results showed that the cognitive operations and the neural substrate underlying inflectional processes rely on specific properties of inflectional classes. Different patterns of cortical activations elicited by verbs from different conjugations were detected for the first time in the left middle frontal gyrus, left pre-supplementary motor area and left anterior cingulate cortex. [ABSTRACT FROM AUTHOR]

Corpus callosum infarcts are rare, constituing 0.6% of cerebral infarcts, most likely due to a rich blood supply from three main arterial systems. These infarcts may present with slowly evolving and non-localizing neurologic signs and symptoms that suggest the diagnosis of neoplasm rather than infarct. In addition, they may exhibit radiologic features more often associated with neoplasm, such as mass-like enhancement or extension across the midline. We describe a patient with corpus callosum infarct presenting with a non specific ataxia-like gait disorder, speech difficulty and left-side weakness. MR imaging disclosed an ischemic area in the body and splenium of the corpus callosum with extension to the right semiovalis centre. Neuropsychological study revealed constructive apraxia, attention reduction, motor programming and inhibiting control involvement. The atypical clinical presentation suggested involvement of the posterior circulation, while apraxia and attention impairment were in accordance with lesion localization. In-depth neuropsychological study is essential in patients with suspected corpus callosum involvement because the neurological signs and symptoms are confounding. The infarct localization in the body and semiovalis centre is an interesting neuroradiological feature. [ABSTRACT FROM AUTHOR]

Cerebral aneurysms are occasionally associated with anomalies of the cerebral arteries. Most reports on anomalies of the anterior cerebral artery have been concerned with hypoplasia, fenestration and the infra-optic course of the A1, variant A1 perforators or Heubner's artery, multichanneled anterior communicating artery, and azygos anterior cerebral artery. Distal anterior cerebral artery (ACA) aneurysms are known to have a poor clinical course and prognosis compared to other supratentorial aneurysms. The presence of the unpaired, distal, postcommunicating (A2) segment of the ACA is very rare in adults. We describe a patient with a ruptured aneurysm arising from the proximal end of the azygos ACA, first surgically treated with clipping and then with endovascular coiling. A 37-year-old woman at 34 weeks'gestation was transferred to our emergency room with sudden onset of severe headache and vomiting. Computed tomography (CT) revealed subarachnoid hemorrhage in the basal cisterna and the sylvian and interhemispheric fissures. Cerebral angiography showed an azygos ACA, a saccular aneurysm at the junction of the azygos ACA and the right A1 segment. A right fronto-temporal craniotomy was performed in the day of admission, and the neck of the aneurysm was clipped. One year later, an angiographic control examination revealed a regrowth of the aneurysm. The patient underwent endovascular treatment with coiling. Aneurysms of the azygos ACA are rare and their pathogenesis and course are still a matter of discussion. Developmental abnormalities or dynamic vessel wall stresses can explain the high incidence of aneurysms in these cases. The association of a rare anatomical variant with an aneurysm in the same location may suggest an embryogenesis alteration in the Willis circulation. [ABSTRACT FROM AUTHOR]