A central question in cognitive neuroscience concerns the extent to which language enables other higher cognitive functions. In the case of mathematics, the resources of the language faculty, both lexical and syntactic, have been claimed to be important for exact calculation, and some functional brain imaging studies have shown that calculation is associated with activation of a network of left-hemisphere language regions, such as the angular gyrus and the banks of the intraparietal sulcus. We investigate the integrity of mathematical calculations in three men with large left-hemisphere perisylvian lesions. Despite severe grammatical impairment and some difficulty in processing phonological and orthographic number words, all basic computational procedures were intact across patients. All three patients solved mathematical problems involving recursiveness and structure-dependent operations (for example, in generating solutions to bracket equations). To our knowledge, these results demonstrate for the first time the remarkable independence of mathematical calculations from language grammar in the mature cognitive system. aphasia ͉ language ͉ mathematics

Neurological complications following cerebral angiography are rare (0.34%), but must be minimized by careful case selection and the prudent use of alternative noninvasive angiographic techniques, particularly in the acute setting. The low complication rate in this series was largely due to the favourable case mix.

Background: Spontaneous intracranial hypotension (SIH) is characterised by postural headache and low opening pressure at lumbar puncture without obvious cause. Cranial magnetic resonance imaging often shows small subdural collections without mass effect, dural enhancement, venous sinus dilatation, or downward displacement of the brain. The condition is thought to be benign. Objectives: To evaluate the incidence of subdural haematoma as a serious complication of SIH. Methods: A prospective survey of all cases of SIH presenting to a large neuroscience unit over a two year period. Results: Nine cases of SIH were seen. Four of these were complicated by acute clinical deterioration with reduced conscious level because of large subdural haematomas requiring urgent neurosurgical drainage. Conclusions: SIH should not be considered a benign condition. Acute deterioration of patients' clinical status may occur secondary to large subdural haematomas, requiring urgent neurosurgical intervention.

High angular resolution diffusion tensor imaging may be more sensitive than conventional MRI or neurologic assessment to the upper motor neuron (UMN) pathology of ALS, but it lacks the specificity required of a diagnostic marker. Instead, it is potentially useful as a quantitative tool for monitoring the progression of UMN pathology.

Endovascular treatment may cause less structural brain damage than surgery and have a more favorable cognitive outcome. However, cognitive outcome appears to be dictated primarily by the complications of SAH.

Objectives-To measure the sensitivity and specificity of five MRI sequences to subarachnoid haemorrhage. Methods-Forty one patients presenting with histories suspicious of subarachnoid haemorrhage (SAH) were investigated with MRI using T1 weighted, T2 weighted, single shot fast spin echo (express), fluid attenuation inversion recovery (FLAIR), and gradient echo T2* sequences, and also by CT. Lumbar puncture was performed in cases where CT was negative for SAH. Cases were divided into acute (scanned within 4 days of the haemorrhage) and subacute (scanned after 4 days) groups. Results-The gradient echo T2* was the most sensitive sequence, with sensitivities of 94% in the acute phase and 100% in the subacute phase. Next most sensitive was FLAIR with values of 81% and 87% for the acute and subacute phases respectively. Other sequences were considerably less sensitive. Conclusions-MRI can be used to detect subacute and acute subarachnoid haemorrhage and has significant advantages over CT in the detection of subacute subarachnoid haemorrhage. The most sensitive sequence was the gradient echo T2*. (J Neurol Neurosurg Psychiatry 2001;70:205-211) Keywords: magnetic resonance imaging; subarachnoid haemorrhage Computed tomography has been the imaging investigation of choice in cases of suspected subarachnoid haemorrhage (SAH) since its introduction into clinical practice because of high sensitivity to acute SAH, short scan times, and widespread availability. Lumbar puncture is performed in cases of suspected SAH with negative CT.The sensitivity of CT to SAH is more than 90% within 1 day of the haemorrhage 1-3 but falls oV rapidly with time and approaches 0% at 3 weeks.1 4 5 Although much of these data relate to previous generations of scanners, more recent results from higher resolution scanners show only modest improvements.2 3 This is because contrast resolution rather than spatial resolution is the limiting factor for sensitivity. Brain CT remains relatively insensitive to SAH more than a few days old especially in cases where the bleed is small. This is a particular problem as these patients are usually in good condition and have the most to lose from a missed diagnosis of SAH and subsequent rebleed from a ruptured aneurysm.As CT cannot exclude SAH, lumbar puncture is used as the longstop of investigation. Lumbar puncture has the advantage that its sensitivity remains high for several weeks after the ictus. 6Conventional MR T1 and T2 weighted images are relatively insensitive to SAH. Scan times for MRI are longer and allow less access to the patient than CT, making it unsuitable for confused or restless patients. For these reasons MRI has not had a role in the detection of SAH until recently. In 1994 Noguchi et al 7 reported the use of a FLAIR sequence in the detection of SAH in three cases. Since then other reports have confirmed the usefulness of FLAIR in this role. [8][9][10][11][12] There has been general agreement that the sensitivity of MRI to SAH increases over the few days after the bleed. 9 10 13 As...

This study investigated the 'latent deficit' hypothesis in two groups of head-injured patients with predominantly frontal lesions, those injured prior to steep morphological and corresponding functional maturational periods for frontal networks (28 years. The latent deficit hypothesis proposes that early injuries produce enduring cognitive deficits manifest later in the lifespan with graver consequences for behavior than adult injuries, particularly after frontal pathology (Eslinger, Grattan, Damasio & Damasio, 1992). Implicit and executive deficits both contribute to behavioral insight after frontal head injury (Barker, Andrade, Romanowski, Morton, & Wasti, 2006). On the basis of morphological and behavioral data, we hypothesized that early injury would confer greater vulnerability to impairment on tasks associated with frontal regions than later injury. Patients completed experimental tasks of implicit cognition, executive function measures and the DEX measure of behavioral insight (Behavioral Assessment of the Dysexecutive Syndrome: Wilson, Alderman, Burgess, Emslie, & Evans, 1996). The Early Injury group were more impaired on implicit cognition tasks compared to controls that Late Injury patients. There were no marked group differences on most executive function measures. Executive ability only contributed to behavioral awareness in the Early Injury Group. Findings showed that age at injury moderates the relationship between executive and implicit cognition and behavioral insight and that early injuries result in long-standing deficits to functions associated with frontal regions partially supporting the latent deficit hypothesis.

Functional MRI (fMRI) may provide a means of locating areas of eloquent cortex that can be used to guide neurosurgeons in their quest to maximize intracerebral tumour resection whilst minimizing post-procedural neurological deficits. This work aimed to develop and provide an initial assessment of such a technique. 19 patients with mass lesions close to the primary motor cortex underwent fMRI at 1.5T. A single shot echo planar technique was used to acquire data corresponding to right and left hand movement. Resultant activation maps were used to aid pre-surgical planning. Data was used in conjunction with an intraoperative navigation system in 13 cases. Activation was attributed to primary motor, primary somatosensory or supplementary motor cortex in 17 of 19 subjects. No permanent changes in motor deficit were detected post surgery. The additional information provided by fMRI, particularly when incorporated into a neuronavigation guided craniotomy, was deemed highly valuable to the neurosurgeon as it enabled safe resection of tumour in anatomical locations previously deemed to be too high risk for safe resection using conventional (non-fMRI-guided) technique. This observation is reinforced by the fact that no patients suffered permanent neurological deficit after radical tumour debulking (surgical estimates >90% tumour resection).