Anterior translocation of language in patients with left cerebral arteriovenous malformation

Awake craniotomy in patients with arteriovenous malformation: A systematic review and meta‑analysis

The present systematic review aimed to identify all the available literature on awake craniotomy (AC) in patients with arteriovenous malformation (AVM) in order to evaluate its safety, risks, benefits and effectiveness. All available literature on AC in patients with AVM was collected and evaluated in an aim to provide a better understanding of its safety, associated risks and benefits. A systematic search for studies employing AC in patients with AVM was conducted using the PubMed, Scopus and ScienceDirect databases without restrictions on the year of publication, language, or study design, from inception up to May 30, 2021. A total of 11 studies published between 2004 and 2021 with 106 patients who underwent ACs were considered eligible. The rate of complete resection was 93% [95% confidence interval (CI), 82 to 100%; I2 0%]. The intraoperative complication rate was 21% (95% CI, 1 to 41%; I2 55%) and the post-operative complication rate was 33% (95% CI, 19 to 48%; I2 40%). During follow-up, the complication rate was 6% (95% CI, 1 to 10%; I2 30%). The post-operative complication rate was higher in the Spetzler-Martin grade (SMG) III-V group (31%; 95% CI, 21 to 42%; I2 46%) than in the SMG I-II group (12%; 95% CI, 2 to 22%; I2 0%). Similarly, the follow-up complication rate was higher in the SMG III-V group (9%; 95% CI, 2 to 16%; I2 34%) than in the SMG I-II group (0%; 95% CI, 0 to 4%; I2 0%). On the whole, the present study provides preliminary evidence to indicate that AC is a possible and useful option for the resection of AVM in selected patients. Well-designed future studies with long-term follow-up are required however, to investigate various aspects of safety and provide solid data for AC in patients with AVM.

Feasibility of awake craniotomy for brain arteriovenous malformations: A scoping review

Background

Brain Arteriovenous Malformations (AVMs) located in proximity to eloquent brain regions are associated with poor surgical outcomes, which may be due to higher rates of postoperative neurological deterioration. Current treatment protocols include stereotactic radiosurgery, transarterial embolization, and surgical resection under general anesthesia. Awake Craniotomy (AC) allows intraoperative mapping of eloquent areas to improve post-operative neurologic outcomes.

Objectives

We reviewed the current literature reporting surgical outcomes and assessed the feasibility of AC for AVM resection.

Methods

The PRISMA guidelines were utilized as a template for the review. Three databases including PubMed, Scopus, and Cochrane Library were searched using a predefined search strategy. After removing duplicates and screening, full texts were analyzed. Outcomes including the extent of resection, intra-operative and post-operative complications, and long-term neurologic outcomes were assessed.

Results

12 studies were included with a total of 122 AVM cases. Spetzler-Martin grading was used for the classification of the AVMs. The asleep-awake-asleep protocol was most commonly used for AC. Complete resection was achieved in all cases except 5. Intraoperative complications included seizures (n = 2) and bleeding (n = 4). Short-term post-operative complications included hemorrhage (n = 3), neurologic dysfunctions including paresis (n = 3), hemiplegia (n = 10), dysphasia/aphasia (n = 6), cranial nerve dysfunction (n = 3), and pulmonary embolism (n = 1). Almost all neurological deficits after surgery gradually improved on subsequent follow-ups.

Conclusion

AVMs may shift the anatomical location of eloquent brain areas which may be mapped during AC. All studies recommended AC for the resection of AVMs in close proximity to eloquent areas as mapping during AC identifies the eloquent cortex thus promoting careful tissue handling which may preserve neurologic function and/or predict the postoperative functional status of the patients We, therefore, conclude that AC is a viable modality for AVMs resection near eloquent language and motor areas.

Cognitive performance in patients with cerebral arteriovenous malformation

OBJECTIVE

A cerebral arteriovenous malformation (cAVM) can change over time and cause symptoms, but clinical studies tend to define only the patients with ruptured cAVMs as symptomatic and do not consider neurocognitive aspects prior to neurosurgical intervention. The objective of this study was to describe the neurocognitive function of patients with ruptured and unruptured cAVMs according to the Spetzler-Martin (SM) grade, flow status, and anatomical topography.

METHODS

In this blinded cross-sectional study, 70 patients of both sexes and ages 18-60 years were evaluated using the Brazilian Brief Neuropsychological Assessment Battery Neupsilin.

RESULTS

Of the 70 patients with cAVMs, 50 (71.4%) demonstrated deficits in at least one of the eight neurocognitive domains surveyed, although they did not exhibit neurological deficits. cAVMs in the temporal lobe were associated with memory deficits compared with the general population. The SM grade was not significantly associated with the results of patients with unruptured cAVMs. However, among patients with ruptured cAVMs, there were deficits in working memory in those with high-grade (SM grade) cAVMs and deficits in executive function (verbal fluency) in those with low-grade cAVMs (p < 0.001).

CONCLUSIONS

This study indicates that patients with untreated cAVMs, either ruptured or unruptured, already exhibit neurocognitive deficits, even the patients without other neurological symptoms. However, the scales used to evaluate disability in the main clinical studies, such as A Randomized Trial of Unruptured Brain Arteriovenous Malformations (ARUBA), do not assess neurocognitive alterations and therefore disregard any deficits that may affect quality of life. The authors' finding raises an important question about the effects of interventional treatment because it reinforces the hypothesis that cognitive alterations may be preexisting and not determined by interventions.

Brain Arteriovenous Malformations Located in Language Area: Surgical Outcomes and Risk Factors for Postoperative Language Deficits

OBJECTIVE

Case selection for surgical treatment of language-area brain arteriovenous malformations (L-BAVMs) remains difficult. This study aimed to determine the surgical outcomes and risk factors for postoperative language deficits (LDs) in patients with L-BAVMs.

METHODS

Patients with L-BAVMs who underwent microsurgical resection between September 2012 and June 2016 were reviewed. All patients had undergone preoperative functional magnetic resonance imaging and diffusion tensor imaging. Both functional and angioarchitectural factors were analyzed regarding the postoperative LD. Functional factors included the eloquence involved, the side of blood-oxygenation level-dependent signal activation and the white-matter fibers (anterior segment, long segment [LS], and posterior segment of arcuate fasciculus, and the inferior fronto-occipital fasciculus) involved.

RESULTS

Sixty-nine patients with L-BAVMs were reviewed. Postoperative short- and long-term LD was found in 32 (46.4%) and 14 (20.3%) patients, respectively. Twelve of the 14 patients with Geschwind's territory L-BAVMs (85.7%) had short-term LD, compared with 10 (34.5%) in Wernicke's and 10 (38.5%) in Broca's area. LS involvement (P = 0.001) and larger nidus size (P = 0.017) were independent risk factors for the short-term LD. Meanwhile, nidus size (P = 0.007), preoperative LD (P = 0.008), and LS involvement (P = 0.028) were independent risk factors for long-term LD.

CONCLUSIONS

L-BAVMs located in Geschwind's territory can cause a high incidence of LD. LS involvement and larger nidus size are risk factors for postoperative short- and long-term LD, and preoperative LD is a risk factor for postoperative, long-term LD.

Cortical plasticity in patients with cerebral arteriovenous malformations

The aim of this review is to ascertain the evidence for cortical plasticity in arteriovenous malformation (AVM) patients. Chronic hypoperfusion due to vascular steal from cerebral AVM can result in a translocation of eloquent neurological functions to other brain areas, a phenomenon known as cortical plasticity. We performed a systematic literature review of the studies that have evaluated cortical plasticity in AVM patients. A total of 22 studies from 1996 to 2014 were included for the analyses. The evaluation of cortical plasticity was performed prior to AVM intervention in 109 patients, and during or after AVM intervention in 18. The most commonly assessed neurological functions were motor in 85% and language in 11% of the former cohort, and motor in 78% and language, cognition, and memory each in 39% of the latter cohort. Functional MRI was the most frequently used method for evaluating cortical plasticity, and was performed in 63% of the former and 56% of the latter cohort. In conclusion, cortical plasticity appears to be influenced by both AVM pathogenesis and intervention. Given the limited evidence that is currently available for cortical plasticity in AVM patients, further studies are warranted to determine its incidence and impact on long term clinical outcomes.

Benzodiazepine use and risk of stroke: a retrospective population-based cohort study

AIM

The aim of this study was to investigate the possible association between benzodiazepine (BZD) use and risk of incident stroke by utilizing data from 2000 to 2003 from the National Health Insurance system of Taiwan.

METHODS

Study subjects consisted of 38,671 patients with new BZD use and 38,663 people without BZD use who were frequency-matched for age, sex and baseline comorbidity with BZD users. All subjects had no history of stroke. Each study patient's case was followed until a new diagnosis of stroke was made or until the patient was censored by loss to follow up, death, or termination of insurance. The study lasted until the end of 2009. A Cox proportional hazards regression model was used to estimate the incidences and hazard ratios (HR) of stroke.

RESULTS

The HR of hemorrhagic stroke was significantly lower in the BZD group when compared with the non-BZD group. For patients aged 20-39 years, the HR of ischemic stroke was significantly higher in the BZD group when compared with the non-BZD group. Compared to the non-BZD group, patients with a lower annual dosage (<1 g) or duration (<30 days) of BZD use had a lower risk of stroke in the elder group (P < 0.0001) and patients with a higher annual dosage (≥ 4 g) or duration (≥ 95 days) of BZD use had a higher risk of stroke in all age groups (P < 0.0001).

CONCLUSIONS

Our findings may suggest neuroprotection under lower-dosage BZD use and neurotoxicity under higher-dosage BZD use.

Brain reorganization after endovascular treatment in a patient with a large arteriovenous malformation: the role of diagnostic and functional neuroimaging techniques

We describe a case of brain cortical reorganization after embolization of a large right temporal arteriovenous malformation. A comprehensive imaging protocol, including functional magnetic resonance imaging (fMRI), cortical thickness analysis and 320-row computed tomography (CT) perfusion was used to provide information on brain plasticity and potential steal phenomenon. A 25-year-old man known for a right temporal grade V Spetzler-Martin classification arteriovenous malformation (AVM) presented with left progressive hemiparesis. He underwent functional 3T magnetic resonance imaging (fMRI), cortical thickness analysis, and CT perfusion (CT 320 row, Aquilion ONE, Toshiba, Tokyo, Japan) before and after endovascular treatment. The results were compared to look for modifications in brain perfusion and organization. An improvement in the left hemiparesis and a reorganization of motor function were observed after endovascular treatment. Modifications in the angioarchitecture and perfusion of an extensive AVM may be accompanied by a functional and structural reorganization of the brain. The location in the so-called eloquent regions may not be sufficient to explain the wide spectrum of symptoms that these patients can present. A more comprehensive approach considering a global involvement of the brain in patients with large AVMs is suggested to achieve the best treatment strategy and to stage treatment in incurable AVMs.

Anesthesia for endovascular neurosurgery and interventional neuroradiology

This article outlines the roles of the anesthesiologist in the management of patients undergoing invasive endovascular procedures to treat vascular diseases, primarily of the central nervous system. This practice is usually termed interventional neuroradiology or endovascular neurosurgery. The article emphasizes perioperative and anesthetic management strategies to prevent complications and minimize their effects if they occur. Planning the anesthetic and perioperative management is predicated on understanding the goals of the therapeutic intervention and anticipating potential problems.

Language and motor mapping during resection of brain arteriovenous malformations: indications, feasibility, and utility

BACKGROUND

Microsurgical resection of arteriovenous malformations (AVMs) located in the language and motor cortex is associated with the risk of neurological deterioration, yet electrocortical stimulation mapping has not been widely used.

OBJECTIVE

To demonstrate the usefulness of intraoperative mapping with language/motor AVMs.

METHODS

During an 11-year period, mapping was used in 12 of 431 patients (2.8%) undergoing AVM resection (5 patients with language and 7 patients with motor AVMs). Language mapping was performed under awake anesthesia and motor mapping under general anesthesia.

RESULTS

Identification of a functional cortex enabled its preservation in 11 patients (92%), guided dissection through overlying sulci down to the nidus in 3 patients (25%), and influenced the extent of resection in 4 patients (33%). Eight patients (67%) had complete resections. Four patients (33%) had incomplete resections, with circumferentially dissected and subtotally disconnected AVMs left in situ, attached to areas of eloquence and with preserved venous drainage. All were subsequently treated with radiosurgery. At follow-up, 6 patients recovered completely, 3 patients were neurologically improved, and 3 patients had new neurological deficits.

CONCLUSION

Indications for intraoperative mapping include preoperative functional imaging that identifies the language/motor cortex adjacent to the AVM; larger AVMs with higher Spetzler-Martin grades; and patients presenting with unruptured AVMs without deficits. Mapping identified the functional cortex, promoted careful tissue handling, and preserved function. Mapping may guide dissection to AVMs beneath the cortical surface, and it may impact the decision to resect the AVM completely. More conservative, subtotal circumdissections followed by radiosurgery may be an alternative to observation or radiosurgery alone in patients with larger language/motor cortex AVMs.

Atypical conduction aphasia and the right hemisphere: Cross-hemispheric plasticity of phonology in a developmentally dyslexic and dysgraphic patient with early left frontal damage

We report the rare case of a patient, JNR, with history of mixed handedness, developmental dyslexia, dysgraphia, and attentional deficits associated with a Klippel-Trenaunay syndrome and a small subcortical frontal lesion involving the left arcuate fasciculus. In adulthood, he suffered a large right perisylvian stroke and developed atypical conduction aphasia with deficits in input and output phonological processing and poor auditory-verbal short-term memory. Lexical-semantic processing for single words was intact, but he was unable to access meaning in sentence comprehension and repetition. Reading and writing deficits worsened after the stroke and he presented a combination of developmental and acquired dysgraphia and dyslexia with mixed lexical and phonological processing deficits. This case suggest that a small lesion sustained prenatally or early in life could induce a selective rightward shift of phonology sparing the standard left hemisphere lateralisation of lexical-semantic functions.

Factors predicting language lateralization in patients with perisylvian vascular malformations. Clinical article

OBJECT

The authors conducted a study to determine the factors associated with right-sided language dominance in patients with cerebrovascular malformations.

METHODS

Twenty-two patients with either arteriovenous malformations (AVMs [15 cases]) or cavernous malformations (7 cases) underwent functional MR (fMR) imaging studies of language function; a 3.0-T head-only unit was used. Lateralization indices were calculated separately for Broca and Wernicke areas. Lesion size, Spetzler-Martin grade, and the distance between the lesion and anatomically defined language cortex were calculated for each patient.

RESULTS

Right-sided language dominance occurred in 5 patients, all of whom had AVMs within 10 mm of canonical language areas. Three patients had right-sided language dominance in the Wernicke area alone whereas 2 had right-sided language dominance in both Broca and Wernicke areas. Wada testing and intraoperative electrocortical stimulation were performed as clinically indicated to corroborate fMR imaging findings.

CONCLUSIONS

The primary factor associated with right-sided language dominance was the AVM being within 10 mm of anatomically defined language areas. The lesion size and the Spetzler-Martin grade were not significant factors. Anomalous fMR imaging laterality was typically confined to the language area proximate to the lesion, with the distal language area remaining in the left hemisphere dominant. This study emphasizes the need to map each case individually in patients with left perisylvian AVMs. Assumptions about eloquent cortex based on anatomical landmarks (a key component of Spetzler-Martin grading) may have to be reconsidered.

GABAergic but not anti-cholinergic agents re-induce clinical deficits after stroke

Our goal was to determine whether the excitatory (i.e., GABA) neurotransmitter system was important in human stroke recovery. We hypothesized that giving midazolam, a GABA(A) agonist, to patients would re-induce clinical deficits to a greater extent than the anti-cholinergic scopolamine. Twelve patients (7 M) who had recovered from hemiparesis and/or aphasia after first-time stroke and 10 age-matched, healthy controls underwent double-blinded drug challenge with midazolam and 90 days later with scopolamine, or vice versa. Language was scored for comprehension, naming and repetition, and motor function was tested with the 9-Hole Peg Test (9HPT) in each hand. The drugs were administered intravenously in small aliquots until mild awake sedation was achieved. The primary outcome was the change scores from baseline to the two drug conditions, with higher scores denoting greater loss of function. Ten of the 12 patients had recovered from hemiparesis and 7 from aphasia. The median time from stroke to participation was 9.3 months (range=0.3-77.9 months). For motor function, analysis of variance showed that change scores on the 9HPT were significantly greater in patients using the previously paretic hand during the drug state with midazolam (p=0.001). Similarly, language change scores were significantly greater among recovered aphasics during the midazolam challenge (p=0.01). In our study, patients demonstrated transient re-emergence of former stroke deficits during midazolam but not scopolamine. These data provide beginning clinical evidence for the specificity of GABA-sensitive pathways for stroke recovery.

Clinical and morphological determinants of focal neurological deficits in patients with unruptured brain arteriovenous malformation

OBJECTIVE

Some patients with brain arteriovenous malformation (BAVM) present with focal neurological deficits (FNDs) unrelated to clinically discernable seizure activity or hemorrhage. The aim of this study is to determine demographic and morphological AVM characteristics associated with FNDs.

METHODS

The 735 patients of the prospective Columbia AVM Databank were analyzed. Univariate and multivariate statistical models were used to test the association of demographic (age, gender), and morphological characteristics (BAVM size, anatomic location, arterial supply, venous drainage pattern, venous ectasia) with the occurrence of FNDs at the time of initial BAVM diagnosis.

RESULTS

Fifty-three patients (7%, mean age 40+/-16years, 70% women) presented with FNDs. The multivariate logistic regression model revealed an independent association of FNDs with increasing age (OR 1.03; 95%-CI 1.00-1.05), female gender (OR 2.14; 95%-CI 1.15-3.97), deep brain location (OR 2.46; 95%-CI 1.24-4.88), brainstem location (OR 5.62; 95%-CI 1.65-19.23), and venous ectasia (OR 1.91; 95%-CI 1.01-3.64). No association was found for BAVM size, lobar location, arterial supply and venous drainage pattern.

INTERPRETATION

Focal neurologic deficits unrelated to seizures or hemorrhage are a rare initial presentation of BAVMs. The predominance of FNDs among brainstem and deeply located BAVMs and the lack of a significant association of BAVM size with FNDs indicate selective white matter pathway-specific vulnerability, the association with patient age a time dependent effect. The higher frequency of FNDs among women suggests gender-specificity of brain tissue vulnerability.

Reperfusion normalizes motor activation patterns in large-vessel disease

OBJECTIVE

Hemodynamic impairment in one hemisphere has been shown to trigger ipsilateral motor activation in the opposite hemisphere on functional imaging. We hypothesized that reversing the hypoperfusion would normalize the motor activation pattern.

METHODS

We studied four patients with high-grade stenosis and impaired vasomotor reactivity (VMR) but no stroke. Functional magnetic resonance imaging motor activation pattern before and after VMR normalization was compared with seven healthy control subjects scanned at an interval of 3 months using voxel-wise statistical parametric maps and region of interest analysis. Subjects performed a repetitive hand closure task in synchrony with 1Hz metronome tone. We used repeated-measures analysis of variance to compute the interaction between group (patients/control subjects) and time by obtaining the average blood oxygen level dependent signal of three motor regions of interest in each hemisphere.

RESULTS

Two patients normalized their VMR after spontaneous resolution of dissection, and two after revascularization procedures. Both voxel-wise statistical maps and region of interest analysis showed that VMR normalization was associated in each case with a reduction in the atypical activation in the hemisphere opposite to the previously hypoperfused hemisphere (p < 0.001).

INTERPRETATION

In the presence of a physiological stressor such as hypoperfusion, the brain is capable of dynamic functional reorganization to the opposite hemisphere that is reversible when normal blood flow is restored. These findings are important to our understanding of the clinical consequences of hemodynamic failure and the role of the ipsilateral hemisphere in maintaining normal neurological function.

Neuropsychological effects of brain arteriovenous malformations

Brain arteriovenous malformations (AVM's) are developmental, chronic lesions that provide unique information about the human brain and can be a useful model for neuroscientists to study cerebral reorganization and hemodynamics. We review the neuroanatomy, epidemiology, natural history, imaging and treatment of brain AVMs, and provide a model with which to better understand neuropsychological functioning and brain reorganization. We suggest that future studies must exclude ruptured AVMs if they wish to further explain focal neurological/cognitive deficits associated with this neurovascular anomaly.

Anesthesia for endovascular neurosurgery and interventional neuroradiology

This review outlines the roles of anesthesiologists in the management of patients undergoing invasive endovascular procedures to treat vascular diseases, primarily of the central nervous system. This practice usually is termed interventional neuroradiology or endovascular neurosurgery. The discussion emphasizes perioperative and anesthetic management strategies to prevent complications and minimize their effects if they occur. Planning anesthetic and perioperative management is predicated on understanding the goals of the therapeutic intervention and anticipating potential problems.

Functional MRI evidence for language plasticity in adult epileptic patients: Preliminary results

The present fMRI study explores the cerebral reorganisation of language in patients with temporal lobe epilepsy, according to the age of seizures onset (early or late) and the hippocampal sclerosis (associated or not). Seven right-handed control volunteers and seven preoperative adult epileptic patients performed a rhyme decision (language condition) and a visual detection (control condition) tasks in visually presented words and unreadable characters, respectively. All patients were left hemisphere dominant for language. Appropriate statistical analyses provided the following preliminary results: (1) patients compared with healthy subjects showed lower degree of hemispheric lateralization with supplementary involvement of the right hemisphere; (2) the degree of hemispheric specialization depends on the considered region; (3) patients with early seizures show signs of temporal and parietal reorganization more frequently than patients with late onset of seizures; (4) patients with early seizures show a tendency for intra-hemispheric frontal reorganisation; (5) associated hippocampal sclerosis facilitates the inter-hemispheric shift of temporal activation. Although our patients were left hemisphere predominant for language, the statistical analyses indicated that the degree of lateralization was significantly lower than in healthy subjects. This result has been considered as the indication of atypical lateralization of language.

Neuropsychological features of lesion-related epilepsy in adults: an overview

Lesional epilepsy is thought to be a direct consequence of focal brain lesions of dysgenetic, neoplastic, vascular, or traumatic origin. It has been estimated that at least half of all epilepsies are the result of such lesions. The current discussion includes an overview of the cognitive and behavioral presentations in adults with epilepsy secondary to focal pathology. The neuropsychological presentation in this population is influenced by many factors, including the location and nature of the underlying lesion, seizure characteristics, the effects of treatment, and patient variables. Few studies attempt to disentangle the specific contributions of these variables to cognitive performance. However, where available studies examining the separable effects of seizure-related variables on cognitive functioning in individuals with lesional epilepsy are also reviewed. This overview includes a discussion of focal malformations of cortical and vascular development and select foreign tissue and acquired lesions.

Localizing and Lateralizing Language in Patients with Brain Tumors: Feasibility of Routine Preoperative Functional MR Imaging in 81 Consecutive Patients1

PURPOSE

To prospectively assess the feasibility of standardized presurgical functional magnetic resonance (MR) imaging for localizing the Broca and Wernicke areas and for lateralizing language function.

MATERIALS AND METHODS

The study was approved by the responsible ethics commission, and patients gave written informed consent. Eighty-one patients (36 female and 45 male patients; age range, 7-75 years) with different brain tumors underwent blood oxygen level-dependent functional MR imaging at 1.5 T with two paradigms: sentence generation (SG) and word generation (WG). Functional MR imaging measurements, data processing, and evaluation were fully standardized by using dedicated software. Four regions of interest were evaluated in each patient: the Broca and Wernicke areas and their anatomic homologues in the right hemisphere. Statistics were calculated.

RESULTS

The SG and WG paradigms were successfully completed by all (100%) and 70 (86%) patients, respectively. Success rates in localizing and lateralizing language were 96% for the Broca and Wernicke areas with the SG paradigm, 81% for the Broca area and 80% for the Wernicke area with the WG paradigm, and 98% for both areas when the SG and WG paradigms were used in combination. Functional localizations were consistent for SG and WG paradigms in the inferior frontal gyrus (Broca area) and the superior temporal, supramarginal, and angular gyri (Wernicke area). Surgery was not performed in seven patients (9%) and was modified in two patients (2%) because of functional MR imaging findings.

CONCLUSION

Functional MR imaging proved to be feasible during routine diagnostic neuroimaging for localizing and lateralizing language function preoperatively.

Hemodynamic impairment as a stimulus for functional brain reorganization

We used functional magnetic resonance imaging to investigate whether hemispheral hemodynamic impairment can play an independent role in the functional reorganization of motor-related activity in the brain. Fourteen patients with large vessel occlusion but no infarct performed a simple motor task with the hand contralateral to the occluded vessel. Statistical parametric maps of regional activity were generated to compare the distribution of motor-related activity among patients with that of control subjects. Patients were classified into normal or abnormal cerebral hemodynamics on the basis of intracerebral vasomotor reactivity using transcranial Doppler and carbon dioxide inhalation. Controls and patients with normal vasomotor reactivity showed typical motor activity in contralateral motor areas. When the 9 patients with abnormal vasomotor reactivity were compared with the 14 control subjects in a single analysis, unique motor activation was identified in ipsilateral motor regions in the nonhypoperfused hemisphere. In a confirmatory analysis, blood oxygen level-dependent (BOLD) signal intensity was averaged in prespecified motor regions of interest. A significant group by hemisphere interaction was identified, driven by higher ipsilateral and lower contralateral hemisphere BOLD signal in patients with abnormal vasomotor reactivity compared with controls (F=12.40, P=0.002). The average ipsilateral motor region signal intensity was also significantly higher in the subgroup of patients with abnormal vasoreactivity and no TIA compared with controls (P=0.04). Our results suggest that hemodynamic impairment in one hemisphere, even in the absence of any focal lesion or any symptoms can be associated with a functional reorganization to the opposite hemisphere.

From the left to the right: How the brain compensates progressive loss of language function

In normal right-handed subjects language production usually is a function oft the left brain hemisphere. Patients with aphasia following brain damage to the left hemisphere have a considerable potential to compensate for the loss of this function. Sometimes, but not always, areas of the right hemisphere which are homologous to language areas of the left hemisphere in normal subjects are successfully employed for compensation but this integration process may need time to develop. We investigated right-handed patients with left hemisphere brain tumors as a model of continuously progressive brain damage to left hemisphere language areas using functional neuroimaging and transcranial magnetic stimulation (TMS) to identify factors which determine successful compensation of lost language function. Only patients with slowly progressing brain lesions recovered right-sided language function as detected by TMS. In patients with rapidly progressive lesions no right-sided language function was found and language performance was linearly correlated with the lateralization of language related brain activation to the left hemisphere. It can thus be concluded that time is the factor which determines successful integration of the right hemisphere into the language network for compensation of lost left hemisphere language function.

Early Experience with 3-T Magnetic Resonance Tractography in the Surgery of Cerebral Arteriovenous Malformations in and around the Visual Pathway

OBJECTIVE

To evaluate of the role of magnetic resonance (MR) tractography on the optic radiation with a 3-T MR unit in the surgery of cerebral arteriovenous malformation (AVM) in and around the visual pathway.

METHODS

Of the 322 patients with cerebral AVMs admitted to our clinic between 1978 and 2005, a study of MR tractography was made on 29 patients. Ten of those patients had AVMs in and around the visual pathway and were included in this study. There were two men and eight women ranging in age from 15 to 64 years (mean age, 34.5 +/- 14.8 yr). All of the patients underwent 3-T tractography of optic radiation (OR) and neuro-ophthalmologic evaluation. Four of the 10 patients underwent surgical resection of the AVM. A postoperative 3-T MR study and a neuro-ophthalmologic evaluation was performed 1 month after surgery in most patients.

RESULTS

The preoperative patients for whom tractography demonstrated a continuous bundle of OR from the medial temporal region to the primary visual cortex had minimal or no visual field loss, whereas the patients for whom the tractography did not show a continuous bundle of OR had significant visual loss. The patients for whom tractography in the postoperative study demonstrated a bundle of OR experienced no postoperative deterioration of the visual field loss, whereas the patients for whom tractography did not demonstrate a bundle of OR exhibited significant visual field loss.

CONCLUSION

This technique is thought to be useful in confirming the integrity of and localizing deviated tract and in evaluating the surgical risk, especially for nonhemorrhagic AVMs in and around the visual pathways, taking some limitations of this method into consideration.

Spatiotemporal patterns of language-specific brain activity in patients with chronic aphasia after stroke using magnetoencephalography

Six participants with chronic aphasia secondary to first-ever ischemic stroke within the middle cerebral artery (MCA) distribution of the left hemisphere and six neurologically intact controls of similar age were given a running recognition memory task for words while the magnetic flux normal to the scalp surface was measured with a whole-head neuromagnetometer. This task had been previously shown to be valid for the localization and lateralization of brain activity specific to receptive language function. As expected, patients exhibited relatively decreased activation in areas known to be involved in receptive language function, including superior temporal gyrus (STG) in the left hemisphere, as well as increased activation of areas outside of the left STG that might potentially support language function. Decreased activation within left STG was associated with a reduction in receptive language in patients, as was increased activation outside of left STG. Results support hypotheses suggesting that peri-lesional areas outside premorbid language areas may assume receptive language function after aphasia secondary to stroke, but that better recovery occurs when putative premorbid language areas are able to normalize.

Dural arteriovenous fistula presents like an ischemic stroke

OBJECTIVE

We report the case of a patient with a dural arteriovenous fistula whose neurobehavioral syndrome was indistinguishable from that of an ischemic stroke.

BACKGROUND

Case studies of dural arteriovenous fistulas primarily describe global cognitive changes like dementia, but detailed neurocognitive evaluations of dural arteriovenous fistula patients are rarely reported.

METHOD

We provide a dural arteriovenous fistula case of a patient who presented with aphasia and other symptoms of stroke. Background history, serial neuropsychological data, and angiographic images are presented.

RESULTS AND CONCLUSIONS

Serial neurocognitive data show the extent to which cognitive deficits are reversed with embolization. The case demonstrates that the mechanisms underlying neurocognitive deficits are specific to the fistula's unique hemodynamic features in addition to the location of the dural arteriovenous fistula.

Pre-frontal executive committee for perception, working memory, attention, long-term memory, motor control, and thinking: a tutorial review

As an explicit organizing metaphor, memory aid, and conceptual framework, the prefrontal cortex may be viewed as a five-member 'Executive Committee,' as the prefrontal-control extensions of five sub-and-posterior-cortical systems: (1) the 'Perceiver' (dominant-right-hemisphere ventral-lateral prefrontal cortex--VL/PERC-PFC) is the frontal extension of the ventral perceptual stream (the VL/PERC system) which represents the world and self in object coordinates; (2) the 'Verbalizer' (dominant-left-hemisphere ventral-lateral prefrontal cortex system--VL/VERB-PFC) is the frontal extension of the language stream (the VL/VERB system) which represents the world and self in language coordinates; (3) the 'Motivator' (ventral/medial-orbital pre-frontal cortex--VMO-PFC) is the frontal cortical extension of a subcortical extended-amygdala stream (the VMO system) which represents the world and self in motivational/emotional coordinates; (4) the 'Attender' (dorsal-medial/anterior cingulate--DM/AC-PFC) is the frontal cortical extension of a subcortical extended-hippocampal stream (the DM/AC system) which represents the world and self in spatiotemporal coordinates and directs attention to internal and external events; and (5) the 'Coordinator' (the dorsolateral prefrontal cortex--DL-PFC) is the frontal extension of the dorsal perceptual stream (the DL system) which represents the world and self in body- and eye-coordinates and controls willed action and working memory. This tutorial review examines the interacting roles of these five systems in perception, working memory, attention, long-term memory, motor control, and thinking.

Midazolam challenge reinduces neurological deficits after transient ischemic attack

BACKGROUND AND PURPOSE

A transient ischemic attack (TIA) in the brain is classically considered a syndrome lasting <24 hours. Having previously shown that an experimental challenge with the GABAA agonist midazolam in recovered stroke patients can reinduce the acute clinical state, we determined whether TIA patients would demonstrate a similar effect.

METHODS

Four right-handed patients participated: 3 with clinical TIA presumed to have affected the left hemisphere within the previous 24 to 72 hours and no evidence of a new lesion on diffusion-weighted and fluid-attenuated inversion recovery imaging, and 1 patient with an asymptomatic temporal arteriovenous malformation. The TIA duration ranged from 30 minutes to 3 hours. Each patient underwent baseline testing for motor function and aphasia, after which intravenous midazolam was delivered until mild drowsiness was detected. Patients were tested during the peak drug effect and again after 2 hours when sedation had dissipated.

RESULTS

No patient showed weakness or aphasia at baseline. After administration of midazolam, all 3 TIA patients demonstrated re-emergence of features that characterized their recent transient neurological syndromes (right-sided weakness and/or aphasia) but no left-sided findings. The arteriovenous malformation patient who had never been symptomatic showed no drug effect. Two hours later, all TIA patients returned to their normal clinical state.

CONCLUSIONS

Patients who had suffered recent transient cerebral ischemic episodes and were neurologically intact with negative diffusion-weighted imaging showed re-emergence of prior focal deficits after administration of a benzodiazepine in a dose that produces light sedation. These findings suggest that presumed TIA may produce neuronal dysfunction beyond the symptomatic period.

Arteriovenous brain malformations: is functional MR imaging reliable for studying language reorganization in patients? Initial observations

PURPOSE

To determine whether the blood flow abnormalities frequently associated with arteriovenous malformations (AVMs) can alter functional magnetic resonance (MR) imaging evaluation of language lateralization and whether reorganization of language function occurs in patients with brain AVMs.

MATERIALS AND METHODS

Eleven patients with left-hemisphere brain AVMs and 10 age-matched control subjects were examined with 1.5-T blood oxygen level-dependent (BOLD) functional MR imaging. Verbal fluency, sentence repetition, and story listening tasks were performed. The functional MR imaging laterality index in the frontal and temporal lobes was defined as the (L - R)/(L + R) ratio, where L and R are the numbers of activated pixels in the left and right hemispheres, respectively. Statistical analyses were performed with Wilcoxon signed rank, Fisher exact, and Kruskal-Wallis tests.

RESULTS

Control subjects had left-sided language dominance, although symmetric pixel counts were observed in the frontal lobes in two subjects and in the temporal lobes in one subject. Six patients had left-sided language dominance similar to that observed in control subjects. Five of these patients had AVMs outside frontal or temporal language areas, without flow abnormalities. Five patients had abnormally right-sided asymmetric indexes (below mean control subject value - 2 SDs), which suggested language reorganization (P <.05). Results of Wada examination and/or postembolization functional MR imaging performed in two of these patients showed that the abnormal laterality indexes were at least partly due to severe flow abnormalities that impaired detection of BOLD MR imaging signal intensity.

CONCLUSION

These data suggest that flow abnormalities may interfere with language lateralization assessment with functional MR imaging.

Functional evaluation of arteriovenous malformations

Detailed knowledge of the angioarchitecture of arteriovenous malformations (AVMs) is necessary in determining the optimal timing and method of treatment of these challenging lesions. Many techniques are available for studying the functionality of surrounding cortical structures of AVMs. These include the use of positron emission tomography, functional magnetic resonance imaging, magnetoencephalography, and direct provocative testing of cortical function. The use of these methods to determine flow dynamics and tissue perfusion is also reviewed. These techniques are discussed in the present study, and their judicious utilization will enhance the safety of AVM therapy.

Neuropsychological function and brain arteriovenous malformations: redefining eloquence as a risk for treatment

Arteriovenous malformations (AVMs) of the brain, thought to begin during fetal development and undergo an unclear maturation process; most often do not become symptomatic until the patient reaches adulthood. Authors of recent prospective studies have suggested that relatively few patients present with neuropsychological abnormalities in the absence of hemorrhage. In general, neuropsychological evaluations in patients with AVMs have yielded mixed results with respect to localization of function, and the authors of most cognitive studies have not been able to demonstrate the nature and degree of impairment seen in acute ischemic stroke in comparable brain regions. Superselective Wada testing prior to therapeutic embolization, functional imaging studies, and intrasurgical cortical mapping have shown redistribution of language and memory to unpredictable regions. Developmental cognitive history in these patients indicates that most will have at least some background of learning problems during the school-age years with varying degrees of severity, reflecting a time when brain reorganization may be occurring. These data suggest that traditional assumptions about the eloquence of brain regions may not hold for patients with AVMs and that establishing treatment risk in the individual patient needs to be made on an empirical basis.

Epidemiology and natural history of arteriovenous malformations

The epidemiology and natural history of cerebral arteriovenous malformations (AVMs) remains incompletely elucidated. Several factors are responsible. With regard to the incidence and prevalence of AVMs, the results of prior studies have suffered because of the retrospective design, the use of nonspecific ICD-9 codes, and a focus on small genetically isolated populations. Recent data from the New York Islands AVM Hemorrhage Study, an ongoing, prospective, population-based survey determining the incidence of AVM-related hemorrhage and the associated rates of morbidity and mortality in a zip code–defined population of 10 million people, suggests that the AVM detection rate is 1.21/100,000 person-years (95% confidence interval [CI] 1.02–1.42) and the incidence of AVM-hemorrhage is 0.42/100,000 person-years (95% CI 0.32–0.55). Contemporaneous data from the Northern Manhattan Stroke Study, a prospective, longitudinal population-based study of nearly 150,000 patients in which the focus is to define the incidence of stroke, suggest the crude incidence for first-ever AVM-related hemorrhage to be 0.55/100,000 person-years (95% CI 0.11–1.61). Efforts are ongoing to study the natural history of both ruptured and unruptured AVMs in these datasets to examine the relevance of prior studies of patients selected for conservative follow up in Finland. In addition, data are being gathered to determine whether risk factors for future hemorrhage, which have previously been established in small case series, are valid when applied to whole populations. Together, these data should help inform therapeutic decisionmaking.

Language representation in a patient with a dominant right hemisphere: fMRI evidence for an intrahemispheric reorganisation

Studies have suggested that congenital left hemispheric (LH) frontal arteriovenous malformations (AVMs) are associated with an early transfer of language to right hemisphere (RH) frontal regions. The question remains whether such anatomofunctional reorganisation is due to RH compensatory abilities or to a general principle of lateral shift. In this study, we used fMRI language paradigms to investigate the case of a patient presenting aphasic symptoms following an haemorrhage due to a right frontal AVM. Prior to surgery, fMRI showed that language processing was confined to the RH, suggesting that language had not shifted during childhood from this congenitally dominant RH to the LH. After surgery, the patient presented severe aphasia that recovered to presurgical level within 70 days. At this time, fMRI showed that language tasks were still not associated with activations in the LH. These results suggest that the principles of early cerebral reorganisation after congenital lesions may differ in the RH and the LH. In addition, they support the idea that efficient restoration of language is achieved if a sufficiently large neuronal network is preserved around the lesion.

Reporting terminology for brain arteriovenous malformation clinical and radiographic features for use in clinical trials

“If you wish to converse with me,” said Voltaire, “define your terms.” How many a debate would have been deflated into a paragraph if the disputants had dared to define their terms!

Will Durant: The Story of Philosophy

Brain plasticity for sensory and linguistic functions: a functional imaging study using magnetoencephalography with children and young adults

In this report, the newest of the functional imaging methods, magnetoencephalography, is described, and its use in addressing the issue of brain reorganization for basic sensory and linguistic functions is documented in a series of 10 children and young adults. These patients presented with a wide variety of conditions, ranging from tumors and focal epilepsy to reading disability. In all cases, clear evidence of reorganization of the brain mechanisms of either somatosensory or linguistic functions or both was obtained, demonstrating the utility of magnetoencephalography in studying, completely noninvasively, the issue of plasticity in the developing brain.

Language localization in cases of left temporal lobe arachnoid cyst: evidence against interhemispheric reorganization

We investigated whether left-hemisphere arachnoid cysts lead to reorganization of the language function using PET. A group analysis demonstrated that patients showed no more right-hemisphere activation than a matched control group. Several patients had clear language localizations in the left hemisphere during language comprehension; none of the patients showed right-hemisphere activation. We conclude that left-hemisphere tissue must suffer considerable compromise before reorganization of language into the right hemisphere becomes necessary. Language activations within the left hemisphere are clearly displaced. This is consistent with mere physical displacement in some patients rather than reorganization within the left hemisphere; in others intrahemispheric reorganization cannot be excluded.

Interhemispheric transfer of language in patients with left frontal cerebral arteriovenous malformation

Cerebral arteriovenous malformations (AVMs) are frequently evaluated before therapeutic embolization by superselective injection of anesthetics into individual arterial branches so as to determine whether permanent occlusion would affect eloquent function. In Experiment 1, we used this adaptation of the Wada procedure to study three right-handed adult patients with left frontal cerebral AVMs by injecting vessels in Wernicke's and Broca's areas, respectively, and assessing language functions. The results showed that superselective testing in the inferior division of the left MCA in all three patients produced a dense Wernicke's aphasia. Injections into the left frontal regions, however, resulted in right paresis in all patients, but no language deficits including no loss of fluency. In Experiment 2, Patient 2 underwent fMRI activation for spontaneous word-list generation using multi-slice echo planar BOLD techniques at 1.5 Tesla. A voxel-by-voxel comparison of rest vs activation for each task was performed with a Z-score threshold of 2.5 SD for activated voxels. There was activation in the right hemisphere in the insula, frontal operculum pars opercularis, and inferior frontal gyrus, an area homologous to Broca's area in the left hemisphere. There was also activation in the left hemisphere in the Rolandic region, but language function was unaffected during Wada testing in this area. These data suggested that features of expressive language were no longer controlled by the left frontal lobe where the AVM was located, and provided new evidence for interhemispheric re-organization under conditions of chronic neurovascular disease.

New concepts in adult brain arteriovenous malformations

Brain arteriovenous malformations are currently attracting increasing attention among clinicians as modern brain imaging techniques facilitate both diagnostic and follow-up evaluation. Their frequent presentation in young individuals, at times with flagrant clinical effects caused by cerebral hemorrhages or seizure disorders, keeps clinicians alert to any improvement in treatment strategies. Recent technical advances in surgical, endovascular, and radiation therapy add to the constantly accumulating data on clinical features, natural course, and treatment outcome in adult arteriovenous malformation patients. This review focuses on new concepts in arteriovenous malformation etiology, classification, treatment, and study approaches.