Prediction of false-positive recognition errors during Wada testing

False-positive (FP) errors during recognition memory testing often interfere with interpretation of Wada test results. This study examined which clinical and neuropsychological variables provide the best prediction of these errors. Fifty-six patients completed the Wada test and the California Verbal Learning Test (CVLT). Subjects with three or more FP errors on the recognition trials of the CVLT were nearly twice as likely to exhibit FP responding during the Wada test. Further analysis indicates that FP errors during the Wada test appear to be the primary result of a stable and liberal response-bias rather than a result of any other neurological or procedure-related factor.     

Tolerability of propofol in Wada testing

Objective:

To assess the tolerability of propofol (PF) in Wada test in an Arab population with temporal lobe epilepsy (TLE).

Methods:

This observational study with consecutive sampling took place in King Fahad Medical City, Riyadh, Saudi Arabia. Nine consecutive patients with mean (+SD) age of 26 (+5.8) years, 6 males and 3 females, underwent Wada test between January 2009 and December 2012. Six of them had left TLE, and 3 had right TLE. Each patient received 10 mg of PF in the internal carotid artery (ICA). Right hemispheric injection was followed by left hemisphere injection after 30 minutes. During the procedure, EEG monitoring showed changes within 5-18 seconds of injection as hemispheric delta slowing. Neuropsychological tests were carried out for localization of memory and language.

Results:

We were able to lateralize speech dominance in 8 patients and memory dominance in 6 patients. Peri-procedural complications included transient euphoria (n=1), transient spasm of ICA (n=1), eye pain (n=1), facial pain (n=1), and generalized tremulousness (n=2). None of the patients exhibited a symptomatic drop in blood pressure.

Conclusions:

We found that PF is well tolerable for the Wada test, with minimally significant complications, although blood pressure should be closely monitored.Wada test has been the gold standard for lateralization of speech and memory since 1960, when it was first introduced by Juhn Wada.1 The basic concept of the Wada procedure is to inject an anesthetic agent into the brain (through the carotid artery) to sedate one hemisphere transiently in order to localize the dominant hemisphere.1 Patients with temporal lobe epilepsy (TLE) who are candidates for temporal lobe resection are at risk of postsurgical language and/or memory impairment.2 The best agent used for the Wada test is sodium amytal (SA) due to its low toxicity, high efficacy, and adequate duration of action.3 However, SA is facing worldwide shortage, which necessitated the search for other alternatives.4 Propofol (PF) was proposed as a potential alternative.4 The objective of our study was to assess the tolerability of PF in the Wada test in an Arab population with TLE.     

Anosognosia and asomatognosia during intracarotid amobarbital inactivation

BACKGROUND: Anosognosia (i.e., denial of hemiparesis) and asomatognosia (i.e., inability to recognize the affected limb as one's own) occur more frequently with right cerebral lesions. However, the incidence, relative recovery, and underlying mechanisms remain unclear. METHODS: Anosognosia and asomatognosia were examined in 62 patients undergoing the intracarotid amobarbital procedure as part of their preoperative evaluation for epilepsy surgery. Additional questions were asked in the last 32 patients studied. RESULTS: During inactivation of the non-language-dominant cerebral hemisphere, 88% of the 62 patients were unaware of their paralysis, and 82% could not recognize their own hand at some point. Only 3% did not exhibit anosognosia or asomatognosia. In general, asomatognosia resolved earlier than anosognosia. When patients could not recognize their hand, they uniformly thought that it was someone else's hand. Dissociations in awareness were seen in the second series of 32 patients. Although 23 patients (72%) thought that both arms were in the air, 31% pointed to the correct position of the paralyzed arm on the table. Despite the inability of 24 of 32 patients (75%) to recognize their own hand, 21% of these patients were aware that their arm was weak, and 38% had correctly located their paralyzed arm on the angiography table. CONCLUSIONS: Anosognosia and asomatognosia are both common during acute dysfunction of the non-language-dominant cerebral hemisphere. Dissociations of perception of location, weakness, and ownership of the affected limb are frequent, as are misperceptions of location and body part identity. The dissociations suggest that multiple mechanisms are involved.     

Wada testing reveals frontal lateralization for the memorization of words and faces.

Neuroimaging studies have suggested that specific regions of the frontal and medial temporal cortex are engaged during memory formation. Further, there is specialization across these regions such that verbal materials appear to preferentially engage the left regions while nonverbal materials primarily engage the right regions. An open question, however, has been to what extent frontal regions contribute to successful memory formation. The present study investigates this question using a reversible lesion technique known as the Wada test. Patients memorized words and unfamiliar faces while portions of their left and right hemispheres were temporarily anesthetized with sodium amytal. Subsequent memory tests revealed that faces were remembered better than words following left-hemisphere anesthesia, whereas words were remembered better than faces following right-hemisphere anesthesia. Importantly, inspection of the circulation affected by the amytal further suggests that these memory impairments did not result from direct anesthetization of the medial temporal regions. Taken in the context of the imaging findings, these results suggest that frontal regions may also contribute to memory formation in normal performance.     

Abnormal Wada and neuropsychological testing results due to topiramate therapy

A 46-year-old man experienced intractable seizures since childhood. Due to lack of response to antiepilepsy drugs (AEDs), he underwent a surgical evaluation that was consistent with seizure onset in the left medial temporal lobe. While on topiramate and carbamazepine, his preoperative neuropsychological scores and sodium amytal (Wada) scores were low and may have excluded him from surgery. Repeat testing on lamotrigine and carbamazepine showed improvement in his scores, allowing him to undergo surgery. Physicians must therefore be cautious in evaluating such test scores while a patient is on topiramate.     

Anosognosia in Dementia

Progressive decline in memory (and other functions) is the defining feature of late-life dementia but affected individuals are often unaware of this impairment. This article reviews recent research on anosognosia in dementia, including methods of assessing anosognosia, its prevalence and developmental course in dementia, its occurrence in different forms of dementia, neuroimaging findings, and hypothesized component mechanisms. The results suggest that anosognosia is eventually exhibited by nearly all persons with dementia. Its occurrence is robustly associated with common dementia-related pathologies and damage to memory and self-referential brain networks and their interconnections.     

Anosognosia in aphasics

The notion that aphasia may be accompanied by some degree of unawareness of the disorder was introduced by Wernicke in 1874. Ever since the idea has prevailed that sensory aphasics, especially jargonaphasics, are not, or but little, conscious of their deviant verbal output. This view was disputed in recent years. It was claimed that anosognosia was not a typical feature of Wernicke's aphasia or of jargonaphasia. However, analysis of the behavior of sensory aphasics shows that some of these patients are not well aware of the deviances in their verbal output. This unawareness may be due to verbal deafness or to disturbed feedback. On the other hand, some aphasics appear to realize that their verbal expression is anomalous but choose to ignore the fact in order to preserve their self-image or to keep up the social intercourse with the environment. Anosognosia can be found in association not only with sensory aphasia but also with monophasia and with modality-specific aphasia, as well as with unilateral neglect and with apraxia. If a patient has anosognosia, the speech therapist must know about it and take it into account, lest it renders therapeutical efforts fruitless.     

Wada testing and fMRI in a polyglot evaluated for epilepsy surgery

Despite advancements in the neurophysiology of language and presurgical evaluation for epilepsy surgery, there is a paucity of information in the literature regarding presurgical evaluation of multilingual patients. We present a case of a 52‐year‐old right‐handed woman with refractory epilepsy who was fluent in six languages and underwent subsequent trilingual presurgical evaluation which included neuropsychological testing, Wada testing, functional magnetic resonance imaging (fMRI), and electrocortical stimulation. These studies suggested a seizure focus in the left temporal lobe and language localization that was predominantly right‐hemispheric; she subsequently underwent left temporal laser interstitial thermal therapy without clinical disturbance in language function while remaining seizure‐free. A multidisciplinary effort was integral in providing an optimal outcome for this patient.     

FMRI reveals functional cortex in a case of inconclusive Wada testing

OBJECTIVES: The intracarotid amobarbital test (Wada test) currently represents the gold standard for preoperative lateralization of hemispheric dominance. Here, we report an epileptic patient with a longstanding extended lesion of the left hemisphere showing absence of motor and speech dysfunction with left carotid amobarbital injection, but tetraplegia and speech arrest with right carotid injection interpreted as a neuroplastic shift of motor and language functions to the right hemisphere. In contrast to the Wada results, motor functional magnetic resonance imaging (fMRI) showed a strong left hemispheric activation with right hand movements. METHODS: Right and left hand motor fMRI was performed. FMRI results and neurophysiological information obtained by motor and sensory evoked potential measurements were compared with the Wada test results. RESULTS: Initial interpretation of neuroplastic shifts of intrinsic left hemisphere functions to the right brain was revised after fMRI results which were confirmed by motor and sensory evoked potentials. CONCLUSION: As motor inactivation usually is thought to be the most robust feature of the Wada test, this case demonstrates that fMRI may reveal residual functional cortex in cases of inconclusive Wada results.     

Anosognosia for neuropsychological impairment

Three aphasic patients with different degrees of impairment and with lesions in language areas which predict differentdegrees of improvement are described. At follow up, patientRD, with an anterior lesion and Broca's aphasia, demonstrated very poor improvement and outcome; patient LAB, with a lesion of posterior language areas and Wernicke's aphasia, had very good improvement and outcome. Finally, patient GH, with a lesion of both anterior and posterior language areas and global aphasia, had the best improvement and an outstanding outcome. We conclude that severity of aphasia and site of lesion, which are powerful prognostic factors in groups of patients, cannot be considered unfailing predictors of improvement and outcome in single patients.     

Anosognosia in neurodegenerative disease

Patients with neurological disorders are often partially or completely unaware of the deficits caused by their disease. This impairment is referred to as anosognosia, and it is very common in neurodegenerative disease, particularly in frontotemporal dementia. Anosognosia has significant impacts on function and quality of life for patients with neurodegenerative disease and their caregivers, but the phenomenon has received little formal study, especially in non-Alzheimer's (non-AD) dementias. Furthermore, few studies have attempted to systematically verify the potential role of specific cognitive impairments in producing anosognosia. As a result, the mechanisms underlying this phenomenon are poorly understood. Episodic memory likely plays an important role. In addition, the frontal lobe systems are important for intact self-awareness, but the most relevant frontal functions have not been identified. Motivation required to engage in self-monitoring and emotional activation marking errors as significant are often-overlooked aspects of performance monitoring that may underlie anosognosia in some patients. The present review offers a working model that incorporates these functions and stipulates specific processes that may be important for awareness of changes in one's abilities. Specification of the specific processes whose potential failure results in anosognosia can establish a roadmap for future studies.     

Handedness, footedness, and language laterality: evidence from Wada testing

A total of 37 candidates for temporal lobe resection for epilepsy completed the Lateral Dominance Examination, a self-report instrument that measures hand and foot preference. Questionnaire results were compared with speech dominance, which had been determined by Intracarotid Sodium Amytal Procedure. Footedness was as good as handedness as a predictor of language laterality.     

One center's experience with complications during the Wada test

This study aimed to define the number and type of complications associated with the Wada test at an academic medical center for comparison to previous reports. We performed a retrospective review of medical records for patients who underwent the Wada test at the University of Michigan between April 1991 and June 2013. Information was collected regarding the angiography procedure and the immediate postoperative period to assess for both clinical and angiographic complications. A total of 436 patients were identified who underwent the Wada procedure between April 1991 and June 2013, and 431 patients were included in the final analysis. Twenty‐five patients (5.8%) had notable clinical events associated with the Wada test. Nine patients (2.1%) had clinical events meeting criteria for complication, which included seizures, status epilepticus, internal carotid artery vasospasm, inadvertent injection of anesthetic in the external carotid artery, and transient encephalopathy. No complications were associated with significant morbidity or mortality. This retrospective review of patients undergoing the Wada test found significantly fewer associated complications in comparison to previously published studies, with no patients experiencing long‐term morbidity. The Wada test should be considered a safe diagnostic tool for lateralizing language and memory.     

Pediatric language mapping: sensitivity of neurostimulation and Wada testing in epilepsy surgery

PURPOSE: Functional mapping of eloquent cortex with electrical neurostimulation is used both intra- and extraoperatively to tailor resections. In pediatric patients, however, functional mapping studies frequently fail to localize language. Wada testing has also been reported to be less sensitive in children. METHODS: Thirty children (4.7 - 14.9 years) and 18 adult controls (18-59 years) who underwent extraoperative language mapping via implanted subdural electrodes at the NYU Comprehensive Epilepsy Center were included in the study. Ten children and 14 adults underwent preoperative Wada testing. Success of the procedures was defined as the identification of at least one language site by neurostimulation mapping and determination of hemispheric language dominance on the Wada test. RESULTS: In children younger than 10.2 years, cortical stimulation identified language cortex at a lower rate than was seen in children older than 10.2 years and in adults (p<0.05). This threshold, demonstrated by survival and chi2 analysis, was sharply defined in our data set. Additionally, Wada testing was more likely to be successful than was extraoperative mapping in this younger age group (p<0.05). CONCLUSIONS: Analysis of our series demonstrates that language cortex is less likely to be identified in children younger than 10 years, suggesting that alternatives to the current methods of cortical electrical stimulation, particularly the use of preoperative language lateralization, may be required in this age group.     

Anosognosia for hemiplegia: somatosensory evoked potential studies.

Somatosensory evoked potential studies in nine patients with anosognosia for left hemiplegia and in one patient with anosognosia for right hemiplegia revealed an absence of response over either hemisphere on stimulation of the median nerve on the hemiplegic side. This apparent lack of cortical processing may underlie the impaired awareness of the hemiplegic side, manifested as anosognosia.     

Transient shivering during Wada test provides insight into human thermoregulation

Purpose: Some patients with pharmacoresistant epilepsy undergoing the Wada test experience transient shivering. The purpose of this study was to investigate various clinical and radiographic characteristics of these individuals to delineate underlying mechanisms of this phenomenon. Methods: A systematic review of prospectively collected information on patients undergoing the Wada test was performed. All demographic, clinical, and radiographic information was obtained and reviewed by the appropriate expert in the field; statistical analysis was performed to determine the predictors of transient shivering. Results: A total of 120 consecutive carotid artery injections in 59 patients were included in the study. Shivering was observed in 46% of the patients, and it was not significantly affected by gender, age, location of epileptogenic zone, brain lesion on magnetic resonance imaging (MRI), side of the first injection, duration of the hemiparesis, or excess slow wave activity on electroencephalography (EEG). However, shivering was more likely to follow sodium amobarbital injection if there was no filling of the posterior circulation on cerebral angiogram. Discussion: Transient shivering during the Wada test is common. A transient but selective functional lesion of the anterior hypothalamus produced by the effects of sodium amobarbital may result in disinhibition of the posterior hypothalamus and other brainstem thermoregulatory centers, thereby inducing transient shivering.     

Dissociation of anosognosia and phantom movement during the Wada test

OBJECTIVE: Patients who misperceive that they are moving their paralysed arm (phantom movements) may not recognise its weakness. Therefore, the relation between phantom limb movements and anosognosia for hemiplegia during selective right hemispheric anaesthesia (the Wada test) was examined. METHODS: Nine patients with intractable epilepsy underwent the Wada test. During the right hemispheric injection, after the onset of hemiparesis, anosognosia was assessed by asking patients if they were weak. The patient's vision was limited such that they could not see the position of their limbs. Phantom movements were tested for by asking patients to attempt to lift their left upper limb, and to demonstrate their left limb's position by placing their right limb in the same position as their left. Proprioception was tested by lifting the patient's paretic upper limb and having patients demonstrate this position by lifting their right limb to the same position. RESULTS: Three patients experienced left phantom limb movements, and five were anosognosic for their hemiplegia. However, phantom movement occurred in only one patient with anosognosia. The other two patients with phantom movement were without anosognosia. The patient with phantom movement and anosognosia had impaired proprioception. The two patients with phantom movement but without anosognosia had intact proprioception. CONCLUSIONS: Phantom movement in the presence of a proprioceptive deficit could contribute to anosognosia. However, anosognosia and phantom movement are dissociable; therefore phantom movement cannot alone account for anosognosia. Because phantom movement occurred with and without proprioceptive deficits, proprioceptive loss is not a prerequisite for phantom movement.