Intravenous methylprednisolone reduces the risk of propofol-induced adverse effects during Wada testing

Noninvasive Prediction of Language Lateralization Through Arcuate Fasciculus Tractography in Patients With Low-Grade Gliomas: Correlation With The Wada Test

Language lateralization is unique to humans, so clarifying dominant side is helpful for removing gliomas involving language areas. This study investigated the arcuate fasciculus (AF) reconstructed by diffusion tensor imaging–based tractography (DTT) in predicting language lateralization in patients with low-grade gliomas. Wada test was performed to determine the language Dominant Hemisphere (DH) and the Contralateral Hemisphere. DTI data [1.5-T magnetic resonance imaging (MRI)] was used to reconstruct AF by two independent operators using a DTT method. Fiber number, volume, and fractional anisotropy (FA) of bilateral reconstructed AF were measured. Lateralization indexes (LIs), including Number Index (NI), Volume Index (VI), and FA Index (FI), were accordingly calculated by mean values. A total of 21 patients with WHO Grade II gliomas in the left hemisphere were included. Every patient received a successful Wada test and reconstruction of bilateral AF. DTT metrics of reconstructed AF, such as fiber number, volume, and FA, showed significantly asymmetric between hemispheres. All the LI (NI, VI, and FI) values were statistically higher in the DH determined by the Wada test. No discrepancy was found between the prediction using the cutoff values of DTT metrics and the results of WADA test. The Kappa values were 0.829, 0.696, and 0.611, indicating NI and VI as more reliable predictor than FI although FI itself may also be feasible. Compared with the Wada test, we consider that DTT of AF is a non-invasive, simple, relatively accurate, and feasible method in predicting language lateralization in patients with low-grade gliomas.

Propofol as a substitute for amobarbital in Wada testing

We describe a patient with equivocal findings on functional MRI (fMRI), who underwent a propofol Wada test, review the literature on this topic and suggest a protocol for the use of propofol for a Wada test. Although fMRI techniques can usually accurately lateralize language, the Wada test remains the gold standard for preoperative lateralization and is occasionally still required if there are non-diagnostic findings on fMRI. Amobarbital, the agent of choice for the Wada test, has become increasingly difficult to obtain and requires regulatory approval, which may delay definitive management and have an impact on patient outcomes. Propofol has been suggested as an alternative to amobarbital, and while there is some published data on this, there is no reported Australian experience to date.

Evaluation of Language Function under Awake Craniotomy

Awake craniotomy is the only established way to assess patients' language functions intraoperatively and to contribute to their preservation, if necessary. Recent guidelines have enabled the approach to be used widely, effectively, and safely. Non-invasive brain functional imaging techniques, including functional magnetic resonance imaging and diffusion tensor imaging, have been used preoperatively to identify brain functional regions corresponding to language, and their accuracy has increased year by year. In addition, the use of neuronavigation that incorporates this preoperative information has made it possible to identify the positional relationships between the lesion and functional regions involved in language, conduct functional brain mapping in the awake state with electrical stimulation, and intraoperatively assess nerve function in real time when resecting the lesion. This article outlines the history of awake craniotomy, the current state of pre- and intraoperative evaluation of language function, and the clinical usefulness of such functional evaluation. When evaluating patients' language functions during awake craniotomy, given the various intraoperative stresses involved, it is necessary to carefully select the tasks to be undertaken, quickly perform all examinations, and promptly evaluate the results. As language functions involve both input and output, they are strongly affected by patients' preoperative cognitive function, degree of intraoperative wakefulness and fatigue, the ability to produce verbal articulations and utterances, as well as perform synergic movement. Therefore, it is essential to appropriately assess the reproducibility of language function evaluation using awake craniotomy techniques.

Alternatives to sodium amobarbital in the Wada test

OBJECTIVE

To review the literature and identify alternatives to sodium amobarbital for use in the Wada test.

DATA SOURCES

A search of PubMed (1960-October 2010) was performed using the following key words alone or in combination: Wada test, intracarotid amobarbital procedure, intracarotid, intraarterial, sodium amobarbital, methohexital, Brevital, pentobarbital, etomidate, propofol, and alternative anesthetics. References of the identified articles were reviewed for relevant information.

STUDY SELECTION AND DATA EXTRACTION

All articles in English identified from the data sources were evaluated. Review included comparative, prospective, and retrospective studies along with case series and case reports.

DATA SYNTHESIS

Methohexital, pentobarbital, etomidate, and propofol have all been studied as alternatives to sodium amobarbital in the Wada test. Four controlled experimental trials, 1 uncontrolled experimental trial, 6 retrospective chart reviews, and 2 case reports were reviewed. Methohexital, pentobarbital, and propofol required a second injection due to their short duration of action. Etomidate was studied as a bolus injection followed by a continuous infusion until the critical speech and memory tests were administered, which differed from the standard Wada test procedure. Patients had an increased risk of seizures with methohexital, whereas 1 patient developed transient respiratory depression immediately after receiving pentobarbital. Furthermore, propofol caused increased tone with twitching and rhythmic movements, which interfered with the completion of the Wada test for 1 patient. All authors concluded that these agents were equivalent to amobarbital for the Wada test.

CONCLUSIONS

Methohexital, pentobarbital, etomidate, and propofol are viable alternatives to sodium amobarbital for use in the Wada test, but each has shortcomings.