Wada and SelectiveWada Tests

25 Wada and Selective Wada Tests

Rachel Jacobs, Nitin Agarwal, Brian T.Jankowitz, and Bradley A. Cross

Abstract

The Wada test has been considered the gold standard for later-alizing language and memory function in the presurgical workup of patients with epilepsy. It has further evolved in its applications in its superselective form with applicability to a plethora of cerebrovascular pathology. This chapter reviews historical manuscripts and provides a review of the approach with a critical analysis of its utility in the era of advanced noninvasive imaging modalities.

Keywords: Wada test, epilepsy, sodium amobarbital

25.1 Goals

1. Present the frequency, clinical indications, and methods of Wada testing and its associated complications.

2. Compare the literature on use of Wada and noninvasive approaches.

3. Analyze the validity of Wada testing for language determination and memory function.

4. Review the literature on posterior cerebral artery (PCA) and superselective Wada.

25.2 Case Example

25.2.1 History of Present Illness

A 53-year-old, left-handed man on aspirin with a history of traumatic brain injury presents for surgical consideration of his medically refractory complex partial epilepsy with secondary generalization since the age of 15 after a motor vehicle accident. The patient reports his seizures start with right eye deviation, head deviation to the right, ringing noises in his ears, “feeling funny,” and unusual odor perception. He continues to have bilateral upper extremity tremors as a side effect from his Depakote. He complains of residual weakness in his right leg and numbness that affects his right foot and palm after a stroke in 2000. A Wada test was recommended prior to a potential left temporal lobectomy.

Past medical history: Mitral valve prolapse, aortic stenosis, cerebrovascular accident, right-sided eye trauma (status postprosthesis).

Past surgical history: Appendectomy, right eye removed, C3-C5 fusion.

Family history: Noncontributory, no family history of seizures.

Social history: 30-pack-year smoking history, social alcohol usage, no drugs of abuse.

Review of systems: As per the history of present illness.

Neurological examination: Remarkable for a mild right facial droop, decreased hearing bilaterally, and mild right hemipa-resis (4 + /5). He has a noticeable tremor of the left greater than right on outstretched upper extremities.

Imaging studies: See Fig. 25.1.

25.2.2 Treatment Plan

The patient underwent selective catheterization and angiography of the bilateral internal carotid arteries (ICAs) followed by administration of 125 mg of sodium Amytal in the left ICA and 200 mg of sodium Amytal in the right ICA followed by language and memory testing and subsequent Mynx closure of right common femoral artery. Wada testing affirmed that the patient harbored a left hemisphere language representation and left memory dominance. After performance of the Wada test, a fronto-temporal grid was implanted with depth electrodes into the hippocampus. Surgical resection was subsequently performed after mapping the location of the seizure focus more definitively

25.2.3 Follow-up

The patient tolerated the Wada test without complication. He initially underwent placement of a frontotemporal grid with depth electrodes into the hippocampus and subsequent resection of the seizure focus. At 1-year follow-up evaluation, the patient has been seizure-free since his surgery.

25.3 Case Summary

1. What would you report as the most common complications associated with the Wada test?

The complication rate associated with angiography and has been reported to range from 0.3% to nearly 11% of patients.¹^,²^,³^,⁴^,⁵ Most complications are associated with the angiogram and not with the injection of amobarbital itself; thus, the main source of complications is thromboemboli. Other sources of morbidity include dissections and groin complications. As modern reports cite lower and lower rates of complications, one would expect a commensurate rate for the Wada test as well.

Fig. 25.1 Anteroposterior (AP) angiographic run performed of the patient’s left internal carotid artery prior to injection of amobarbital for Wada testing.

Fig. 25.2 (a) Carotid angiography delineates a pseudoaneurysm of the pericallosal anterior cerebral artery (ACA) (lateral view, arrow). Superselective angiography prior to injection of Amytal demonstrates the aneurysm, (b) Control angiography after Onyx embolization demonstrates obliteration of the aneurysm with Onyx casting the lesion (lateral view, c, arrow).

2. What patient factors would you consider when deciding on your recommendations for Wada testing?

Both patient’s age and medical comorbidities are important patient factors when deciding on Wada testing. Neurologic complications are significantly more common in patients 55 years of age or older and in patients with cardiovascular disease.³ In the study by Loddenkemper et al, older age was a risk factor for stroke (47 years as compared with 32 years) and dissection (52 years as compared with 32 years), whereas younger age (21 years as compared with 32 years) was a risk factor for seizures.⁴

4. In which cases may the Wada test be omitted prior to surgical resection?

Although decisions should be made on a case-by-case basis, the Wada test may possibly be omitted in the preoperative evaluation in a patient with right temporal lobe epilepsy if there is an evidence of typical left hemispheric language dominance from functional imaging.¹ Also, combined structural and functional imaging in conjunction with neuropsychological testing could be used as opposed to the Wada testing for patients at high risk of memory decline.⁶ Some centers consider functional magnetic resonance imaging (flvIRI) to be a reasonable “triage test,” and Wada testing is indicated when flvIRI does not provide straightforward left lateralization.⁷ As functional imaging improves and resultant ambiguity decreases, the use of the Wada test may become reserved for a narrower patient population.

4. Can the Wada test be more broadly applied?

Wada tests may also be performed superselectively to identify clinically relevant neurologic deficits. This procedure can be employed to detect eloquent cortex perfused by feeding arteries, and therefore prior to embolization, one can anticipate potential neurologic deficits. The following case demonstrates utilization of the superselective Wada.

A 43-year-old male who previously underwent craniotomy for resection of a left frontal glioma and subsequent radiation was found to have an anterior cerebral artery (ACA) pseudoaneurysm on follow-up imaging, confirmed angiographically ( Fig. 25.2a). The patient underwent superselective Wada testing with 30 mg of intra-arterial sodium amobarbital infused into the right pericallosal artery resulting in no discernible neurologic changes ( Fig. 25.2b). He thus underwent embolization of the pseudoaneurysm and parent vessel with Onyx 34 without complication ( Fig. 25.2c). Imaging studies: See Fig. 25.2.