Super-Selective Wada Test for Pre-Surgical Leg Motor Function Assessment: A case report

doi:10.21203/rs.3.rs-3580779/v1

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Case Report

Super-Selective Wada Test for Pre-Surgical Leg Motor Function Assessment: A case report

https://doi.org/10.21203/rs.3.rs-3580779/v1

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Journal Publication

published 29 Jan, 2024

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Introduction: Wada test is well-known to assess lateralization of memory and language functions, however super-selective Wada (ss-Wada) to evaluate motor leg function is rare. We present a ss-Wada test within the anterior cerebral artery (ACA) to assess the motor function of the leg.

Methods: Retrospective chart review.

Results: Comprehensive phase-I/II surgical evaluation revealed an ictal focus around the left post-central gyrus with immediate involvement around left para-central regions. To avoid potential right leg motor dysfunction with the surgery, the patient underwent a ss-Wada procedure. Angiography revealed bilateral ACAs were supplied by the left A1 segment. Super-selective microcatheter injection of amobarbital into the left ACA was performed to avoid cross-filling the contralateral ACA. The ss-Wada test confirmed no right leg motor impairment. Afterward, a craniotomy with direct cortical stimulation confirmed that the left-sided ictal/peri-ictal zone had no clear leg motor function. Patient underwent disconnection of that region and remained seizure free at 10-month post-op follow up without any motor or sensory deficits in the right limbs.

Conclusion: This case demonstrates the proof of concept for ss-Wada in assessing lower extremity motor function. The ss-Wada procedure accurately predicted no motor deficits in right leg, consistent with preserved motor function post-surgery.

ssWada

cortical mapping

epilepsy surgery

motor function

amobarbital

The Wada test, or the intra-carotid sodium amobarbital procedure, is a widely recognized method for evaluating patients with intractable focal epilepsy before neurosurgery, specifically to preserve critical areas for memory and language function [1]. Sodium amobarbital is injected into one of the internal carotid arteries (ICAs) to temporarily suppress neurological function in the targeted area [2]. While the Wada test is well-known to assess lateralization of memory and language functions, the application of super-selective Wada (ss-Wada) to evaluate motor function pre-surgery is rare.

In this case report, we implemented a super-selective Wada (ss-Wada) procedure to assess the motor function of the left anterior cerebral artery territory before surgery.

History and presentation

A 21-year-old ambulatory male presented with a history of perinatal left middle cerebral artery (MCA) stroke resulting in right hemiparetic cerebral palsy with no significant motor function in the right upper extremity and focal drug-resistant epilepsy. His seizure onset was at 9 months of age, with a seizure-free period from 3 to 12 years of age. However, at 12 years old, the frequency of seizures increased to three per week. Seizure semiology consisted of tingling sensations in his arm, dystonic movements, and clonic jerking of the right arm and the right leg, lasting about one minute, with preserved awareness and speech function. Despite prior attempts with six different anti-seizure medications along with vagus nerve stimulation device, the patient's seizures remained poorly controlled, necessitating consideration of surgical options.

Phase-I and II evaluation

Neuropsychology evaluation indicated borderline intelligence and low average language skills. MRI revealed a chronic left MCA infarct. Computed tomography angiography showed dual supply of both anterior cerebral arteries (ACAs) from the left internal carotid artery (ICA). Interictal electroencephalography (EEG) showed frequent left frontal and anterior temporal sharp and slow waves. An ictal EEG showed a typical focal seizure with the onset over the left central-parietal region. Positron emission tomography scan showed decreased metabolism in the left temporal and medial left frontal lobes. Single positron emission tomography study showed a relative increased perfusion in the left frontal lobe along the anterior medial infarct. Magnetoencephalography showed two foci of irritability in the left frontal lobe at the superior and anterior-inferior borders of the encephalomalacia. Furthermore, f-MRI showed a shift of extremity motor and language functions to the right cerebral hemisphere. For further delineation of ictal focus, the patient underwent stereo-encephalography (s-EEG) with total of 12 electrodes, focusing on the left MCA encephalomalacia, covering left frontal-central-parietal and temporal regions (Fig. 1). s-EEG showed seizure onset around the left post-central gyrus (LFH electrode) with immediate spread to areas adjacent to pre- and post-central regions (LFG, LFF, LFE and LPA electrodes). Bedside extra-op cortical stimulation showed right arm/hand movements with LFH/LFG electrode stimulation. The patient’s case was discussed at an interdisciplinary epilepsy surgery conference. To ensure precise evaluation and avoid potential right leg motor dysfunction, the clinical team decided on a ss-Wada test before proceeding with the surgery.

ss-WADA procedure

A 6 French femoral sheath was inserted into the left femoral artery. A 5 French diagnostic catheter was used to perform cerebral angiography with Omnipaque 300 mg/ml contrast medium. The angiogram revealed an atretic right A1 segment, with the left A1 segment supplying both ACA’s (Fig. 2, X-ray images). There was a hypoplastic left MCA, consistent with the patient’s previous history of left MCA distribution stroke. A 6 French guide catheter was then placed in the distal cervical left ICA. Under roadmap guidance, an SL-10 microcatheter (Boston Scientific) was advanced over Synchro 2 microwire (Stryker Neurovascular) to catheterize the proximal A2 segment of the left ACA. Super-selective angiogram through the microcatheter confirmed opacification of the left ACA only. The ssWada test commenced, and we assessed right leg motor function with continuous EEG monitoring. Administration of 25 mg of amytal into the left ACA did not result in any right leg motor weakness despite EEG slowing over the left frontocentral region. A second 25 mg dose of amytal 30 seconds later again failed to result in right leg weakness. We then waited 10 minutes and repeated the ssWADA with injection of 100 mg amytal into the left ACA. This again failed to result in right leg motor weakness, despite EEG slowing over the left frontocentral region. The ssWada test concluded once the EEG returned to normal and the left frontocentral slowing resolved, corroborating the earlier f-MRI findings.

Surgery

Following the ss-Wada, a craniotomy with EMG/motor evoked potentials was performed. Activation of the motor evoked potentials was observed in the right and left foot muscles upon direct intra-op cortical stimulation of the interhemispheric fissure along the mesial precentral gyri on the right hemisphere. However, direct cortical stimulation of post-central gyri and the presumed left leg/foot motor regions, including left precentral gyri as well as interhemispheric left paracentral region did not activate any motor evoked potentials on the right leg/foot. Consequently, the decision was made to disconnect the ictal onset zone (see Fig. 1) as no motor leg function was elicited in this region.

Outcome

Patient remained seizure free at 10-month post-op follow up without any additional motor or sensory deficits in the right limbs compared to baseline.

The Wada test is a useful tool for assessing language and memory function before surgery. Furthermore, it provides valuable evidence of seizure lateralization and can predict seizure relief outcomes after surgery, with ongoing investigations continuing to explore its potential applications [5]. However, the documented use of ss-Wada for evaluating motor function before surgery remains limited. Urbach et al. conducted 10 MCA Wada procedures on nine patients to assess risk for motor deficit before surgery, demonstrating the MCA Wada test's ability for evaluating residual motor functions, including in patients with developmental or early acquired hemispheric lesions [3]. Fujimoto et al. utilized the Wada test through injection of ICA to assess motor function in six patients with hemispherical refractory seizures intended for surgical intervention, successfully predicting post-surgical fine motor deficits [4]. In our case, neuroimaging studies revealed a dual supply of ACAs from the left ICA; thus, we decided to inject sodium amobarbital directly into the left ACA through a transfemoral catheter to avoid crossing of injection to contralateral side, allowing us to target our patient's left ACA territory, and evaluate right leg motor strength. The lack of motor weakness in the right leg after the amobarbital injection into left ACA led to decision to proceed with the resection of ictal zone confidently. This ss-Wada successfully predicted gross motor outcomes after the surgery.

To our knowledge, this is a novel case and provides a proof of concept for ss-Wada in assessing motor leg function through injection of ACA. While using ACA ss-Wada for risk assessment of motor deficits before neurosurgery remains relatively uncommon, our patient's case demonstrated its effectiveness. The ss-Wada procedure accurately predicted no motor deficits in the patient’s right leg, consistent with preserved motor function post-surgery. Furthermore, the patient has remained seizure-free at 10-month post-op follow up with no motor or sensory deficits. Further research is warranted to explore the full potential of the Wada test in guiding surgical decisions and improving outcomes.

FUNDING

No funding was received for this article.

CONFLICTS OF INTEREST

The authors report no conflicts of interest concerning the patients or methods used in this study or findings specified in this paper.

CONTRIBUTIONS

AK: writing, reviewing, and editing.

CS: writing, reviewing, and editing.

IM, JS, SK, RS, and SD: reviewing and editing.

CK: concept, design, writing, reviewing, and editing.

ETHICAL APPROVAL

This case was approved by the Institutional Review Board.

INFORMED CONSENT

Formal consent is not required for this type of case report.

Baxendale S. The Wada test. Current Opinion in Neurology 22 2009.
Halder S, Juel BE, Nilsen AS, Raghavan LV, Storm JF. Changes in measures of consciousness during anesthesia of one hemisphere (Wada test). Neuroimage 2021; 226.
Urbach H, Von Oertzen J, Klemm E et al. Selective middle cerebral artery Wada tests as a part of pre-surgical evaluation in patients with drug-resistant epilepsies. Epilepsia 2002; 43.
Fujimoto A, Okanishi T, Nishimura M, Kanai S, Sato K, Enoki H. The Wada test might predict postoperative fine finger motor deficit after hemispherotomy. Journal of Clinical Neuroscience 2017; 45.
Simkins-Bullock J. Beyond speech lateralization: A review of the variability, reliability, and validity of the intracarotid amobarbital procedure and its nonlanguage uses in epilepsy surgery candidates. Neuropsychology Review 10 2000.
Ramey WL, Martirosyan NL, Lieu CM, Hasham HA, Lemole GM, Weinand ME. Current management and surgical outcomes of medically intractable epilepsy. Clinical Neurology and Neurosurgery 115 2013.

No competing interests reported.

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Journal Publication

published 29 Jan, 2024

Read the published version in Child's Nervous System →

Editorial decision: Revision requested
15 Jan, 2024
Reviews received at journal
20 Nov, 2023
Reviewers agreed at journal
20 Nov, 2023
Reviewers invited by journal
20 Nov, 2023
Submission checks completed at journal
09 Nov, 2023
Editor assigned by journal
09 Nov, 2023
First submitted to journal
08 Nov, 2023

You are reading this latest preprint version

Super-Selective Wada Test for Pre-Surgical Leg Motor Function Assessment: A case report

Status:

Journal Publication

Version 1

Abstract

Figures

INTRODUCTION

CASE REPORT

History and presentation

Phase-I and II evaluation

ss-WADA procedure

Surgery

Outcome

DISCUSSION

CONCLUSION

Declarations

References

Additional Declarations

Status:

Journal Publication

Version 1