Neuropsychological Function and Brain Arteriovenous Malformations: Redefining Eloquence as a Risk for Treatments

Ronald M. Lazar, Ph.D., Departments of Neurology and Neurological Surgery, Columbia University College of Physicians and Surgeons, New York, New York

Neurosurg Focus. 2001;11(5) 

In This Article

Superselective WADA Testing for Eloquent Function

Prior to conventional surgery or radiosurgery, many patients are treated by angiographically guided injection of embolic material into arteries supplying the AVM that will reduce flow, ultimately producing thrombosis.[31] Before superselective injection of glue, a frequently used thrombogenic agent at many centers, it is common practice to first determine whether the tip of the catheter has been placed inadvertently proximal to the nidus of the AVM so that permanent closure might affect eloquent function, such as language, memory, vision, and motor control.[6,15,24,25] This preembolization assessment is usually composed of injection of an anesthetic agent along with a contrast agent in a procedure that is based on the technique of Wada and Rasmussen of injecting amobarbital sodium into the internal carotid arteries of patients with epilepsy to determine cerebral dominance for language and memory prior to surgery.[29] During such testing for eloquent brain regions in patients with AVM prior to embolization, the injection of anesthetic agents is performed in arterial pedicles distal to the circle of Willis.

One of the earliest reports was a case study in which a patient with a left posterior temporal AVM underwent speech-evoked magnetoencephalography, superselective Wada testing, and direct electrical stimulation of the cortex during surgery.[19] Except for some reading errors, the clinical examination of language was normal. The topographic map of the magnetic component to stimulation with auditory syllables showed a source that was displaced superiorly to the probable location in the auditory cortex. Superselective Wada testing showed no deficit in receptive or expressive language with selective injection of the posterior temporal branch into superior temporal gyrus, and naming and repetition were not affected during stimulation at seven of eight usual language sites in the temporal and inferior parietal cortex in the vicinity of the AVM. During the postoperative course the patient displayed a mild expressive aphasia, which fully resolved 2 weeks later.

Lazar, et al.,[9] took advantage of the superselective Wada procedure in AVM patients to address possible redistribution of language. It was found that when right-handed adult patients with left temporoparietal AVM underwent selective anesthetic injections into the left prefrontal region, all of them developed major language symptoms including loss of comprehension, fluent speech with paraphasias, and perseveration that resembled Wernicke aphasia. To address the cerebral localization of language in patients with left frontal AVMs, three patients underwent the same language evaluation as those who harbored the posterior AVMs.[11] Anesthetic injection into the vessels supplying the inferior division of the left middle cerebral artery produced the expected Wernicke area, verifying left cerebral dominance for language in each case. Superselective study in the left frontal regions, however, resulted in mild right-sided paresis in all patients, but no language abnormality and there was no loss of fluency. Embolization of vessels feeding the AVM then took place without significant morbidity in a region where traditional assumptions of eloquence might have precluded treatment.

Preembolization superselective Wada testing has also shown unpredictable redistribution of other cognitive functions.[12] In this small case series, in one patient with a left parietal AVM and a right temporal AVM oral reading was controlled by the right hemisphere and reading comprehension was subserved by the left hemisphere. A patient with a left medial AVM displayed the presence of an anterograde amnesia and alexia but not aphasia with a left superior temporal artery injection.

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