View source for Wada test

{{Short description|Neurological test of the brain hemispheres}}
{{Infobox diagnostic
| name            = Wada test
| image           =
| alt             =
| caption         =
| pronounce       = 
| purpose         =establishes cerebral language and memory
| test of         =
| based on        =
| synonyms        =  Intracarotid sodium amobarbital procedure
| reference_range =
| calculator      =
| DiseasesDB      = <!--{{DiseasesDB2|numeric_id}}-->
| ICD10           = <!--{{ICD10|Group|Major|minor|LinkGroup|LinkMajor}} or {{ICD10PCS|code|char1/char2/char3/char4}}-->
| ICD9            =
| ICDO            =
| MedlinePlus     = <!--article_number-->
| eMedicine       = <!--article_number-->
| MeshID          =
| OPS301          = <!--{{OPS301|code}}-->
| LOINC           = <!--{{LOINC|code}}-->
}}
The '''Wada test''', also known as the '''[[carotid artery|intracarotid]] [[sodium]] [[amobarbital]] procedure''' (ISAP) or '''Wada-Milner Test''', establishes [[cerebral cortex|cerebral]] language and memory representation of each [[cerebral hemisphere|hemisphere]].

==Method==
Medical professionals conduct the test with the patient awake. A [[barbiturate]], usually sodium amobarbital, is introduced into one of the [[internal carotid arteries]] via a [[cannula]] or intra-arterial [[catheter]] from the [[femoral artery]]. The drug is injected into one hemisphere at a time through the right or left internal carotid artery. If the right carotid is injected, the right side of the brain is inhibited and cannot communicate with the left side. The effect shuts down any language and/or memory function in that [[Cerebral hemispheres|hemisphere]] in order to evaluate the other hemisphere. An [[EEG]] recording at the same time confirms that the injected side of the brain is inactive as a neurologist performs a neurological examination. The neurologist engages the patient in a series of language and memory related tests. They evaluate the memory by showing a series of items or pictures to the patient and—within a few minutes, as soon as the effect of the medication dissipates—testing the patient's ability to recall.<ref>{{cite web|url=http://my.clevelandclinic.org/services/neurological_institute/epilepsy/diagnostics-testing/wada-test|title=Wada Test - Cleveland Clinic|website=Cleveland Clinic}}</ref> The test is typically administered by a neuropsychologist as a result of expertise in psychometric testing. Correlation with formal neuropsychological testing has some predictive power regarding seizure outcome following anterior temporal lobectomy.<ref>{{cite journal|pmid=9240237 | volume=38 | title=Neuropsychological evaluation in epilepsy surgery. | year=1997 | journal=Epilepsia | pages=S18–23 | doi=10.1111/j.1528-1157.1997.tb04535.x| last1=Loring | first1=D. W. | issue=Suppl 4 | doi-access=free }}</ref>

There is currently great variability in the processes used to administer the test, and so it is difficult to compare results from one patient to the other.<ref>{{cite journal |author=Hermann B |title=Wada test failure and cognitive outcome |journal=Epilepsy Currents |volume=5 |issue=2 |pages=61–2 |year=2005 |pmid=16059438 |doi=10.1111/j.1535-7597.2005.05206.x |pmc=1176310}}</ref>

==Uses==
The test is usually performed prior to [[Ablative brain surgery|ablative surgery]] for [[epilepsy]] and sometimes prior to tumor resection. The aim is to determine which side of the brain is responsible for certain vital cognitive functions, namely [[Speech communication|speech]] and [[memory]]. The risk of post-operative cognitive change can be estimated, and depending on the surgical approach employed at the epilepsy surgery center, the need for awake [[Craniotomy|craniotomies]] can be determined as well.{{citation needed|date=August 2020}}

The Wada test has several side-effects. Drastic [[Personality alteration|personality]] changes are rarely noted, but [[disinhibition]] is common. Also, contralateral [[hemiplegia]], [[hemineglect]] and shivering are often seen.{{cn|date=January 2023}} After injection on the side of the speech-dominant hemisphere, typically the left, the patient experiences transient [[aphasia]], ie. impaired speech and language or the inability to express or understand language.<ref>{{cite book |last=Luria |first=Aleksandr Romanovich |author-link=Alexander Luria |date=1980 |title=Higher Cortical Functions in Man |edition=2nd |translator-last=Haigh |translator-first=Basil |url= |location=New York, NY |publisher=Basic Books Inc. |page=98 |isbn=0-465-02960-4}}</ref> Though the patient may not be able to talk, sometimes their ability to sing is preserved.{{citation needed|date=August 2020}} This is because music and singing uses a different part of the brain than speech and language.{{citation needed|date=March 2023}} Recovery from the anesthesia is rapid, and EEG recordings and distal grip strength may be used to determine when the medication has worn off. Generally, recovery of speech is dysphasic (contains errors in speech or comprehension) after a language dominant hemisphere injection.{{citation needed|date=August 2020}}

Though generally considered a safe procedure, there are at least minimal risks associated with the [[Angiography|angiography procedure]] that guides the catheter to the internal carotid artery, perhaps related to the physician's experience.{{citation needed|date=August 2020}}  Researchers are looking into non-invasive ways to determine language and memory laterality—such as [[fMRI]], [[Transcranial magnetic stimulation|TMS]], [[magnetoencephalography]], and [[near-infrared spectroscopy]].{{citation needed|date=August 2020}}

==History==
The Wada test is named after Japanese neurologist and epileptologist [[Juhn Atsushi Wada]], of the [[University of British Columbia]].<ref>Loring, D.W., Meador, K.J., Lee, G.P., King, D.W. (1992).  Amobarbital Effects and Lateralized Brain Function: The Wada Test.  New York: Springer-Verlag.</ref><ref>{{cite journal | author = Wada J | year = 1949 | title = A new method for the determination of the side of cerebral speech dominance. A preliminary report of the intra-carotid injection of sodium amytal in man | journal = Igaku to Seibutsugaki, Tokyo | volume = 14 | pages = 221–222 }}</ref> He developed the test while he was a medical resident in Japan just after{{fact|date=January 2022}} World War II, when he was receiving training in [[neurosurgery]]. Wada developed the technique of transient hemispheric anesthetization through carotid amytal injection to decrease the cognitive side effects associated with bilateral electroconvulsive therapy.<ref>{{cite journal | author = Wada J | year = 1997 | title = Youthful Season Revisited | journal = Brain and Cognition | volume = 33 | issue = 1| pages = 7–10 | doi=10.1006/brcg.1997.0879| pmid = 9056271 | s2cid = 5530070 }}</ref>  He published the initial description of motor, sensory, language, and effects on the "conscious state" in 1949, in [[Japanese language|Japanese]]. During his fellowship at the [[Montreal Neurological Institute]], he introduced the test to Dr. [[Brenda Milner]] and associates, who modified the test to assess language laterality and memory function prior to a unilateral lobectomy. As this is now the primary use of the procedure, some neuropsychologists argue for it to be renamed the Wada-Milner Test in recognition of her significant contributions.<ref>{{cite web |last1=Andrew-Gee |first1=Eric |title=Doctor Juhn Wada revolutionized epilepsy surgery (Obituary) |url=https://www.theglobeandmail.com/canada/article-doctor-juhn-wada-revolutionized-epilepsy-surgery/ |website=The Globe and Mail |access-date=29 December 2023 |date=4 May 2023}}</ref><ref>{{cite web |last1=Loring |first1=David |last2=Meador |first2=Kimford |title=History of the Wada Test |url=https://med.emory.edu/departments/neurology/_documents/loring_meador_wada_history_chapter.pdf |publisher=Oxford Handbook of History of Clinical Psychology}}</ref>

== In Popular Culture ==
* [[Grey's Anatomy (season 5)|Grey's Anatomy season 5]], [https://abc.go.com/shows/greys-anatomy/episode-guide/season-05/523-heres-to-future-days episode 23, Here's to Future Days]: Mention of the Wada test at 00:06:13<ref>{{Citation|title=Here's to Future Days (2009)|url=https://www.imdb.com/title/tt1435078/mediaviewer/rm2344781824|language=en|access-date=2019-02-03}}</ref> and showing Hollywood's portrayal of the test<ref>{{Citation|title=Here's to Future Days (2009)|url=https://www.imdb.com/title/tt1435078/mediaviewer/rm2395113472|language=en|access-date=2019-02-03}}</ref> at 00:12:31.

==See also==
* [[Lateralization of brain function]]

==References==
{{reflist}}

{{Eponymous medical signs for nervous system}}
{{Central nervous system tests and procedures}}

[[Category:Diagnostic neurology]]
[[Category:Neuropsychology]]