This test is named after John A. Wada, the neurologist who first described it. The Wada test is a physiologic and neuropsychological test whereby one part of the brain is chemically suppressed by superselectively injecting a short-acting anesthetic substance (such as sodium amobarbital, sodium methohexital, or propofol) into a specific feeding artery. Complete neuropsychological evaluation is performed prior to and after injecting the anesthetic.

The test is usually used prior to performing epilepsy surgery for language and memory lateralization testing and to guide the surgeon regarding the potential loss of language or memory after resection. In this scenario, the drug is injected selectively into the internal carotid artery. Superselective cerebral or spinal artery branch Wada testing, with or without electroencephalogram (EEG) and evoked potential testing, can also be performed during arteriovenous malformation embolization.

Functional magnetic resonance imaging (MRI) is increasingly considered a less invasive and cost-effective option for language lateralization, especially in left-lateralization, proceeding with Wada testing for atypical language dominance.

Magnetic resonance imaging (MRI) is the most sensitive imaging modality used for both diagnosis and surveillance in multiple sclerosis. Lesions seen on MRI represent underlying demyelination. Lesions within the brain typically involve the white matter tracts but can also involve portions of the gray matter.

Characteristic lesion locations:

• • Cerebral hemispheres: periventricular, subcortical, and perpendicular to lateral ventricle
  
• • Lesion perpendicular in a triangular shape is also referred to as Dawson fingers
  
• • Spinal cord: The cervical cord is the most common location, but lesions can be found in other portions as well.

Lesion shape:

• • Lesions are typically ovoid in shape.
  
• • Tumefactive lesions are lesions that are greater than 2 cm in diameter and can cause mass effect.

Patterns of enhancement seen on MRI:

• • FLAIR—lesions are typically hyperintense
  
• • T1 weighted images—lesions appear hypointense
  
• • T2 weighted images—lesions appear hyperintense
  
• • T1 weighted + gadolinium contrast—lesions that enhance represent areas of active demyelination
  
  
  
  • • These lesions can be ring enhancing (closed or open ring)