Laboratory testing is a major component of the comprehensive evaluation of cognitive decline. The current American Academy of Neurology (2007) practice recommendations for evaluation of reversible causes of dementia include testing for vitamin B₁₂ deficiency and hypothyroidism. These laboratory tests are recommended in addition to structural imaging (noncontrast head CT or MRI studies) and evaluation of depression to rule out so-called pseudodementia, or dementia-like symptoms that stem from depression. Syphilis serology screening is necessary only in patients with dementia who are at risk for neurosyphilis. Neuropsychological testing is also recommended. It can be very useful for differentiating between dementia and pseudodementia, for distinguishing among the many types of dementia, and for determining whether a patient is responding to treatment.