primary acalculia and anarithmetia. However, damage to various but not necessarily identified areas of the brain can cause computational difficulties, as various cognitive functions are necessary to execute mathematical calculations. Diagnosis Because acalculia is a symptom of the more commonly known Gerstmann's syndrome, it may be difficult to solely diagnose acalculia. Instead, it may be labeled as one of its symptoms, and lead to the eventual diagnosis of Gerstmann's syndrome. "Provided that general mental impairment and significant aphasic disorder can be excluded as primary factors, the presentation of deficits such as agraphia, acalculia, and right-left confusion should alert the clinician to the possibility of focal posterior parietal lobe disease." (Disorders) Structural and functional neuroimaging may be of further value in determining the existence of underlying neurologic abnormalities. Screening Common screening procedures for acalculia include asking the patient to answer questions about order, conducting memory tests to rule out the possibility of a mental disorder, confrontation naming (naming parts of objects), reading tests, writing tests, calculation tests, finger naming, clock drawing, and left/right orientation testing. The writing tests, spelling tests, finger naming, and left/right orientation are all tests to confirm the presence of Gerstmann's syndrome. Acalculia is one out of four defining components of Gerstmann's syndrome; the other three components are agraphia, finger agnosia, and right/left confusion. Typically, acalculia is present because of Gerstmann's syndrome or it is linked with other disorders. It is imperative to note that there is "difficulty separating calculation disorders from disruptions in other domains". This is why testing functions besides calculation abilities is crucial for the screening of acalculia- so that other disorders can be ruled out. More extensive testing includes "brain mapping techniques such as position emission tomography (PET), functional magnetic resonance imaging (fMRI), and event related potentials (ERP), which have helped to illuminate some of the functional anatomical relationships for number processing". A basic examination of numerical abilities in brain-damaged patients should include both verbal and non-verbal aspects of number processing. The following tests are suggested: Forward and backward digit span. Forward and backward counting. Symbolic transcoding (reading aloud and taking dictation of simple and multidigit numerals). Single-digit arithmetic. To reduce the contribution of input and output deficits to the patient's performance, problems may be simultaneously presented in written form and read aloud by the examiner. Familiar multiplication problems and simple subtractions should be tested in priority, as they reflect rote verbal and quantity-based