Figure 1. A Diagnostic Algorithm for the Evaluation of a Patient with Intellectual Disability of Unknown Cause.

Evaluation for copy-number changes with the use of array comparative genomic hybridization (CGH) should be performed early in the diagnostic workup. Indications for magnetic resonance imaging (MRI) include macrocephaly or microcephaly, asymmetric neurologic findings, intractable epilepsy or focal seizures, abnormal movements (e.g., dystonia, chorea, or other extrapyramidal findings), hypotonia or long tract signs, facial stigmata associated with developmental brain abnormalities, and a history of a progressive neurologic disorder.