Diagnostic methods and recommendations for the cerebral creatine deficiency syndromes. 
Primary care pediatricians and a variety of specialist physicians strive to define an accurate diagnosis for children presenting with impairment of expressive speech and delay in achieving developmental milestones.  Within the past two decades, a group of disorders featuring this presentation have been identified as cerebral creatine deficiency syndromes (CCDS).  Patients with these disorders were initially discerned using proton magnetic resonance spectroscopy of the brain within a magnetic resonance imaging (MRI) examination.  The objective of this review is to provide the clinician with an overview of the current information available on identifying and treating these conditions.  We explain the salient features of creatine metabolism, synthesis, and transport required for normal development.  We propose diagnostic approaches for confirming a CCDS diagnosis.  Finally, we describe treatment approaches for managing patients with these conditions.