SLC2A1 and hyperinsulinemic hypoglycemia, familial, 4: Thus, analysis of cerebrospinal fluid in IEMs presenting with MD is essential and should be considered as a 1st Tier biochemical investigation, especially in cases of ataxia, dystonia, or HRS, taking into account the need for the precise diagnosis of certain IEMs (monoamine neurotransmitter disorders, GLUT-1 deficiency, etc.)with the consequent establishment of a specific treatment (8, 13).