An approach to the early diagnosis of pediatric neurotransmitter diseases (PNTD), and especially dystonia, is outlined in a report from the University Children’s Hospital, Dusseldorf, Germany; and Institute of Child Health, University College, London, UK. Symptoms suggestive of biogenic monoamine PNTD include, dystonia, myoclonic epilepsy, mental retardation, oculogyric crises, neonatal hypoglycemia, and aggressive behavior. Childhood-onset dystonia or parkinsonism-dystonia is the hallmark of dopamine deficiency and PNTD. Screening tests for dystonia caused by neurometabolic disorders in children <2 years include CBC, plasma amino acids, homocysteine, lactate and pyruvate, uric acid, creatinine; urine organic acids and sulfite; blood biotinidase, acyl-carnitine, and diopterin; white cell hexosaminidase; and serum transferrin isoelectric focusing. If these tests are nondiagnostic, a lumbar puncture and the following CSF investigations are advised: cells, protein, glucose, lactate, amino acids, pterins, and 5-methyltetrahydofolate. Potentially treatable inborn errors of metabolism causing dystonia in young children include biotinidase deficiency, methylmalonic aciduria, glutaric aciduria type 1, succinylsemialdehyde dehydrogenase deficiency, and purine nucleoside phosphorylase deficiency. Other dystonias in young children, usually having a poor prognosis and recessively inherited, include Pelizaeus-Merzbacher disease, Lesch-Nyhan syndrome, sulfite oxidase and molybdenum cofactor deficiency, infantile neuronal ceroid lipofuschinosis, infantile Gm2 gangliosidosis, Niemann-Pick type A, and mitochondrial encephalomyelopathies. Dystonias presenting in children >2 years of age are either acquired, especially post-streptococcal infectious encephalitides, or primary genetic with family history (idiopathic or paroxysmal, L-dopa-responsive with diurnal variation (Segawa’s disease), and myoclonic dystonia). Older children with primary dystonia should receive a trial of L-dopa for at least 3 months. 
COMMENT. The term dystonia is used for a symptom or abnormal movement disorder. Dystonia is characterized by intermittent or continuous muscle spasms that are generalized (dystonia musculorum deformans) or segmental (localized to the neck (spasmodic torticollis), upper limb, or lower limb), and primary genetic or acquired (post-perinatal asphyxia, trauma, toxins, or vascular). In primary hereditary dystonias, the mode of transmission is variable. One form with high incidence in Ashkenhazi Jews is probably autosomal dominant. The first symptom in hereditary dystonia is an involuntary posturing of one portion of the body, most commonly a plantar, flexion-inversion movement of the foot, commonly misdiagnosed as a hysterical gait. In treatment, trihexyphenidyl (Artane) is used in Ashkenazi Jewish patients, and Levodopa, alone or with a decarboxylase inhibitor (Sinemet), in patients with late onset dystonia. Cryothalamectomy is a surgical approach rarely entertained in children with medically-intractable hemidystonia.
CSF analysis and magnetic resonance spectroscopy in the diagnosis of neurotransmitter diseases are reviewed by Hyland K , and Novotny EJ Jr et al . The CSF compounds measured are homovanillic acid (end product for dopamine metabolism), 5-hydroxyindoleacetic acid (for serotonin), and 3-methoxy-4-hydroxyphenylglycol (for norepinephrine). MRS methods are under investigation for the measurement of neurotransmitters in the brain. Abnormalities of motor cortex excitability preceding voluntary movement in patients with dystonia have been studied by Gilio F et al . Dystonic movements are commonly triggered or made worse by voluntary action.