A case of autism successfully treated with very-low-dose levodopa for early-onset antipsychotic-induced tardive movement disorder manifested by dropped head syndrome

Atypical antipsychotics, often used to manage aggressiveness and mood instability associated with autism spectrum disorder (ASD), can cause severe side effects, such as tardive dystonia (TD), an often irreversible tardive movement disorder subtype. Dropped head syndrome (DHS), a rare manifestation of extrapyramidal disorders, may also represent a rare form of neck TD. A 15-year-old man with severe autism and intellectual disability was prescribed risperidone (1 mg/day) to manage impulsive and aggressive behaviors. After 2 months of treatment, the patient started showing DHS symptoms, diminished activity, and lack of facial expressions. Based on the observed fluctuation of dystonic symptoms, very-low-dose levodopa therapy (VLDT; 0.5–1 mg/kg/day) was started due to the persistence of symptoms 2 months after discontinuing risperidone. Remarkably, the patient showed improved facial expression, activity levels, and neck control within 2 days. After 7 months of treatment, the patient maintained complete improvement in overall symptoms. This case presented an atypical manifestation of DHS, with early-onset TD even after short-term exposure to low-dose atypical antipsychotics, indicating susceptibility of the dopaminergic system. Thus, clinicians should be cautious in the administration of atypical antipsychotics for ASD and vigilant in monitoring TD development. Furthermore, the fluctuation in dystonic symptoms and rapid response to VLDT indicate similarities to dopa-responsive dystonia, highlighting a potential therapeutic avenue for refractory conditions in similar clinical scenarios.