Clinical and demographic factors differentiate patients with functional (psychogenic) stereotypies (FS) of functional movement disorders (FMDs) from patients with tardive dyskinesia (TD).

 By Marielle Fares, Pharm.D

January 26, 2018- The phenomenology of FS typical of FMDs is similar to that seen in TD, but the clinical and demographic features of patients are different, an observational study showed.

Jose F. Baizabal-Carvallo with the Parkinson’s disease Center and Movement Disorders Clinic in the Department of Neurology at the Baylor College of Medicine in Houston, Texas and with the Department of Internal medicine at the University of Guanajuato in Guanajuato, Mexico and his colleague reported their findings in the June 26, 2017 issue of the Journal of Neurology.

FMDs present a wide symptomatology such as tremor, dystonia, parkinsonism, and stereotypic movements defined as repetitive coordinated movement occurring involuntarily. Tardive dyskinesia (TD) results after exposure to dopaminergic receptor blocking drugs (DRBDs) such as antipsychotic drugs and manifests as stereotypies. Classic TD is characterized by orolingual-facial, limb and trunk stereotypies, and respiratory dyskinesia. This study compares FS features reported in patients with FMDs with those reported in TD patients.

Researchers selected 19 patients with FS symptoms from a total of 184 patients with FMDs and compared their clinical and demographic features with those of 65 patients with TD .Both patient groups showed symptoms of orolingual dyskinesia, limb and trunk stereotypies, and respiratory dyskinesia.

Patients with FS exhibited symptoms consistent with stereotypies seen in FMDs, such as sudden onset of abnormal movement, marked distractibility and unexplained marked improvement or worsening over periods of time. Those in the TD group had a previous psychiatry diagnosis and were treated with DBRBs. TD was also associated with adult-onset disease.

Investigators reported that “features such as younger age at onset, lack of self-biting, uncommon chewing-like movements, lingual without mouth movements, and tremor with features observed in functional cases suggested a functional etiology rather than a drug-induced movement disorder.” In addition, abnormal speech was shown to be highly specific (0.90) to functional orolingual dyskinesia yet rarely affected in patients with TD.

The authors concluded that “similar to TD, FS patients may present with orolingual, limb, and trunk stereotypies as well as respiratory dyskinesia, but they can be differentiated from TD by the presence of clinical features typical of FMD.”

This study was entirely conducted by the authors who declared no conflict of interests.

Journal of Neurology. Published in June 26, 2017