Psychogenic movement disorders are characterized by the presence of abnormal movements or absence of normal movement not attributable to an organic neurologic disorder and considered to be psychologically mediated. A large movement disorder clinic estimated the prevalence of psychogenic movement disorders to be 5.3%, a rate higher than both the prevalence of Huntington disease and restless leg syndrome in the same clinic.

While recent imaging research has pointed to an abnormal network of neuronal activation, the mainstay of treatment for these patients remains psychotherapy.

Psychogenic movement disorders have been called a “crisis for neurology” as patients are often unaccepting of the diagnosis, few treatments exist, and few patients have been shown to improve in the published case series.

Worsening this already grim picture is lack of discourse between neurology and psychiatry regarding these patients; while this is an ideal disease model for partnership between psychiatry and neurology, there are significant differences between the two fields' perspectives towards this disorder that make collaboration difficult. Differences in terminology alone begin to illustrate this divide: the term “psychogenic movement disorder” has gained popularity among many neurologists and is presented as a separate chapter in movement disorder textbooks, but this phrase has little diagnostic specificity for psychiatrists and is not found in the current Diagnostic and Statistical Manual of Psychiatry (DSM-IV-TR) or textbooks of psychiatry.

The differences between neurology and psychiatry go beyond terminology and extend into nosology, as not all patients with psychogenic movement disorders meet criteria for its closest approximation in the DSM-IV-TR, conversion disorder with motor symptom or deficit.

Even when collaborative efforts are made between interested neurologists and psychiatrists, these patients present a unique dilemma in treatment. Many patients lack clear psychological distress.

In psychogenic movement disorders this is particularly problematic. The neurologist is sometimes unable to offer a definitive test to the patient to “prove” the neurological diagnosis (although neurophysiologic testing can be helpful in some cases), and suggests to the patient the appropriate treatment is to refer the patient to psychiatry, but the psychiatrist to whom the patient is referred is faced with a patient who may have ongoing abnormal movements, who denies any psychological symptoms and refuses to believe that the movements are “in my mind.” Patients who are resistant to the possibility that there may be a psychologic etiology of their illness may be confused as to why they are now having to see a psychiatrist and resist the formation of a therapeutic alliance. If the psychiatrist is also unsure of the diagnosis, this compounds the problem. The patient's firmly held belief that they have an “organic” neurologic illness may lead them to drop out or be discharged from psychiatric care, much to the frustration of both neurologists and psychiatrists.

With greater awareness for psychogenic movement disorders in the literature as well as in clinical practice, more neurologists will feel supported in making the diagnosis and referring these patients to psychiatry. With a greater understanding of the psychogenic movement disorder terminology, comorbidities in psychogenic movement disorder patients, and treatment options, psychiatrists may be better able to care for these patients ¹⁾.

A patient presented at the Department of Neurosurgery, University of California Los Angeles, USA after 5 years of chronic DBS of the subthalamic nucleus (STN) for presumed Parkinson's disease. A dopamine transporter (DAT) scan (DaTscan) showed normal DAT distribution in the striatum. A positron emission tomography (PET) scan showed no abnormal metabolic patterns. Further psychiatric and neurological evaluations revealed that the patient was suffering from a psychogenic movement disorder. The patient displayed no sign or symptom from the stimulation, and DBS did not lead to any benefits or side effects for this patient.

Langevin et al., argue that the absence of side effects, the normal DaTscan, and PET scan after 5 years of chronic stimulation illustrate the safety of DBS on neural tissue ²⁾