Organic vs. psychogenic tics

Abstract

Organic vs. psychogenic tics Dear Editor, We would like to comment on Mejia and Jankovic's paper: "Secondary Tics and Tourettism". First, it is remarkable that secondary tics were twice as prevalent in males (65.1%) as in females (34.8%). The higher prevalence of Tourette's syndrome (TS) in males is well-known, and this study could point to a greater susceptibility of males to develop tics be the cause TS or not. Second, some points remained unclear, such as the criteria for diagnosing psychogenic tics. As the rate of 10.3% is quite high, the criteria used should have been specified. Others have documented psychogenic movement disorders (PMD) prevalence rates in about 3.3% of the cases, but tics were rarely found in their samples. 1 The cited reference 2 provides a diagnostic guideline for PMD such as dystonia, tremor, paroxistic dyskinesia, parkinsonism, gait disorders, hemifacial spasm, spasmodic dysphonia, and myoclonia, but has not included psychogenic tics. Fahn and Williams classified patients in four categories (documented, clinically established, probable and possible) based on the level of certainty of having psychogenic dystonia. This classification is often used for other movement disorders. They define documented PMD as involuntary movements which are persistently relieved by psychotherapy, suggestion, placebo, or the patient is witnessed as being free from the involuntary movements when supposedly unobserved; and clinically established PMD are movements which are inconsistent or incongruent with classic descriptions of the acknowledged movement disorder, associated with other psychogenic signs on neurological examination, multiple somatizations, or obvious psychiatric disturbance. The probable and possible categories have less clinical evidence being often excluded from most studies. 3 Thomas and Jankovic 2 describe indicators of presence of PMD including abrupt onset with disability soon or immediately after onset; response to placebo or suggestion, selective disability, dramatic resolution, increase with attention and cessation with distraction. Those criteria may not differentiate organic from psychogenic tics. Tic disorders usually have a waxing and waning course, may begin abruptly and with maximal severity. Tics may also be under some voluntary control, thus, temporary suppression of symptoms may often occur. Their intensity may also vary with attention (usually decreasing with distraction), a differential feature of psychogenic tremor that may not be valid for tics. 2 Organic movement disorders are more frequently misdiagnosed as psychogenic than the opposite, 4 and their coexistence is very common. 1 The current diagnostic criteria used for PMD are not definitive and should be considered rather as a useful guide for clinical investigation. Conversive disorder should be considered after the exclusion of neurological diagnoses.

A positive diagnosis of functional (psychogenic) tics

“…There are no studies assessing the prevalence of functional tics in the general population; studies published so far have analysed populations of patients either with tics or with FMDs. Thirdly, as Sampaio and Hounie [8] have previously argued, none of these studies used specific criteria for the diagnosis of functional tics. The 11 cases reported in this study were seen in a specialist quaternary movement disorders clinic over the past 3 years in which approximately 250 patients with FMDs are seen per year.…”

“…The diagnosis of functional tics is challenging because the commonly used criteria that differentiate FMDs from organic movement disorders (sudden onset, distractibility, suggestibility, temporary remissions and a fluctuating course) are common clinical features also of organic tics. This may be why specific diagnostic criteria for functional tics have never been identified , with the two most commonly used diagnostic schemes for FMDs, the Fahn−Williams criteria and their revised version proposed by Gupta and Lang , do not provide any specific advice for functional tics as they do for other FMDs such as tremor, dystonia and myoclonus. As another example of this problem, Thomas and Jankovic's suggested indicators of FMDs (abrupt onset with maximal disability soon or immediately after onset, response to placebo or suggestion, selective disability, dramatic resolution, increase with attention and cessation with distraction) do not seem likely to be able to help in differentiating organic from functional tics.…”