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Chisholm T, Morehouse RL. Adult headbanging: sleep studies and treat- ment. Sleep 1996; 19 : 343 \200\2236 . This page intentionally left blank CHAPTER 31 Psychogenic Movement Disorders Isabel Pare s and Mark J. Edwards Introduction Psychogenic movement disorders (PMDs) are one presentation of \200\230functio nal \200\231 neurological symptoms, one of the most common diagnoses made in neurological p ractice. Patients can present with tremor, fi xed postures of the limbs, jerks, slowness, o r other com- binations of abnormal movements which are incongruous with movement disorders that occur in neurological disease. Th e terms used to describe these patients range from t he general (functional, hysteria) to those that propose a psychological etiology (psycho- g enic, psychosomatic, conversion disorder, somatization disorder) and those that indicate wh at patients do not have (non-organic, medically unexplained). Th is varied terminology high lights a lack of consensus and understanding of underlying mechanisms. Recently, there has been a shift away from pure psychodynamic explanations of PMD and other functional disorder s towards the implementa- tion of more neurobiological models. Th is chapter covers the cur - rent state of knowledge regarding diagnosis, pathophysiology, and management of these pat ients. Because of the widespread use of the term \200\230psychogenic \200\231 to describe these patients within medical literature we will use this term here, but in doing so we rej ect the assumption that PMD and other functional disorders are proved to be caused by under lying psychological trauma. 10 \200\22315% of patients (8). Children can also develop PMDs, with gait disorder and trem or the most commonly seen. In a series of children with PMDs the average age at onset was 1 2.3 years, with a clear female predominance (80%) (9). PMDs are only rarely reported in tho se aged over 65. Diagnosis and phenomenology As with other functional neurological disorders, there has been a shift in diagnostic practice away from considering the diagnosis of PMD as a diagnosis o f exclusion, towards the use of positive diagnostic criteria. In addition, there has been a rejection amongst movement disorder specialists of the requirement for a co-existent psych ological disorder or trauma to be present in order to make the diagnosis (10). Th erefore, while psychiatric diagnoses such as conversion disorder require the presence of a psycholog ical trig- gering event, most movement disorder neurologists state that they make the diagn osis on positive clinical signs (see below) and incongruity with movement disorders known t o be due to neuro- logical disease. One reason for this shift is that psychological dis- tu rbance is a common counterpart to organic neurological disease (and indeed is common in the general population) and therefore it is not reliable as a predictor of PMD. Secondly, epid emiological work in PMD (and in other functional neurological disorders) has shown a surpri sing similarity in numbers of life events and psychi- atric disorder in most patients compa red with control populations (11, 12). Epidemiology Th e true prevalence of PMD is not certain as there is a lack of consensus on diagnostic criteria and diff erent methodologies have been used to ascertain cases. Th e re ported estimates of prevalence of PMD range from 1 to 9% of general neurological clinic ref errals (1 \200\2233). Th e frequency in adult movement disor- ders clinics ranges from 2 to 4%, and is up to 20% in more spe- cialized clinics (4). General clues from history and examination Th ere are some general clues from history and e xamination which can help point to the presence of a PMD. It is important to note that none of these features are entirely specifi c for PMDs and diag- nosis should not be based on t hese features alone. PMDs are oft en of sudden onset with rapid progression to maximum seve rity and they may have a pattern of spontaneous remissions, paroxysmal exacerbations, and r elapses. Patients may experience a shift in phe- nomenology over time (tremor turning to ab normal posture, for example), and may have a history of previous unexplained medical sympto ms. Th e mean age at onset described in larger case series is between 37 and 50 years (5), and in about 70% of the cases patients present with tremor or dystonia. PMDs are more common in women, except for parkinsonism for which both sexes are equally predis- posed (6, 7). PMDs usually occur as a single neurological diagnosis, but can be associated with co-existe nt organic neurological disorders in Oxford Textbook of Movement Disorders 340 General clues on clinical examination include the co-existence of other psychogenic signs s uch as \200\230give-way \200\231 weakness, \200\230false \200\231 weak- ness (e.g. positi ve Hoover \200\231s sign), or non-physiological patterns of sensory loss on clinical examin ation. Table 31.1 Summary score of a battery of electrophysiological tests for the diagnosis of ps ychogenic tremor (16) Electrophysiological test Incorrect tapping performance at: Points \227\206 1 Hz 1 Psychogenic tremor Psychogenic tremor (PT) is the most common form of PMD (3, 5). Patients typically have a combination of rest, postural, and inten- tion tremor. Arm tremor is overw helmingly the most common manifestation of PT, usually sparing the fi ngers, but isolated t remor of other body parts (legs, head, palate) can also be seen. Th e onset of the tremor i s abrupt in a large number of patients, oft en follow- ing a physical injury (13). \227\206 3 Hz 1 \227\206 5 Hz 1 Entrainment, suppression, or pathological frequency shift at: \227\206 1 Hz 1 \227\206 3 Hz 1 \227\206 5 Hz 1 Pause or 50% reduction in amplitude of tremor with ballistic movements 1 A range of clinical tests, supplemented by tremor recordings using accelerometry and EMG, h as been suggested to be helpful in distinguishing PT from organic tremor. Th ese techniques gener- ally rely on distracting the patient \200\231s attention away from the tremor. Th i s usually makes organic tremor worse, but in PT tends to cause it to stop or signifi cantly change in frequency. Tonic activation before tremor onset 1 Coherence of bilateral tremors 1 Increase of TP (as surrogate of tremor amplitude) 1 Cut-o \200 score for psychogenic tremor: \211 3 points TP, total power of the spectra be tween 1 and 30 Hz A range of distraction tasks has been assessed, including cogni- tive distracters (serial s ubtraction), tapping with an unaff ected limb at a diff erent frequency to the tremor, and making a sudden ballis- tic movement with the other hand. With clinical assessment alone (w ithout supplementation with tremor recordings), tapping tasks are most sensitive and specif i c for distinguishing essential tremor from PT. Self-paced cognitive tasks are not very ef f ective. Using tremor recordings, tapping tasks have again been shown to be help- ful in d istinguishing PT from organic tremors (14). Here, patients with PT may \200\230entrain \200\231 to the tapping frequency, may show a shift in tremor frequency towards the tapping frequency, or may instead be inexplicably unable to perform the tapping task correctly wit h their normal hand. Th is illustrates an important point with distraction tasks which is t hat performance of the task must be adequate to draw attention away from the tremoring limb . Th is is probably why self-paced tasks (whether cognitive or motor) are not good at dis- criminating patients with PT from organic tremor. Ballistic move- ments of the non-tremorin g limb cause a small pause in the tremor in patients with PT (15). Additional electrophysio logical character- istics include a paradoxical worsening of the tremor with loading (which typically damps organic tremor), and co-contraction at the onset of tremor. be classifi ed as a PMD or a form of organic movement disorder. Almost two decades aft er B hatia and colleagues concluded that \200\230at present it is impossible to decide whether this distressing syndrome is a true functional disorder of the CNS, or is of psychogenic or igin \200\231 (17), the concept of fi xed dystonia is in transition towards a more integrat ed view of brain dysfunction beyond the dualistic vision of this disorder (18). Psychogenic dystonia aff ects predominantly the limbs, and rarely the neck \200\223shoulder region or jaw (19). Psychogenic blepharospasm has recently been reported (20). Patients ar e typically female and in their twenties and thirties. Psychogenic dystonia is typically fi xed, while organic dystonia tends to produce mobile ab normal postures. Fixed postures can be seen in certain organic disorders such as corticobas al degenera- tion or dystonia due to basal ganglia lesions, but additional clinical signs a nd abnormal neuroimaging tests help to make the correct diagnosis in these cases. Less comm only, patients with psychogenic dystonia can present with non-fi xed postures of the limbs, trunk, and neck. Psychogenic dystonia usually has a clear precipitating factor (typically a peripheral injur y) and an abrupt onset. Patients with fi xed dystonia commonly have pain as a major feature of the disor- der, overlapping with chronic regional pain syndrome type 1 (21). Th e role of psychological factors underlying dystonia complicating chronic regional pain syndrome re mains a source of considerable controversy. Recently these tests have been compared head to head in a group of patients with PT and a m ixed group of patients with organic tremors (PD, dystonic tremor, essential tremor, neuropa thic tremor) (16). No single test was found to be of suffi cient sensitivity and specifi ci ty to distinguish PT from organic tremor, most prob- ably refl ecting diff erent mechanisms in diff erent patients for gener- ating the tremor. For example, tremors generated by co-c ontraction were much more resistant to distraction. Th e authors calculated a cut-off score from a group of tests which could eff ectively distin- guish PT from organic tremor, but t his requires confi rmation in a prospective study (Table 31.1). An unusual distribution of dystonia given the age of onset can be a further clue that point s toward psychogenic dystonia. Primary dystonia has a very typical anatomical distribution which depends on age of onset: generalized (with classic limb onset) in individuals younger than 25 years, focal involving upper limb in individuals aged between 25 and 45 years, and focal involving the craniocervi- cal area in individuals aged more than 45 \200\22350 year s. Importantly, unusual distribution given the age of onset can also be a clue to secondary /neurodegenerative dystonia and these disorders should be ruled out. In psychogenic dystoni a there is typically an absence of task/position specifi city commonly seen in organic dyst onia and Psychogenic dystonia Th e concept of psychogenic dystonia classically refers to patients wi th fi xed abnormal postures of the limb that typically are triggered by apparently minor in jury. Th ere is considerable disagreement and debate about the nature of fi xed dystonia, a nd whether it should CHAPTER 31 Psychogenic Movement Disorders 341 patients oft en do not have sensory tricks. Some patients do develop limb contractures, dem onstrating maintenance of postures even when unobserved. spinal myoclonus or propriospinal myoclonus were best classifi ed as psychogenic (27). Psychogenic parkinsonism Psychogenic parkinsonism (PP) is relatively rare, accounting for 1 0% of cases of PMD (28). Th e diagnosis is not always easy, and a detailed clinical history and physical examination looking for positive clinical signs of psychogenicity is required . All features of parkinsonism can be present. In a series of nine patients, seven had a pr edominant tremor form and only two had an akinetic \200\223 rigid form (29). Th is indicate s that \200\230true \200\231 psychogenic parkin- sonism, rather than people who have psych ogenic rest tremor, is probably very rare. In such patients, rigidity may be present but fe els similar to voluntary oppositional resistance against passive movements rather than true cogwheel rigidity. Movements may appear to be very eff ortful and slow, but true bradykine sia with decrementing amplitude with rapid repetitive movements is not seen. When patients with PP are distracted, the velocity of the movements can normalize. Postural stability tes ting may lead to dramatic loss of balance and falls. Speech oft en becomes stuttering or \200\230baby-like \200\231, or is produced with an unusual accent. Handwriting is labored a nd irregular, but without typical micrographia (6). It is important to recognize that place bo response can be quite size- able in patients with organic Parkinson \200\231s disease wh ere it is asso- ciated with dopamine release (30), so caution needs to be taken in interpre ting response to placebo in patients with suspected PP. Dopamine transporter (DAT) SPECT sc anning is a useful test for investigating the integrity of the nigrostriatal system and dis - criminating PP from PD. Th is test will be abnormal in patients with organic PD and norma l in PP. It is important to emphasize that normal DAT scans are also seen in patients with organic postsynaptic causes for parkinsonism, such as drug-induced par- kinsonism. It has b een suggested that some patients with PP may have underlying organic PD (28, 29, 31). Again , positive clinical signs rather than imaging studies are essential to make the correct dia gnosis. It can be diffi cult to demonstrate distractibility of postures in fi xed dystonia. Th is m ay be because, in contrast with psycho- genic tremor, maintenance of postures does not requ ire signifi cant attentional resources, although critics of the suggestion that these patie nts have a psychogenic origin of dystonia could equally argue that distractibility is not s een as the condition is not psychogenic. However, in some patients rhythmic movements of an other limb performed while manipulating the fi xed limb can reveal some \200\230giv- ing w ay \200\231 of the fi xed posture. It has recently been reported that some patients with fi xed dysto- nia can respond immedia tely (within minutes) and dramatically to botulinum toxin injections (22). Th is is in cont rast with the known physiological eff ects of botulinum toxin which usually take 36 \200 \22372 hours to become apparent. Th erefore the response seen in these patients is likely t o be due to a placebo eff ect and helps to con- fi rm that such patients are diff erent fro m those with typical organic dystonia. Psychogenic myoclonus Up to 10% of patients with myoclonus have been reported to have a psy chogenic etiology (23, 24). Psychogenic myoclonus can be chal- lenging to diff erentiate fr om organic myoclonus as it is diffi cult to convincingly demonstrate distractibility in pat ients with intermit- tent movements. Variability in the distribution of jerks from day to d ay, distractibility (in those with very frequent jerks), unusual trig- gering of jerks, exc essive startle response, or response to suggest- ion can suggest a psychogenic origin. Elec trophysiological tests can be particularly helpful in supporting the clinical diagnosis. Si mple recording of the duration of the jerks can be of benefi t, particularly to demonstrate variability in duration and recruitment pattern of EMG bursts, suggestive of a non-organic cause. Consistent bursts of duration less than 75 ms are unlikely to be psychogenic, as EM G bursts of this duration cannot be generated voluntarily. However, the converse is not tru e, as some forms of organic myoclonus (e.g. brainstem myoclonus, spinal segmental myoclonus ) may have EMG burst lengths longer than 75ms. If jerks are stimulus sensitive and the late ncy between the stimulus and the jerk is within the range of voluntary reaction time (>150m s), this supports the diagnosis of psychogenic myoclonus. A cortical spike 20 ms before the jerk and/ or the presence of a giant somatosensory evoked potential would not be expected in psychogenic myoclonus. Th e most defi nitive test to confi rm the psychogenic origin of the myoclonus is detection of the readiness potential or Bereitschaft spotential (BP). Th i s slowly rising EEG potential starts around 1.5 seconds before voluntary self-paced movemen t, and refl ects activity in brain areas associated with movement preparation (25). Th is p otential can be recorded in patients with psychogenic myoclonus, but has never been reporte d in patients with organic myoclonus. It requires a number of jerks to be recorded and aver aged (usually at least 30), so is not suitable for those with very infrequent jerks. Th ose with jerks more than every 4 \200\2235 seconds are also unsuitable for recording. A recent study of the presence of BP preceding abnormal movements demonstrated that the clinical di agnosis of organic spinal myoclonus made by move- ment disorders experts is commonly incorr ect, as many of them were preceded by a BP (26). Th is study and an independent study confi rmed that most patients carrying a diagnosis of idiopathic Psychogenic gait disorder Psychogenic disorders of posture and gait are common, and are the major manifestation in 8 \200\22310% of patients with psychogenic move- ment disorders (32 ). Abnormal gait can be an isolated phenomenon in patients with PMD or mixed with other cli nical manifestations. In the largest series reported (33) the proportion of pure psychogeni c gait disorder was 5.7% of PMD, and this increased to 42.3% when the mixed type was includ ed. Clinical descriptions date back to the nineteenth century. Paul Blocq was the fi rst to use the term asta- sia \200\223abasia. In this manifestation of psychogenic gait disturban ce, patients veer from side to side when walking, oft en waving the arms at the same time. Th ey seem continuously about to lose their bal- ance, but tend not to. Th is ability to sh ift the center of gravity from one side to the other without losing balance is a demonstrat ion of good balance in contrast with the patient \200\231s subjective report of poor balanc e. Other features of psychogenic gait disorders include nar- row base, hesitation, dramatic response to Romberg \200\231s test and tests of postural stability, \200\230uneconomic \200\231 postures, or excessive slowness. Because patterns of gait can be rather unusual in some organic dis- orders (e.g. Huntington \200\231s disease, generalized dystonia), consid er- able clinical experience in both psychogenic and organic disorders can be required to m ake a clear diagnosis. Oxford Textbook of Movement Disorders 342 Other PMDs: psychogenic chorea, tics, and paroxysmal movement disorders Psychogenic chorea is extremely rare. So far, only two patients have been reported, one of them with a family history of Huntington \200\231s disease (34). Here, clues to the diagnosis were normal sacc adic eye movements, absence of motor impersistence, and a marked decrease in chorea when th e patient was distracted during per- formance of voluntary repetitive movements. paroxysmal disorders have rarely been mentioned in the literature (3). As organic paroxysma l disorders such as paroxysmal kinesi- genic dyskinesia, paroxysmal non-kinesigenic dyskine sia, and par- oxysmal exercise-induced dyskinesia, or even focal seizures, are by defi niti on brief and reversible, the clinical diagnosis can be very dif- fi cult. However, organic counterparts have typical precipitating fac- tors and the length of the attacks is also wel l defi ned for each type; therefore incongruous features can raise suspicion of a psychogen ic basis. It is of great importance to see an attack (e.g. by getting the patient to video an episode). Oft en, EEG and video-recording of the attack are important in reaching the di agnosis. Psychogenic tics are also rarely described. Surprisingly, in a series of patients with tics reported by Mejia and Jankovic (35), 16 out of 155 (10.3%) were considered to have psychog enic tics (35). Th e rather high frequency of psychogenic tics in this sample was sub- sequ ently questioned. It was argued that the criteria used to give the diagnosis of psychogenic ity in these patients was not specifi ed and that typical indicators of PMD, such as abrupt onset, response to placebo or suggestion, or increase with attention and cessation with di straction, may not help to diff erentiate organic from psy- chogenic tics as organic tics m ay also begin abruptly and be under some voluntary control, and intensity can vary with att ention. Th is highlighted the need for well-defi ned criteria to characterize psy- chogenic tics. Diagnostic criteria Diagnostic criteria have been developed to operationalize diag- nosis o f PMDs. Th e most widely used criteria, developed by Fahn and Williams (36), divide PMDs in to four categories of diagnostic certainty: documented, clinically established, prob- able, and possible. In fact, these criteria were fi rst developed for psychogenic dystonia alone , but were later expanded to cover all PMDs. Gupta and Lang (37) have suggested revisions t o these criteria (Table 31.2) which delete the \200\230possible \200\231 category as being not suffi ciently specifi c for PMDs, and also seek to introduce the A \200\230paroxysmal \200\231 component to the disorder is an important clue that the diso rder may be psychogenic, but \200\230pure \200\231 psychogenic Table 31.2 Diagnostic classi \201 cation of psychogenic movement disorders Fahn and Willia ms (36) Persistent relief by psychotherapy, suggestion, or placebo has been demonstrated, w hich may be helped by physiotherapy, or the patient was seen without the movement disorder when believing him/herself unobserved Gupta and Lang (37) Persistent relief by psychotherapy, suggestion, or placebo has been dem onstrated, which may be helped by physiotherapy, or the patient was seen without the moveme nt disorder when believing him/herself unobserved 1 Documented Clinically established Th e movement disorder is incongruent/inconsistent with typical movement disorder plus at l east one of the following three: \227\206 other psychogenic signs \227\206 multiple somat izations \227\206 obvious psychiatric disturbance Plus other features: the movement disorder is incongruent/inconsistent with typical movemen t disorder plus at least one of the following three * : \227\206 other psychogenic signs \227\206 multiple somatizations \227\206 obvious psychiatric disturbance Minus other featu res: the movement disorder is incongruent/ inconsistent with typical movement disorder with out any other features * \227\206 Th e movement disorder is incongruent/inconsistent Probable ** with typical movement disorder \227\206 Th e movement disorder is congruent/consistent and there are psychogenic signs \227\206 Th e movement disorder is congruent/consistent and there are multiple somatizations Possible *** \227\206 Th e movement disorder is congruent/consistent and \227\206 Th e movement disorder is congruent/consistent and there are there is evidence of an emotional disturbance psychogenic signs \227\206 Th e movement disorder is congruent/consistent and there are multiple somatizations \227\206 Th e movement disorder is congruent/consistent and there is evidence of an emotional disturbance \227\206 Electrophysiological evidence proving a psychogenic movement Laboratory-supported de \201 nite disorder (primarily in cases of psychogenic tremor and psychogenic myoclonus) According to the Gupta and Lang proposal, the \200\230documented \200\231 and \200\230cli nically established \200\231 \200\230plus or minus other features \200\231 categories can be grouped under the term \200\230clinically de \201 nite \200\231. Gupta and Lang propose reclassifying patients in the \200\230probable \200\231 category according to the Fahn and Williams classi \201 cation, under \200\230clinically establish ed \200\231 (those with incongruent/ inconsistent movement disorders) or \200\230possible \200\231 (those with congruent/consistent movement disorders). * Gupta and Lang also questioned the utility of retaining the \200\230possible \200\231 c ategory as this generally represents patients with organic movement disorders with addition al psychiatric problems rather than a true \200\230possible psychogenic movement disorder \200\231. CHAPTER 31 Psychogenic Movement Disorders 343 concept of a laboratory-supported level of certainty, for exam- ple using recordings of pre -movement potentials in psychogenic myoclonus. Shill and Gerber (38) proposed alternative c riteria, but these have been criticized for relying so heavily on historical factors such a s \200\230disease modeling \200\231 that it is possible to make a diagnosis of PMD without reference to the movement disorder phenomenology. disorder arose from a malfunction in the part of the brain receiving and interpreting senso ry and aff ective information. More modern conceptions of somatoform disorders have tended to focus on the way in which normal physiological sensory input might be mis- interpreted b y an individual as pathological and signifying illness (41). Models, such as that proposed by Kirmayer and Taillefer (41), propose an interaction between somatic sensations (normal p hysio- logical experiences, those induced by emotional arousal, sensations arising from org anic physical illness), pre-existing personality, previous illness experience, and societal factors that enhance the secondary gain of the sick role (disability benefi ts, social res ponse of others to illness) (41). Th e fundamental neurobiological pro cess that underpins this model is excessive attention that is directed towards the triggering somatic sensation s which amplifi es them and maintains the patient \200\231s abnormal (enhanced) perception of these sensations. Th ese are then reported by the patient as symp- toms (e.g. pain). Recently, these criteria have been assessed with regard to inter-rater reliability, and hav e been found to demonstrate moder- ate to poor reliability for the probable and possible ca tegories. Th is work suggests that new criteria, which perhaps include more spe- cifi c dir ection as to the positive physical signs that predict PMDs rather than the unspecifi ed \200\230incongruency \200\231 with organic movement disorders, might improve reliability. Pathophysiology We have already discussed how the movements that occur as part of PMDs are quantifi ably diff erent from those seen in organic movement disorders mainly by virtue of the fact that they resemble movements that are made voluntarily. Th is leads naturally to t wo logical possibilities. Either movements are deliberately feigned by patients, or there m ust be another process by which movements that appear voluntary are not experienced as such by patients. Th e category of conversion disorder is based on the concept introduced by Breuer and Freud between 1893 and 1895, and later extended by Freud alone. Here, the role of a psychologica l stres- sor is paramount. Th is stressor is proposed to set off a defensive reaction of su ppressing (or repressing) the memory of this stres- sor. While this may relieve the distres s associated with the stressor, Breuer and Freud proposed that the \200\230psychic energy \200\231 displaced from its proper place by this process is \200\230converted \200\231 int o a somatic symp- tom which may bear some symbolic association with the original stressor ( 42). Th is somatic symptom is unconscious as the source of the energetic displacement is re pressed and the process occurs outside awareness. Although the energy displacement mechanis m proposed by Freud has been discarded, the idea that functional symptoms relate to a conve rsion of psychological distress retains considerable popularity.