How Psychogenic is Dystonia? Views from Past to Present

Alexander G. Munts; Peter J. Koehler

Disclosures

Brain. 2010;133(5):1552-1564. 

In This Article

Discussion

There has been a continuous vacillation between psychogenic and organic explanations for (i) primary generalized dystonia, (ii) cervical dystonia, (iii) writer's cramp and (iv) CRPS-related fixed dystonia. Although at first sight the attributions of the terms psychogenic and organic in Table 2 seem quite obvious, it seems more realistic to assume a spectrum with two ends between which attributions were moving. Moreover, the discussion between an organic and psychogenic aetiology has not always been explicit (particularly in the 19th century). The opinions of several authors could only be derived or interpreted from their hypotheses on aetiology and their therapies.

An example is Schwalbe's description of hysterical symptoms in siblings with generalized dystonia. In the late 19th century, Charcot considered hysteria a neurosis, similar to paralysis agitans, epilepsy and chorea, which were diseases without known pathology. For paralysis agitans he expected that the lesion would be discovered (Goetz et al., 1995). Hysteria appeared as a more difficult obstacle for Charcot's clinical-anatomic method and, when describing male traumatic neurosis, he moved towards a psychological conception of hysteria (Goetz et al., 1995). This was further elaborated by Freud and his followers (Koehler, 2003). Hysteria evolved from a disease in which an organic pathophysiology was suspected but not found, to a psychogenic disease in the late 19th and early 20th century. Recent functional imaging studies in these patients have shown specific cerebral abnormalities (Vuilleumier, 2001, 2005). From these studies it is suspected that affective or stress-related factors modulate cerebral sensorimotor representations through interactions between limbic and sensorimotor networks. It is hypothesized that primitive reflexive mechanisms of protection and alertness, which are partly independent of conscious control, are involved.

Primary Generalized Dystonia

The patients of Oppenheim made him move to the organic end of the spectrum, whereas Freud and his followers in psychoanalysis, moved in an opposite direction. The improved description of the 'clinical entity' in the 1940s (Herz), the new hereditary cases described in the 1950s (Zeman) and the limited efficacy of psychotherapy in torsion dystonia, as well as the effects of surgical treatments and the lesion studies in the 1960s (Eldridge, Cooper and Denny-Brown, respectively) pushed the explanatory ideas back into the organic. This culminated in Eldridge and Fahn's 1975 statement (published in 1976). However, a new movement towards psychogenesis soon followed with the recognition of psychogenic dystonia. Meanwhile, the remaining dystonias kept their position on the organic side of the spectrum, not in the least because of the discovery of the DYT1 gene. Nevertheless, one cannot be too rigid because dystonic disorders with a genetic origin can be triggered by emotional stress (Breakefield et al., 2008).

Cervical Dystonia

Bell and Duchenne probably assumed an organic cause for cervical dystonia (Table 2). Not much later Charcot, and certainly his student Brissaud, moved to the psychogenic view, in which the interpretation of observing the 'geste antagoniste' played an important role. At the time, such terms as 'torticolis mental' and 'torticollis hystericus' were used on both sides of the Atlantic and dealt with likewise. Psychological and surgical treatments were applied simultaneously in different patients at different places around the 1940s. After Marsden's 1975 presentation, the aetiological ideas on cervical dystonia clearly moved away from the psychogenic to the organic side of the spectrum.

Writer's Cramp

To explain writer's cramp, Ramazzini used such terms as 'fatigue' and 'failure of power'. These should be interpreted in the humoral pathophysiological concepts of the time, i.e. animal spirits that flow through the nerves with less power than usual. One would be inclined to consider an organic aetiology here; however, we may question whether Ramazzini was concerned with this question at all. From Bell's description a century later and also from Romberg's work, an organic viewpoint may be recognized. Duchenne again used the term 'functional', which does not necessarily imply that he meant a psychogenic aetiology. A clearer distinction came about in the early 20th century, when Mohr mentioned personality characteristics and a psychological factor, and suggested psychoanalysis for treatment. An interesting position was taken by Kinnier Wilson, assuming cortical dysfunction but comparing it to hysteria. Once more, Marsden's 1975 presentation pushed the aetiology of writer's cramp towards the organic side, with a few exceptions in the 1980s.

Fixed Dystonia Related to Complex Regional Pain Syndrome

Charcot's demonstration of two patients with 'oedème bleu des hystériques' occurred in a period in which he was moving towards a psychological explanation of hysteria. Marsden et al. expressed the opinion that the similarities between CRPS cases with dystonia over the world suggested its existence as a distinct clinical syndrome (Marsden et al., 1984). In contrast, Sa et al. stressed that most cases satisfied the criteria for psychogenic dystonia, and should, therefore, be considered as such (Sa et al., 2004). But these are based on expert opinion. Such statements are not like a gold standard and should, therefore, be used with caution. Moreover, it is remarkable that the reasons why CRPS-related fixed dystonia is considered psychogenic are at least partly the same as the arguments that were used in the past to explain why focal dystonia was psychogenic (Table 3): (i) the dystonia in CRPS may be considered incongruent with classical dystonia; (ii) it may be inconsistent over time; (iii) weakness, described in the majority of CRPS cases, might be interpreted as false; (iv) sensory abnormalities, which fit the diagnosis of CRPS, might be interpreted as false sensory findings; and (v) sometimes, psychiatric abnormalities are present. In recent times significant motor cortex abnormalities were found in CRPS (Schwenkreis et al., 2003; Maihofner et al., 2007; Gieteling et al., 2008).

It is clear that the discussions on the psychogenic or organic aetiology of dystonia have been emotional. In some of the periods, particularly during the 20th century, strong believers as well as non-believers may be recognized. Charcot isolated hysterical disorders from other neurologic diseases. In his view, environmental factors ('agents provocateurs') were involved in its pathogenesis. The rise of the psychoanalytic movement, following the work of Freud at the beginning of the 20th century, caused important disagreements between supporters of organic and psychogenic explanations. This was not specific to the interpretation of dystonia, but more generally reflected the division between biologically and psychoanalytic oriented neuropsychiatrists at the time. The success and popularity of psychoanalysis, as well as the lack of an organic substrate for dystonia, encouraged psychogenic theories. As the 20th century proceeded, knowledge in favour of a somatic origin of early-onset generalized dystonia accumulated. Marsden, a leading neurologist in movement disorders, convinced the neurological community in the 1970s and 1980s that both generalized and focal dystonia were somatic entities. However, psychogenic dystonia re-emerged, but as a special category. Nowadays, psychogenic dystonia is thought to be 'common' in specialized movement disorders clinics (Espay et al., 2006).

The recognition of the hereditary character of dystonia played an important role in attributing an organic nature in the first as well as the last decades of the 20th century. If dystonia had existed as an entity and its hereditary character had been recognized previously, it would probably have been interpreted in a different way, because of the particular concepts of the late 19th century. In this period several neuroses were considered hereditary, in fact a favourite subject in the interpretation models of Charcot (Féré, 1884). Similar to contemporary psychiatrists [the French Benedict-Augustin Morel (1809–1873) and Valentin Magnan (1835–1916)], he assumed that degeneration was a constitutional factor in certain families ('neuropathic families') in which neuroses including hysteria, alcoholism and epilepsy could be transformed during the passage from one generation to the next. Hysteria in a parent could be inherited as epilepsy in the child (Berrios and Beer, 1995; Goetz et al., 1995). In the 20th century, following delineation of dystonia as an entity and following new discoveries in genetics, the hereditary character led to new insights. Today it is recognized that >14 genes are implicated in different monogenic dystonia syndromes, which are frequently inherited as autosomal dominant conditions with reduced penetrance. Most cases of early-onset torsion dystonia are associated with the DYT1 gene mutation (Breakefield et al., 2008). Familial occurrence of cervical dystonia or writer's cramp has been described but appears to be rare (Defazio et al., 2007).

Medical problems nearly always unravel because of the advent of a new technology, skill or understanding of a hitherto unknown system of disease. One example is the unravelling of the electric nature of nerve action in the 18th and 19th century. Ideas on whether or not animal electricity existed and played a role in the nature of nerve conduction were put forward at the end of the 18th century by Galvani and denied by Volta (Piccolino, 1998; Koehler et al., 2009). The confirmation had to await more sophisticated sensitive measuring devices such as the galvanometer invented by Du Bois-Reymond in the 1840s, after which observation of the action potential became possible.

What will be the future 'sophisticated sensitive measuring device' that will finally lead to the understanding of dystonia? We believe that the increasing knowledge resulting from neurophysiological and imaging studies, combined with genetic methods, will provide the insight that the explanation of dystonia cannot just be interpreted in terms of organic or psychogenic. These modern methods may show that the interaction of genetic and environmental factors is more complex than was previously thought. When reviewing the pathophysiology of primary adult-onset focal dystonia, Defazio et al. (2007) suggest that in human focal dystonia there may be an overload of a predisposed sensory system resulting from peripheral injury or repetitive motor activity in a certain part of the body, or both, causing sensory receptive changes in the corresponding cortical brain areas and leading to abnormal regulation of inhibitory interneuronal mechanisms at the brainstem or spinal cord level (Defazio et al., 2007). There seems to be an abnormality of sensorimotor integration and cortical excitability beyond the symptomatic body part. In both generalized and focal dystonia, neurophysiological and functional imaging studies indeed point towards abnormalities in the sensorimotor circuitry, which result in a vulnerable central nervous system. Some of these phenomena have been found in asymptomatic gene carriers, as well as in representations of unaffected body parts. It is suspected that a 'second hit' is needed to bring the central nervous system out of balance, which leads to dystonia (Defazio et al., 2007; Breakefield et al., 2008). Musician's dystonia is an interesting example. In a transcranial magnetic stimulation study, cortical changes were found in musicians compared to healthy controls, and these changes were more marked in those with musician's dystonia. It is hypothesized that musician's dystonia is a form of training-induced dystonia (Rosenkranz et al., 2005).

These suggestions, in particular the assumption of abnormal regulation of inhibitory interneuronal mechanisms at the brainstem or spinal cord level, bring us back to Sherringtonian neurophysiology as already suggested by Denny-Brown in the 1960s, when he found that damage in different anatomical structures could have the same consequence; pointing to a basic neurophysiological principle, the final common path, that had been conceived around the turn of the 19th to the 20th century by his teacher Charles Scott Sherrington (1857–1952) (Sherrington, 1906; Burke, 2007). This may still be a valid explanation of the phenomenology, if not the underlying causation of dystonia in modern terms.

Today, psychogenic dystonia is considered a disorder that results from an underlying psychiatric illness. Its diagnostic criteria have remained unchanged for decades (). In the meantime, however, the border between neurology and psychiatry has been less well defined. For example, schizophrenia (Hendler et al., 2009), autism (Mostofsky et al., 2009) and primary dystonia (Breakefield et al., 2008) are now considered neurofunctional disorders. Additionally, it has been shown recently that patients with cervical dystonia or blepharospasm have distinct neuropsychiatric and personality profiles of the anxiety spectrum (Lencer et al., 2009). Another study shows high psychiatric comorbidity in cervical dystonia, which is unlikely to be a mere consequence of chronic disease and disfigurement (Gundel et al., 2003). It is attractive to see psychogenic disorders as the consequence of functional crashes in anatomically normal brains. In these disorders, abnormalities found in neurophysiological and functional imaging studies may be interpreted as signs of organic dysfunction. We have only traced two transcranial magnetic stimulation studies on psychogenic dystonia. Interestingly, one of these found similar abnormalities in both organic and psychogenic dystonia: reduced short and long-interval intracortical inhibition and cortical silent period, and an increased cutaneous silent period (Espay et al., 2006). The other study detected difference: patients with organic dystonia had an increased response to paired associative stimulation compared to patients with psychogenic dystonia (Quartarone et al., 2009). The authors of the latter study concluded that abnormal plasticity is a hallmark of organic dystonia in contrast to psychogenic dystonia.

If we hypothesize further, assuming abnormal regulation of inhibitory interneuronal mechanisms as mentioned above, neurophysiological and functional imaging studies may help to explain dystonia in CRPS due to peripheral injury leading to similar sensory receptive changes. Such mechanisms may also be in play in dissociation disorders, including conversion disorder (Marshall et al., 1997; Vuilleumier, 2001, 2005; Cojan et al., 2009; Seritan et al., 2009), thereby associating primary dystonia, CRPS-related fixed dystonia, and sensory and motor disorders in conversion disorder.

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