The first step in the diagnosis of a psychogenic disorder, like most medical conditions, is to be suspicious of the possibility of that diagnosis. In movement disorders, that suspicion rests on the phenomenology of the abnormal pattern of movements and on certain clues (1) in the history and examination. Fixed postures are sustained postures that resist passive movement, and such fixed postures are highly likely to be due to a psychogenic dystonia (2, 3, 4).

Once a psychogenic movement disorder is suspected, the next step is to establish the correct diagnosis, that is, document that the abnormal movements are indeed due to a psychogenic etiology. Just being suspicious that the signs and symptoms are psychogenic is insufficient for the diagnosis of documented psychogenic disorder. Fahn and Williams (2) categorized patients into four levels of certainty as to the likelihood of their having a psychogenic movement disorder. These four degrees of certainty are (i) documented psychogenic disorder, (ii) clinically established psychogenic disorder, (iii) probable psychogenic disorder, and (iv) possible psychogenic movement disorder. This classification has been used by subsequent authors (5, 6, 7). In order for the disorder to be documented as being psychogenic, the symptoms must be relieved by psychotherapy, by the clinician utilizing psychological suggestion including physiotherapy, by administration of placebos (again with suggestion being a part of this approach), or by the patient being witnessed as being free of symptoms when left alone, supposedly unobserved (1). Two special problems exist: (i) when the abnormal movements are paroxysmal, because getting better at times is part of a paroxysmal syndrome, so one cannot be certain if the improvement was due to the psychotherapeutic treatment for psychogenicity; and (ii) if the abnormal movements had led to a fixed posture that resists passive movement possibly due to the development of contractures.

A contracture in a muscle is a shortened muscle that is resistant to passive stretch and is usually due to fibrosis of the muscle, ligaments, tendons, or the joints, preventing the muscle from stretching to its normal length. (An ankylosed joint due to bony growth would also result in a fixed posture and would be in the differential diagnoses of fixed postures along with contracture. X-rays would be able to detect such ankylotic joints, and we will not consider ankylosis any further.) The contracture thus presents as a fixed posture, that is, a posture that cannot be relieved by the examiner trying to straighten out the abnormally positioned body part. However, a fixed posture due to psychogenicity may be due to a contracture or may resemble a contracture, merely by resisting passive movement. How to distinguish between a contracture and a noncontracture fixed posture is the essence of this chapter. The ultimate, documented diagnosis of a psychogenic dystonia, as stated above, depends on getting the patient better; getting better, in terms of relieving fixed postures, depends on knowing if contractures are present and if noncontractured fixed postures are present.

The shortened muscle, if due entirely to a contracture, is electrically silent. Metabolic diseases, such as McArdle disease (8) due to muscle phosphorylase deficiency, can cause electrically silent contractions, thus technically physiologic contractures (9). But these disorders do not lead to persistent contractures. This type of physiologic contracture appears with protracted exercise, and is most readily seen in phosphorylase deficiency with anaerobic exercise, where the muscle’s energy is derived from glycolysis and not
mitochondria. Further discussion of physiologic contractures is not part of this chapter.