Descriptive Psychopathology: The Signs and Symptoms of ...

184 Section 3: Examination domainsSpecific idiopathic movement disturbanceThe many idiopathic movement disturbances are broadly categorized as those wheremovement is inhibited, such as weakness and paresis without atrophy, 131 and thosewhere an abnormal movement occurs but the etiology is deemed psychological,e.g. “psychogenic” myoclonus, 132 tremor, 133 dystonia (spasmodic, fixed, torticollis,torsion), globus hystericus (difficulty swallowing), and Parkinsonism. 134In specialty clinics, conversion dystonia and tremor are the most common(>50%), followed by tic, myclonus and Parkinsonism. 135 Among persons in thegeneral population with a conversion disorder diagnosis, over half have anidiopathic movement problem, commonly weakness and paresis without atrophy.136 Studies of neurologic patients estimate the diagnosis of conversion disorderbetween one and 9%. 137The pathophysiology of idiopathic movement disturbancesThe pathophysiology of idiopathic movement disturbance is unclear. There are threealternative considerations to the psychogenic model. The movement disturbancesrepresent: (1) subtle motor system regulatory dysfunction and is a distinct pathophysiologicdisorder, (2) feigned behavior, or (3) features of a primary psychiatric orneurologic condition and do not exist independent of these conditions.The subtle motor system model proposes that idiopathic movement disturbancesare expressions of a subtle but specific abnormal neurologic process. Theevidence for this understanding is weak. Neuropsychological studies focus on theright hemisphere, because as the “non-language” hemisphere with arousal andemotional expression and receptive functions it is hypothesized as the site of thedynamic unconscious. A few studies report bi-frontal and non-dominant hemisphereimpairment in patients with conversion diagnoses. 138 Others propose adisconnection between sensory processing and awareness, 139 a disconnectionbetween pre-conscious processing of emotion, perception and memory, 140 anda defect in mapping of the body state. 141 The disconnections are presumedfunctional not structural, resulting in disrupted motor–perceptual coordinationleading to neglect and abnormal or non-movement. 142 The preparation to moveand the attempt to move fail to activate the sensory motor cortex to properlyguide movement. 143 This loss of feedback is also proposed as an explanation forcatatonia, a condition that is often misinterpreted as conversion disorder.Neuroimaging studies consist of small samples and case reports. Patients withmotor conversions are reported to exhibit cortical hypometabolism and areunable to properly generate 144 or fully use motor programs 145 because of corticalfunctioning being disrupted by limbic system over-activation. 146 The disruptionis between the brain systems of intention and motor execution and the result isnon-movement. 147 The metabolic dysfunction also appears contralateral to the