It is imperative that patients suspected of having conversion disorder receive a thorough neurological and medical evaluation. As previously discussed, neurologic conditions may coexist with conversion disorder. In their follow-up study, Gatfield and Guze (1962) found that the conversion symptoms of 21% of patients diagnosed with conversion disorder were actually attributable to neurologic disease. Slater and Glithero (1965) reported that 30% of patients originally diagnosed with conversion disorder were found to have organic illness that apparently accounted for their original presentation. Other studies found that less than 30% of cases of conversion disorder were incorrectly attributed to a medical cause (Carter 1949; Dickes 1974; Folks et al. 1984; Hafeiz 1980). It is important to keep in mind that patients diagnosed with conversion disorder may have an undiagnosed or unrecognized medical illness and that up to 70% will eventually develop a disease that might in some way explain the pathology initially presented.
The incidence of misdiagnosis may be declining. Watson and Buranen (1979) found after a 10-year follow-up period that 25% of diagnoses of conversion disorder were in fact false-positive diagnoses. In a more recent 4-year follow-up study, Kent et al. (1995) found that only 13% of patients were initially misdiag-nosed. Even though the rate of misdiagnosis has declined, these studies confirm that medical illness continues to be the cause of the original presenting complaint in a substantial number of patients initially diagnosed with conversion disorder. For this reason, it is imperative that patients thought to have conversion disorder receive a thorough neurological and medical evaluation. Conversion disorder should not be considered a diagnosis of exclusion. Rather, it is a well-defined entity that mimics neurological processes. On the other hand, the presence of a neurological condition does not preclude the diagnosis of conversion disorder. In fact, as previously noted, some studies indicate that conversion symptoms may occur in patients who have a true organic disorder. Possible organic disorders to consider include mostly occult or difficult-to-diagnose neurological disorders, which may mimic or present with primarily neurological symptoms. These include systemic lupus erythematous, myasthenia gravis, multiple sclerosis, Parkinson's disease, a true seizure disorder, and the effects of various medications, drugs of abuse, and alcohol on the central nervous system.
At the same time, it is important that medical and neurologic disorders not be overdiagnosed. Studies show that there is an average of 6-8 years' delay before conversion disorder is diagnosed
(Bowman 1993), usually because of previous misdiagnosis of and treatment for medical, neurological, or other psychiatric conditions. Some diagnostic tests may actually cause iatrogenic damage, which in turn may validate the patient's perceived deficits. Similarly, some medications (e.g., benzodiazepines, anticonvulsants, neuroleptics) may promote depersonalization, dissociative states, mental slowing, or a "hangover" effect, which patients may misunderstand and which may further promote their feeling of lack of control.
Psychiatric diagnoses that should be considered and ruled out before diagnosing conversion disorder include pain disorder and sexual dysfunction (both of which are diagnoses of exclusion according to DSM-IV-TR Criterion F). Other psychiatric diagnoses that may better explain the symptoms are psychotic disorders (in the case of hallucinations or psychotic presentation, including nonculturally sanctioned psychotic-like presentations), anxiety disorders (in the case of shortness of breath or difficulty swallowing), dissociative disorders (because they share symptoms such as dissociation and neurological dysfunction or changes), and the other somatoform disorders (e.g., somatization disorder and hypochondriasis). Finally, as previously discussed, the possibility of factitious disorder or malingering must be considered.
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