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To the Editor: H. Brent Solvason, Ph.D., M.D., et al. (1) described a woman seen with leg weakness and back pain who was initially diagnosed as suffering from conversion disorder and subsequently turned out to have sporadic Creutzfeldt-Jakob disease. The authors usefully highlighted how organic disease may be important in generating symptoms that are medically unexplained, either directly by effects on brain function or because of more complex behavioral responses to illness. They also showed how our current somatoform classification leaves little room for a dual diagnosis of organic and functional disorder. This unsatisfactory either/or philosophy is perhaps one reason why doctors are reluctant to diagnose conversion disorder in the first place.
There is another important reason why doctors are reluctant to diagnose conversion disorder—the common belief that such patients have a high likelihood of developing neurological disease in the long term. This view has principally arisen from a widely cited but flawed 1965 article (2) that suggested that up to 61% of patients diagnosed with hysteria will eventually develop neurological disease. However, in the last decade, a number of studies have shown that for patients who have seen a neurologist, the rate of misdiagnosis at follow-up is actually between 5% and 10% (3–6). This is a level comparable with those for other neurological and psychiatric disorders.
An additional issue is whether Creutzfeldt-Jakob disease could have been diagnosed during the patient’s lifetime in this case. Recent advances have aided the detection of sporadic Creutzfeldt-Jakob disease. CSF 14-3-3 protein has a sensitivity of 94% and specificity of 84% (better than a periodic EEG) (7), and T2-weighted magnetic resonance imaging (MRI) shows a bilateral basal ganglia high signal in about two-thirds of patients but only 7% of appropriate comparison subjects (8). Such MRI abnormalities are usually not mentioned in radiology reports and need to be specifically excluded (8). Given the clinical suspicion of Creutzfeldt-Jakob disease in this patient, these tests may have helped to make a diagnosis during her lifetime.
Clinical vigilance for a missed diagnosis of neurological disease in cases of conversion disorder is essential. It would be a shame, however, if this case conference reinforced the erroneous idea that the development of neurological disease in such cases is the norm. Failure to make a positive diagnosis of conversion disorder can have serious adverse consequences. The patient may be denied appropriate treatment management that vitally depends on persuading him or her that the symptoms are reversible and not due to disease. We should not withhold the diagnosis simply because we occasionally get it wrong.
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