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The authors’ observations
No neurologic or pathologic explanation is found for Ms. M’s symptoms. Imaging reveals no lesions to explain her intermittent upbeat nystagmus, which localizes to the pons and caudal medulla.2
Conversion disorder. Ms. M, however, appears to meet DSM-IV-TR criteria for conversion disorder (Box), which is thought to result from intense psychological distress in persons who can only express such emotions somatically. Her complaints had specific precursors: she was newly separated from her son and had marked the anniversary of her daughter’s death, which intensified her persistent mourning. We link both circumstances temporally to symptom onset. Also, lack of interest in her serious motor symptoms could be the “la belle indifference” typical of conversion disorder.
Ms. M, however, appears highly suggestible. Her physical symptoms improve soon after her attending psychiatrist suggests that treating her depression will decrease her movements. The neurologists also notice day-to-day fluctuations in her gait disturbance and jerking movements. Distraction techniques produce objective improvement in both symptoms.
DSM-IV-TR diagnostic criteria for conversion disorder
Is Ms. M faking her symptoms? Mental disorders and medical field employment both increase the risk of factitious disorder.3 In caring for her parents, Ms. M often felt unappreciated and may be trying to enter the sick role that they had filled.- One or more symptoms or deficits affecting voluntary motor or sensory function that suggest a neurological or other general medical condition.
- Psychological factors are judged to be associated with the symptom or deficit because the initiation or exacerbation of the symptom or deficit is preceded by conflicts or other stressors.
- The symptoms or deficit is not intentionally produced or feigned (as in factitious disorder or malingering).
- The symptom or deficit cannot, after appropriate investigation, be fully explained by a general medical condition, or by the direct effects of a substance, or as a culturally sanctioned behavior or experience.
- The symptom or deficit causes clinically significant distress or impairment in social, occupational, or other important areas of functioning or warrants medical evaluation.
- The symptom or deficit is not limited to pain or sexual dysfunction, does not occur exclusively during the course of somatization disorder, and is not better accounted for by another mental disorder.
Specify type of symptom or deficit:
With motor symptom or deficit
With sensory symptom or deficit
With seizures or convulsions
With mixed presentation
Source: Diagnostic and statistical manual of mental disorders (4th ed-text rev). Copyright 2000.
American Psychiatric Association. Reprinted with permission.
In malingering, the patient seeks external incentives for feigned behavior. The role of secondary gain must be considered, as Ms. M’s illness has reunited her with her son, who visits her regularly at the hospital.
Ms. M’s evaluation, however, uncovers no evidence that she is intentionally producing symptoms.
Follow-up: The answer becomes clear
One month after discharge to inpatient rehabilitation, Ms. M is readmitted to the neurology unit. Her uncontrollable limb jerks and ataxia are worse, and she appears demented and near mute. At that time, we learn that the CSF sample sent during her first admission is positive for protein 14-3-3.
Ms. M is diagnosed with Creutzfeldt-Jakob disease (CJD), a spongiform encephalopathy secondary to prion disease. She dies 6 days later. Sporadic CJD is confirmed at autopsy.
The authors’ observations
The literature lists no comprehensive differential diagnosis for conversion disorder, probably because presentations are diverse and the symptoms overlap with innumerable neurologic and medical conditions. This is underscored by the broad differential diagnosis for Ms. M’s ataxia.
In a study to identify organic syndromes initially diagnosed as conversion disorder,4 10 of 85 patients (11.8%) were initially misdiagnosed and later found to have dyskinesia, amyotrophic lateral sclerosis, multiple system atrophy, extrapyramidal syndrome, multiple sclerosis, dementia, Parkinson’s disease with psychogenic aggravation, lung cancer with cerebral metastases, and radicular syndrome. CJD and conversion disorder also share many symptoms (Table).
Correct diagnosis of conversion disorder calls for ruling out neurologic and medical conditions. Ms. M’s upbeat nystagmus prompted aggressive neurologic evaluation. Although horizontal nystagmus has been reported rarely in conversion disorder,5 vertical nystagmus has not. One case report6 describes vertical nystagmus as the first clinical sign of CJD.
Leading clinical symptoms of CJD include progressive dementia, myoclonus, cerebellar ataxia, visual problems, and extrapyramidal signs.7 Ms. M’s uncontrollable movements and jerks, although not classically myoclonic, were similar to this common finding. She did not present with dementia, but her rapidly progressive end-stage mental status changes were characteristic of CJD.
Sporadic CJD accounts for 84% of transmissible spongiform encephalopathies. Genetic, iatrogenic, and variant CJD forms (linked to bovine spongiform encephalopathy, or “mad-cow disease”) account for other cases.8 Psychiatric symptoms are a more-common manifestation of variant CJD9 but have been reported in sporadic CJD.10