This patient has an apparent conversion disorder, manifested as both functional visual loss and left-sided lower-extremity weakness. Her neurological workup and laboratory investigations revealed no obvious explanation for symptoms. Furthermore, the patient has been under significant psychological stress. She also demonstrates detachment (la belle indifférence) that is unexpected, given the nature of her condition. Although this finding is not specific to or diagnostic for conversion disorders, it has frequently been associated.
Conversion disorder, also called functional neurologic disorder, is an illness of symptoms of altered voluntary motor or sensory function. The motor symptoms of conversion disorder frequently manifest as weakness, paralysis, and/or abnormal movement. The sensory symptoms of this condition may manifest as anesthesia, blindness, and/or hearing loss. Other possible presentations of conversion disorder include nonepileptic seizures, episodes of unresponsiveness, or aphonia (loss of speech). The basic idea of a conversion disorder is that an individual takes a psychological problem, situation, or conflict and "converts it" into a physical symptom. What is key is that the patient does so without knowing it.
A diagnosis of conversion disorder requires the following:
At least one altered or impaired voluntary motor or sensory function
Clinical findings demonstrate an incompatibility between symptoms and recognized medical or neurologic disease
Symptoms cannot be better explained by another medical or mental disorder
Symptoms cause clinically significant distress or impairment in social, occupational, or other important areas of functioning
Diagnosing conversion disorder is challenging because it is a diagnosis of exclusion. Clinicians should remember that, although it may appear that symptoms cannot be explained by another medical disorder, eliminating all other possible causes entirely is generally not possible. However, a thorough investigation of any reasonable and relevant potential medical conditions is required before the diagnosis of conversion disorder can be considered.
The exact prevalence of conversion disorder is unknown. Estimates suggest that 20%-25% of general hospital patients have individual conversion symptoms. However, only 5% of those experiencing conversion symptoms meet the criteria for full diagnosis. The incidence of conversion disorder is estimated to be 4-12 cases per 100,000 population. In psychiatric settings, this estimate increases to 11-22 cases per 100,000 population.
Certain risk factors are associated with the onset of conversion disorders. Female sex is more commonly associated with conversion disorder; it occurs in women 2-10 times more frequently than in men. Low socioeconomic status and low education level are also common among individuals with conversion disorder. This association is further reflected by data that demonstrate higher prevalence of conversion disorder in third-world countries and rural populations. A history of significant psychosocial trauma, such as physical or sexual abuse, is also common in patients who develop conversion disorder.
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Cite this: Jeffrey S. Forrest, Alexander B. Shortridge. A 23-Year-Old With Blindness After a Fall She Can't Remember - Medscape - Nov 27, 2019.