Conversion sensory symptoms associated with parietal lobe infarct: case report, diagnostic issues and brain mechanisms.

This case report suggests that diagnostic difficulties and brain mechanisms related to conversion disorder associated with cerebral lesions differ from those related to conversion disorder without cerebral lesions. A 35-year-old divorced woman was admitted to a psychiatric inpatient unit with multiple physical complaints. The symptoms first appeared 5 years previous and 2 months after a sexual assault. Three years later, she began to experience ill-defined sensory symptoms confined to the left half of her body (splitting the midline). Results of neurologic consultations were equivocal because of the subjective nature of the complaints, which were viewed as conversion symptoms. A magnetic resonance imaging scan demonstrated an old infarct in the right parietal lobe, suggesting a physical origin of the patient's symptoms. However, normal somatosensory-evoked responses from the affected area contributed little to establishing the diagnosis. The results of all further investigations to identify causes of the vascular pathology were negative. The multiple ill-defined somatic symptoms, the distribution of sensory symptoms and the resolution of symptoms with psychotherapy established the diagnosis of conversion disorder superimposed on a pre-existing right parietal lesion. This case highlights the importance of clinical features in establishing a diagnosis such as this. We suggest that reactivation of implicit sensory memories (represented at the thalamic level and resulting from decreased corticofugal inhibitions due to the lesion) may contribute to the formation of sensory conversion symptoms in individuals with parietal lobe lesions.