364 CHAPTER 8
opposite the affected hand (each hemisphere of the brain controls and registers
sensations from the opposite side of the body); these brain areas are involved in
attention and motor control, respectively. When retested 2–4 months later, after the
symptoms had disappeared, the patients’ brains functioned normally (Vuilleumier
et al., 2001). These fi ndings suggest that the decreased sensitivity to stimuli that can
occur in conversion disorder arises from decreased activity of sensory brain struc-
tures. Thus, at least for these patients, the disorder directly refl ects brain events; it is
not some form of malingering or faking of symptoms.
However, other researchers report that the brain does respond even though
conscious perception is absent (for example, see Hoechstetter et al., 2002; Lorenz,
Kunze, & Bromm, 1998). Taken together, the fi ndings suggest that conversion dis-
order is not a direct consequence of impaired brain areas that register peripheral
sensations, but rather refl ects abnormal operation of brain areas that interpret sen-
sations andmanage other brain areas (that is, areas that are involved in “executive
functions”). At least in some cases, abnormal processing in brain areas responsible
for executive functions might inhibit brain areas that process sensation and pain or
that produce movements, which in turn causes them to fail to function properly.
Finally, it is important to note that conversion disorder is sometimes incorrectly
diagnosed. One study, for example, found that many patients who suffered seizures
and were diagnosed with conversion disorder in fact had neurological abnormalities
in one cerebral hemisphere, typically the right (Devinsky, Mesad, & Alper, 2001).
Thus, in some cases, the symptoms of conversion disorder may refl ect, at least in
part, underlying medical problems. In fact, the results of one study of patients diag-
nosed with conversion motor paralysis suggest that as many as half of those patients
may have a genuine medical problem (Heruti et al., 2002).Genetics At least in some cases, conversion disorder may run in families, but it is
diffi cult to disentangle the role of genes from that of modeling the behavior of fam-
ily members (Schulte-Korne & Remschmidt, 1996). For example, if a parent never
uses one hand, it is possible that a child may come to imitate that behavior, and thus
not use that hand.8.5 • Brain Activation in Conversion
Disorder: Healthy Limb Versus Affected
Limb Brain areas activated when the skin of the
healthy, nonaffected limb was stimulated (top row)
compared to those activated when the skin of the
affected limb was stimulated (bottom row); arrows
show the key areas of activation (Mailis-Gagnon
et al., 2003). It’s clear that the scans in the bottom
row show much less activation.
Source: A. Mailis-Gagnon, MD, et al., Neurology 2003;60:1501–1507.
© 2003 American Academy of Neurology.Figure 8.5g5