Frontal and occipital perfusion changes in dissociative
identity disorder
Vedat Sar
a,
!
, Seher N. Unal
b
, Erdinc Ozturk
a
a
Clinical Psychotherapy Unit and Dissociative Disorders Program, Department of Psychiatry, Medical Faculty of Istanbul, University of Istanbul,
Istanbul, Turkey
b
Department of Nuclear Medicine, Medical Faculty of Istanbul, University of Istanbul, Istanbul, Turkey
Received 16 April 2006; received in revised form 14 December 2006; accepted 26 December 2006
Abstract
The aim of the study was to investigate if there were any characteristics of regional cerebral blood flow (rCBF) in dissociative
identity disorder. Twenty-one drug-free patients with dissociative identity disorder and nine healthy volunteers participated in the
study. In addition to a clinical evaluation, dissociative psychopathology was assessed using the Structured Clinical Interview for
DSM-IV Dissociative Disorders, the Dissociative Experiences Scale and the Clinician-Administered Dissociative States Scale. A
semi-structured interview for borderline personality disorder, the Hamilton Depression Rating Scale, and the Childhood Trauma
Questionnaire were also administered to all patients. Normal controls had to be without a history of childhood trauma and without
any depressive or dissociative disorder. Regional cerebral blood flow (rCBF) was studied with single photon emission computed
tomography (SPECT) with Tc99m-hexamethylpropylenamine (HMPAO) as a tracer. Compared with findings in the control group,
the rCBF ratio was decreased among patients with dissociative identity disorder in the orbitofrontal region bilaterally. It was
increased in median and superior frontal regions and occipital regions bilaterally. There was no significant correlation between
rCBF ratios of the regions of interest and any of the psychopathology scale scores. An explanation for the neurophysiology of
dissociative psychopathology has to invoke a comprehensive model of interaction between anterior and posterior brain regions.
© 2007 Elsevier Ireland Ltd. All rights reserved.
Keywords: Dissociative disorder; Borderline personality disorder; Neurophysiology; Orbitofrontal lobe; Occipital lobe; Childhood trauma
1. Introduction
The essential feature of dissociative disorders is a
disruption in the usually integrated functions of
consciousness, memory, identity, and perception of the
environment. The disturbance may be sudden or gradual,
transient or chronic (American Psychiatric Association,
1994). Dissociative identity disorder is characterized by
the presence of two or more distinct personality states
or identities within a single person that take control of
his or her behavior recurrently. Each personality state
may have different access into memory resulting in a
state-dependent inability to recall important personal
information. These alter personalities are characterized
by different emotional responses, cognitions, moods,
and perceived self-images. Dissociative identity dis-
order is considered as a post-traumatic developmental
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Psychiatry Research: Neuroimaging 156 (2007) 217–223
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!
Corresponding author. Istanbul Tip Fakültesi Psikiyatri Klinigi 34390
Capa Istanbul, Turkey. Tel.: +90 212 236 02 14; fax: +90 212 261 70 04.
E-mail address: vsar@istanbul.edu.tr (V. Sar).
0925-4927/$ - see front matter © 2007 Elsevier Ireland Ltd. All rights reserved.
doi:10.1016/j.pscychresns.2006.12.017

psychopathology closely related to child abuse and
neglect (Putnam, 1997).
Although the DSM-IV (American Psychiatric Associ-
ation, 1994) defines other types of dissociative disorders
as well (i.e. dissociative amnesia, dissociative fugue, de-
personalization disorder, and dissociative disorder not
otherwise specified), we chose to limit the study group to
patients with dissociative identity disorder, because it is
the most complex, chronic, and severe of these diagnostic
categories, and it is usually superposed to other disso-
ciative disorders on a symptomatological level. In fact,
dissociative symptoms and disorders may accompany
other psychiatric disorders as well (Sar and Ross, 2006).
Substance abuse (Karadag et al., 2005), borderline
personality disorder (Sar et al., 2003, 2006), obsessive-
compulsive disorder (Lochner et al., 2004), post-traumat-
ic stress disorder (Briere et al., 2005), acute stress disorder
(Spiegel et al., 2000), eating disorders (Farrington et al.,
2002), pathological gambling (Grant and Kim, 2003),
kleptomania (Grant, 2004) and even schizophrenia (Ross
and Keyes, 2004) are among them. A somatoform type of
dissociation is also described which is proposed to be the
underlying mechanism in conditions characterized by
medically unexplained symptoms; i.e. conversion symp-
toms (e.g. pseudoseizures), psychogenic pain, and somati-
zation disorder (Nijenhuis et al., 1996; Sar et al., 2004).
Thus, beyond constituting a group of disorder on its own,
dissociation as a mental mechanism may play a role in
various psychiatric disturbances or it may confound them.
Its relationship to childhood adverse events increases its
importance as a mental mechanism further.
Brain imaging studies on series of patients with
dissociative identity disorder are rather scarce. One
study using single photon emission computed tomog-
raphy (SPECT) demonstrated bilateral orbitofrontal
hypoperfusion and left (dominant hemisphere) lateral
temporal hyperperfusion (Sar et al., 2001). A positron
emission tomography study using scripts for symptom
provocation in 11 women with dissociative identity
disorder revealed the existence of different patterns of
regional cerebral blood flow (rCBF) for different
senses of self (Reinders et al., 2003). The authors
presented evidence for the medial prefrontal cortex and
the posterior associative cortices to have an integral
role in conscious experience.
In a single case, functional magnetic resonance im-
aging demonstrated bilateral hippocampal inhibition
(with inhibition stronger on the right side) while the
patient was switching from host to alter personality
(Tsai et al., 1999). The right parahippocampal and me-
dial temporal regions were also inhibited, as were small
regions of the substantia nigra and globus pallidus. In
contrast, switching back toward the host personality
involved only right hippocampal activation. One of two
previous single case SPECT studies yielded a mean
perfusion increase of 10.7% in the left temporal lobe
when assessed during activations of four alter person-
ality states (Saxe et al., 1992) and the other yielded an
increase of perfusion in right temporal lobe (Mathew
et al., 1985). In a recent volumetric study on patients
with dissociative identity disorder and healthy controls,
the sizes of the amygdala and the hippocampus were
diminished in a dissociative group (Vermetten et al.,
2006).
The first hypothesis of this study was that there would
be rCBF differences among patients with dissociative
identity disorder compared with normal controls. The
second hypothesis was that there would be diminished
perfusion rates in orbitofrontal regions bilaterally.
Findings of a previous study (Sar et al., 2001) and theo-
retical considerations concerning neurodevelopmental
consequences of childhood traumatization (Shore, 1996;
Forrest, 2001) led us to these hypotheses.
2. Methods
2.1. Participants
Twenty-one patients (14 women and 7 men) who
fully met the DSM-IV (American Psychiatric Associa-
tion, 1994) criteria for dissociative identity disorder and
nine healthy volunteers (6 women and 3 men) who did
not have any childhood trauma history participated in
the study. All cases were patients in the Dissociative
Disorders Program at the Department of Psychiatry,
Istanbul Medical Faculty Hospital, Istanbul University.
Written informed consent was obtained from all subjects
after the procedures had been fully explained. All
patients were right handed. None of the participants had
any physical disorder. All patients were drug-free for at
least 1 month.
In all patients, intra-interview switching of person-
ality states and dissociative amnesia had been observed
clinically several times. Beside clinical examinations
by a senior psychiatrist (V.S.) with extensive clinical
and research experience in general psychiatry and in
dissociative disorders specifically, all patients were
evaluated using the Structured Clinical Interview for
Dissociative Disorders (SCID-D) (Steinberg, 1994)
and the Dissociative Experiences Scale (Bernstein and
Putnam, 1986). Fifteen patients were assessed using
the Clinician-Administered Dissociative State Scale
(CADSS) (Bremner et al., 1998) and the Hamilton
Depression Scale (Williams, 1978) as well. Childhood
218 V. Sar et al. / Psychiatry Research: Neuroimaging 156 (2007) 217–223