Perfusion SPECT in Asperger Syndrome: Severe Bilateral Frontal,
Parietal and Temporal Hypoperfusion
Ne?e ?LG?N*, Nahide G?K?ORA*, K?v?lc?m G?C?YENER**
Asperger syndrome is an autistic psychopathy affecting boys predominantly and is characterised by deficits in verbal and non-verbal language, social skills, cognitive functioning and an abnormal repertoire of behaviours. Current research, however, has failed to identify the neurobiological mechanisms that underlie autism or those cortical brain regions, if any, that are abnormal. The other main characteristics of Asperger syndrome are solitariness, impaired empathy and emotional detachment, increased sensitivity at times with porous ideation. Circumscribed interest patterns and unusual styles of communication, specific developmental delays, including delays of language related skills, are much common when compared with other schizoid personality disorders and IQ is generally slightly above the average (1-3). In this case report, we present a severe bilateral frontal, parietal and temporal perfusion abnormality in a subject with Asperger syndrome. Previously right and/or left occipital hypoperfusion has been reported in Asperger syndrome (4-5).
A 21-year-old right handed male was admitted to the psychiatry unit because of affective lability, facial isolation and fame paranoid ideations. He had clumsy, tip-toe type walking and a monotonous speech with a high pitched voice. His cognitive abilities were highly developed (IQ level higher than 90) and was a graduate from the university; school of arts. He had intellectual interests such as reading science fiction, listening to classical music and painting. His motor behaviour was uncoordinated but no specific neurologic abnormality was observed other than his clumsy, small step tip-toe walking. His CT and MRI scan did not reveal any abnormality.
The patient was placed in quiet environment with an intravenous line for the injection of 15 mCi 99 m Tc-HMPAO. SPECT imaging was performed 10-30 minutes after the injection, using single heat SPECT (LEAP collimator, 360 degrees, 30 second/frame, 64x64 martix). Transaxial, sagittal and coronal images were obtained after reconstruction using a high frequency cut-off filter. The images showed a severely hypoperfused brain. Markedly abnormal bilateral frontal, parietal and temporal perfusion abnormalities were observed while perfusion was relatively spared in occipital cortex and anterior cingulate (Figure 1).
During normal development of the brain hyperfrontality develops by the age of 1 to 2 years (6). The establishment of hyperfrontality is considered to be associated with the appearance of higher cortical functions and the disappearance of primitive reflexes. Therefore, in general, the absence of hyperfrontality might reflect delay of brain functional maturation. It is well known that autism is a behaviourally defined developmental disorder that refers to individuals with deficits in social interaction, communication and imaginative play, and range of interests and activities.
In this case, the loss of hyperfrontality is accompanied by bilateral, parietal and temporal hypoperfusion. In the absence of any structural brain abnormality, these hypometabolic areas may explain the functional state or pathology around the usual association areas which may be responsible for the characteristic features in autism. Even though various regional functional disturbances in central nervous system could be observed from case to case in subjects with Asberger syndrome, regional perfusion abnormalities in higher cortical areas observed by SPECT in the absence of any anatomically defined abnormalities may be a pattern reflecting the "state" of immature brain function rather than the "trait". On the other hand, this failure to function at high level association areas in autism may be due to a main underlying biochemical "neurotransmitter specific" abnormality which may then affect the brain metabolism. Further work is warranted for the elucidation of these theories and the "state versus trait phenomenon" in explanation of the regional perfusion abnormalities in higher cortical areas observed in Asberger syndrome.
ADDRESS FOR CORRESPONDENCE:
Dr. Ne?e ?LG?N
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Bah?elievler, Ankara, TURKEY