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Chronic CO Poisoning:


Pet Scan - Neuropsychological Evaluation Study:

Title:
Quantitative PET scan findings in carbon monoxide poisoning: Deficits seen in a matched pair

Authors:
Pinkston, J.B., Wu, J.C., Gouvier, W.D., Varney, N.R.

Date:
2000

Journal:
Arch. Clin. Neuropsychology, 15 (6), pgs. 545-553.

Abstract:
BACKGROUND: Quantitative positron emission tomography (PET) was utilized to establish the degree and localization of central nervous system dysfunction in 2 adult patients, 3 years status post-chronic carbon monoxide poisoning.

METHODS: The individual PET scans were compared against a composite scan made up of 32 normals using a 2 transform statistical parametric map.

RESULTS: neuropsychological findings indicated marked anterior frontal lobe syndrome in the context of far-above-average intelligence, memory, and language. They also showed manifest frontal symptoms in activities of daily living that resulted in vocational disability in each case. PET analysis revealed substantially decreased metabolism in the orbitofrontal and dorsolateral prefrontal cortex as well as in areas of the temporal lobe for each individual. Individual scans were very similar and consistent with patient's presenting symptoms, and changed life circumtances.

CONCLUSIONS: This report represents the first quantitative functional neuroimaging study relevant to carbon monoxide poisoning.

Location of Authors:
Louisiana State University; University of California at Irvine, & Veteran's Administration Medical Center. James B. Pinkston, 236 Audubon Hall, Department of Psychology, Louisiana State University, Baton Rouge, LA 70803-5501


More on Results:

This study involves what the author's claim is a "matched pair" of subjects, who experienced CO exposure for 3 years (ie. chronic). They were found to have abnormal PET (Positron Emission Tomography) 3 years after the CO exposure ended. The report indicates that the neuropsychological deficits and PET imaging abnormalities were nearly identical for the two subjects.

Both subjects were right-handed, middle-aged people, married to one another many years. The man was a head architect and the woman a head accountant. Neither had any significant psychological or neurological history. They were exposed to CO (of unstated concentration) for a period of 3 years in their home, where at least one of the victims (man - Mr.) worked. The CO source was faulty furnace exhaust ducting.

Mr. and Mrs. had neuropsychological testing 3-times over 3 years, ie. serial testing. The tests included the Wechsler Adult Intelligence Scale, Wechsler Memory Scale, Benton Visual Retention Test, Tinker-Toy Test, Wide Range Achievement Test-revised, Dichotic Listening, etc. PET imaging was carried out after the last neuropsychological evaluation, ie. 3 years after CO had ended. Each subject was given 5 mCi Fluorine-18-deoxyglucose (FDG) intravenously.

Mr. scored 132 in I.Q., while Mrs. scored 145. Both CO victims were found to have an "anterior frontal lobe syndrome". This was characterized by indecisiveness, mental passivity, and disorganization (a vocational disability). Mr., the architect, performed very poorly on the Tinker-Toy Test, a test he should have excelled at based on his training and profession.

Table 1. Areas of Hyper- and Hypo-metabolism in CO Victims Mr. and Ms as revealed by PET scanning.

Mr. - Metab. Decrease Mr. - Metab. Increase . Ms. - Metab. Decrease Ms. - Metab. Increase
Orbitofrontal Cortex, bilat.
Dorsolateral Prefrontal Cortex
Inferior Temporal Gyrus
Temporal Tips
Hippocampus
Visual Cortex
Frontal Eye Fields
Ventrolateral Prefrontal Cortex
Superior Parietal Lobule
Inferior Parietal Lobule
Thalamic Metabolism, bilateral
Basal Ganglia (caudate, putamen, globus pallidus)
Frontal Pole
Somatosensory Cortex
Motor Cortex
. Orbitofrontal Cortex
Dorsolateral Prefrontal Cortex
Inferior Temporal Gyrus
Temporal Tips
Hippocampus
Visual Cortex
Amygdala
Middle Temporal Gyrus
Dorsal Thalamus
Cerebellum
Somatosensory Cortex
Inferior Parietal Lobe


Limitations / Weaknesses of the Study

  • No air or blood carbon monoxide values are given during the exposure period. We don't know how severe the CO exposure was, when it occurred, etc. From a toxicologic point of view (ie. dose-response relationship) this is an enormous deficiency in understanding what happened.
  • No EEG, CT, MRI, or SPECT data are given; eg. the authors missed a splendid opportunity to show that PET picks up damage from CO, while CT, MRI, etc. usually does not.
  • The medical history is missing; assurance of no traumatic head injury is lacking
  • Testing of memory did not use the best testing tools available.
  • No physical or emotional residual symptoms/effects were provided in the report; it is virtuallly a certainty that some were elicited.
  • No Index scores were provided in the report.


    From: Pinkston, J.B., Wu, J.C., Gouvier, W.D., Varney, N.R. (2000) Quantitative PET scan findings in carbon monoxide poisoning: Deficits seen in a matched pair. Arch. Clin. Neuropsychol., 15, 545-553.



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