Continuing Decline of Memory Skills with Significant Recovery of Intellectual Function Following Severe Carbon Monoxide Exposure: Clinical, Psychometric, and Neuroimaging Findings

Extensive clinical, psychometric, and neuroimaging data are presented and interpreted with regard to a 35-year-old, White male college graduate who was exposed to severe carbon monoxide (CO) poisoning. The patient was comatose for 21 days following the exposure. Several other people, who were in the same room as the patient, died due to the toxic effects of the CO. The patient was employed premorbidly as a systems level lead computer programmer. The patient received medical and neuropsychological follow-up for 3 years post-CO exposure. Neuropsychological evaluations revealed a gradual, but incomplete recovery of general intellectual function. The patient continued to exhibit severe memory deficits with some evidence for small additional memory decline over time. Characteristic and permanent vestibular and gait disturbances were also noted, along with a variety of neuropsychological deficits that improved over time with the exception of memory function. The patient also experienced significant affective and personality changes. Neuroimaging studies reveal a generalized cortical atrophy as shown by significantly enlarged ventricles and a ventricle-to-brain ratio that exceeded 4 standard deviations above the norm. The observed atrophic changes are consistent with CO-induced anoxic type injury, which was also accompanied by bilateral lesions of the globus pallidus, caudate, and hippocampus. Despite obtaining average levels of general intellectual functioning over time, significant memory impairments, depression, and personality disturbances severely impaired the patients' vocational recovery and ability to return to work.