Academic journal article Environmental Health Perspectives

MRI and Neuropsychological Correlates of Carbon Monoxide Exposure: A Case Report. (Grand Rounds in Environmental Medicine)

Academic journal article Environmental Health Perspectives

MRI and Neuropsychological Correlates of Carbon Monoxide Exposure: A Case Report. (Grand Rounds in Environmental Medicine)

Article excerpt

A 45-year-old woman experienced long-term, chronic exposure to carbon monoxide in the restaurant kitchen where she was employed as a cook. After returning to the restaurant after 5 days off work, she noticed that her symptoms returned immediately; she then aired out the room and called the gas company. Approximately 6 hr after a leak was detected, the patient went to the hospital, where her carboxyhemoglobin was found to be within normal Emits and results of a neurologic examination were described as normal. Based on her symptoms, the patient believed she had been exposed to CO for at least 1 year before the leak was discovered. Initially, she experienced flu-like symptoms, which eventually resolved. At the time of her first neuropsychological evaluation (17 months after the exposure was identified), her persisting complaints included difficulties in reading, writing, speaking and word retrieval. The test results were consistent with secondary frontal lobe dysfunction associated with subcortical disorders such as those seen after CO exposure. Results of a subsequent neuropsychological examination (29 months postexpnsure) showed slight improvement in performance, but her performance was still consistent with mild frontal/subcortical dysfunction. Although the initial screening of a brain magnetic resonance image (MRI) performed 15 months after the exposure was interpreted as being within normal limits, two subsequent blind reviews of the same scans identified multiple bilateral lesions in the basal ganglia, which were consistent with chronic CO exposure. We present this case as an example of the utility of MRI and neuropsychological examinations in detecting central nervous system dysfunction secondary to CO exposure. Key words: carbon monoxide, neuropsychology, toxicant-induced encephalopathy, neuroimaging, MRI, neurobehavioral methods.

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Case Presentation

A 45-year-old white, college-educated, right-handed woman was referred to the Boston University Neurology Associates Neuropsychology Service by her neurologist. She was reportedly exposed to carbon monoxide while at work in a restaurant and suffered from subsequent changes in behavior and cognition. She was referred for an evaluation to rule out CO-associated central nervous system (CNS) dysfunction. She was initially seen on 15 April 1998.

According to the patient, she discovered that she had been exposed to CO in November 1996, when she came to work early, noticed the smell of gas, and called the gas company. She said that the gas company employee informed her that there were extremely high levels of CO in the kitchen where she worked as a restaurant cook. The patient went to the hospital approximately 6 hr after leaving her workplace on the day she called for help, but, at that time, her carboxy-hemoglobin was reportedly not elevated and no focal neurologic signs were noted. She explained that she had been off work for 5 days and, immediately upon arriving at work the morning the leak was detected, she sought fresh air and did not have further exposure. The restaurant was then closed for 2 weeks so the furnace, which was the source of the CO fumes, could be replaced. The patient believed that CO had been leaking into her workplace for at least a year, given the duration of her symptoms.

We were unable to obtain a copy of the gas company reports on levels taken on the day that the leak was identified (the company refused to release them to us). Because no records were available on the levels of CO before the gas leak was identified, it was impossible to model the apparent chronic, long-term exposure to CO experienced by the patient. However, correspondence in the medical record and communication with the insurance company for the building in which the exposure occurred documented the existence of exposure.

The patient was not certain when her symptoms began, but she said that they peaked in January-April 1996. …

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