Atypical Parkinsonism following Occult Carbon Monoxide Exposure (P5.254)

OBJECTIVE: To describe a case of occult carbon monoxide poisoning presenting as Parkinsonism and neuropsychiatric symptoms. BACKGROUND: Carbon monoxide (CO) gas is a leading cause of death and injury due to poisoning worldwide. CO impairs hemoglobin oxygen carrying capacity and causes hypoxic injury in vulnerable tissues in the nervous system and myocardium. Acutely, CO poisoning can manifest as headache, nausea, dizziness, seizures, coma, and myocardial infarction. However, delayed neurologic manifestations, including parkinsonism, akinetic mutism, cognitive impairment, and personality changes, can occur many weeks after the initial exposure. DESIGN/METHODS: Case report RESULTS: A 43-year-old man presented with a two week history of progressive psychomotor retardation and gait difficulties. Neurological examination revealed profound parkinsonism and neuropsychiatric abnormalities including cognitive impairment, abulia, and flattened affect. MRI demonstrated focal hyperintensities in globus pallidus and posterior limb of the internal capsule bilaterally on T1 and T2-weighted MR sequences. Arterial blood gas showed normal carboxyhemoglobin level, and serum levels of cyanide, arsenic, lead, and mercury were also normal. History revealed a suspected recent exposure to persistently elevated CO in an enclosed space. The patient was given a brief trial of carbidopa-levodopa without symptomatic improvement. Low-dose bromocriptine and modafinil were initiated with modest improvement in lethargy and concentration. Following inpatient rehabilitation and a short skilled-nursing facility stay, he achieved functional independence and returned home. At four months follow-up, he was living independently with minor cognitive impairment. By eight months, the patient had returned to full time employment. CONCLUSIONS: Carbon monoxide poisoning is a leading cause of death and injury due to poisoning worldwide, and may present insidiously with a delayed neurologic syndrome without obvious exposure history. It is important to consider CO poisoning in patients presenting with new neuropsychiatric complaints and Parkinsonism so that the causal source may be identified and removed and indicated treatment initiated. Study Supported by: not applicable Disclosure: Dr. Raja has nothing to disclose. Dr. Dutta has nothing to disclose. Dr. Kwan has nothing to disclose.