Cognitive impairment and parkinsonism as a manifestation of delayed neuropsychological sequelae after carbon monoxide poisoning: a case report

We report a case of delayed neuropsychological sequelae manifesting as cognitive impairment and parkinsonism in a 72-year-old woman who attempted suicide by carbon monoxide poisoning 20 years earlier. was admitted after a fall-related traumatic brain injury resulting in bilateral sub-dural haemorrhages and seizures. She had hypertension, hyperlipidaemia, and depression. She had undergone mastectomy for right breast cancer 20 years earlier. She needed assistance in all instrumental activities of daily living (IADLs) and most basic ADLs. She had deficits in all six of the neurocognitive domains, with severe executive dysfunction, impaired language with paucity of spontaneous speech, and impaired memory and attention for 10 years. She was apathetic with low mood. Notably, in her early 50s, she had attempted suicide by CO poisoning and required mechanical ventilation for 10 days, after which her cognitive and functional deficits developed. Examination revealed features of parkinsonism with hypomimia, bilateral cogwheeling and lead-pipe rigidity of the upper limbs, generalised bradykinesia, and slow gait with decreased arm swing. Her abbreviated mental test score was 8/10. Her mini-mental state examination score was 22/30, with impairments in orientation and visuospatial tasks and unimpaired three-item recall. Her Geriatric Depression scale score was 11/15. She had vitamin B12 deficiency (<111 pmol/L) [normal range, 145-637 pmol/L) and was administered vitamin B12 replacement. Test results of and profiles, thyroid