![]() Standard pulse oximetry cannot differentiate between carboxyhaemoglobin and oxyhaemoglobin. Non-smokers may have up to 3% carboxyhaemoglobin whilst smokers may have levels significantly higher at 10%. Cerebellar abnormalities in CO-poisoned patients are rare, and in one study that examined variables predictive of subsequent adverse outcomes, cerebellar abnormalities on presentation were associated with an increased risk of cognitive sequelae at 6 weeks. ![]() ![]() These lesions are microscopically necrotic and are foci of necrosis or demyelination. Anatomical studies undertaken on brains of CO poisoned patients have shown abnormalities in the globus pallidus, other basal ganglia structures, hippocampus, cortex and cerebellum. The restricted diffusion seen in our patient’s cerebellum may have been caused by ischaemia. Magnetic resonance imaging (MRI) can reveal abnormal findings in CO-poisoned patients and is more sensitive than CT for their detection. Initial CT brain imaging was unremarkable. As the duration of unconsciousness was unknown, brain imaging was undertaken after arterial blood gas analysis confirmed CO exposure. Our patient presented in an unconscious state with no focal signs on examination. Examination is usually unremarkable but may show subtle cognitive disturbance. Symptoms of poisoning are non-specific and vary from mild constitutional upset to coma, myocardial ischaemia and death. Sources of CO include inadequate ventilation of appliances, faulty heating equipment and engine motors. Subsequent electroencephalogram (EEG) was unremarkable but importantly was undertaken 3 days post presentation.Ĭarbon monoxide (CO) is a colourless, odourless, tasteless and non-irritant gas. This pattern has only rarely been reported in CO poisoning and usually MRI was not undertaken in the acute setting. Subsequent collateral history was suggestive of a complex partial seizure disorder as the cause of her initial collapse family members recounted multiple episodes of behavioural arrest, altered consciousness and mutism in the past.Īn MRI was performed 17 h post admission and revealed bilateral symmetrical restricted diffusion in the white matter of the cerebellar hemispheres (Figure 1). She made a prompt recovery and was extubated 8 h later. ![]() She was transferred to the intensive care unit and maintained on 100% oxygen. A diagnosis of encephalopathy secondary to CO poisoning was made. She was intubated and ventilated, and an emergent CT of the brain was reported as normal. Electrocardiogram revealed no features of ischaemia and cardiac enzyme levels were normal. Co-oximetry of a blood gas sample showed a carboxyhaemoglobin level of 26%. The rest of the examination was unremarkable. Neurological examination revealed equal and reactive pupils in the midline with no focal abnormalities. The duration of unconsciousness was unknown. Vital signs were recorded as a pulse rate of 78 beats per minute, temperature of 35☌, blood pressure of 110/68 mmHg and a respiratory rate of 18 breaths per minute, with oxygen saturations as assessed by pulse oximetry of 98%. The Glasgow Coma Scale score on arrival to the emergency department was 3/15. A 78-year-old lady was brought to the emergency department, having been found unconscious next to a running lawnmower. ![]()
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