15th August 2024

You are asked to review a patient on the ward whose consciousness level has remained low for several days

You are asked to review a patient on the ward whose consciousness level has remained low for several days. She is an 84-year-old lady who was admitted with presumed hypoactive delirium secondary to an E. coli urinary tract infection and subsequent bacteraemia. This has been treated with targeted antibiotic therapy, but her conscious level has failed to improve.

Her medical background includes moderate Alzheimer’s dementia, for which she is on donepezil. Other medications include amlodipine, ramipril, mirabegron, and paracetamol, as required.

Recent blood tests show no focal abnormality, with the exception of a chronic normocytic anaemia. Her inflammatory markers have normalised. Her HbA1c is 54 mmol/mol. The observations are notable only for a tachycardia of 119 bpm.

On examination, her GCS is E1V1M4, but she is protecting her own airway. There are no added airway sounds, the chest is clear, and the heart sounds are normal. The abdomen is soft. You note that there is sustained leftward deviation of gaze. The F1 doctor reports that she has also noted some leftward nystagmus on previous examination.

Which is the single most diagnostic investigation?

Select the SINGLE most appropriate option from the list below. Select ONE option only.