Background: I'm a doctor with 3 years experience in acute medicine. AMA
Clearing some MRI misconceptions: 1. It's indicated ASAP in specific emergencies and will change how we manage them. For acute ischaemic stroke, it detects patients within the recomended time window for thrombolysis. Simply, it shows the cellular swelling in the brain, gives an estimate of the onset and we decide the risk/benefits of dissolving the clot. Second use, for cauda equina syndrome. Again we're looking for acute CNS tissue damage, this time from spinal chord compression, and the change in management is emergency neurosurgery (good luck getting them out of bed without an MRI) For herpes encephalitis, MRI is debatable because you can start empiric treatment. But I've seen it done.
Another misconception for the first use scenario in stroke. The MRI sequences we're interested in only take 1-3min and CT doesn't help us. But in my experience the whole scan takes 2h to organize, so point of care MRI is a game changer. Every minute counts when you're saving brain tissue. And Lower definition with artifacts are acceptable because you're looking for gross changes in a critically unwell patient.
Bonus: A report from when I managed my first suspected stroke as a junior doctor.
"49yo lady day 1 post op for total knee replacement (elective admission). Commorbidities of hypertension, obesity and osteoarthritis. She was just started on apixaban and gabapentin as per protocol, when I was asked to see her for new onset upper limb bilateral tremor.
On examining her I found the symptoms had started 1h ago. She was presenting bilateral upper limb ataxia as well, reflexes were reduced on the left and there was numbness corresponding to C4 dermatome. At this point I was worried about acute stroke whithin the 4h window for thrombolysis. I discussed the case with the acute stroke consultant and examined the patient with him. We requested an MRI brain to assess for acute posterior circulation stroke, because he thought time of onset was unclear (as per WAKE-UP protocol). I acompanied the patient to neuroradiology services. The MRI sequences we were most interested was DWI and FLAIR which only took a few minutes. We quickly scanned through the images noting there were was no DWI-FlAir mismatched high intensity signal areas within the brain parenchyma. This allowed us to rule out acute ischaemic stroke.
6h later the symptoms subsided and I was satisfied they were due to an adverse reaction to gabapentin."