A) aneurysmal SAH
B) nonaneurysmal SAH
The objective of this question is to highlight the importance of history taking in ICU - unfortunately, a lost art! Persistent anosmia is common after subarachnoid hemorrhage (SAH), but it provides a clue that SAH was probably aneurysmal. Persistent anosmia is 3-5 times more common after aneurysmal than nonaneurysmal SAH.
There could be many CNS or non-CNS related causes for persistent anosmia. CNS reasons include neurodegenerative diseases such as Alzheimer's, Parkinson's, dementia with Lewy bodies, ischemia to any component of the central olfactory pathway, Kallmann syndrome, idiopathic intracranial hypertension, multiple sclerosis (MS), and tumors.
COVID-19 has so far shown transient anosmia though news channels have reported anecdotal cases of persistent anosmia.
1. Greebe P, Rinkel GJ, Algra A. Anosmia after perimesencephalic nonaneurysmal hemorrhage. Stroke 2009; 40:2885.
2. Wermer MJ, Donswijk M, Greebe P, et al. Anosmia after aneurysmal subarachnoid hemorrhage. Neurosurgery 2007; 61:918.