Sudden sensorineural olfactory loss: a structured narrative review and proposal for a standardised terminological...

Sudden loss of smell - particularly when sensorineural in origin - is a clinically disabling condition that the medical community has never adequately named. Patients presenting with acute olfactory loss encounter a field without shared definitions, dedicated ICD codes, or guidelines built around their specific presentation. The consequence is diagnostic delay, terminological inconsistency in the literature, and a research base that cannot be meaningfully synthesised.

This paper reviews the evidence on sudden sensorineural olfactory loss, demonstrates that existing terminology is inadequate, and proposes a single new clinical term: Sudden Sensorineural Olfactory Loss (SSNOL). Two descriptive aetiological categories are introduced solely to guide future research, not as additional terminology.

A structured narrative review was conducted using PubMed, Embase, and Scopus databases. Studies were selected based on relevance to sudden olfactory dysfunction, neural pathway mechanisms, diagnostic imaging, and clinical management. Both primary research articles and systematic reviews published between 2000 and 2024 were considered.

The evidence describes a condition with serious, sometimes permanent neural consequences. Post-viral olfactory loss - which received relatively limited specialist attention before the COVID-19 pandemic - was suddenly experienced by hundreds of millions of people, exposing how poorly the field was equipped to respond. Diagnostic tools are blunt. Treatment options are thin. Olfactory training is the only intervention with consistent evidence behind it. None of this will improve without better terminology to organise research around.

We propose the term "Sudden Sensorineural Olfactory Loss" (SSNOL) as the sole terminological contribution of this paper, modelled on the established precedent of sudden sensorineural hearing loss (SSNHL). To guide future research, two descriptive aetiological categories are described - SSNOL-Viral and SSNOL-Idiopathic - presented as hypothesis-generating models to support future research design. Traumatic olfactory loss is explicitly excluded from the SSNOL definition and should be managed under existing post-traumatic frameworks.