The purpose of this paper is to review the current evidence in diagnosing olfactory disorders and suggest an algorithmic approach to patients with relevant complaints. Age-associated olfactory loss is often multifactorial and requires a careful history and physical exam.
A table demonstrating the common causes of olfactory disorders is given describing the aetiology under the headings - obstructive / conductive (septal deviation, nasal polyposis, sinonasal neoplasms), sensorineural (ageing, post infection, neurodegenerative) delineating anatomic obstruction and mixed (CRS, sinonasal surgery, medication). MRI is helpful for further evaluation of sinonasal tumors skull-base diseases, lesions with intracranial or facial soft-tissue extension, and confirmation of agenesis of the olfactory bulb as in Kallmann syndrome. Psychophysical tests have a role in screening patients at risk for Parkinson’s and Alzheimer’s disease, but there is lack of evidence regarding timing and patient selection. Olfactory training is suggested to be an emerging modality in patients with post-infection olfactory loss. Patients with CRS may require medical management and surgical treatment for alleviation of their symptoms.
The key points are as follows:
- All patients with impaired olfaction should undergo complete nasal endoscopy and psychophysical olfactory testing.
- At present, olfactory testing cannot be used as a guide for prognostication or to direct potential therapy.
- There is no unique characteristic that can be used to predict which CRS phenotype will have the greatest improvement in olfaction after endoscopic sinus surgery.
- Olfactory training is a promising non-invasive treatment modality for improvement of post-infection hyposmia and anosmia.
- Safety counselling is an indispensable part of the treatment in patients with olfactory disorders.