Smell loss or anosmia can be due to many varied causes, such as acute head trauma, a severe cold, chronic sinusitis, nasal polyps, neurological conditions, and rarely tumors. An important distinguishing factor is the acuity of onset. Acute smell loss can be due to a severe upper respiratory infection or head trauma. Viruses can cause cell death of the olfactory neurons, and head trauma can shear off the olfactory nerves. Both have the potential for recovery, as olfactory nerves can regenerate, though it can take years.
A common cause of chronic smell loss is chronic sinusitis, which through inflammation can cause swelling of the sinus mucosa, and will block the path of odor molecules to the olfactory groove. Fortunately a combination of nasal topical steroids, prednisone and surgery may be able to improve smell.
Brain tumors of the olfactory groove (or anterior base of skull) can cause a gradual smell loss. These can include esthesioneuroblastoma or meningiomas – treatment would be surgical resection.
Chronic sinusitis with polyps is chronic sinusitis with more inflammation where the normal lining of the sinuses, the mucosa, becomes swollen and edematous forming small grape-like polyps. These physically block the passage of smell molecules. Surgery can help with this.
There is some data out of Stanford showing that olfactory retraining is a beneficial therapeutic option for patients with smell loss. This is a simple, cheap treatment option for patients with smell loss that Dr. Meier offers.
Josh Meier, M.D. F.A.R.S.