Disturbances of olfaction and their causes

1. Big picture

Olfaction is clinically important because smell disturbance may be a simple ENT problem such as rhinitis, but it can also be the first clue to head trauma, basal skull fracture, frontal/olfactory groove tumor, temporal lobe epilepsy, herpes simplex encephalitis, Parkinson disease, or dementia.

For the exam, the key is not to list every rare cause, but to answer three questions:

1. What type of smell disturbance is present?

2. Is it peripheral/nasal, olfactory nerve/bulb/tract, or cortical/temporal?

3. Is there a dangerous cause: trauma with cerebrospinal fluid leak, tumor, encephalitis, seizure, or neurodegeneration?