Head and Neck Imaging

Anosmia

loss of the sense of smell. It can be classified as:

  • central (lesion of the olfactory receptor, olfactory bulb or tract, or related parts of the central nervous system);

  • peripheral (interference of access of odorants to the olfactory receptors by obstruction of the nasal cavities);

  • reflex (disease in some other part of the body); and

  • functional (no apparent causal lesion).

    Imaging techniques, such as CT and MRI, may be useful in the mapping and differential diagnosis of lesions causing central or peripheral olfactory disturbance. Common causes of peripheral olfactory disturbance are sinonasal inflammation and sinonasal tumours. Central olfactory disturbance may be secondary to head trauma (by shearing of olfactory filaments as they go through the cribriforme plate, or by contusion of the cerebral cortex, particularly the frontal and temporal lobe); Kallmanns syndrome is the most common entity causing congenital anosmia. Anosmia is also present in various degenerative neuropsychiatric disorders, and it is sometimes encountered in AIDS patients and rarely in patients with brain tumours.

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