Juvenile nasopharyngeal angiofibroma| aetiology, diagnosis, treatment

Definition: Anosmia is complete loss of sense of small, while hyposmia is diminished sense of smell.

Causes of Anosmia and Hyposmia

Nasal:

I. Obstruction: the small particles do not reach the olfactory mucosa e.g. Deviated septum, nasal polyps and nasal synechiae.

II. Misdirection of air current (disruption of nasal aerodynamics or turbulence):

• Destruction of alae nasi e.g. granulomas and tumors.
• Aggressive removal of turbinates.

Mucous membrane changes:

• In allergic rhinitis there is excess secretions which wash out the small particles.
• In atrophic rhinitis, the mucus is too thick to dissolve the smell particles.

Interference with nerve endings:

• Degeneration of nerve endings as in atrophic rhinitis.
• Post infleunza neuritis of olfactory nerve endings.
• Diabetic neuritis
• Lead poisoning.

Intracranial:

• Congenital absence of olfactory bulbs and nerves.(rare)
• Fracture base of skull involving the anterior cranial fossa.
• Basal meningitis.
• Tumors of anterior cranial fossa e.g.: meningioma and neuroblastoma leading to compression of olfactory pathway.

Psychogenic:

Malingering: The patient will deny smell of any odor even irritant odors which stimulate trigeminal nerve (ammonia).

Tests of smell:

• Subjective: Measuring the minimum perceptible odor, Identification test.
• Objective: Olfactory evoked response.

Cacosmia:

Definition: Bad odor perceived by patient and sometimes his contacts.

Causes:

• Neglected foreign body in the nose.
• Atrophic rhinitis.
• Maxillary sinusitis especially of dental origin.

Parosmia (Hallucination of smell):

Abnormal sense of smell which is perceived by patient alone, this disorder is found in many psychiatric disorders as schizophrenia and depression.

Hyperosmia:

Increased sense of small, it is met in some psychiatric diseases or irritative lesions of olfactory bulb. It may also lead to migraine (migraine related hyposmia).

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