TOC  | ID |  Neurology

March 2004

KP - Head & Neck Surgery Topic of the Month: Anosmia

CC: "I can't smell"

HPI: This 54 year old gentleman presented with a complaints of decreased smell that started a few months after elective knee surgery. The patient denied any recent URI's, chronic sinusitis, head trauma, or allergy symptoms. Examination of the nasal cavity revealed healthy pink mucosa without any obstructing lesions. A CT scan of the sinuses revealed only mild mucosal swelling, and a head CT was normal.

The patient was given a trial of nasal steroids without any benefit. The patient sought evaluation at a nasal dysfunction clinic where they attributed his anosmia to a subclinical viral infection which was essentially nonreversible. He was counseled on the need for smoke and natural gas detectors, and awareness of potential food poisoning.

Diagnosis: Anosmia

CAUSES: Conductive vs. Sensorineural

CONDUCTIVE:

• § Deficit from odorants reaching olfactory epithelium
• § Most common cause of smell disorder; often treatable
• § Include: URI, nasal polyps, sinus disease, deviated nasal septum, rhinitis, tumors

SENSORINEURAL:

• § disorders of olfactory neuroepithelim or central pathways
• § usually permanent
• § post-viral olfactory dysfunction: direct viral damage to neuroepithelium
• § 5% head trauma patients have anosmia due to shearing across cribriform plate
• § manipulation of septum and osteotomies may cause shearing of olfactory nerves

OTHER CAUSES:

• § Neurologic: MS, epilepsy, Parkinson's, Alzheimer's
• § Endocrine: Kallman's syndrome, Cushing's, DM, adrenocortical insufficiency, hypothyroidism
• § Metabolic: renal failure, liver dysfunction
• § Nutritional: vitamin and mineral deficiency, Korsakoff's psychosis
• § Psychiatric: depression, schizophrenia
• § Intracranial surgeries, tumors, or infections (meningitis)
• § Drugs (ethanol, amphetamines, topical cocaine, aminoglycosides, tetracyclines, cigarette smoke), chemical exposures

CLINICAL EVALUATION

1. § History and Physical: most informative in determining site of lesion
2. § Smell disorders can usually be differentiated from taste disorders; many will note a change in taste sensation with anosmia, even with normal taste testing
3. § Evaluate for signs of nasal allergy, infection, polyps, masses, structural disorders
4. § If olfactory cleft appears normal, a sensorineural loss is diagnosed

TESTING

Standardized (scratch and sniff) or common items (coffee, ammonia, water)

• § Normosmic patient senses coffee and ammonia, not water
• § Anosmic patient senses ammonia (trigeminal stimulant), not coffee or water
• § Malingerer does not sense any, usually associated with tearing from eye

Imaging: used when no obvious cause, or if PE dictates further evaluation

• Coronal and axial head CT: details mucosal disease, structural abnormality, masses

TREATMENT

• § Depends on accurate diagnosis of the etiology involved
• § Awareness of patient's risk of food poisoning, and need for smoke and natural gas detectors

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