TOC  | Neuro

REF: Cleveland Clinic J of Med   April 2002;69:329 Norman M Mann  

Drugs that can cause impaired smell or taste

• Antidepressants & anticonvulsants:
  amitriptyline, carbamazepine, clomipramine, clozapine, desipramine, doxepin, fluoxetine, imipramine, lithium, phenytoin, trifluoperazine

• Antihistamines & cold medications:
  chlorpheniramine, loratadine, pseudoephedrine, terfenadine

• Antihypertensives & cardiac medications:
  acetazolamine, adenosine, amiloride, benazepril & hydrochlorothiazide, betaxoloo, captopril, clonidine, diltiazem, enalapril, ethacrynic acid, nifedipine, propranolol, spironolactone

• Anti-inflammatories:
  auronofin, colchicine, dexamethasone, diclofenac, dimethyl sulfoxide, fgold, hydrocortisone, d=penicillamine penicillamine

• Antimicrobials:
  ampicillin, ciprofloxacin, clarithromycin, ofloxacin, streptomycin, tetracyclines

• Antineoplastics:
  cisplatin, doxorubicin, methotrexate, vincristine

• Bronchodilators & other asthma medications:
  albuterol, cromolyn Na, flunisolide, metaproterenol, terbutaline

• Lipid-lowering drugs:
  cholestyramine, clofigrate, fluvastatin, gemfibrozil, lovastatin, pravastatin

• Muscle relaxants & drugs for parkinsonism:
  baclofen, dantrolene, levodopa

• Radiation therapy: radiation of the head

• Vasodilators:
  dipyridamole, nitroglycerin pattch

Types of Smell Impairment:    (Normosomia is the name given to normal smell.)

• Hyposmia - diminished sense of smell

• Parosmia - aberrant odor perception, either without an odor stimulus (phantosmia) or with an odor stimulus (distortion)

• Anosmia - total loss of smell

Loss of smell can be the result of either mechanical obstruction of or neurologic damage to the nasal cavity, the neuroepithelium in the nasal canal, or the central olfactory elements.

Some of the Causes of Smell Impairment:

• Drugs - see above drugs that impair smell & taste.

• Rhinitis

• Viral infection that damages peripheral olfactory receptors & neural pathways to the brain.

• Head trauma

• Nasal polyps or tumors

• Endocrine conditions as diabetes, hypothyroidism, & hypogonadism.

• Aging - almost everyone has some type of smell impairment by age 60 or 70, hald of those in their 80s are anosmic.

• Environmental toxins - as arsenic, benzene, carbon disulfide, cadmium, sulfur dioxide, chlorine, chronimium fumes, & cigarette smoke.

• Neurologic diseases:  Parkinsonism, Temporal lobe epilepsy

• Psychiatric conditions

• Congenital defects

• Autoimmune disorders as Sjogren syndrome.

Smell Testing:

• Simple office smell test with chocolate, coffee, or perfume.

• The UPSIT (U of Penn Smell Identification Test - Sensonics. Inc.)

• Brain or MRI of brain, sinuses & nose are often required.

Treatment of Impaired Smell

• Treat & correct the underlying problem.

• Drugs: topical nasal corticosteroids for nasal disorders

• Antibiotics, decongestans, antihistamines for rhinitis or sinusitis as indicated.

• Surgery: endoscopic nasal & sinus surgery as indicated.

• Reassurance & Clonazepam, gabapentin may be helpful when no cause is found.

Taste Impairment         (Normogeusia - normal taste)

• Hypogeusia - diminished taste

• Dysgeusia - distorted taste

• Aliageusia - altered taste, usually plesant

• Phantogeusia - persistent abnormal taste in the absence of a stijulus

• Ageusia - no taste  (rare)

The taste system detects sweet, sour, bitter, & salty qualities & protects us from ingesting possibly harmful substances.
Taste receotir cekks are found in the taste buds in the mouth, throat, larynx, & esophagus.  Four different cranial nerves (the V, VII, IX, & X nerves) provide the sensory coverage of the tongue & mouth.  THe V Trigeminal nerve is responsible for dtecting the burning sensation caused by peppers & ammonia.  Taste stimulants require salivary secretion to get to the taste buds.

Causes of taste dysfunction

• Aging

• Drugs & metal exposure or pesticide exposure

• Inflammation in the mouth

• Infection that reduces blood flow to the tongue & interferes with saliva production & leads to injury of cell receptos

• Gastroesophageal Reflux GERD (common cause)

• Systemic conditions such as diabetes, Sjogren syndrome, pernicious anemia, & Crohn disease

• Trauma of head

• Surgical procedures & Radiation treatment

Taste Testing

• Whole-mouth taste test to evaluate the intensity of different concentrations of sweet, sour, salty, & bitter taste solutions.  Flavor can be enhanced by monosodium glutamate.

• Spatial taste test to assess different areas of the mouth.  A cotton swab dipped in a special taste solution is placed in different areas of the mouth.

• Flavor discrimination test to evaluate the combination of both taste & smell sensation with four different solution with a different degree of sweetness.

• Electrogustometry with weak electrical currents

• Somatosensory testing to measure contact detection & spatial acuity thresholds with Semmes-Weinstein monofilaments.

Treatment of Impaired Taste

• Treat underlying causes.

• Dental therapy & antibiotics for mouth infection.  Clotrimazole troches for any mouth candidiasis.

• GERD anti-acid treatment as indicated

• Elimination of the offending drugs or chemicals.

• Tricyclic antidepressants & Clonazepam can be helpful in cases of dysgeusia & burning mouth disorder ( a condition most prevalentin post-minopausal women).

• Referral to A Smell & Taste Center as UCSD Nasal Dysfunction Clinic, San Diego, California

12122002