Harrison's Manual of Medicine
OTHER CRANIAL NERVE DISORDERS
Disorders of the Sense of Smell
Olfactory nerve (I) disorders are due to interference with access of the odorant to the olfactory neuroepithelium (transport loss), injury to receptor region (sensory loss), or damage to central olfactory pathways (neural loss). The causes of olfactory disorders are summarized in Table 190-2 ; most common other than aging are severe upper respiratory infections, head trauma, and chronic rhinosinusitis. Although more than half of people between 65 and 80 years of age suffer from olfactory dysfunction that is idiopathic (presbyosmia), it is increasingly recognized that a number of neurodegenerative disorders are accompanied by olfactory impairment. Pts often present with a complaint of loss of the sense of taste even though their taste thresholds may be within normal limits.
| 22q11 deletion syndrome AIDS/HIV infection Adenoid hypertrophy Adrenal cortical insufficiency Age Alcoholism Allergies Alzheimer’s disease Amyotrophic lateral sclerosis (ALS) Anorexia nervosa Asperger’s syndrome Ataxias Attention deficit/hyperactivity disorder Behcet’s disease Bardet-Biedl syndrome Chagas’ disease Chemical exposure Chronic obstructive pulmonary disease Congenital Cushing’s syndrome Cystic fibrosis Degenerative ataxias Depression Diabetes Down’s syndrome Epilepsy Facial paralysis Fibromyalgia Frontotemporal lobe degeneration Gonadal dysgenesis (Turner’s syndrome) Granulomatosis with Polyangiitis (Wegener’s) Guamanian ALS/PD/dementia syndrome Head trauma Herpes simplex encephalitis Hypothyroidism Huntington’s disease Iatrogenesis Idiopathic inflammatory myopathies Kallmann’s syndrome Korsakoff’s psychosis Laryngopharyngeal reflux disease Legionnaires’ disease Leprosy Liver disease Lubag disease Medications Migraine Multiple sclerosis Multi-infarct dementia Myasthenia gravis Narcolepsy with cataplexy Neoplasms, cranial/nasal Nutritional deficiencies Obstructive pulmonary disease Obesity Obsessive compulsive disorder Orthostatic tremor Panic disorder Parkinson’s disease (PD) Pick’s disease Posttraumatic stress disorder Pregnancy Pseudohypoparathyroidism Psychopathy Radiation (therapeutic, cranial) REM behavior disorder Refsum’s disease Renal failure/end-stage kidney disease Restless leg syndrome Rhinosinusitis/polyposis Schizophrenia Seasonal affective disorder Sjögren’s syndrome Stroke Systemic sclerosis Tobacco smoking Toxic chemical exposure Upper respiratory infections Usher syndrome Vitamin B12 deficiency |
Treatment: Disorders of the Sense of Smell
- Therapy for allergic rhinitis, bacterial rhinitis and sinusitis, polyps, neoplasms, and structural abnormalities of the nasal cavities is usually successful in restoring the sense of smell.
- There is no proven treatment for sensorineural olfactory losses; fortunately, spontaneous recovery can occur.
- Cases due to exposure to cigarette smoke and other airborne toxic chemicals can recover if the insult is discontinued.
- Preliminary data suggests that pts with hyposmia may benefit from repeated smelling of odors (such as eucalyptol, citronella, eugenol, and phyenyl ethyl alcohol) over weeks or months; the usual paradigm is to smell odors before going to bed and again upon awakening each day.
- The use of zinc and vitamin A is controversial, and there does not appear to be much benefit beyond replenishing established deficiencies.
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