OTHER CRANIAL NERVE DISORDERS
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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
Adrenal cortical insufficiency
Amyotrophic lateral sclerosis (ALS)
Attention deficit/hyperactivity disorder
Chronic obstructive pulmonary disease
Frontotemporal lobe degeneration
Gonadal dysgenesis (Turner’s syndrome)
Granulomatosis with Polyangiitis (Wegener’s)
Guamanian ALS/PD/dementia syndrome
Herpes simplex encephalitis
Idiopathic inflammatory myopathies
Laryngopharyngeal reflux disease
Narcolepsy with cataplexy
Obstructive pulmonary disease
Obsessive compulsive disorder
Parkinson’s disease (PD)
Posttraumatic stress disorder
Radiation (therapeutic, cranial)
REM behavior disorder
Renal failure/end-stage kidney disease
Restless leg syndrome
Seasonal affective disorder
Toxic chemical exposure
Upper respiratory infections
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.