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 187-2); 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
Attention deficit/hyperactivity disorder
Chronic obstructive pulmonary disease
Frontotemporal lobe degeneration
Gonadal dysgenesis (Turner’s syndrome)
Guamanian ALS/PD/dementia syndrome
Herpes simplex encephalitis
Narcolepsy with cataplexy
Obsessive compulsive disorder
Obstructive pulmonary disease
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
- 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.
- A nonblinded study reported that pts with hyposmia may benefit from smelling strong odors before going to bed and upon awakening over the course of several months.