OTHER CRANIAL NERVE DISORDERS

OTHER CRANIAL NERVE DISORDERS is a topic covered in the Harrison's Manual of Medicine.

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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.

TABLE 190-2: Disorders and Conditions Associated with Compromised Olfactory Function, as Measured by Olfactory Testing

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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