The Lack of Smell
Many patients present with a loss of smell. The majority present after the loss of existing sense of smell went away. Some of these can be attributed to blockage (polyps, infection, tumors, etc), some to destruction (infection, toxin, etc), some to metabolic disorders (diabetes, thyroid, etc) and there are those that are inherited, life-long disorders. All lead to risk (can not smell spoiled food, can not detect smoke, etc) or decreased quality of life (effect on taste and smell, lack of perception of subtle smells in environment, etc). Many do not find it of importance to be pursued. I would argue that any change of physiology that is noted and persists should be examined. It may not be of life-threatening concern (nasal cancer for example) but it can certainly be examined and considered – we all know the adage, early detection equals early cure. Late stage anything is bad to find.
What about those born without smell. Well a recently published and interesting article discussed this. Those who are born without a sense of smell (called hyposmia) can be divided into two groups. One group, called Type I, have genetic abnormalities that show up in brain, gonadal and other somatic (body) abnormalities. These individuals will typically have a family history of smell disorders. Another group, Type II patients don’t have a family history of smell loss nor any somatic abnormalities and lack the family history. In general, it is reported that 12% of individuals born without a sense of smell are type I and 88% type II. It is interesting that both have a similar degrees of loss of smell.
When examining the patient who presents with a complaint of loss of smell it is important to elicit any history of nasal or systemic disease, head injury or any pathology which contributed to their smell loss. It is also important to learn if the patient was the result of a normal pregnancy and delivery and normal developmental milestones. Learning of a loss of smell function is usually a gradual discovery, with most reporting learning this around age 9–12 years. Generally discovered after noting others are able to notice and respond to odors they could not.
Evaluating patients is critical to learn more. Evaluation should include an extensive history, physical examination of their head and neck, measurements of of smell and taste, laboratory studies of blood, urine, saliva and nasal mucus as well as radiology exams.
If there are not found anatomical, infectious, neoplastic, or other disorders as cause, and it is thought to be possibly inherited, some have tried pharmacological therapies. Response to theophylline has been shown. Theophylline can lead to onset of side effects which vary from mild symptoms of irritability to more severe symptoms of sleep disturbance, tachycardia (fast heart rate) and gastrointestinal discomfort. Use of this agent can be dangerous and must be considered with caution.
Theophylline is a long known drug and belongs to the class of drugs known as methylxanthines. It has been used for over 100 years! Olfactory receptors are interesting. They have neither blood vessels nor lymphatics and do not exhibit mitosis (nuclear division). The olfactory system is dependent on stem cell regeneration to grow receptors. Growth factors are critical to this process. Theophylline may play a role in this.
You can learn more about this topic by looking to this article:
American Journal of Otolaryngology
Vol 37, Issue 3 May-June 2016 pages 175-181
Initiation of Smell Function in Patients with Congenital Hyposmia
If you have any questions regarding disorders of ear, nose, throat, cancer, thyroid / parathyroid, please do not hesitate to call. ENT is trained in 7 core areas during a 5 year residency after medical school inclluding allergy, facial plastic and reconstructive surgery, head and neck, laryngology, otology, pediatric otolaryngology, and rhinology. We are the only surgical specialty dedicated solely to this area above the clavicles.
Philip Harris, M.D. FACS MidMichigan Physicians Group Midland / Gladwin / Bay City Phone (989) 839-6201 www.midmichigan.org/mpg