Smell training after a brain injury - Specialist Nutrition Rehab

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26 Oct 2021

Smell training after a brain injury

Are you screening your clients with a brain injury, for changes to their sense of smell and “taste”?  If you do identify a change or deficit, what strategies are you offering clients in order to help them cope or even help to improve their sense of smell?

Up to 66% of people after a traumatic brain injury, have an olfactory impairment.1,2 The most common impairments are:

  • anosmia – no sense of smell
  • hyposmia – a reduce sense of smell

Many clients (over 50%!) are unaware of these changes/deficits to their sense of smell, and yet the impact of smell loss on quality of life is significant.2  Smell loss can negatively affect the pleasure from eating and drinking (as well as the food choices people make), mood, relationships and can also impact personal safety (eg. inability to smell gas or a fire) and personal hygiene.2.

Complaints of “tasteless” or “bland” food can be a good clue that smell loss may be a problem.  Most people don’t realise that the majority of the flavour from food actually comes from smell molecules going up the back of the throat into your nose (called retronasal smell).  That means food lacking in flavour generally relates more to a diminished sense of smell, versus a problem with taste buds (which only detect sweet/sour/salty/bitter/umami).  Changes to the true sense of taste after a brain injury, is much less common and only happens in about 19% of cases.3

If smell loss is identified, then smell training is one of the key strategies used try and improve smell function.

 

What is smell training?

Smell training is a bit like “physio for the nose,” and involves smelling four different odours twice daily for 4-6 months.4  Usually one odour is used from each of the following categories: flowery, fruity, spicy and resinous and the majority of research has been done on using the scents from rose, eucalyptus, lemon, and cloves. 4   Smell training isn’t limited to these four smells however, and research suggests that varying the odours every 12 weeks can produce better outcomes.5  You want to avoid using odours which also stimulate non-olfactory nerves, such as onion, alcohol, mint/menthol and chilli.6

Smell training is certainly worth trying, because it is a low cost therapy (under £50) which can be done at home and takes only 2-4 minutes per day.   Clients can either make their own smell training kits (see below) or pre-made smell kits can be purchased directly from the charity Abscent.

 

How smell training can help

The olfactory system has incredible neural plasticity and ability to regenerate, which explains why smell training can be successful. 4,7

Smell training has been found to significantly improve smell function in up to 36% of people with post-traumatic olfactory impairment within eight months.1   The success rate in this population jumps to 50%, when the smell training is combined with a short course of corticosteroids(7), although this isn’t routinely recommended due to the risks associated with that medication.8  Smell training has been shown to be even more effective (up to 68%), if the smell loss is non-traumatic and due to an infection or virus instead.9  The reason people respond differently to smell training, is because brain injuries can result in damage to the olfactory nerve fibers (eg. shearing) or olfactory cortex, whereas smell loss due to a virus or infection does not always damage the nerve fibres or brain in the same way.1

 

Additional information and resources

For additional resources on smell training, how to make your own smell training kit and general considerations for smell loss, check out:

  • Abscent – a charity dedicated to helping people with smell loss
  • Fifth Sense – a charity dedicated to helping people with smell loss
  • For a pictorial, step-by-step guide for making your own smell training kit, get in touch with us at info@specialistnutritionrehab.co.uk.
  • For dietary strategies that increase the pleasure from eating following smell loss, CLICK HERE to read our previous blog post on this topic.
  • Brief Questionnaire on Olfactory Disorders (which rates the impact of smell loss on quality of life — see link under “supplementary material”).

The dietitians at Specialist Nutrition Rehab, specialise in helping clients with smell and taste impairments following a brain injury, spinal cord injury or complex orthopaedic trauma.  To make a referral or for more information, contact us at: 0121 384 7087 or info@specialistnutritionrehab.co.uk.

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