What treatment options are available for persistent anosmia 2 years after COVID-19 infection?

From the Guidelines

Olfactory training should be the primary treatment approach for persistent anosmia 2 years after COVID-19 infection, as it has shown benefit in improving olfactory function. According to the ESCMID rapid guidelines for assessment and management of long COVID 1, olfactory training has been consistently shown to be effective in managing postinfectious olfactory dysfunction, including COVID-19-related anosmia.

Key aspects of olfactory training include:

• Performing the training twice daily for at least 3-6 months
• Using four distinct scents like rose, eucalyptus, lemon, and clove
• Sniffing each scent for 15-20 seconds while focusing on memory recall of the smell

Other treatment options that may be considered include:

• Intranasal corticosteroids, such as mometasone furoate, although a low-quality RCT found no difference in rates of olfactory recovery when combined with olfactory training 1
• Oral supplements like alpha-lipoic acid, which has been suggested as a potential therapy, although more research is needed
• Insulin fast-dissolving film for intranasal delivery, which has shown promise in a small, low-quality RCT 1

It is essential to note that the evidence for these treatments is limited, and consultation with an ENT specialist or smell disorder clinic is recommended to discuss individualized treatment options and potential experimental therapies. Recovery from anosmia can be slow and partial, and patients should maintain realistic expectations while continuing treatment efforts.

From the Research

Treatment Options for Persistent Anosmia

• There are several treatment options available for persistent anosmia 2 years after COVID-19 infection, including:
  • Oral corticosteroids and olfactory training, which have been shown to be safe and potentially beneficial in helping patients recover from olfactory loss due to COVID-19 2
  • Olfactory training alone, which has been found to be effective in improving olfactory function in some patients 3
  • Co-ultramicronized palmitoylethanolamide with luteolin (um-PEA-LUT), an anti-neuroinflammatory supplement, which has been shown to be effective in improving olfactory function when used alone or in combination with olfactory training 3
  • Nasal irrigation with intranasal steroid/mucolytic/decongestant solution, which has been found to be potentially effective in improving olfactory function, although the evidence is very uncertain 4

Mechanisms of Anosmia

• The mechanisms of COVID-19-induced anosmia are not fully understood, but may involve:
  • Inflammation of the olfactory clefts and damage to the olfactory epithelium or olfactory central nervous system by SARS-CoV-2 5
  • Dysautonomia, which can lead to an augmentation in the resistance to cerebrospinal fluid outflow by the cribriform plate, and further causing congestion of the glymphatic system with subsequent toxic build-up in the brain 6
  • Neurotropism of SARS-CoV-2, which can lead to neuroinflammation and neuronal excitotoxicity 6

Prognosis and Recovery

• Most patients with COVID-19-induced anosmia can fully or partially recover their olfactory function for varying durations 5
• The recovery of olfactory function can be influenced by various factors, including the severity of the COVID-19 infection, the presence of underlying diseases, and the effectiveness of treatment 5
• Some patients may experience persistent anosmia, which can be associated with dysautonomia and other neurological symptoms 6