Post-traumatic loss of smell requires careful assessment of the accident mechanism, chronology, medical records and current function. The expert must also establish whether the claimant has genuinely lost taste, or whether reduced flavour perception is being described as taste loss.
Smell and taste should not be treated as interchangeable.
Most of what people describe as the taste of food depends on smell. Someone who can still identify sweet, salty, sour and bitter sensations may nevertheless say that food has no taste because its flavour has disappeared. True loss of taste is comparatively uncommon. UCLH guidance notes that reported taste loss is linked to impaired smell and that complete loss of taste itself is rare.
The history should therefore separate the two senses, can the claimant detect sugar or salt? Can they recognise strong odours? Is smell completely absent, reduced or distorted? Do familiar items smell unpleasant or different? Are odours perceived when none are present?
These distinctions identify different presentations. Anosmia means complete loss of smell, while hyposmia describes reduction. Parosmia is a distorted response to an odour, and phantosmia refers to the perception of a smell that is not present. A report that simply records “loss of smell and taste” leaves too much unexplained.
The mechanism must be clinically plausible.
Head trauma may affect smell in several ways, facial injury or swelling may obstruct airflow through the nose. Trauma may damage the nerve fibres passing between the nasal cavity and the brain. Contusion or haemorrhage may affect the olfactory bulbs, tracts or brain areas involved in recognising odours. International consensus guidance identifies nasal obstruction, injury to the olfactory nerves and damage to central olfactory structures as recognised mechanisms of post-traumatic impairment.
The expert should establish whether there was a direct blow to the head or face, loss of consciousness, post-traumatic amnesia, nasal injury, skull fracture or intracranial abnormality. Emergency imaging and hospital records may provide relevant evidence.
The severity of the head injury is relevant, but it does not decide the issue alone. Smell disturbance can be reported after both major and minor trauma. Equally, a serious head injury does not prove that it caused every later sensory complaint.
The proposed mechanism must fit the claimant’s individual presentation.
Chronology needs more than one date.
The expert should ask when the claimant first noticed the change, when it was first reported and whether the symptoms have altered.
A claimant may not recognise smell loss immediately. During the initial stages of a head injury, more pressing symptoms may dominate. The problem may become apparent only when the person returns home, eats a familiar meal or fails to notice a strong household odour, this could explain a short delay in reporting. A longer gap would require closer examination.
Emergency department, GP, ENT, neurology and rehabilitation records should be reviewed. The expert should consider whether smell or taste was mentioned during consultations dealing with other head-injury symptoms. Where the records contain repeated detailed histories but no reference to sensory loss, the omission may carry weight.
It is not conclusive. Medical records are selective documents, not complete transcripts. The report should explain the significance of the gap rather than silently accepting or rejecting the claimant’s account.
Alternative causes must be addressed.
The timing of symptoms after an accident may support causation, but it does not exclude other explanations.
Earlier records may reveal nasal polyps, chronic rhinitis, sinus disease, previous head trauma or an existing smell disorder. Viral infection, including COVID-19, may be relevant. Medication, ageing, smoking and some neurological conditions may also affect smell.
The expert should ask whether the claimant had a respiratory infection around the time symptoms began and whether nasal congestion was present. A pre-accident history of altered smell does not necessarily defeat causation; the accident may have aggravated an existing problem. That requires a different opinion from one of entirely new loss.
Where competing causes cannot be distinguished, the report should say so. Temporal association should not be converted into medical certainty.
Self-report should be supported by formal testing.
Smell loss is difficult to assess through ordinary clinical examination. Asking a claimant to identify coffee or perfume in the consulting room is not a substitute for validated testing. Psychophysical smell tests may assess odour identification, detection threshold and discrimination. Commonly used methods include the Sniffin’ Sticks system, and the University of Pennsylvania Smell Identification Test. Consensus guidance recognises standardised testing as part of the assessment of olfactory dysfunction.
Such testing can establish whether impairment is present and indicate its severity. It cannot, on its own, determine when the loss began or what caused it. The result must be interpreted with the accident history, medical records and specialist examination.
Where genuine gustatory loss is alleged, separate taste assessment may be required. The ability to detect basic tastes can be tested rather than inferred from the claimant’s enjoyment of food. A general medical expert may record the reported symptoms but should consider ENT, rhinology or specialist smell-and-taste evidence where diagnosis, causation or prognosis falls outside their expertise.
Imaging is not automatically required.
A normal routine head scan does not disprove olfactory injury. Standard imaging performed during acute care may be directed towards fractures, bleeding or other immediate complications rather than detailed assessment of the olfactory pathways.
Neither should every claimant with smell loss be sent for further imaging. NICE advises considering neuroimaging where unexplained loss of smell or taste lasts for more than three months. It does not recommend routine neurological referral solely because smell or taste was lost immediately after a head injury.
The wording matters. It does not mean that persistent post-traumatic anosmia requires no clinical assessment. ENT examination may be needed to exclude obstruction or other nasal causes. Further imaging should be guided by the presentation, existing investigations and specialist judgement.
The effect extends beyond enjoyment of food.
The functional consequences should be recorded specifically. Loss of smell can affect appetite, nutrition, cooking, personal hygiene, relationships and work. A chef, gas engineer or worker exposed to chemicals may face different occupational consequences from someone whose work does not depend on odour recognition.
There are also safety implications, a person with anosmia may not detect smoke, leaking gas or spoiled food. NHS guidance advises people with smell loss to account for these hazards rather than relying on odour as a warning.
The report should identify the precautions the claimant has adopted and whether practical restrictions remain. Statements that smell loss has “ruined daily life” should be explored through examples rather than repeated without analysis.
Prognosis must remain measured.
Post-traumatic olfactory dysfunction can persist, and recovery may be limited. NICE’s supporting rationale states that smell loss following head trauma is often permanent.
That does not justify declaring permanence immediately. The time since injury, degree of impairment and evidence of any improvement should be considered. Distorted smells may appear during recovery, although they can themselves be distressing. The research base remains imperfect, particularly when predicting recovery for an individual.
Olfactory training may be considered. A systematic review and meta-analysis found that some patients with post-traumatic dysfunction achieved clinically significant improvement, while also calling for better controlled studies. It should therefore be presented as a low-risk rehabilitative option with uncertain individual benefit, not a promised cure.
Loss of smell or taste following head trauma is not proved by chronology alone, and it is not disproved by normal routine imaging. The evidence should combine a detailed history, contemporaneous and earlier records, a plausible mechanism, standardised sensory testing and consideration of alternative causes.
The strongest medico-legal opinion does not merely state that the symptom followed the accident. It explains whether the alleged loss is measurable, whether the trauma caused it and what effect it now has on the claimant’s safety and function.
