Is loss of taste and smell a normal symptom after a concussion?

Loss of Taste and Smell After Concussion

Loss of taste and smell can occur after concussion, though it is not among the most common symptoms, affecting approximately 3-38% of concussion patients depending on severity. 1, 2

Prevalence and Mechanism

• Post-traumatic anosmia (loss of smell) and dysgeusia (altered taste) can occur after head trauma of varying severity, including mild traumatic brain injury (mTBI) such as concussion 3, 2
• The mechanism likely involves:
  • Direct trauma to olfactory nerve fibers as they pass through the cribriform plate
  • Shearing injuries to the olfactory bulbs
  • Contusion of olfactory brain regions
  • Secondary inflammation affecting olfactory pathways

Clinical Characteristics

• Smell and taste dysfunction can manifest as:
  • Decreased smell acuity (hyposmia)
  • Distortion of smell (dysosmia)
  • Decreased taste acuity (hypogeusia)
  • Distortion of taste (dysgeusia) 3
• These symptoms can occur even after minimal head trauma and may not appear immediately, sometimes developing months after the initial injury 3

Assessment and Prognosis

• According to a 2022 study, the prevalence of smell dysfunction one week after concussion was:
  • Severe hyposmia: 3% of patients
  • Moderate hyposmia: 6% of patients
  • Mild hyposmia: 29% of patients
  • Normal smell function: 62% of patients 4
• Recovery patterns vary:
  • Some patients (approximately 35%) with head trauma-induced olfactory loss show improvement over time 5
  • Recovery may take several years in some cases 5
  • Some research suggests a possible degenerative effect on olfactory function with longer time since concussion 2

Clinical Implications and Management

• Patients with persistent smell/taste dysfunction after concussion should be included in the list of postconcussive symptoms requiring specialist referral 1
• These symptoms should be identified during initial assessment and documented in discharge instructions 1
• Patients experiencing these symptoms should:
  • Refrain from strenuous mental or physical activity until symptom-free
  • Be referred to a specialist in traumatic brain injury if symptoms persist beyond 3 weeks 1
  • Be advised about safety concerns (e.g., installing gas/smoke alarms, checking food expiration dates) 6

Treatment Options

For persistent anosmia after concussion:

• Olfactory training is recommended as first-line treatment
  • Involves systematic exposure to different strong odors
  • Practice twice daily for at least 12 weeks
  • Sniff each odor for 10-20 seconds with focus and concentration 6
• Intranasal corticosteroids may be considered in combination with olfactory training 6

When to Seek Further Evaluation

Patients should return for re-evaluation if they develop:

• Worsening headache
• Repeated vomiting
• Confusion or memory problems
• Focal neurologic deficits
• Abnormal behavior
• Increased sleepiness
• Seizures 1

Important Caveats

• Complaints of taste loss often actually reflect loss of smell function, as flavor perception depends heavily on retronasal olfaction 7
• While not life-threatening, persistent anosmia significantly decreases quality of life and should be addressed proactively 6
• Recent research suggests that smell dysfunction is not necessarily associated with concussion severity or recovery time, so routine testing may not be warranted as a biomarker 4