xRead - Olfactory Disorders (September 2023)

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PATEL et al.

TABLE VII.14 Section evidence summary: Related to seizures or epilepsy Author Year LOE Study design Study groups

Clinical end point

Conclusions Quantitative

912 patients with epilepsy 794HCs

Olfactory psychophysical tests (eg, UPSIT R and SS-TDI)

Kurshid et al 878

2019 2a

Systematic review and meta-analysis

meta-analysis indicates significant olfactory deficits in patients with epilepsy, most prominent in TLEand mixed-frontal epilepsy confirmed significant olfactory deficit in patients with TLE, also noting the use of olfactory testing to differentiate TLE from other forms of epilepsy as well as using olfactory testing to predict patient selection and outcome in surgical procedures to treat it Resolution of olfactory auras after mesial temporal lobectomy in all patients Systematic review

Hwang

2020 3a

Systematic review without meta-analysis

Patients with TLE Patients with other forms of epilepsy

Olfactory psychophysical tests (eg, UPSIT R and SS-TDI)

et al 879

Chen

Resolution of olfactory symptoms Resolution of seizures Clinical characteristics of patients with olfactory aura

2003 4

Case series

217 Chinese patients who underwent temporal lobectomy for medically intractable TLE

et al 880

HC = healthy control; LOE = level of evidence; SS-TDI = Sniffin’ Sticks threshold, discrimination, identification combination; TLE = temporal lobe epilepsy; UPSIT R = University of Pennsylvania Smell Identification Test.

OD is prevalent and may be a core deficit in patients with ASD and OCD but not those with ADHD. Aggregate grade of evidence : C (Level 4: one moder ately sized quantitative meta-analytic study and one qual itative review). L Related to seizures, migraine, or other headache activity Migraine and epilepsy are the two best known paroxysmal neurologic disorders. Olfactory disturbances are common in each disorder and may include olfactory hallucinations, changes in OF or sensitivity, and intolerance to odors, par ticularly during acute attacks. Olfactory hallucinations have been recognized as a potential feature of seizure activity or the aura that pre cedes it, but less well known is the potential for interictal olfactory deficit or dysfunction in patients with epilepsy. A 2019 systematic review and meta-analysis demonstrated that olfactory deficits were common in patients with epilepsy, being most prominent in patients with temporal

lobe epilepsy and mixed-frontal epilepsy. Among patients with epilepsy, sex, age, smoking status, education, handed ness, and age of illness onset were significantly correlated to olfactory performance. 878 In a systematic review performed among patients with temporal lobe epilepsy, Hwang et al 879 found that olfac tory testing could be used to differentiate temporal lobe epilepsy from other forms of epilepsy with high sensitivity and specificity, as well as being useful in predicting appro priate patient selection and outcomes from surgical inter vention to treat these patients. Olfactory hallucinations may accompany other sensa tions such nausea/stomach pain and fear in patients with epilepsy. 880 Less than 20% of patients with temporal lobe epilepsy experience olfactory hallucinations, and it is not necessarily more common than motor or sensory auras. 881 Mesial temporal lobe epilepsy typically results from func tional or structural changes to areas of the limbic sys tem, such as the amygdala and hippocampus. These struc tures of the olfactory cortex receive olfactory information from the OB and become activated during functional MRI (fMRI) in response to odor intensity. 882 In a study of 12 patients with temporal lobe epilepsy with olfactory auras