Phantosmia and Dysgeusia following Endoscopic Transcribriform Approaches to Olfactory Groove Meningiomas

Olfaction preservation in olfactory groove meningiomas: a systematic review

Olfactory groove meningiomas (OGM) are a skull base neoplasm that represents between 8 and 13% of all intracranial meningiomas. Approach selection focuses on achieving frontal lobe decompression, gross total resection and vision preservation. Recently, there has been a focus on olfaction and considering its preservation as a quality-of-life outcome measure. An electronic search of the databases Medline, Scopus, Embase, Web of Science and Cochrane library databases was performed and data extracted according 2020 Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) statement. Six articles were selected for inclusion mainly based due to reporting quantitative outcomes for olfaction assessed by a smell identification test (e.g. sniffin' sticks). Objective olfaction preservation can be achieved with a variety of surgical approaches. More research which includes objective assessment of olfactory function and ideally as well QoL outcome measures is needed to further optimize the treatment pathways in OGM patients.

Parosmia and Phantosmia: Managing Quality Disorders

Purpose of Review

The purpose of this review was to summarize the current knowledge on parosmia and phantosmia and introduce support and treatment algorithms for the two qualitative olfactory disorders.

Recent Findings

Recent literature regarding parosmia has revealed that patients with the disorder are mainly triggered by certain substances, including thiols and pyrazines. In 2015, the existing "olfactory training" regimen was improved to more effectively treat post-infectious olfactory loss and was named "modified olfactory training" (MOT). It was also found in 2022 that MOT is also effective against COVID-19-induced parosmia.

Summary

Parosmia, the distortion of smells, is a symptom in qualitative olfactory disorders that severely affects patients' mental well-being and enjoyment of their everyday lives. The condition was first documented in 1895 and can affect up to 5% of the general population. Etiologies of parosmia include sinonasal diseases, viruses, surgeries, traumatic brain injury, neurological and psychiatric conditions, toxic chemicals, and medications. Parosmia has seen a surge in cases since the onset of the COVID-19 pandemic and is linked to changes in brain structure following an infection. The evaluation of the symptom is done using surveys, smell identification tests, fMRI, MRI, PET/CT, and gas chromatography. Treatment for parosmia can vary in duration, which makes it essential to focus not only on helping the patients regain normosmia, but also on supporting the patient through the recovery journey. Parosmia should not be confused with phantosmia, in which the distortion of smells occurs in the absence of olfactory stimuli. The etiology of phantosmia can vary from infections and traumatic brain injury to psychiatric disorders like schizophrenia. Unlike parosmia, the treatment of phantosmia is less straightforward, with an emphasis on determining the etiology and providing symptomatic relief.

Smell Preservation following Unilateral Endoscopic Transnasal Approach to Resection of Olfactory Groove Meningioma: A Multi-institutional Experience

Introduction  Olfactory groove meningiomas (OGMs) are often associated with loss of smell following resection. Loss of smell has a measurable impact on quality of life. Smell preservation has been previously described in open approaches for early stage or unilateral OGMs. Evidence of smell preservation in endoscopic approaches is lacking. Design  A multi-institutional retrospective review was performed on consecutive patients who underwent unilateral endoscopic endonasal resection of OGM. A gross total resection was achieved with preservation of the contralateral olfactory cleft and bulb. Olfactory function was assessed with a six-point olfactory symptom score and the Sniffin' Sticks 12-item smell identification test (SS-12). Contralateral olfactory bulb volume was measured on postoperative magnetic resonance imaging. Results  Four patients (age 42.0 ± 7.5, 75% female) were assessed. Olfactory function was assessed at 21.8 ± 5.6 months following surgery. All patients reported some degree of smell preservation (75% described a slight/mild impairment in smell or better). Olfactory identification was preserved with an SS-12 score of 9 ± 1.4 (anosmia defined as ≤6). The olfactory bulb volume was calculated to be 47.4 ± 15.9 mm ³ (normal >40 mm ³ ). Conclusion  Smell preservation is possible following unilateral endoscopic endonasal resection of carefully selected OGM.