Protocol for postmortem bedside endoscopic procedure to sample human respiratory and olfactory cleft mucosa, olfactory bulbs, and frontal lobe

We present a protocol for the rapid postmortem bedside procurement of selected tissue samples using an endoscopic endonasal surgical technique that we adapted from skull base surgery. We describe steps for the postmortem collection of blood, cerebrospinal fluid, a nasopharyngeal swab, and tissue samples; the clean-up procedure; and the initial processing and storage of the samples. This protocol was validated with tissue samples procured postmortem from COVID-19 patients and can be applied in another emerging infectious disease. For complete details on the use and execution of this protocol, please refer to Khan et al. (2021)1 and Khan et al. (2022).2.

Biopsy of the olfactory epithelium from the superior nasal septum: is it possible to obtain neurons without damaging olfaction?

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Olfactory biopsies from the superior part of the nasal septum did not significantly affect smell capacity.

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These biopsies obtain high rates of olfactory neurons.

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The described procedure also provides olfactory epithelium proper for morphological analysis.

Introduction

Olfactory epithelium biopsy has been useful for studying diverse otorhinolaryngological and neurological diseases, including the potential to better understand the pathophysiology behind COVID-19 olfactory manifestations. However, the safety and efficacy of the technique for obtaining human olfactory epithelium are still not fully established.

Objective

This study aimed to determine the safety and efficacy of harvesting olfactory epithelium cells, nerve bundles, and olfactory epithelium proper for morphological analysis from the superior nasal septum.

Methods

During nasal surgery, 22 individuals without olfactory complaints underwent olfactory epithelium biopsies from the superior nasal septum. The efficacy of obtaining olfactory epithelium, verification of intact olfactory epithelium and the presence of nerve bundles in biopsies were assessed using immunofluorescence. Safety for the olfactory function was tested psychophysically using both unilateral and bilateral tests before and 1 month after the operative procedure.

Results

Olfactory epithelium was found in 59.1% of the subjects. Of the samples, 50% were of the quality necessary for morphological characterization and 90.9% had nerve bundles. There was no difference in the psychophysical scores obtained in the bilateral olfactory test (University of Pennsylvania Smell Identification Test [UPSIT®]) between means before biopsy: 32.3 vs. postoperative: 32.5, p = 0.81. Also, no significant decrease occurred in unilateral testing (mean unilateral test scores 6 vs. 6.2, p = 0.46). None out of the 56 different odorant identification significantly diminished (p > 0.05).

Conclusion

The technique depicted for olfactory epithelium biopsy is highly effective in obtaining neuronal olfactory tissue, but it has moderate efficacy in achieving samples useful for morphological analysis. Olfactory sensitivity remained intact.

The olfactory bulb and olfactory mucosa obtained from human cadaver donors as a source of olfactory ensheathing cells

During the last decade, olfactory ensheathing cells (OECs) have been successfully applied in multiple experimental approaches aimed to repair damaged mammalian spinal cord. Some of these experiments have consequently been translated into clinical trials. Finding a reliable source of human OECs that is easily accessible and can ensure a sufficient number of cells is a major prerequisite for conducting studies on OEC-mediated spinal cord regeneration. Here, we present a procedure for obtaining olfactory bulbs (OBs) and olfactory mucosa (OM) simultaneously from adult cadaver heart-beating donors for OEC isolation and analyze some of the factors that may condition successful OEC culture. We show that the results of OEC culture from OBs (10 cases) correlated significantly with warm ischemia time (WIT) as well as the initial viability of the isolated cells. Efficient OEC culture was possible when the WIT for the OB was up to 20 min. Brain damage, assessed by determination of S100B serum level, was not related to the success of OEC culture from the OB. Cadaver OM (7 cases) was shown to be a more reliable source of human OECs than the OB. In most of the examined cases the efficacy of culturing OECs from cadaver OM obtained even 180 min after cardiac arrest was comparable to that of living patients. The method of obtaining OBs and OM from cadavers enables the use of an alternative source of primary adult human OECs for further preclinical and clinical studies on their neurotrophic properties.

Resection of the inferior superior turbinate: does it affect olfactory ability or contain olfactory neuronal tissue?

BACKGROUND

One approach to the sphenoid sinus involves resection of the inferior portion of the superior turbinate. There is general agreement from anatomic investigations that this area contains olfactory mucosa. This study will determine if olfactory tissue can be found in the superior turbinate mucosa of patients with chronic sphenoiditis and what effect its removal has on a patient's olfactory ability.

METHODS

The inferior one-third of the superior turbinate removed during endoscopic sphenoidotomy was stained with olfactory marker protein antibody, a marker for mature olfactory tissue. The specimens were graded for content of olfactory neuronal elements. All patients underwent uninasal 12-item smell identification testing before surgery and at least 3 weeks after surgery.

RESULTS

Fifty-five superior turbinate samples were taken from 31 patients. Nine (16%) of 55 samples contained olfactory neuronal elements that stained with olfactory marker protein. When comparing the pre- and postoperative smell test results, 52% of the nostrils had no more than a one-item change, 35% of the nostrils had a more than one-item improvement, and only 12% had more than a one-item loss. None of the nostrils with a loss of olfactory ability after the surgery showed olfactory neuronal elements in their superior turbinate specimens.

CONCLUSION

There is olfactory mucosa in approximately one-sixth of the superior turbinate specimens removed during the endoscopic transethmoidal sphenoidotomy procedure. Although 12% of the patients had a loss of olfactory ability in this study, none of the loss could be attributed to excision of olfactory tissue.

Long-term follow-up of surgically treated phantosmia

OBJECTIVES

To determine whether transnasal excision of olfactory epithelium is a safe, effective therapy and to learn more of the pathogenesis of phantosmia by studying the histological features of the excised mucosa.

DESIGN

A retrospective study consisting of a medical record review and telephone survey. Follow-up ranged from 1 to 11 years (average, 5.4 years). Excised tissues were histologically processed and descriptively compared with normal and other abnormal olfactory tissues.

SETTING

Tertiary university medical referral centers.

PATIENTS

All patients who presented to the primary author (D.A.L.) from 1988 to 1999 with unremitting phantosmia lasting longer than 4 years.

INTERVENTION

Olfactory testing and transnasal endoscopic excision of olfactory mucosa.

MAIN OUTCOME MEASURES

Tested olfactory function, patients' perception of phantom odor resolution, and histological findings.

RESULTS

Of 8 patients, 7 have complete and permanent resolution of their phantosmia. Postoperatively, the single nostril olfactory ability in the operated-on nostril is decreased in 2 nostrils, remains unchanged in 7, and is improved in 1. The excised olfactory mucosa generally shows a decreased number of neurons, a greater ratio of immature to mature neurons, and disordered growth of axons with some intraepithelial neuromas.

CONCLUSIONS

Surgical excision of olfactory epithelium is an effective and safe method to relieve phantosmia while potentially preserving olfactory ability. The abnormal histological features of the excised olfactory tissue suggest at least some pathological condition in the peripheral olfactory system. This nasal surgery requires intensive olfactory evaluation and follow-up. It is also extremely difficult with significant risks, and therefore should be limited to specialized centers.

Disruption of the olfactoretinal centrifugal pathway may relate to the visual system defect in night blindness b mutant zebrafish

We describe here a dominant mutation, night blindness b (nbb), which causes an age-related visual system defect in zebrafish. At 4-5 months of age, dark-adapted nbb(+/-) mutants show abnormal visual threshold fluctuations when measured behaviorally. Light sensitizes the animals; thus early dark adaptation of nbb(+/-) fish is normal. After 2 hr of dark adaptation, however, visual thresholds of nbb(+/-) mutants are raised on average 2-3 log units, and rod system function is not detectable. Electroretinograms recorded from nbb(+/-) mutants are normal, but ganglion cell thresholds are raised in prolonged darkness, suggesting an inner retinal defect. The visual defect of nbb(+/-) mutants may be likely caused by an abnormal olfactoretinal centrifugal innervation; in nbb(+/-) mutants, the olfactoretinal centrifugal projection to the retina is disrupted, and the number of retinal dopaminergic interplexiform cells is reduced. A similar visual defect as shown by nbb(+/-) mutants is observed in zebrafish in which the olfactory epithelium and olfactory bulb have been excised. Homozygous nbb fish display an early onset neural degeneration throughout the CNS and die by 7-8 d of age.

Successful treatment of phantosmia with preservation of olfaction

A 26-year-old woman had an 8-year history of phantosmia in her left nostril. The phantosmia could be eliminated by nostril occlusion or cocainization of the olfactory epithelium on the involved side. Because her symptoms and testing suggested a peripheral problem, a full-thickness "plug" of olfactory epithelium from under the cribriform plate (including all the fila olfactoria) was excised. At 5 weeks postoperatively, the phantosmia was completely gone, and her olfactory ability had returned to preoperative levels. Either the removal of abnormal peripheral olfactory neurons from the nose or the interruption of incoming signals to the olfactory bulb eliminated the phantosmia. This form of therapy for phantosmia offers an alternative to more radical procedures such as olfactory bulbectomy and may offer a significant sparing of olfactory ability.