Implication of photic sneeze reflex in ophthalmology.

Background: Photic sneeze reflex (PSR) also known as autosomal dominant compelling helioophthalmic outburst is a rare condition characterized by uncontrolled sneezing in response to bright light. The exact mechanism causing this is poorly understood. However, various hypotheses have been proposed. Ophthalmic examination involves exposing the patient to bright light like slit lamp, indirect ophthalmoscopy, and surgical microscope, which can trigger sneezing in PSR patients. Purpose: The purpose of this video is to draw light to this rare phenomenon and its implication in ophthalmic surgery. Synopsis: A 74-year-old male patient presented with diminution of vision in left eye. On routine slit lamp and IDO examination, patient had repeated sneezing. We diagnosed him to have photic sneeze reflex. He had pseudophakic bullous keratopathy in the right eye and senile immature cataract in the left eye. Taking into consideration his one eyed status and PSR, measures were taken accordingly and cataract surgery was performed uneventfully. We describe in this video the challenges encountered with this phenomenon and approach in such cases. Highlights: In this video, we tried to give an idea about photic sneeze reflex and its theories. Also, we tried to bring out the impact of PSR on ophthalmologic practice. Video link: https://youtu.be/KMZ_PC0hzhI.

Intraoperative Sneezing Secondary to Indirect Olfactory Nerve Stimulation.

Sneezing is a poorly understood, protective reflex response. It's characterized by the following sequence: eye closure, inspiration, glottic closure, forced expiration with sudden glottic opening, and release of an elevated intrathoracic pressure creating a flow of explosive air through the nose.1 Studies have indicated an anatomic sneezing area of the brainstem corresponding to the central recipient zone of the nasal sensory neurons in the lateral medulla.2 The traditional pathophysiology of the sneeze is thought to begin by stimulation of the distal branches of the trigeminal nerve within the nasal mucosa. Afferent neural stimuli are transmitted to the trigeminal ganglion and then the lateral medulla. The efferent phase then begins, giving rise to the sneezing sequence described earlier.1 In addition to direct nasal irritation, sneezing has been shown to be triggered by several other causes (Table 1). This suggests that alternative mechanisms of sneeze induction other than direct nasal stimulation exist. We report a case of a 34-year-old man undergoing an awake craniotomy for a recurrent World Health Organization grade 2 oligodendroglioma (IDH-mutant, 1p19q-codeleted, ATRX preserved). During the operation we elicited a sneeze response on 3 occasions on stimulation of the olfactory nerve (Video 1). Although we cannot completely exclude costimulation of the sensory trigeminal terminations in the anterior fossa floor, the actual sneezing occurred during tumor peeling away from the arachnoid surface overlaying the olfactory nerve. This suggests a potential accessory route of sneeze stimulation involving the olfactory nerve distinct from the previously described trigemino-related, autonomic (sympathetic and parasympathetic systems) and psychogenic etiologies.

Sneezing reflex is mediated by a peptidergic pathway from nose to brainstem.

Sneezing is a vital respiratory reflex frequently associated with allergic rhinitis and viral respiratory infections. However, its neural circuit remains largely unknown. A sneeze-evoking region was discovered in both cat and human brainstems, corresponding anatomically to the central recipient zone of nasal sensory neurons. Therefore, we hypothesized that a neuronal population postsynaptic to nasal sensory neurons mediates sneezing in this region. By screening major presynaptic neurotransmitters/neuropeptides released by nasal sensory neurons, we found that neuromedin B (NMB) peptide is essential for signaling sneezing. Ablation of NMB-sensitive postsynaptic neurons in the sneeze-evoking region or deficiency in NMB receptor abolished the sneezing reflex. Remarkably, NMB-sensitive neurons further project to the caudal ventral respiratory group (cVRG). Chemical activation of NMB-sensitive neurons elicits action potentials in cVRG neurons and leads to sneezing behavior. Our study delineates a peptidergic pathway mediating sneezing, providing molecular insights into the sneezing reflex arc.

Considerations and Management of a Laryngeal Fracture after Sneezing.

Non-traumatic laryngeal fracture is uncommon but should be suspected whenever patients present with dysphonia, odynophagia, dysphagia, neck crepitus, or hemoptysis following a sneeze or coughing episode. Physical examination coupled with computed tomography is essential for making the diagnosis. Management can vary depending on the severity of the case, but the general approach is similar to any trauma. In this report, we describe a non-traumatic laryngeal fracture that occurred following a forceful sneeze. The case was notable for the presence of pneumomediastinum, independent mobility of the thyroid ala, and operative intervention was pursued to repair the fracture.

Remedia Sternutatoria over the Centuries: TRP Mediation.

Sneezing (sternutatio) is a poorly understood polysynaptic physiologic reflex phenomenon. Sneezing has exerted a strange fascination on humans throughout history, and induced sneezing was widely used by physicians for therapeutic purposes, on the assumption that sneezing eliminates noxious factors from the body, mainly from the head. The present contribution examines the various mixtures used for inducing sneezes (remedia sternutatoria) over the centuries. The majority of the constituents of the sneeze-inducing remedies are modulators of transient receptor potential (TRP) channels. The TRP channel superfamily consists of large heterogeneous groups of channels that play numerous physiological roles such as thermosensation, chemosensation, osmosensation and mechanosensation. Sneezing is associated with the activation of the wasabi receptor, (TRPA1), typical ligand is allyl isothiocyanate and the hot chili pepper receptor, (TRPV1), typical agonist is capsaicin, in the vagal sensory nerve terminals, activated by noxious stimulants.

Propagation of viral bioaerosols indoors.

Here we look into the spread of aerosols indoors that may potentially carry viruses. Many viruses, including the novel SARS-CoV-2, are known to spread via airborne and air-dust pathways. From the literature data and our research on the propagation of fine aerosols, we simulate herein the carryover of viral aerosols in indoor air. We demonstrate that a lot of fine droplets released from an infected person's coughing, sneezing, or talking propagate very fast and for large distances indoors, as well as bend around obstacles, lift up and down over staircases, and so on. This study suggests equations to evaluate the concentration of those droplets, depending on time and distance from the source of infection. Estimates are given for the safe distance to the source of infection, and available methods for neutralizing viral aerosols indoors are considered.

Transformative Approach To Investigate the Microphysical Factors Influencing Airborne Transmission of Pathogens.

Emerging outbreaks of airborne pathogenic infections worldwide, such as the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, have raised the need to understand parameters affecting the airborne survival of microbes in order to develop measures for effective infection control. We report a novel experimental strategy, TAMBAS (tandem approach for microphysical and biological assessment of airborne microorganism survival), to explore the synergistic interactions between the physicochemical and biological processes that impact airborne microbe survival in aerosol droplets. This innovative approach provides a unique and detailed understanding of the processes taking place from aerosol droplet generation through to equilibration and viability decay in the local environment, elucidating decay mechanisms not previously described. The impact of evaporation kinetics, solute hygroscopicity and concentration, particle morphology, and equilibrium particle size on airborne survival are reported, using Escherichia coli MRE162 as a benchmark system. For this system, we report that (i) particle crystallization does not directly impact microbe longevity, (ii) bacteria act as crystallization nuclei during droplet drying and equilibration, and (iii) the kinetics of size and compositional change appear to have a larger effect on microbe longevity than the equilibrium solute concentration.IMPORTANCE A transformative approach to identify the physicochemical processes that impact the biological decay rates of bacteria in aerosol droplets is described. It is shown that the evaporation process and changes in the phase and morphology of the aerosol particle during evaporation impact microorganism viability. The equilibrium droplet size was found to affect airborne bacterial viability. Furthermore, the presence of Escherichia coli MRE162 in a droplet does not affect aerosol growth/evaporation but influences the dynamic behavior of the aerosol by processing the culture medium prior to aerosolization, affecting the hygroscopicity of the culture medium; this highlights the importance of the inorganic and organic chemical composition within the aerosolized droplets that impact hygroscopicity. Bacteria also act as crystallization nuclei. The novel approach and data have implications for increased mechanistic understanding of aerosol survival and infectivity in bioaerosol studies spanning the medical, veterinary, farming, and agricultural fields, including the role of microorganisms in atmospheric processing and cloud formation.

Respiratory droplet generation and dispersal during nasoendoscopy and upper respiratory swab testing.

Respiratory particle generation and dispersal during nasoendoscopy and swab testing is studied with high-speed video and laser light illumination. Video analysis reveals droplet formation in three manoeuvres during nasoendoscopy - sneezing, vocalization, and nasal decongestion spray. A capillary bridge of mucus can be seen when a nasoendoscope exits wet nares. No droplet formation is seen during oral and nasopharyngeal swab testing. We outline the following recommendations: pull the face mask down partially and keep the mouth covered, only allowing nasal access during nasoendoscopy; avoid nasal sprays if possible; if nasal sprays are used, procedurists should be in full personal protective equipment prior to using the spray; withdrawal of swabs and scopes should be performed in a slow and controlled fashion to reduce potential dispersion of droplets when the capillary bridge of mucus breaks up.

Effects of a selective androgen receptor modulator (SARM), GSK2849466A, on stress urinary incontinence and bladder activity in rats with ovariectomy-induced oestrogen deficiency.

OBJECTIVES: To report the effect of a selective androgen receptor modulators (SARMs) on the urethral continence mechanisms in a rat model of stress urinary incontinence (SUI) induced by bilateral ovariectomy (OVX). MATERIALS AND METHODS: Female Sprague-Dawley rats with bilateral OVX were used. Rats were divided into five groups; sham operated, vehicle-treated OVX, low-dose SARM-treated OVX (GSK2849466A: 0.005 mg/kg/day, per os [p.o.]), high-dose SARM-treated OVX (GSK2849466A: 0.03 mg/kg/day, p.o.) and dihydrotestosterone (DHT)-treated OVX (1 mg/kg/day, subcutaneous) groups. After 4 weeks of SARM treatments or 3 weeks of DHT treatment (6 weeks after OVX), rats were subjected to evaluation of the sneeze-induced continence reflex using microtransducer-tipped catheter methods, sneeze-induced leak-point pressure, and continuous cystometry measurements, followed by histological analyses of urethral tissues. RESULTS: (i) OVX significantly impaired urethral continence function after 6 weeks to induce SUI during sneezing. (ii) Low-dose SARM treatment restored urethral baseline pressure (UBP) without affecting the amplitude of urethral response during sneezing (A-URS), partially reversing OVX-induced SUI during sneezing. (iii) High-dose SARM treatment reversed decreases in both UBP and A-URS, more effectively preventing SUI during sneezing. (iv) DHT treatment only restored A-URS without affecting UBP, partially preventing OVX-induced SUI during sneezing. (v) The high-dose SARM treatment induced hypertrophy of the striated and smooth muscle around the urethra. (vi) SARM treatment did not affect bladder function in sham or OVX rats. CONCLUSION: Treatment with SARMs could be a more effective modality for the treatment of SUI than DHT, without affecting bladder function, by enhancing smooth- and striated muscle-mediated urethral function under stress conditions such as sneezing.

Peak Sinus Pressures During Sneezing in Healthy Controls and Post-Skull Base Surgery Patients.

OBJECTIVES/HYPOTHESIS: Patients are frequently advised to sneeze with an open mouth and avoid nose-blowing following an endoscopic endonasal approache (EEA) to the skull base, despite a lack of quantitative evidence. This study applies computational fluid dynamics (CFD) to quantify sinus pressures along the skull base during sneezing. STUDY DESIGN: Case-control series. METHODS: Computed tomography or magnetic resonance imaging scans of four post-EEA patients and four healthy controls were collected and analyzed utilizing CFD techniques. A pressure drop of 6,000 Pa was applied to the nasopharynx based on values in the literature to simulate expiratory nasal airflow during sneezing. Peak pressures along the skull base in frontal, ethmoid, and sphenoid sinuses were collected. RESULTS: Significant increases in skull base peak pressure was observed during sneezing, with significant individual variations from 2,185 to 5,685 Pa. Interestingly, healthy controls had significantly higher pressures compared to post-EEA patients (5179.37 ± 198.42 Pa vs. patients 3,347.82 ± 1,472.20 Pa, P < .05), which could be related to higher anterior nasal resistance in unoperated healthy controls (0.44 ± 0.22 vs. 0.31 ± 0.16 Pa/mL/sec for patients, P = .38). The sinus pressure buildup may be due to airway resistance functioning as a valve preventing air from being released quickly. Supporting this theory, there was a strong correlation (r = 0.82) between peak skull base pressure and the ratio of anterior resistance to total resistance. Within-subject variation in pressures between different skull base regions was much lower (average = ~5%). CONCLUSIONS: This study provided the first quantitative analysis of air pressure along the skull base during sneezing in post-EEA patients through CFD, suggesting that pressure buildup may depend on individual anatomy. LEVEL OF EVIDENCE: 3b Laryngoscope, 130:2138-2143, 2020.

A genome-wide association study on photic sneeze reflex in the Chinese population.

Photic sneeze reflex (PSR) is an interesting but yet mysterious phenotype featured by individuals' response of sneezing in exposure to bright light. To uncover the underlying genetic markers (single nucleotide polymorphisms, SNPs), a genome-wide association study (GWAS) was conducted exclusively in a Chinese population of 3417 individuals (PSR prevalence at 25.6%), and reproducibly identified both a replicative rs10427255 on 2q22.3 and a novel locus of rs1032507 on 3p12.1 in various effect models (additive, as well as dominant and recessive). Minor alleles respectively contributed to increased or reduced risk for PSR with odds ratio (95% confidence interval) at 1.68 ([1.50, 1.88]) for rs10427255 and 0.65 ([0.58, 0.72]) for rs1032507. The two independent SNPs were intergenic, and collectively enhanced PSR classification by lifting the area-under-curve value in ROC curve to 0.657. Together with previous GWAS in other populations, the result substantiated the polygenic and non-ethnicity-specific nature behind the PSR phenotype.

Aerosol emission and superemission during human speech increase with voice loudness.

Mechanistic hypotheses about airborne infectious disease transmission have traditionally emphasized the role of coughing and sneezing, which are dramatic expiratory events that yield both easily visible droplets and large quantities of particles too small to see by eye. Nonetheless, it has long been known that normal speech also yields large quantities of particles that are too small to see by eye, but are large enough to carry a variety of communicable respiratory pathogens. Here we show that the rate of particle emission during normal human speech is positively correlated with the loudness (amplitude) of vocalization, ranging from approximately 1 to 50 particles per second (0.06 to 3 particles per cm3) for low to high amplitudes, regardless of the language spoken (English, Spanish, Mandarin, or Arabic). Furthermore, a small fraction of individuals behaves as "speech superemitters," consistently releasing an order of magnitude more particles than their peers. Our data demonstrate that the phenomenon of speech superemission cannot be fully explained either by the phonic structures or the amplitude of the speech. These results suggest that other unknown physiological factors, varying dramatically among individuals, could affect the probability of respiratory infectious disease transmission, and also help explain the existence of superspreaders who are disproportionately responsible for outbreaks of airborne infectious disease.

Sneeze and pop: a ruptured varicocele; analysis of literature, guided by a well-documented case-report.

BACKGROUND: An acute scrotal hematoma, secondary to a spontaneous rupture of a varicocele is still a rare presentation in daily practice. However, multiple case reports have been reported. Sudden increase in abdominal pressure, resulting to an increased venous pressure can lead to a rupture of the varicocele. Literature search shows that due to uncertainty of the diagnosis, explorative surgery is often performed, sometimes resulting in unnecessary orchiectomies. The objective of this study was to determine classical clinical presentation of patients with a spontaneous rupture of a varicocele, determine the diagnostic procedure, and give an insight in the follow-up. CASE PRESENTATION: We present a case of a 24-year old male with acute scrotal swelling after sneezing. Subsequently, we carried out a systematic literature search to identify all eligible studies to determine classic clinical presentation of spontaneous ruptures of a varicocele. CONCLUSION: The literature search shows that clinical presentation of idiopathic spontaneous scrotal hematomas is similar to testicular torsion, epididymo-orchitis, malignancy, or (incarcerated) inguinal hernia making differential diagnosis difficult. Especially when there has been increased abdominal pressure or strenuous activity preceding the symptoms, and the swelling is left sided, it should be included in the differential diagnosis for patient with acute inguinoscrotal swelling. Colour Doppler-Ultrasonography is recommended to distinguish between other causes of acute scrotum. The hematoma is usual self-limiting, justifying conservative treatment. Early surgical intervention is indicated with signs of ischaemia due to obstruction, infection of the hematoma, or uncertain diagnosis (i.e. malignancy). However, physicians should be cautious with direct exploration, as it led to unnecessary orchiectomy in 25% of patients. The hematoma can increase in size up to 3 months post-event, and it can take up to 15 months to completely resolve.

The Dangers of Sneezing: A Review of Injuries.

BACKGROUND: Sneezing is an almost universal daily phenomenon as a reflex to evacuate irritants from the nasal cavities. An autonomic-controlled buildup of intrathoracic pressure against a closed glottis followed by sudden release results in a burst of 1 kPa of air through the upper airway. Active intervention to limit a sneeze can be deleterious. Closure of the airway during a sneeze can result in over 20 times the airway pressures resulting in a variety of untoward events. This review summarizes all reported injuries that occurred as the result of a sneeze. OBJECTIVE: The objective of this review is to summarize the risks of closed-airway sneezing and determine if there are any trends which can help understand such injuries. METHODS: A comprehensive literature review was performed from 1948 to 2018 to identify all reports of sneeze-related injuries. Information was compiled from reports to gain insights into comorbidities and risk factors for sneeze injuries. RESULTS: There were 52 unique reports of sneeze-related injuries in the literature that were categorized into 6 areas of injury: intrathoracic, laryngeal/pharyngeal, ocular/orbital, intracranial/neurological, otologic, and other. The mean age of subjects who suffered a sneeze injury was 40 years old (range: 15-84 years), with 81% being male gender. Thirty percent had a risk factor for injury of prior trauma (5) or respiratory compromise (5). CONCLUSION: A variety of injuries can occur during a sneeze, especially when a closed-airway sneeze is attempted, and high Valsalva pressure is transmitted to the other systems. Men are more at risk for these injuries with the majority occurring in patients with no known risk factor. When triggered, a sneeze should be allowed to proceed without intervention to prevent associated injuries.

Spontaneous pneumocephalus and subdural hemorrhage after sneezing.

Spontaneous pneumocephalus is defined as the presence of air in the absence of intracranial factors. The management of spontaneous pneumocephalus can be conservative or surgical, and surgical intervention could be urgently required if clinical deterioration is rapid. Here, we report a case of pneumocephalus and subdural hemorrhage after sneezing. A 24-year-old male reported to our emergency department with a chief complaint of headache and dizziness. The patient gave a history of onset of headache and dizziness after 2 episodes of heavy sneezing. There was neither a history of recent traumatic episode or previous surgery, nor any signs and symptoms of recent fever or upper respiratory tract infections. Physical examination showed no specific findings. Computed tomography was performed, which showed subdural hemorrhage and PNC in the left occipital lobe, left hemomastoid, and maxillary hemosinus. A neurosurgeon was consulted, who suggested admission in the intensive care unit. An otolaryngologist was then consulted for the left ear otorrhea and hearing impairment. Otoscopic examination showed hemotympanum of the left ear, for which pain control and conservative treatment was suggested. The patient was transferred to general ward 4 days later, since the following brain computed tomography showed resolution of the hemorrhage, and discharged 6 days later because of the improved signs and symptoms. Pneumocephalus and intracranial hemorrhage can occur without a history of trauma or surgery. Special attention is required if headache, dizziness, or other neurologic signs and symptoms occur immediately after sneezing. Intracranial hemorrhage and penumocephalus should be considered in the differential diagnosis.

High luteinizing hormone weakens urinary continence mechanisms in association with prostaglandin E2 elevation in a postmenopausal rat model.

AIMS: To explore the role of luteinizing hormone (LH) in the urinary continence mechanism, urethral function was investigated using a postmenopausal rat model with high serum LH concentrations and the postmenopausal rat model given a gonadotropin releasing hormone (GnRH) antagonist to lower LH concentrations. METHODS: Adult female rats were divided into: 1) sham group; 2) ovariectomy group (OVX) with removal of bilateral ovaries; 3) OVX and GnRH-antagonist administered group (OVX + G); and 4) sham and GnRH-antagonist administered group (Sham + G). Urethral function was evaluated by the sneeze-induced urethral continence reflex experiment, and serum LH and prostaglandin E2 (PGE2) concentrations were measured. RESULTS: In the sneeze-induced urethral continence reflex experiment, urethral baseline pressure (UBP) and the amplitude of the urethral response during sneezing (A-URS) were measured. The UBP was significantly decreased in the OVX group than in the other groups. A-URS was significantly lower in the OVX group than in the Sham group, but with no significant difference compared with the OVX + G group. Lowering the serum LH by a GnRH-antagonist improved UBP to the same level as in the Sham group. The serum PGE2 concentration was significantly higher in the OVX group than in the other groups. CONCLUSIONS: The results suggested that the increased serum LH concentration in the OVX rat model worsened the continence mechanism. This mechanism is probably associated with an increased PGE2 concentration, because PGE2 caused urethral smooth muscle relaxation. A GnRH-antagonist might improve urinary incontinence by decreasing the serum LH and PGE2 concentrations.

Snap, crackle and pop: when sneezing leads to crackling in the neck.

Spontaneous perforation of the pharynx is an unusual condition. Due to its non-specific presentation and general lack of awareness, diagnosis and intervention may be delayed resulting in potential complications. This case reports a rare spontaneous perforation of the pyriform sinus after a forceful sneeze, leading to cervical subcutaneous emphysema and pneumomediastinum.

Sneezing in Primary Headaches With Cranial Autonomic Symptoms: Pathophysiological Considerations. A Series of Case Reports.

OBJECTIVE: To report a case series of sneezing systematically occurring in two cases with migraine and cranial autonomic symptoms and two with cluster headache. BACKGROUND: Sneezing occurring systematically during cluster headache or migraine is a rare condition. Sneezing has been described as a specific trigger for migraine. METHODS: Case reports. CASE SERIES: We describe four patients with primary headaches, presenting systematic sneezing at a definite time of premonitory, postdromal, or headache phase. All of these headaches were associated with cranial autonomic symptoms. CONCLUSION: Sneezing is a symptom associated with primary headaches. The definite place of sneezing in these patients suggests a particular implication of hypothalamus in the pathophysiology of these cases.