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Spontaneous pneumomediastinum (SPM) is an unusual clinical entity that most frequently follows episodes of increased intrathoracic pressures. While typically a benign condition, potentially fatal complications of SPM must be considered and ruled out with each case. We aim to present the first case of croup-associated SPM in the otolaryngology literature and to discuss clinical, diagnostic and management principles. Days following the diagnosis of viral croup, a 7-year-old asthmatic girl presented with unstable vital signs and severe SPM. The patient was urgently taken to the operating room for an endoscopic airway evaluation, which revealed only a mild bacterial croup superinfection. Conservative treatment with inpatient monitoring and antibiotic therapy successfully resolved the episode. SPM should be immediately considered in the differential diagnosis of any patient presenting with cervical emphysema, especially in association with asthma, cough or strenuous activity. Following exclusion of other causes of SPM, conservative and supportive therapies are the mainstays of SPM management.

The use of the ultrasonic dissector in head and neck surgery is becoming more prevalent. Although initially designed for use in laparoscopic abdominal surgery, potential advantages such as reduced incision size, hemostasis and reduced operative time has helped ultrasonic dissector use become more widespread. The ultraincision allows a simultaneous cut and coagulation at reduced energy, providing a clean, dry operative field with potential reduced risk to adjacent structures. It finds particular application in thyroid and parathyroid surgery, and is becoming more commonly used in parotidectomy, submandibular gland removal, neck dissection, and glossectomy. Ultrasonic dissection technology is continually improving, and with the development of more efficient, ergonomic dissectors, its use is set to increase in the head and neck.

Background. Use of the ultrasonic dissector in thy- roid surgery is becoming more prevalent, with reduced opera- tive time and incision size reported. We assessed the value of the harmonic scalpel in routine thyroid lobectomy. Methods. We conducted a single blind, prospective pilot study of 52 euthyroid patients requiring thyroid lobectomy. Those with lesions not suitable for resection through a 4-cm incision, a history of thyroiditis, or uncontrolled thyroid dysfunction were excluded. Patients were allocated to 1 of 2 groups: group I (n 5 31), thyroid lobectomies using conventional surgical techniques; or group II (n 5 21), thyroid lobectomies using the ultrasonic dissector. Results. Outcomes for the 2 patient groups were compara- ble. There was no significant difference in operative time or inci- sion size. Conclusions. The ultrasonic dissector does not confer any quantifiable benefit in routine thyroid lobectomy when compared with conventional techniques. This is the first reported series in which its use has not reduced operative time. V

Cautery-assisted palatal stiffening operation (CAPSO) is a recently developed single office-based procedure performed with local anesthesia for the treatment of palatal snoring. A midline strip of soft palate mucosa is removed, and the wound is allowed to heal by secondary intention. The flaccid palate is stiffened, and palatal snoring ceases. This prospective study evaluated the ability of CAPSO to treat obstructive sleep apnea syndrome (OSAS). Twenty-five consecutive patients with OSAS underwent CAPSO. Responders were defined as patients who had a reduction in apnea-hypopnea index (AHI) of 50% or more and an AHI of 10 or less after surgery. By these strict criteria, 40% of patients were considered to have responded to CAPSO. Mean AHI improved from 25.1+/-12.9 to 16.6+/-15.0 (P = 0.010). The Epworth Sleepiness Scale, a subjective measure of daytime sleepiness, improved from 12.7+/-5.6 to 8.8+/-4.6 (P

Obstruction of the nasolacrimal duct is a common congenital abnormality reported in up to 84% of neonatal patients [J. Yohendran, A.C. Wignall, E.J. Beckenham, Bilateral congenital dacryocystocoeles with concurrent intranasal mucocoeles causing respiratory distress in a neonate, Asian J. Surg. 29 (2) (2006) 109-111; M.J. Cunningham, J.J. Woog, Endonasal endoscopic dacryocystorhinostomy in children, Arch. Otolaryngol. Head Neck Surg. 124 (1998) 328-333; D. Guery, E.L. Kendig, Congenital impotency of the nasolacrimal duct, Arch. Ophthalmol. 97 (1979) 1656-1658]. Rarely, obstruction results in the development of an intranasal lacrimal duct cyst, or dacryocystocoele, which arises inferolateral to the inferior turbinate [H.R. Jin, S.O. Shin, Endoscopic marsupialisation of bilateral lacrimal sac mucoceles with nasolacrimal duct cysts, Auris Nasus Larynx 26 (1999) 441-445]. These lesions can cause nasal obstruction and, when bilateral, significant respiratory compromise. We present the case of a 3-day-old infant with bilateral intranasal lacrimal duct cysts causing nasal obstruction and intermittent respiratory compromise. The diagnosis was suspected on clinical examination and confirmed on MRI. The patient was successfully managed by bilateral endoscopic marsupialisation and probing of the nasolacrimal ducts. We also present a review of the literature surrounding investigation and management of intranasal lacrimal duct cysts.

Floquet operator techniques are applied to a chemical reaction 2X→Y, to which X molecules are supplied periodically in time. The reaction is modeled as a death process with periodic immigration of the species X. We find the Floquet transition operator for this stochastic process, and we obtain exact expressions for the time‐dependent probability distribution of the number of X molecules in the system, and the first and second moments of this distribution. The Floquet spectrum reveals the dynamics of the reaction process which is regular in this case. Numerical results for small systems are provided. The first moment agrees with the predictions of a kinetic model, while, as expected for small systems, fluctuations about the mean are significant.

I demonstrate stochastic resonance in a discrete-state, continuous-time random walk in one dimension. The probabilities for the walker to step to the right or to the left depend on an external field. The field varies in space and time such that the walker feels a bistable, periodically modulated random potential. Unbiased random forces act on the walker in addition to the field. When the field is strong relative to the unbiased forces, the walker is confined to a single well, and a power spectrum shows low noise levels and little power at the modulation frequency. When the field is weak relative to the unbiased forces, the walker moves erratically between the wells, and a power spectrum is noisy. For intermediate field strengths, the walker moves periodically from one well to another, and the power at the modulation frequency increases dramatically with respect to the noise level. In this respect, the behavior of the discrete-state model is analogous to the standard, continuous-state Langevin models.