Development of a patient specific artificial tracheal prosthesis: design, mechanical behavior analysis and manufacturing.

There is a need to create patient specific organ replacements as there are differences in the anatomical dimensions among individuals. High failure rates in tracheal prosthesis are attributed to the lack of mechanical strength and flexibility, slow rate of growth of ciliated epithelium and leakage of interstitial fluid into the lumen. This paper proposes a methodology of design, simulations and fabrication of a patient specific artificial tracheal prosthesis for implantation to closely mimic the biomechanical properties of the natural trachea, and describes the prototype device and its materials. Results show that the patient-specific trachea prosthesis has mechanical properties approximate that of normal tracheal rings. The user centric tracheal prosthesis is demonstrated to be a promising candidate for tracheal replacement.

A bioabsorbable microclip for laryngeal microsurgery: design and evaluation.

Epithelial flaps created during laryngeal microsurgery require apposition to facilitate proper healing. Current technologies are restricted by minimal access of the surgical site, posing various limitations in application. In this paper, we propose a novel magnesium-based bioabsorbable microclip, discuss our design considerations and evaluate the microclip's feasibility as a miniature wound closure device. Ex vivo experiments demonstrate that the microclip fastens securely to the vocal fold, while in vivo studies show bioabsorbability and a lack of adverse side effects, suggesting that the microclips are viable as implantable devices.

Design of a mechanical larynx with agarose as a soft tissue substitute for vocal fold applications.

Mechanical and computational models consisting of flow channels with convergent and oscillating constrictions have been applied to study the dynamics of human vocal fold vibration. To the best of our knowledge, no mechanical model has been studied using a material substitute with similar physical properties to the human vocal fold for surgical experimentation. In this study, we design and develop a mechanical larynx with agarose as a vocal fold substitute, and assess its suitability for surgical experimentation. Agarose is selected as a substitute for the vocal fold as it exhibits similar nonlinear hyperelastic characteristics to biological soft tissue. Through uniaxial compression and extension tests, we determined that agarose of 0.375% concentration most closely resembles the vocal fold mucosa and ligament of a 20-year old male for small tensile strain with an R(2) value of 0.9634 and root mean square error of 344.05±39.84 Pa. Incisions of 10 mm lengthwise and 3 mm in depth were created parallel to the medial edge on the superior surface of agar phantom. These were subjected to vibrations of 80, 130, and 180 Hz, at constant amplitude of 0.9 mm over a period of 10 min each in the mechanical larynx model. Lateral expansion of the incision was observed to be most significant for the lower frequency of 80 Hz. This model serves as a basis for future assessments of wound closure techniques during microsurgery to the vocal fold.

Stridor in Parkinson's disease: a case of 'dry drowning'?

OBJECTIVES: (1) To present a rare case of stridor secondary to prolonged laryngospasm in a patient with Parkinson's disease, and (2) to review the literature on stridor in Parkinson's disease. METHODS: We report a 73-year-old Parkinson's disease patient who developed acute stridor due to prolonged laryngospasm triggered by overspill of excessive secretions. The literature was reviewed, following a Medline search using the keywords 'Parkinson's disease' and 'stridor' or 'airway obstruction' or 'laryngospasm' or 'laryngeal dystonia' or 'bilateral vocal cord palsy'. RESULT: Only 12 previously reported cases of stridor in Parkinson's disease patients were identified. Causes included bilateral vocal fold palsy (eight cases), laryngospasm (five), and dystonia of the jaw and neck muscles (two). The mechanism of laryngospasm in our patient was similar to 'dry drowning', and has not previously been described. CONCLUSION: Laryngospasm can be triggered in Parkinson's disease by excessive secretions entering the larynx. The mechanism is similar to 'dry drowning'. Treatment focuses on reducing secretions. The use of botulinum toxin to reduce spasm is inappropriate in this situation. This case emphasises the importance of recognising different causes of stridor in Parkinson's disease patients, as this affects management.

Epstein-Barr virus-associated smooth muscle tumour mimicking bilateral vocal process granuloma.

A case is presented of a 36-year-old Chinese woman with a renal transplant for end-stage renal failure due to Goodpasture's syndrome. She presented with a year's history of throat discomfort and acid regurgitation into her throat. Videolaryngoscopy revealed bilateral vocal process granuloma, presumed to be due to gastroesophageal reflux. A four-week course of high dose omeprazole was prescribed. On follow up a month later, the granulomas had enlarged, and laser excision was undertaken. Histological and immunohistochemical staining was consistent with Epstein-Barr virus-associated smooth muscle tumour. This is believed to be the first reported case in the English literature of such a tumour affecting the vocal process. The aim of this paper is to present the pathogenesis, clinical behaviour and treatment of Epstein-Barr virus-associated smooth muscle tumour, and to review the literature concerning the differential diagnosis of polypoid vocal process lesions.

Cortical excitability changes associated with musical tasks: a transcranial magnetic stimulation study in humans.

Neuroimaging studies have suggested differences in cortical activation in human vocalization and musical tasks. However, functional neurophysiological evidence on cortical excitability changes is lacking. We utilized transcranial magnetic stimulation to demonstrate changes in cortical excitability during overt humming and singing tasks. The findings complement those from neuroimaging and support the existence of separate bilateral deep-seated neural networks, as distinct from those for vocalization.

Imaging the sphenoid sinus: pictorial essay.

This paper focuses on the spectrum of sphenoid sinus lesions that may be seen radiologically and the mapping of disease extent. Imaging plays a central role in the assessment of sphenoid sinus disease. Although primary sphenoid sinus disease is uncommon, this sinus is nevertheless affected secondarily by a variety of pathological processes.

Isolated sphenoethmoid recess polyps.

Isolated sphenoethmoid recess (SER) polyps are rare. They usually arise from the sphenoid sinus. We report six patients with SER polyps as the only abnormal clinical finding at initial presentation. All cases were investigated with outpatient biopsy and computed tomography (CT) or magnetic resonance (MR) imaging. Pre-operative histology revealed three cases of inflammatory disease, two cases with inverted papilloma, and one case of an ectopic pituitary adenoma arising from the sphenoid sinus. One of the inflammatory polyps arose directly from the mucosa around the sphenoid ostium. The other five cases involved the sphenoid sinus. Except for the ectopic pituitary adenoma all the polyps were managed by transnasal endoscopic surgery. We emphasize that isolated SER polyps may signify existing sphenoid pathology and a pre-operative biopsy is valuable for planning surgery.

Sphenoid sinus mucocoele presenting with isolated oculomotor nerve palsy.

We describe two cases of sphenoid sinus mucocoele. Both presented with isolated oculomotor nerve palsy. Mucocoeles involving only the sphenoid sinus are uncommon. They are probably under-diagnosed as they may be asymptomatic or cause non-specific symptoms. Nasal symptoms occur infrequently but the close relationship of the sphenoid sinus to the orbital apex means that ocular symptoms including cranial nerve palsies are a common presenting feature. Involvement of the third cranial nerve in isolation is rare but has important neurosurgical implications which must be excluded before this symptom is attributed to the sphenoid sinus.

Chondrosarcoma of the petrous apex. Dilemmas in diagnosis and treatment.

A case of chrondrosarcoma of the petrous temporal bone is presented. Chondrosarcomas rarely occur intracranially and typically present apex mass. The dilemmas faced in the diagnosis and treatment of petrous apex chondrosarcomas are discussed. This case also gives interesting insight into the natural history of this tumour.

Endoscopic management of orbital apex lesions.

Lesions of the orbital apex often present a diagnostic dilemma. Clinical assessment and imaging studies are helpful but a tissue biopsy is often required. The morbidity associated with transcranial approaches to the orbital apex may outweigh the benefits of obtaining a biopsy by these routes. Fine needle aspiration cytology of orbital apex lesions can be performed but there are disadvantages with this method. We describe a transnasal endoscopic technique to biopsy the orbital apex. The technique was used successfully to obtain a tissue diagnosis in six patients with orbital apex lesions. This enabled commencement of definitive treatment. There were no significant complications. The transnasal approach to the orbital apex using the endoscopes is reliable. Endoscopes provide excellent illumination, magnification, and a panoramic view of the operative field.

Epithelial-myoepithelial carcinoma of the parotid gland. An unusual cause of ear canal stenosis.

Epithelial-myoepithelial carcinoma (EMC) accounts for approximately one per cent of salivary gland tumours. This tumour is gaining wider recognition following inclusion into the WHO histological classification of salivary gland tumours in 1990. Salivary gland tumours characteristically present with an enlarging mass. We describe an unusual presentation of a salivary gland tumour with stenosis of the external ear canal in the absence of a palpable mass. EMC usually arises from the salivary glands but isolated cases have been described arising primarily from the paranasal sinuses, trachea and lacrimal gland. The management of this tumour is still evolving with surgical excision being the main-stay of treatment. The efficacy of radiotherapy has not yet been established but high local recurrence rates despite apparently adequate excision and the possibility of a multicentric origin of the tumour may herald an increasing role for radiotherapy in the future. We stress the importance of awareness of adjacent structures when considering the cause of cartilaginous canal stenosis.