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Biomedical subjects

J C Dort

Publications and source records attributed to J C Dort.

At least 19 recordsLinked to original sources
PubMed2001

Screening for cerebellopontine angle tumours: conventional MRI vs T2 fast spin echo MRI.

BACKGROUND: Unilateral audiovestibular symptoms are commonly seen in clinical practice and are rarely caused by retrocochlear pathology. However, clinicians are often required to rule out potentially serious causes of these unilateral symptoms. Gadolinium enhanced magnetic resonance imaging (GdMRI) is the most accurate test for detecting small cerebellopontine angle lesions and also screens the adjacent CNS structures. Its main disadvantage is the cost of the procedure. METHODS: We studied 100 consecutive patients with both GdMRI and a newer MRI screening study utilizing unenhanced T2-weighted fast spin echo (fse) MRI. Acquired images were randomly assessed by a panel of three neuro-radiologists. RESULTS: We found that the screening (fse) MRI was as sensitive and specific when detecting cerebellopontine angle tumors. CONCLUSIONS: We conclude that T2-weighted fse MRI is a safe and cost-effective alternative to GdMRI and offers better diagnostic utility when compared to auditory brain stem response (ABR) and CT scans.

Brain Stem↗
PubMed2000

Screening strategies for neonatal hearing loss: which test is best?

OBJECTIVE: The objective of this study was to evaluate the accuracy and cost effectiveness of three different methods of hearing screening in newborns. DESIGN: A prospective, randomized cohort design was used. One hundred and five newborns were tested in this preliminary study. SETTING: The study was conducted in a tertiary care hospital setting in both the well baby and special care nurseries. METHODS: Consenting subjects had their hearing tested using automated auditory brainstem response (AABR), distortion-product otoacoustic emissions, and click-evoked otoacoustic emissions. The time to perform the tests was recorded and the cost of each test was calculated. MAIN OUTCOME MEASURES: The main outcomes measured were the time taken to perform each test, the pass/fail rate for each test, and the estimated cost of the tests. RESULTS: In this small cohort of patients, we found that AABR was the most accurate test, but it took longer to perform and was more expensive than either of the otoacoustic emission tests. However, the sensitivity and specificity of otoacoustic emissions were less than that of AABR. Test time decreased as the examiner gained experience, and we anticipate that experience will also result in better accuracy for the otoacoustic emission tests. CONCLUSIONS: Hearing screening in a hospital-based newborn population is both feasible and cost effective. Although AABR was more expensive, its better accuracy must be considered. As technology improves, the cost of all three tests will diminish. More robust conclusions cannot be made based on this small patient population.

Canada↗
PubMed1999

Monitoring respiratory function and sleep in the obese Vietnamese pot-bellied pig.

Development of drug treatments for obstructive sleep-disordered breathing has been impeded by the lack of animal models. The obese pig may be a suitable animal model, as it has been reported to experience sleep-disordered breathing resembling human obstructive sleep apnea. The purpose of this paper is to describe in detail techniques for chronic instrumentation of the obese Vietnamese pot-bellied pig and to study respiratory function during sleep. Under general anesthesia, four obese pigs were instrumented for long-term recording of intrapleural and tracheal pressures, genioglossal EMG, and bioelectric signals related to sleep. A custom-fitted face mask was used to record respiratory variables including airflow, snoring, and expired CO(2). Most chronic instrumentation provided robust signals for up to 6 wk after installation. All pigs displayed sleep-disordered breathing characterized by increased resistance to airflow, snoring, inspiratory flow limitation, and possible sleep disruption. Apneas and hypopneas were not a feature of breathing during sleep in these animals. Nonetheless, this animal preparation may be useful for exploring possible drug treatments for obstructive sleep-disordered breathing.

Animals↗
PubMed1997

Asymmetric hearing loss: toward cost-effective diagnosis.

OBJECTIVE: Unilateral audiovestibular symptoms are commonly seen in clinical practice, and the treating physician frequently considers retrocochlear disease in the differential diagnosis. These considerations often precipitate a lengthy and expensive battery of tests. This study was conducted to evaluate the diagnostic yield of the various tests available in the investigation of these symptoms and to recommend changes to practice patterns, if appropriate. METHODS: We examined a cohort of 310 patients with unilateral audiovestibular symptoms who were referred to our radiology department for investigation. All patients had complete auditory assessments, and 144 underwent auditory evoked potential testing (ABR). There were 258 contrast-enhanced CT (CECT) scans and 86 gadolinium-enhanced MRI (Gd-MRI) scans performed. RESULTS: A total of 12 cerebellopontine angle (CPA) tumours were diagnosed. CONCLUSIONS: MRI is the diagnostic tool of choice in patients with asymmetric sensory neural hearing loss (ASHL), but it is expensive and not always easily available. Analysis of diagnostic accuracy of CECT and ABR, both used as screening tests, demonstrate their limitations and reveals that CECT is no more accurate than ABR, although it is three times more costly. Based on these data, we have changed our diagnostic approach to patients with unilateral audiovestibular symptoms. Patients are either evaluated with MRI or are screened initially with ABR based on clinical suspicion. CECT is no longer routinely included in the evaluation of patients with ASHL. Finally, newer emerging MRI techniques promise faster and less expensive examinations with increased diagnostic accuracy.

Algorithms↗
PubMed1997

Magnetic resonance imaging of the extratemporal facial nerve of the rat.

OBJECTIVE: Magnetic resonance imaging (MRI) is an evolving technology that is being investigated for application in the study of the facial nerve. At the present time the majority of investigators use paramagnetic contrast agents, and the clinical utility of MRI for evaluation of facial paralysis is unproved. This study investigated both normal and injured rat facial nerves without contrast enhancement. METHOD: Anatomic dissection and histologic studies were performed to better define the location of the facial nerve. A surface coil was used to improve image resolution. RESULTS: Proton-weighted images showed that the normal facial nerve was a solid structure while the injured facial nerve was bright on T2-weighted images. CONCLUSION: MRI is a potentially useful method of investigating patients with facial nerve dysfunction. Further research is needed to clarify its role.

Animals↗
PubMed1997

Biochemical changes in denervated muscle identified by magnetic resonance spectroscopy.

OBJECTIVE: Magnetic resonance spectroscopy (MRS) has the potential to noninvasively delineate early biochemical changes in denervated muscle. In this study, we examine metabolic changes in denervated rat facial muscles using quantitative invitro 1H and 31P MRS. METHODS: Forty male Wistar rats were subjected to transection of the facial nerve trunk on the left and sham exposure on the right, and allowed to recover. The animals were then reoperated at 1, 2, 4, or 8 weeks after the initial procedure. EMG of the facial muscles and facial nerve conduction studies were performed at both time points, and facial muscles were harvested from normal and control sides at the second procedure. Perchloric acid extracts of facial muscles were then prepared for analysis using MRS. RESULTS: The results showed a progressive time-dependent decrease in Cr, PCr, Pi, ATP, and ADP all on the transected side. CONCLUSION: This study is an important step in the development of clinically relevant noninvasive methods of assessing and quantifying degeneration in nerve-muscle systems.

Adenosine Diphosphate↗
PubMed1996

Posttraumatic macroglossia complicated by hyaluronidase injection.

A patient with posttraumatic macroglossia has been presented. A literature review reveals that this is a rare sequela of tongue injury and is usually of acute onset. The delayed symptom of swelling in this patient and the exacerbation of swelling in association with hyaluronidase suggest a causal relationship between the two events. Macroglossia has not been reported in association with hyaluronidase injection, and it is recommended that the drug not be used to treat swelling after tongue injury.

Adult↗
PubMed1995

Nonmetallic foreign bodies of the skull base: a diagnostic challenge.

Cases of physical trauma have become more common in emergency departments, since life in modern society has become increasingly dangerous. Foreign bodies in the head and neck region are more common, therefore, and management principles are well-defined. Typically, these foreign bodies are metal, plastic, or glass and often easily diagnosed; however, wooden foreign bodies pose special problems for the physician and, therefore, warrant separate consideration. We present the case of a 21-year-old male who was stabbed in the submental region with a large wooden stake and discuss the surgical and follow-up treatment of this interesting case, including the roles and limitations of angiography, computerized tomography, and magnetic resonance imaging.

Adult↗
PubMed1994

CO2 laser repair of the facial nerve: an experimental study in the rat.

The facial nerve is often injured by trauma, infection or during the course of tumour resection. Many techniques of nerve anastomosis have been described with the current standard nerve repair using the microscope and monofilament suture. The purpose of this study was to evaluate the CO2 surgical laser as a tool for facial nerve anastomosis. Following preliminary electrical measurements 36 nerves were anastomosed using either laser or conventional monofilament suture. Laser anastomosis had neither beneficial nor detrimental effects on nerve regeneration. This method of anastomosis may be advantageous when surgical access is limited. In addition this study found that the use of CO2 laser as a dissecting or vapourizing tool in proximity to intact facial nerves results in degenerative changes.

Anastomosis, Surgical↗
PubMed1994

Unilateral vestibular deafferentation: a model of adaptation.

After acute loss of peripheral vestibular function, a centrally adaptive process takes place. Clinical measurements of vestibular adaptation are useful, both diagnostically and as a means of following patients after acute vestibular deficits. Ocular torsion is one measurement that can be used to follow these acutely disabled patients. The measurement is made from fundus photographs and is technically easy to perform and interpret. We present a pilot study from our Vestibular Disorders Clinic using fundus photography to measure the optic nerve head-foveal angle in six patients undergoing unilateral vestibular neurectomy, with subsequent analysis resulting in a speculative mathematical model of vestibular compensation in the roll plane. While the identification or selection of patients with significant ocular torsions from the vestibular population remains ill-defined, fundus photography remains an easy and useful method of following compensation in postoperative patients.

Adaptation, Physiological↗
PubMed1994

Acute epiglottitis in adults: diagnosis and treatment in 43 patients.

Epiglottitis (supraglottitis) is an acute infection involving the supraglottic larynx that usually occurs in children, but can also affect adult patients. The purpose of this study was to retrospectively analyze diagnostic and treatment methods in adults with epiglottitis seen over a 10-year period at the Winnipeg Health Sciences Centre. Forty-three epiglottitis patients over the age of 16 were treated between 1982 and 1992. Treatment was individualized according to airway status at presentation, and not based on clinical staging protocols. A total of 29 patients were treated conservatively, whereas 14 patients were intubated immediately. One expectantly managed patient had to be intubated on the ward, and one patient died from septicemia. No presenting symptom or sign reliably predicted the need for intubation. Epiglottitis is seen in adults and can be easily and safely diagnosed by either indirect or flexible laryngoscopy. Endotracheal intubation is the safest and most direct means of securing the airway in severely affected patients. Staging systems are useful for retrospective data analysis, but should not be relied on to predict the course of patients with an inherently unpredictable disease.

Acute Disease↗
PubMed1994

Cholesteatoma: diagnosis and staging by CT scan.

Chronic otitis media is frequently seen in otolaryngologic practice. Cholesteatoma is less common and can present a diagnostic challenge. Temporal bone imaging studies are often used both to support the clinical diagnosis of cholesteatoma and to ascertain the extent of the disease. The exact role of CT in patients with cholesteatoma is unclear. This retrospective study compares CT with the operative findings in 44 patients operated on for cholesteatoma. Results show that while CT can detect abnormalities in the temporal bone, its ability to diagnose cholesteatoma is poor. We conclude that CT should be used selectively in those patients presenting diagnostic dilemmas or when other concomitant pathology (i.e., complications, recurrent disease, etc.) is suspected.

Adolescent↗
PubMed1993

Solitary fibrous tumour: report of two new locations in the upper respiratory tract.

Solitary fibrous tumours are uncommon spindle cell neoplasms generally associated with serosal surfaces, especially the pleura ('localized fibrous mesothelioma'). Recently, these tumours have been documented in extraserosal sites. We report two solitary fibrous tumours, including one occurring in the paediatric age group, arising in two previously unreported locations, parapharyngeal space and epiglottis. These cases expand the range of sites where this tumour may originate and confirm the tendency of extrapleural cases to involve the upper respiratory tract and adjacent structures.

Adolescent↗
PubMed1991

Primary extramedullary plasmacytoma of the salivary glands.

Primary extramedullary plasmacytomas (PEMP) are uncommon plasma cell neoplasms that generally occur in the submucosal tissue of the upper airway. Salivary gland PEMP is an extremely rare condition. This report describes a unique case of PEMP in the parotid gland associated with pulmonary amyloidosis. A review of all salivary gland PEMP's suggests that they behave similarly to PEMP's in other locations. The treatment of choice for localized disease is radiotherapy which should include regional lymphatics. Local control can be achieved in the majority of cases. The minority of patients develop systemic metastases and die from their disease. Chemotherapy can control disseminated disease and may induce remission.

Aged↗
PubMed1991

Laryngeal examination: a comparison of mirror examination with a rigid lens system.

Indirect mirror laryngoscopy is the standard screening examination used in patients with complaints referable to the larynx and upper aerodigestive tract. The purpose of this study was to prospectively evaluate, in 100 patients, the diagnostic accuracy and examination success rate of indirect laryngoscopy versus a rigid rod examination. Fifty-two percent of mirror examinations were successful as were 83% of rod exams. This was a significant difference in success rate. From the 29 patients who underwent direct laryngoscopy, one false negative and one false positive mirror examination and one false positive rod examination were found. We conclude that the mirror is a useful screening tool so long as strict examination criteria are used. The rigid rod adds further diagnostic information in those patients who cannot be evaluated with a mirror.

Equipment Design↗