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Biomedical subjects

P A Fagan

Publications and source records attributed to P A Fagan.

At least 19 recordsLinked to original sources
PubMed2006

Complications of keratosis obturans.

Three patients with extensive keratosis obturans were treated during a 12-month period. One presented with an idiopathic sensorineural hearing loss and was found to have keratosis obturans in the contralateral, asymptomatic ear. The disease process had resulted in a horizontal semicircular canal fistula in what was now, effectively, the only hearing ear. The second patient had an extensive dehiscence of the tegmen tympani. The third presented with a facial palsy. An automastoidectomy cavity was present, with circumferential skeletonization of the descending facial nerve over a length of 1.5 cm and dehiscence of the temporomandibular joint and jugular bulb. All three patients were successfully treated by surgical formalization of their automastoidectomy cavities. They appeared to represent cases of keratosis obturans rather than external auditory canal cholesteatoma, on the basis of previously published reports.These complications and patterns of bone erosion have not previously been described in keratosis obturans. The third patient is believed to have the most extensive case of keratosis obturans yet described.

Aged↗
PubMed2004

Facial nerve outcome in non-vestibular schwannoma tumour surgery.

PROBLEMS/OBJECTIVES: Tumour size, intra-operative electrophysiologic thresholds and postoperative facial nerve function have been demonstrated to be important predictors of ultimate facial nerve function after vestibular schwannoma surgery. In general little attention has been given to the prediction of outcome of facial nerve function in non-vestibular schwannoma tumour surgery of the cerebellopontine angle (CPA). METHODOLOGY: A prospective study was performed to assess the predictive value of patient, tumour histology and electrophysiologic factors in the estimation of ultimate facial nerve outcome after this form of surgery. RESULTS: Sixteen patients satisfied the requirements of the study. Poor long-term facial nerve outcome was associated with abnormal pre-operative facial nerve function, facial nerve schwannomas, premeatal meningiomas and electrophysiologic stimulation thresholds of greater than 0.1 mA. CONCLUSIONS: It is concluded that tumour histology and pre-operative facial nerve function are additional factors that must be considered in the prediction of facial nerve function after non-vestibular schwannoma surgery of the CPA.

Aged↗
PubMed2002

Predictive factors of long-term facial nerve function after vestibular schwannoma surgery.

OBJECTIVE: To assess predictive factors of long-term facial nerve function in a series of patients undergoing vestibular schwannoma surgery and to evaluate the reproducibility of the relevant parameters. STUDY DESIGN: Prospective. SETTING: Three tertiary referral neurotology units in two separate countries. PATIENTS: A total of 67 patients, with normal preoperative facial function and an anatomically intact facial nerve postoperatively, undergoing vestibular schwannoma surgery during a sequential 18-month period. INTERVENTIONS: Recording of intraoperative stimulus amplitudes (minimum intensity medial to the tumor after excision) and postoperative facial nerve function up to 2 years after surgery. MAIN OUTCOME MEASURES: Long-term facial nerve function related to tumor size, early postoperative facial nerve function, and intraoperative electrophysiologic intensities. RESULTS: Multivariate logistic regression model identified tumor size and the minimum intensity required to provoke a stimulus threshold event medial to the tumor after excision as independent predictors of a favorable initial outcome. Immediate facial nerve function was the only independent predictor of long-term normal function. The sensitivity of this predictor was 95% (95% confidence interval [CI], 89-100%); specificity, 83% (95% CI, 62-100%); positive predictive accuracy, 96% (95% CI, 91-100%); and negative predictive accuracy, 77% (95% CI, 54-100%). CONCLUSION: The combination of electrophysiologic intensities and tumor size are reproducible and better predictors of initial facial nerve function than any individual parameter, but long-term facial nerve function is more likely to have a better outcome if the nerve is left intact and a per-operative graft repair is not performed. The study suggests that although the best available predictor of overall long-term facial nerve outcome is the level of early postoperative function, this factor is not useful in surgical rehabilitation decision making.

Adolescent↗
PubMed2001

Delayed facial palsy after vestibular schwannoma surgery.

OBJECTIVE: there is a lack of uniformity in the literature of the definition of delayed facial palsy (DFP) after vestibular schwannoma surgery. The aim of this study was to attempt to provide a clear definition of this clinical entity. METHODS: a prospective study was undertaken of all patients, with an intact facial nerve postoperatively, undergoing vestibular schwannoma surgery during a 16-month period. Delayed facial palsy was defined as any worsening of facial function after the initial assessment of postoperative function. RESULTS: a total of 67 patients, operated on between February 1994 and June 1995 satisfied the requirements of the study. Eight of the 67 patients developed a worsening of facial function after the first postoperative day. There were three males and five females with an age range of 29-73 years (mean, 53 years). CONCLUSION: DFP should be defined as any deterioration of facial function after vestibular schwannoma surgery.

Adult↗
PubMed2001

Schwannoma of the chorda tympani.

The authors present a rare clinical entity in a schwannoma of the chorda tympani. The case is discussed including the difficulty in making the diagnosis and management.

Adult↗
PubMed2001

Transtemporal facial nerve schwannoma without facial nerve paralysis.

Facial schwannoma is a relatively rare but well documented lesion, presenting either as a mass or with facial nerve symptoms. In this report, an extensive facial schwannoma, extending from the brain stem to the periphery with minimal facial nerve symptoms and normal facial function is presented.

Adult↗
PubMed1999

Prediction of postoperative facial nerve function in acoustic neuroma surgery.

There is a need for an uncomplicated, consistent method to predict facial nerve function after acoustic neuroma surgery. A prospective study with a 2-year follow-up of 35 patients undergoing acoustic neuroma surgery was performed assessing how well intraoperative facial nerve monitor electrophysiological thresholds and facial function postsurgery can predict ultimate nerve function. Tumour size was a strong predictor of immediate (P-value < 0.0005) and long-term facial nerve function (P-value = 0.004). Immediate facial nerve function was strongly predicted by stimulus intensity (P-value = 0.007) and there was a suggestion of a relationship between long-term facial nerve response and stimulus intensity. It was not possible to predict delayed facial dysfunction nor the extent or timing of recovery of abnormal function. It is concluded that the combination of facial function at 1 month postsurgery with tumour size and stimulus thresholds is the best available indicator of ultimate facial function.

Adult↗
PubMed1999

Solitary fibrous tumor of the cerebello-pontine angle.

A case is presented of solitary fibrous tumor occurring in the cerebello-pontine angle. There have been only two other reported cases of a solitary fibrous tumors in this region. Imaging studies showed the tumor to be characteristic in shape and position of an acoustic tumor. However, at surgery the tumor was found to have a "rock hard" consistency. Solitary fibrous tumor differs from acoustic schwannoma and meningioma in its histopathological features and in this case, regrowth, after incomplete excision, was extremely rapid.

Case Reports↗
PubMed1998

Imaging destructive lesions of the petrous apex.

Cholesterol granuloma and cholesteatoma are the two most common destructive lesions of the petrous apex. Arachnoid cyst is less common. These three expansile lesions are often indistinguishable on clinical grounds. Cholesterol granulomas can be treated effectively through internal drainage into the mastoid cavity or middle ear. Cholesteatomas, however, are managed by more aggressive and complicated removal, which often mandates the sacrifice of hearing. Symptomatic arachnoid cysts are amenable to simple surgical drainage. Therefore, accurate preoperative recognition on computed tomography (CT) and magnetic resonance imaging (MRI) is important in planning proper treatment. Thirteen cases of destructive lesions of the petrous apex are analyzed. The authors' experience illustrates that the "typical" CT and MRI radiographic features are diagnostic in some cases, but not in all. In this study the pathologic findings have been correlated with the radiologic features on both MRI and CT.

Adolescent↗
PubMed1998

The cerebellopontine angle: does the translabyrinthine approach give adequate access?

A long-standing but unfounded criticism of the translabyrinthine approach is the misperception that this approach does not give adequate access to the cerebellopontine angle. Because of what is perceived as limited visualization and operating space within the cerebellopontine angle, some surgeons still believe that the translabyrinthine approach is inappropriate for large acoustic tumors. In this study, the surgical access to the cerebellopontine angle by virtue of the translabyrinthine approach is measured and analyzed. The parameters are compared with those measured for the retrosigmoid approach. This series objectively confirms that the translabyrinthine approach offers the neurotologic surgeon a shorter operative depth to the tumor, via a similar-sized craniotomy. This permits superior visualization by virtue of a wider angle of surgical access. Such access is achieved with the merit of minimal cerebellar retraction.

Cerebellopontine Angle↗
PubMed1998

Pneumocephalus after acoustic neuroma surgery.

OBJECTIVE: The study was conducted to describe the diagnosis and management of pneumocephalus after acoustic tumor resection. STUDY DESIGN: The study design was a retrospective chart review. SETTING: The study was conducted as a tertiary otologic referral to the senior authors' practices (PAF, MDA). PARTICIPANTS: Three patients operated on for acoustic tumor in St. Vincent's General Hospital and the Scottish Hospital, Sydney, Australia, were studied. INTERVENTION: Observation in both cases and surgery in a case in which tension pneumocephalus was progressive were performed. MAIN OUTCOME MEASURE: Recovery will follow either spontaneously or after intervention. RESULTS: All patients had an uneventful recovery. CONCLUSION: In most cases, spontaneous resolution occurs. However, if surgical re-exploration is indicated, it is best performed via the blind sac subtotal petrosectomy of Fisch.

Aged↗
PubMed1996

An NMR study of [d(CGCGAATTCGCG)]2 containing an interstrand cross-link derived from a distamycin-pyrrole conjugate.

Minor groove binding compounds related to distamycin A bind DNA with high sequence selectivity, recognizing sites which contain various combinations of A.T and G.C base pairs. These molecules have the potential to deliver cross-linking agents to the minor groove of a target DNA sequence. We have studied the covalent DNA-DNA cross-linked complex of 2,3- bis(hydroxymethyl)pyrrole-distamycin and [d(CGCGAATTCGCG)]2. The alkylating pyrrole design is based on the pharmacophore of mitomycin C and is similar in substructure to another important class of natural products, the oxidatively activated pyrrolizidine alkaloids. Ligand-DNA NOEs confirm that the tri(pyrrole-carboxamide) unit of the ligand is bound in the minor groove of the central A+T tract. Unexpectedly, it is shifted by 1 bp with respect to the distamycin A binding site on this DNA sequence. The cross-link bridges the 2-amino position of two guanine residues, G4 and G22. The C3.G22 and G4.C21 base pairs exhibit Watson-Crick base pairing, with some local distortion, as evidenced by unusual intensities observed for DNA-DNA NOE cross-peaks. The model is compared with a related structure of a cross-linked mitomycin C:DNA complex.

Base Sequence↗
PubMed1996

NMR study of the conformation of the 2-aminopurine:cytosine mismatch in DNA.

DNA polymerase makes errors by misincorporating natural DNA bases and base analogs. Because of the wide variety of possible mismatches and the varying efficiency with which they are repaired, structural studies are necessary to understand in detail how these mispairs differ and can be distinguished from standard Watson-Crick base pairs. 2-Aminopurine (AP) is a highly mutagenic base analog. The objective of this study was to determine the geometry of the AP x C mispair in DNA at neutral pH. Although several studies have focused on the AP x C mispair in DNA, there is not as of yet consensus on its structure. At least four models have been proposed for this mispair. Through the use of NMR spectroscopy with selective 15N-labeling of exocyclic amino nitrogens on bases of interest, we are able to resolve ambiguities in previous studies. We find here that, in two different DNA sequences, the AP x C mispair at neutral and high pH is in a wobble geometry. The structure and stability of this base mispair is dependent upon the local base sequence.

2-Aminopurine↗
PubMed1996

The management of dysphagia in jugular foramen surgery.

From 1985-1994, the Skull Base Unit at St. Vincent's Hospital, Sydney, operated on 61 patients with tumours involving the jugular foramen. Pre-operative assessment by a Speech Pathologist and the institution of swallowing techniques prior to surgery have improved post-operative morbidity. Ancillary procedures at the time of surgery were not required in the majority of cases. An individual assessment of each patient early in the postoperative period was found to be more important with regard to the benefits of supplementary surgery. The majority of patients with dysphagia settled with conservative management and only a few underwent ancillary surgery. It is perceived that the cortical and subcortical control of swallowing is a major factor in the rehabilitation of these patients.

Adolescent↗
PubMed1996

Osteoma of the internal auditory canal: case report.

A 42-year-old man with normal hearing presented with a long history of vertigo and tinnitus. CT scan showed large osteomata of the internal auditory canal. Magnetic resonance imaging (MRI) was normal. The osteomata were removed surgically via the retrosigmoid approach and examined histologically. His symptoms were abolished. As MRI has become the gold standard in the search for small acoustic tumours it is likely that symptomatic bony lesions, rare though they are, will be missed if MRI is the sole imaging modality. A review of the literature is included.

Adult↗