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Biomedical subjects

N Martin

Publications and source records attributed to N Martin.

At least 199 records · Page 11Linked to original sources
PubMed1992

Trigeminal neuromas: assessment of MRI and CT.

We report four cases of trigeminal neuroma. One of the patients had von Recklinghausen's neurofibromatosis with plexiform neurofibromas of the branches of the trigeminal nerve. MRI provided more information than CT as regards the spread of tumour: extension to the mandibular and maxillary division of the trigeminal nerve was well demonstrated on sagittal and coronal sections. This examination yielded an accurate census of the intraocular plexiform neurofibromas and allowed a correct preoperative diagnosis to be obtained. With Gd-DOTA, better definition of the outline of the tumours and of cystic components was obtained. However, CT was better for demonstration of bone erosions.

Adult↗
PubMed1992

Haemangioma of the petrous bone: MRI.

Gd-DTPA-enhanced MRI provided accurate demonstration of the site and extension of a haemangioma of the petrous bone. Enhanced-MRI could allow early detection and differentiation from the other more common tumours of the geniculate ganglion area, thereby permitting the surgeon to remove the tumour, while preserving the facial nerve. CT is, however, required to display the characteristic ossification in these tumours.

Contrast Media↗
PubMed1992

A computational account of deep dysphasia: evidence from a single case study.

We present a case study of a patient, NC, who demonstrates the defining characteristics of deep dysphasia including semantic errors in repetition and an inability to repeat nonwords. In addition, NC's single word repetition and lexical decision performances are influenced by the imageability of the word input. NC also demonstrates a severely restricted phonological short-term memory (one digit, one word). Although his phonological discrimination is good in a minimal pairs judgment task, it becomes impaired when a delay is imposed or rehearsal is prevented between presentation of each member of a pair. NC's output is fluent but contains many formal paraphasias and neologisms. NC's total language profile is evaluated within the framework of Dell's (1986) interactive spreading activation model of language production. Adapting this output model to input processes, we account for all of NC's deep dysphasic symptoms as well as his pattern of production in a way that is more parsimonious than other attempts to model this disorder. In particular, we suggest that the semantic and formal paraphasias in naming and repetition result from a pathological increase in the rate of decay of primed nodes in the semantic-lexical-phonological network. This rapid decay increases the probability that phonologically and/or semantically related lexical nodes primed by top-down and bottom-up feedback during the operation of lexical activation and retrieval will be activated and selected instead of the lexical target. The advantages of using this model to account for aphasic symptoms and the implications for other lexical theories are discussed.

Adult↗
PubMed1992

Central effects of epidural and intravenous clonidine in patients anesthetized with enflurane/nitrous oxide. An electroencephalographic analysis.

Epidural clonidine produces regional anesthesia as well as sedation and a decrease in anesthetic requirements. To assess these effects, the electroencephalogram (EEG) was recorded after epidural or intravenous (iv) injection of clonidine during enflurane/N2O anesthesia. Eighteen ASA physical status 1 women undergoing vaginal hysterectomy were allocated randomly to receive epidural clonidine (8 micrograms.kg-1 in 4 ml over 2 min) and iv saline (10 ml over 14 min); or epidural saline (4 ml over 2 min) and iv clonidine (8 micrograms.kg-1 in 10 ml over 14 min); or epidural saline (4 ml over 2 min) and iv saline (10 ml over 14 min). The level of anesthesia was kept constant beginning 10 min before and until 44 min after epidural injection. EEG power spectral analysis was performed throughout the study period using a 2-min average of 8-9-s epochs. Clonidine significantly reduced EEG total power only after epidural administration (P less than 0.05). Relative power increased in the delta band in both the epidural and iv clonidine groups (P less than 0.001). The depression of the total EEG power after epidural injection could be explained neither by systemic absorption alone nor by hemodynamic variations. It may represent the contribution of the direct spinal action of this alpha 2-adrenergic agonist to general anesthesia.

Anesthesia, General↗
PubMed1992

Corneal opacity in LCAT disease.

Deficiency of lecithin:cholesterol acyltransferase, LCAT disease, is one of the dyslipoproteinemias with characteristic lipid deposits in the cornea. The present report documents the clinicopathologic abnormalities of one case in which a full-thickness corneal specimen was obtained at the time of corneal transplantation. The characteristic clinical abnormality was a progressive corneal opacification with a peripheral arcus that extended into the sclera. The pathologic abnormality consisted of vacuoles prevalent in the anterior corneal stroma by light microscopy and containing extracellular, membranous deposits by electron microscopy. These observations confirm and supplement the previous six pathologic reports of corneal changes in LCAT disease and demonstrate, for the first time, histopathologic evidence of unesterified cholesterol in the corneal stroma of LCAT disease.

Corneal Opacity↗
PubMed1992

Rheumatoid arthritis in twins: a study of aetiopathogenesis based on the Australian Twin Registry.

The 1980 cohort of the Australian Twin Registry contains 3808 pairs of twins, 258 of whom self reported a diagnosis of rheumatoid arthritis (RA) in one or both subjects. Seventy two pairs were lost to follow up by 1990. The remaining 186 pairs received a self administered questionnaire, followed, if necessary, by telephone interviews to them, their general practitioners, and their specialists. Twenty discordant and three concordant pairs of twins were verified as having RA. The prevalence of RA in this sample was 0.40%. There was an 89% false positive rate for the self reported diagnosis of RA. Pairwise concordance percentages for RA were as follows: monozygotic 21% (95% confidence interval (CI) = 6 to 44), dizygotic 0% (95% CI = 0 to 25). It was concluded that: (a) there is a high false positive rate in self reporting RA; (b) the prevalence of RA in Australia may be less than the 0.8-1.0% often quoted; and (c) genetic factors play some part in the aetiopathogenesis of RA but do not account entirely for its determination.

Adolescent↗
PubMed1992

[Imaging of the facial nerve and the petrous apex].

From its origin in the pons to its extracranial exit with a long intrapetrous course, the facial nerve raises various diagnostic problems related to the site and extent of the lesions, which involves the whole field of petrous pathology. The study of the pathology of the neighbouring petrous apex completes this regional analysis. Today, in accordance with the anatomical loco-regional complexity, MRI is the predominant modality of diagnostic imaging (but must be associated with CT to allow the more accurate detection of subtle bone changes); it will be at best directed by the clinical and functional data which reflect the underlying pathophysiologic mechanisms.

Cranial Nerve Diseases↗
PubMed1992

[Hemangioma of the petrous bone. Diagnosis and treatment].

Hemangiomas of the temporal bone are benign, vascular and are tumors. The diagnosis is in most cases made during the operation because the symptoms are non conclusive. Two cases were recently observed: one simulating a Meniere disease while the tumor was developed close to the jugular bulb and the endolymphatic sac; the second invaded the geniculate area and the petrous apex and was revealed by a progressive facial palsy.

Facial Paralysis↗
PubMed1992

MRI anatomy of the acoustic-facial bundle in vivo.

In this study performed on 5 healthy volunteers the authors used oblique axial, coronal and sagittal MRI sections suitable to be anatomical configuration of the acoustic-facial bundle and were able to individualize the nerves forming this bundle throughout their course, with the sole exception of the intermediate nerve (VII2). They also analysed the relations of these nerves between themselves and with the other elements of the cerebellopontine angle. In addition, a proton-density sequence (SE, 6,000/30 ms) made it possible to differentiate in vivo between the grey matter and the white matter sufficiently to individualize the principal nuclei and tracts of the brain stem, and in particular the main vestibulo-cochlear central pathways.

Adult↗
PubMed1991

Extended retrolabyrinthine transtentorial approach to petroclival lesions.

In this communication, an extension of the retrolabyrinthine approach that has permitted safe, effective access to the petrous tip and clivus is presented. The basic technique involved complete mastoidectomy, preservation of the middle and inner ear structures, removal of the sigmoid and middle fossa plates, middle and posterior fossa craniotomies, ligation of the superior petrosal sinus, and division of the tentorium. Nine cases that exemplified the versatility of this approach constituted the basis of this paper: 2 cholesteatomas, 2 basilar artery aneurysms, 2 chordomas, and 3 meningiomas. The indications for, and complications of, this method have been discussed.

Adult↗
PubMed1991

[Infratemporal extension of tumors of the skull base].

The tumors of the middle and posterior portion of the skull base may extend extracranially. The spread of the tumors towards the infratemporal fossa is rare. Among 23 skull base tumors with extracranial extension which were diagnosed during the last 5 years, only two middle ear epidermoid carcinomas extended into the infratemporal fossa. Subtotal surgical removal of tumors was obtained in both cases through a subtotal petrectomy with an ultrasonic aspiration of the extracranial extension followed by transcutaneous irradiation. One case is followed free of disease 2 years and a half after the beginning of the treatment. The spread of the tumor into the infratemporal fossa might not be of poor prognosis.

Aged↗
PubMed1991

[Contribution of magnetic resonance imaging in the evaluation of chronic otitis].

Thirty four patients with a chronic otitis were evaluated prospectively by magnetic resonance imaging (MRI) to delineate its contribution in the diagnosis of middle ear masses. The results were correlated to the CT and the surgical and pathological findings. MRI permitted to differentiate the inflammatory tissues from either cholesteatoma, cholesterol granuloma and cerebromeningeal hernia.

Chronic Disease↗
PubMed1991

[Meningocerebral hernia and defects of the tegmen. Diagnosis and surgical treatment].

Eight defects of the tegmen tympani or antri have been operated on during the last two years. Among these cases, 4 brain herniae were associated with the defect of the tegmen. Magnetic resonance imaging permitted to evaluate accurately the space occupying lesions into the mastoid cavity and disclosed the brain and/or meningeal herniations. The defect of the tegmen was oblitered through a middle fossa approach whereas the hernia was resected through a mastoid approach when necessary.

Adult↗