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Biomedical subjects

J M Tew

Publications and source records attributed to J M Tew.

At least 73 records · Page 4Linked to original sources
PubMed1993

Transpetrosal approach: surgical anatomy and technique.

Transpetrosal operations have been shown to offer distinct advantages over traditional operations in approaching lesions of the petroclival area. Confusion about these approaches exists due to the variety of names given to these procedures and the lack of detailed descriptions needed to perform them. After extensive review of the literature, we have determined that all transpetrosal techniques fall into one of two categories: anterior petrosectomy or posterior petrosectomy. Combining one of these procedures with existing conventional procedures accurately describes all existing transpetrosal operations and eliminates confusion over nomenclature. In addition, through a series of cadaveric dissections and operative experience, we have detailed each of these procedures as a series of steps that will enable the surgeon to understand the unfamiliar anatomy of the temporal bone and to perform these transpetrosal techniques.

Brain Neoplasms↗
PubMed1993

Seizure control after surgery on cerebral arteriovenous malformations.

Prediction of seizure control after surgery on cerebral arteriovenous malformations (AVM's) is currently unavailable. Between 1982 and 1990, 54 patients (30 males, 24 females) with epilepsy caused by a supratentorial cerebral AVM, without prior manifestation of intracranial hemorrhage, were surgically treated. Patients ranged in age from 11 to 59 years at seizure onset and from 13 to 70 years at surgery; the duration of seizure history ranged from several months to 27 years. The AVM's were located in the temporal (17 cases), frontal (15), parietal (10), rolandic (two), and occipital (two) regions; eight were multilobular. All patients underwent preoperative electroencephalography, intraoperative electrocorticography, and total excision of the AVM; additional cortical excision was performed in 25 cases. Remote seizure foci were identified in the ipsilateral mesial temporal structure in 10 patients with AVM's located in the lateral or posterior temporal lobe and in one with an AVM in the anterior frontal region. Two patients required a second operation to remove a remote seizure focus. Among the 54 patients, there were no operative deaths. After surgical treatment, two patients developed hemiparesis, one had contralateral paresthesia of limbs, two suffered partial visual field defects, and five experienced temporary speech disturbances. Postoperative results of seizure control during follow-up study (mean duration 4.8 years) were excellent in 38 patients (70.4%), good in 10 (18.5%), fair in five (9.3%), and poor in one (1.9%). Results appear to correlate with age at seizure onset, duration of seizures, location of lesions, and cortical excision. Excellent results were shown in 18 (60%) of 30 patients whose age at seizure onset was 30 years or less and in 20 (83.3%) of 24 whose age at seizure onset was greater than 30 years. Eighteen (90%) of 20 patients had excellent results when seizure duration was 1 year or less; only 25% of these underwent cortical excision. Twelve (71%) of the 17 temporal AVM's were associated with demonstrable epileptic foci. Secondary epileptogenesis can occur in humans with supratentorial cerebral AVM's; cortical excision in selected patients can improve the outcome of seizure control. Early surgery of a cerebral AVM in young patients presenting with epilepsy is an important consideration.

Adolescent↗
PubMed1992

Development of cerebral arterial innervation: synchronous development of neuropeptide Y (NPY)- and vasoactive intestinal polypeptide (VIP)-containing fibers and some observations on growth cones.

The pre- and postnatal development of sympathetic fibers containing neuropeptide Y (NPY) and parasympathetic fibers containing vasoactive intestinal polypeptide (VIP) supplying the cerebral arteries were studied with immunohistochemistry in rats. The innervation patterns and densities of NPY and VIP fibers were similar at all stages of development and similar to that previously reported for norepinephrine (NE). There was a striking reorganization of the innervation pattern of all three fiber systems between the first and second postnatal weeks. At all stages of development prior to the first postnatal week, growth cones were present on individual fibers at the distal part of major cerebral arteries and the middle segment of the basilar artery. The growth cones had a range of shapes from blunt to stellate, lanceolate or filiform. NPY and VIP immunoreactive granules were commonly present. The present results taken with our earlier developmental study of NE fibers (J. Comp. Neurol., 271 (1988) 435-444), demonstrate that: (1) both sympathetic and parasympathetic perivascular nerves on immature cerebral vessels develop with similar sequences: first longitudinal fibers and fiber bundles are present; these transform to a meshwork pattern and finally transform again into the mature, predominantly circumferential pattern; (2) both the classical (NE) and peptidergic transmitters (NPY) within the sympathetic system appear to develop identically in terms of time of appearance, innervation patterns, densities and reorganization.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic Fibers↗
PubMed1992

Association of meningiomas with dural "tails"; surgical significance.

Intracranial meningiomas are characteristically benign tumours with a tendency to recur following surgical resection. Our group is investigating the pathogenesis of meningioma recurrence. In our initial studies we identified two cases of dural "tails" associated with intracranial meningiomas. Gadolinium-enhanced magnetic resonance images were utilized to identify the dural "tails" preoperatively. These images aided us in performing a more complete surgical resection of the meningiomas. Histopathological confirmation of meningotheliomatous cell infiltration into the dural "tails" demonstrates their surgical significance.

Adult↗
PubMed1992

Tumors of the lateral wall of the cavernous sinus.

The lateral dural wall of the cavernous sinus is composed of two layers, the outer dural layer (dura propria) and the inner membranous layer. Tumors arising from the contents of the lateral dural wall are located between these two layers and are classified as interdural. They are in essence extradural/extracavernous. The inner membranous layer separates these tumors from the venous channels of the cavernous sinus. Preoperative recognition of tumors in this location is critical for selecting an appropriate microsurgical approach. Characteristics displayed by magnetic resonance imaging show an oval-shaped, smooth-bordered mass with medial displacement but not encasement of the cavernous internal carotid artery. Tumors in this location can be resected safely without entering the cavernous sinus proper by using techniques that permit reflection of the dura propria of the lateral wall (methods of Hakuba or Dolenc). During the last 5 years, the authors have identified and treated five patients with interdural cavernous sinus tumors, which included two trigeminal neurinomas arising from the first division of the fifth cranial nerve, two epidermoid tumors, and one malignant melanoma presumed to be primary. The pathoanatomical features that make this group of tumors unique are discussed, as well as the clinical and radiological findings, and selection of the microsurgical approach. A more favorable prognosis for tumor resection and cranial nerve preservation is predicted for interdural tumors when compared with other cavernous sinus tumors.

Adult↗
PubMed1991

Surgical approaches to thoracic disc herniations.

Early diagnosis of thoracic disc herniations has become more common with the advent of spinal magnetic resonance imaging (MRI). This early diagnosis combined with choosing the optimal surgical approach, to ensure adequate decompression without excessive cord and root manipulation, will achieve the optimum results. It is now clear that more lateral and anterior approaches to the thoracic spine are required to achieve this goal. We report our experience in the operative management of 21 patients with thoracic disc herniation using three different surgical approaches: transpedicular-transfacetal, posterolateral-extrapleural (costotransversectomy) and transthoracic-transpleural. The clinical and radiologic findings and results in all of our cases are reviewed as are the technique of and indication for each of the three surgical approaches.

Adult↗
PubMed1991

Management of the acoustic neuroma in an only hearing ear.

Heightened physician awareness of the sociologic and psychologic trauma related to deafness coupled with an increased emphasis on early diagnosis has prompted the employment of sophisticated diagnostic studies in an attempt at identification of an acoustic neuroma as a cause of hearing loss. Because profound bilateral hearing impairment is a catastrophic event, the management and care of an individual with an eighth nerve lesion in an only hearing ear remains a significant challenge for both patient and physician. In this article we will summarize our experience with this unique patient population through case presentations that will include diagnostic testing and intraoperative and perioperative findings. The literature regarding diagnosis and management will be reviewed. Recommendations for options available in the care of these patients will be discussed.

Journal Article↗
PubMed1991

The Dolenc technique for cavernous sinus exploration (cadaveric prosection). Technical note.

This report describes a surgical approach to the cavernous sinus. Based on the work of Parkinson, Dolenc, and other pioneering investigators, a comprehensive surgical approach for the treatment of lesions of the cavernous sinus is distilled and presented in 12 simple steps. The approach to surgical exploration of this region is divided into an extradural and intradural phase, each with six steps. The bony, neural, and/or vascular structures of each step are discussed. These steps may be used in their entirety for total exploration of the cavernous sinus, but also in part for lesions that involve only limited regions of the cavernous sinus. Either by design or circumstance, every intracranial neurosurgeon will eventually be led to the cavernous sinus region, and a clear understanding of cavernous sinus anatomy should be part of their armamentarium.

Cadaver↗
PubMed1990

Radiation-induced cerebral aneurysms.

The association between vasculopathy and radiation is well recognized. Generalized arterial disruption and subsequent stenosis and occlusion is most often described. Additional vascular phenomenon, such as pseudoaneurysm formation, aneurysmal dilatation and aneurysmal rupture, are less common. We document a case of a cerebral aneurysm formation and rupture in the field radiated for cerebral neoplasm.

Astrocytoma↗
PubMed1990

Surgical management of brain stem vascular malformations.

Vascular malformations of the brain stem are a histologically heterogenous collection of lesions which most often present with sudden and progressive neurologic deficit related to haemorrhage. Since 1987 the authors have treated eleven cases of brain stem vascular malformation. Seven of the patients were treated with complete surgical extirpation of the haematoma and malformation because of progressive neurologic deficit. Four additional patients made a full neurologic recovery and are being carefully observed for signs suggestive of the need for surgical treatment. Complete surgical excision of brain stem vascular malformations is mandatory for patients with progressive neurologic deficit related to recurrent haemorrhage.

Adult↗
PubMed1990

Concurrent intradural and extradural meningiomas of the cervical spine.

A case of an extradural spinal meningioma presenting with a separate intradural meningioma at the same cord level is reported. Review of the English literature on spinal epidural meningiomas reveals a high incidence of concurrent intradural tumors in patients with epidural meningiomas. This leads to the conclusion that the intradural space should be evaluated carefully when an epidural meningioma is encountered.

Adult↗
PubMed1990

Diagnosis and treatment of vascular brain-stem malformations.

Vascular malformations are a common cause of spontaneous brain-stem hemorrhage in young normotensive individuals. These lesions are no longer cryptic. Magnetic resonance (MR) imaging has renewed interest in the treatment of this disorder because of the precise accuracy in diagnosis and localization of these lesions that it affords. The MR image demonstrates characteristic findings of multiple hemorrhages of varying ages surrounded by a hypointense peripheral zone of hemosiderin. Five cases of vascular brain-stem malformation diagnosed with MR imaging are described. The vascular malformations could be demonstrated as "flow void" areas in three cases. Three patients were treated surgically and vascular malformations were confirmed: all three patients improved postoperatively. Two patients were treated nonsurgically; one of these recovered from a second hemorrhage and the other experienced neurological deterioration after a single hemorrhage. High-energy radiotherapy was not effective for the one vascular malformation treated by this method. This experience suggests that surgical exploration should be considered for vascular brain-stem malformations when the diagnosis is confirmed by MR criteria and the clinical course and lesion are both progressive in character.

Adult↗
PubMed1990

Surgical management of epilepsy associated with cerebral arteriovenous malformations.

Between 1982 and 1986, 27 patients with seizure disorders due to cerebral arteriovenous malformation (AVM) were surgically treated by the authors. These patients had no history or clinical manifestation of intracranial hemorrhage. All were treated with anticonvulsant agents by their neurologists but became disabled due to inadequate control of seizures by medication, side effects of the anticonvulsant drugs, or the effects on their professional lives of even infrequent seizures. The age of the patients ranged from 13 to 61 years. There were 13 males and 14 females. The AVM's were smaller than 2 cm in four patients, between 2 and 4 cm in five, and larger than 4 cm in 18. The most frequent location of the AVM's was in the temporal lobe, followed by the frontal, parietal, and occipital lobes. All patients had preoperative electroencephalography (EEG) and intraoperative electrocorticography. Intraoperative recording of the amygdala and the hippocampus by depth electrodes was performed if the AVM's were located in the temporal lobe. Superficial or posterior temporal lobe AVM's often have remote seizure foci that involve the amygdala and hippocampus. All patients underwent craniotomy and total excision of their AVM's. Surgery was carried out under local anesthesia to allow localization by electrical stimulation if the AVM involved the speech area or the sensorimotor cortex. Based on the EEG findings, excision of the epileptogenic lesion in addition to the AVM was performed in 18 patients. In seven patients with AVM's located in the temporal lobe, remote seizure foci were identified and excised. The remote epileptic activity was particularly prominent in AVM's in the temporal lobe and usually involved mesial temporal structures. Microscopic study of excised seizure foci showed gliosis in 26 cases, hemosiderin deposits in 10, and focal hemorrhage in four. There were no operative deaths. Two patients developed a hemiparesis and three suffered temporary dysphasia after surgery. Two patients had visual field deficits. The results of postoperative seizure control during the average follow-up period of 3 years 11 months were excellent in 21 patients, good in three, fair in two, and poor in one. The latter patient, whose epileptic lesion was not completely excised because of its location in the motor cortex, had poor seizure control postoperatively. Another patient required a second operation to remove a remote seizure focus. In this series, proposed mechanisms of seizure associated with cerebral AVM include focal cerebral ischemia secondary to arteriovenous shunting, gliosis of the surrounding brain, and a secondary epileptogenesis in the temporal lobe.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1989

Cerebral arterial innervation: II. Development of calcitonin-gene-related peptide and norepinephrine in the rat.

The pre- and postnatal development of trigeminal calcitonin-gene-related peptide (CGRP)- and sympathetic norepinephrine (NE)-containing nerves supplying the cerebral arteries was studied with immunohistochemistry in rats. At 18-19 days in utero (E 18-19), CGRP fibers were present only as one or two longitudinal bundles zigzagging along the anterior cerebral artery and anterior communicating artery. Growth-cone-like swellings were found at the terminals of individual fibers. In contrast, at this same prenatal age NE fibers were present as a meshwork on all cerebral arteries. The density of NE fibers was higher in the rostral than in the caudal parts of the circle of Willis; growth cones were present on individual fibers at the middle segment of the basilar artery and distal parts of major cerebral arteries. At postnatal day 1-2 (PND 1-2; date of birth = PND 1), the outgrowth of CGRP axons extended along the walls of the middle cerebral and internal carotid arteries. These axons were relatively straight and unbranched. At the same time, NE fibers increased in number and density and continued to form the meshwork pattern on all cerebral arteries. At the end of the first postnatal week, all the longitudinal NE bundles on the rostral part of the circle of Willis began to form circular arborizations. At the end of the second postnatal week, the pattern of NE innervation had completely changed, consisting almost entirely of circumferential rather than tangential fibers. Beginning in the first postnatal week, CGRP fibers increased greatly in number and density and began to form a meshwork pattern. At the second postnatal week, the pattern of CGRP innervation, compared to the pattern at fetal and neonatal stages, had changed significantly, consisting predominantly of a meshwork pattern. By 4 weeks after birth, both the NE and CGRP fiber systems achieved adult densities and patterns. The present results demonstrate the following: 1) Both sympathetic-NE and trigeminal-CGRP innervation of cerebral arteries begin in utero; the NE system innervates corresponding parts of the vessels earlier than the CGRP system. 2) Both NE and CGRP fibers are more dense in the rostral than in the caudal segments of the circle of Willis; this rostrocaudal gradient is expressed in both density and pattern by the earliest fibers of both neurochemical systems and is maintained throughout all developmental stages.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenergic Fibers↗
PubMed1989

The quinolinic acid model of Huntington's disease: locomotor abnormalities.

In contrast to other excitotoxins, such as kainic acid, quinolinic acid (QA) may spare a specific population of striatal neurons that is also spared in Huntington's disease (HD). Although several histological and biochemical experiments support the use of QA as a model for HD, to date no behavioral experiments have been performed to examine the suitability of this model. The present study explored the behavioral effects of bilateral intrastriatal microinjections of four doses (75, 150, 225, 300 nmol) of QA in the male rat. Using a multidimensional analysis of spontaneous locomotion (Digiscan activity) and a record of metabolic indicators, such as weight loss, a dose-dependent effect was found. The 75-nmol dose had no significant effect on locomotion or feeding behavior. In contrast, the 150- and 225-nmol doses induced hyperactivity and weight loss, whereas the 300-nmol dose was lethal. The results obtained suggest that striatal injections of 150-225 nmol of QA induce behavioral deficits qualitatively similar though quantitatively less than those which are seen after similar injection of 3 nmol of kainic acid and which have been reported to be comparable to the symptomatology of HD. Together with QA's possible greater histological selectivity, the present results support the use of QA-induced striatal lesions as a behavioral model of Huntington's disease.

Animals↗
PubMed1989

Blunt arterial injuries associated with multiple trauma.

In this retrospective study, we reviewed the records of 62 patients who were treated at a tertiary care community teaching hospital between 1977 and 1987 for major arterial injury caused by blunt trauma. Nearly half (45%, 28/62) of the injuries were to the thoracic aorta, 24% (15/62) were to arteries of the head and neck, 21% (13/62) were to the arteries of the extremities, and 10% (6/62) were to abdominal arteries. Twenty-eight thoracic aortic transections were repaired, 25 with Dacron grafts and three by primary repair. One patient developed an adventitial hematoma in the thoracic aorta, which was evacuated. Two patients required nephrectomies secondary to renal artery injury. Ten patients with internal carotid artery dissection were successfully treated with anticoagulation therapy. Eight (13%) of the 62 patients died: four from exsanguination, one from cardiac tamponade, one from renal failure, one from pulmonary emboli, and one from cerebral infarction secondary to intracerebral edema. Such injuries are amenable to treatment, with patient and end-organ viability, if recognized and treated promptly by the trauma surgeon.

Abdomen↗
PubMed1989

Effect of insulin on acute experimental cerebral ischemia in gerbils.

We studied the effects of insulin with and without food deprivation on experimental cerebral ischemia in 197 gerbils. Ischemia was induced by unilateral common carotid artery occlusion for 4 hours. Gerbils were divided into four experimental groups and were studied for up to 1 week of survival: Group A (n = 50) was fed but received no insulin, Group B (n = 50) was deprived of food for 24 hours before surgery but received no insulin, Group C (n = 49) was fed and received daily injections of 0.1 IU lente insulin for 3 days before surgery, and Group D (n = 48) was deprived of food and received daily insulin injections. Insulin treatment was continued in Groups C and D after surgery. Blood glucose levels of all gerbils were determined before treatment (overall mean +/- SEM 88.0 +/- 12.4 mg/dl) and before carotid artery occlusion (Group A 92.2 +/- 18.3 mg/dl, Group B 81.4 +/- 11.7 mg/dl [p less than 0.05 different from before treatment], Group C 92.8 +/- 22.3 mg/dl, and Group D 66.1 +/- 24.0 mg/dl [p less than 0.001 different from before treatment]). Among the four groups, 52 gerbils died within 1 week. Neurologic deficits were scored and histologic evidence of the infarcts was graded in survivors at 1 week. Group C gerbils had the best stroke index scores. Histologic evaluation revealed that 35.9% of Group A, 21.1% of Group B, 13.9% of Group C (p less than 0.05 compared with Group A), and 28.1% of Group D survivors developed cerebral infarcts.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗