PubMed Health⌕ Search

Biomedical subjects

M K Morgan

Publications and source records attributed to M K Morgan.

At least 55 records · Page 3Linked to original sources
PubMed1994

Syndactyly and intracranial arteriovenous malformation: case report.

A case of a 14-year-old boy with syndactyly of all limbs and intracranial dural arteriovenous malformation (AVM) is presented. A failure of differentiation of cerebral vessels, possibly at 3 weeks gestational age, is discussed along with several alternative theories relating to the pathogenesis of dural AVMs. The embryogenesis of syndactyly, occurring as an arrest of normal interdigital tissue regression at 5-7 weeks gestational age, is also reviewed. It is postulated that a single common intrauterine environmental insult of vascular origin occurring during the second month of gestation, is the reason for their simultaneous manifestation.

Adolescent↗
PubMed1994

Extracranial-intracranial saphenous vein bypass for carotid or vertebral artery dissections: a report of six cases.

The management of carotid or vertebral artery dissections has generally been either conservative (with anticoagulation) or surgical (by proximal ligation or trapping procedures). However, identification and management of those patients with a high risk of stroke recurrence have been difficult. Six patients with carotid or vertebral artery dissections underwent a total of seven surgical procedures involving intracranial interpositional saphenous vein bypass grafts anastomosed distally beyond the point of dissection with trapping of the intermediate diseased section of the artery. It is suggested that this procedure be used in patients who have bilateral carotid or vertebral artery disease, persistent angiographic abnormalities (particularly aneurysms), or recurring ischemic events while undergoing anticoagulation therapy, or in whom anticoagulation is undesirable. This procedure has benefits over current surgical options because of the maintenance of high flow, the avoidance of abnormal watershed areas of flow, and the elimination of the risk of emboli. The procedure is compared to previous techniques of extracranial-intracranial bypass.

Adult↗
PubMed1994

Primary ependymoma of a cranial nerve. Case report.

Ependymomas arising from peripheral or spinal nerves are extremely rare. Other ectopic ependymomas are found mostly in the sacrococcygeal region, possibly in association with developmental anomalies. The case of an ependymoma arising from a cranial nerve in a 40-year-old man is described.

Adult↗
PubMed1993

Complications of surgery for arteriovenous malformations of the brain.

A series of 112 patients undergoing complete surgical resection of arteriovenous malformations (AVM's) of the brain between 1974 and 1990 were analyzed for complications and 12-month outcomes. The cohort consisted of 44 patients with small AVM's (< 2 cm in diameter), 43 patients with medium-sized AVM's (2 to 4 cm in diameter), and 25 patients with large AVM's (> 4 cm in diameter). There was a 3.6% series mortality rate and an 18% morbidity rate. One of the four deaths was caused by normal perfusion pressure breakthrough. Analysis of logistic regression found that the most important factor influencing the occurrence of complications in this series was AVM size (p = 0.005) and that the occurrence of complications (p < 0.001) and the neurological grade at the time of surgery (p < 0.004) both significantly contributed to the outcome at 12 months. This study stresses the importance of defining complications in terms of rigid criteria when analyzing AVM series in order to allow for a correct evaluation of the risk:benefit ratio of surgery. Furthermore, it emphasizes the need for a separate analysis of the importance of complications upon outcome.

Adolescent↗
PubMed1992

Controversies in the management of brainstem cavernous angioma: report of two cases.

Two cases of cavernous angioma involving the medulla oblongata are presented. Both cases underwent surgical excision with excellent outcome. The use of surgery via craniectomy is contrasted with stereotactic radiosurgery in light of the known natural history of the lesions. As a result, it is suggested that surgical excision provides immediate protection from the risks of recurrent haemorrhage, establishes a tissue diagnosis, allows complete removal at the primary intervention, avoids complications of radiation-induced damage and is performed more easily in these vascular anomalies due to the presence of a capsule with surrounding gliotic tissue. Additionally, it is implied that the natural history of lesions in this region is still unclear. For these reasons, it is suggested that surgical excision should be the primary therapeutic intervention for cavernous angiomata that involve the brainstem.

Adult↗
PubMed1992

Physical mapping of repetitive extragenic palindromic sequences in Escherichia coli and phylogenetic distribution among Escherichia coli strains and other enteric bacteria.

Repetitive extragenic palindromic (REP) sequences are highly conserved inverted repeat sequences originally discovered in Escherichia coli and Salmonella typhimurium. We have physically mapped these sequences in the E. coli genome by using Southern hybridization of an ordered phage bank of E. coli (Y. Kohara, K. Akiyama, and K. Isono, Cell 50:495-508, 1987) with generic REP probes derived from the REP consensus sequence. The set of REP probe-hybridizing clones was correlated with a set of clones expected to contain REP sequences on the basis of computer searches. We also show that a generic REP probe can be used in Southern hybridization to analyze genomic DNA digested with restriction enzymes to determine genetic relatedness among natural isolates of E. coli. A search for these sequences in other members of the family Enterobacteriaceae shows a consistent correlation between both the number of occurrences and the hybridization strength and genealogical relationship.

Base Sequence↗
PubMed1992

Direct embolectomy of the basilar artery bifurcation. Case report.

The case is presented of a 27-year-old man who developed a basilar artery bifurcation embolus encompassing Hilal microcoil as a complication following therapeutic embolization. An immediate direct surgical approach to the basilar artery bifurcation enabled the microcoil and associated thrombus to be removed and flow to be restored in the basilar artery and its distal branches. Postoperatively, the patient made a good recovery and on discharge was neurologically normal with the exception of a right third nerve palsy. This case suggests that in selected patients a direct surgical approach to the top of the basilar artery may be possible for treatment of emboli.

Adult↗
PubMed1991

A ventricular infusion technique for the evaluation of treated and untreated hydrocephalus.

Patients considered to have a possible disorder of the circulation of the cerebrospinal fluid (CSF) were prospectively randomized on clinical and computed tomographic grounds into one of four categories: low probability of a disorder of circulation of the CSF (n = 14); high probability of a disorder of the circulation of the CSF (n = 10); low probability of shunt malfunction (n = 10); and high probability of shunt malfunction (n = 9). Patients with possible disorders of the circulation of the CSF who did not meet the entry criteria for each of these categories were excluded from this study. A ventricular catheter connected to a subgaleal Rickham reservoir not in continuity with a shunt system (if this was present) either was inserted into each patient or was in place from previous surgery. Infusion studies were conducted by the infusion of 1 ml/min of normal saline through a 25-gauge needle inserted through the skin into the Rickham reservoir. A separate 25-gage needle was inserted into the Rickham reservoir for continuous recording of intracranial pressure. There were 43 infusion studies that were included in the four categories. Recordings of baseline intracranial pressure for a high probability of a disorder of the circulation of the CSF did not differ significantly from a low probability of a disorder of the circulation of the CSF. Baseline intracranial pressure for a high probability of shunt malfunction was significantly higher than the low probability of a disorder of the circulation of the CSF group and the low probability of shunt malfunction group; there was, however, marked overlap in values between these groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1991

Pineal teratoma and its relationship to intracerebral development: case report.

A teratoma of the pineal region in a 20-year-old Australian Aborigine is presented in which an unusual location of the straight sinus and tentorium cerebelli suggests that the tumor arose before 4 months of gestation. In addition, this case provides some insight into the development of the falx cerebri, which might arise from the midline fusion of the left and right tentoria cerebelli caused by the dorsal development of the telencephalon.

Adult↗
PubMed1991

A familial coincidence of pseudotumor cerebri and communicating hydrocephalus.

A family in which the mother and two of four daughters had a diagnosis of pseudotumor cerebri and one son developed communicating hydrocephalus is described. The other two daughters both have a long history of headaches but no signs of intracranial hypertension. The argument is advanced that there exists a defect of cerebrospinal fluid absorption common to pseudotumor cerebri and communicating hydrocephalus.

Adolescent↗
PubMed1990

Rorschach structure of a hospitalized sample of Vietnam veterans with PTSD.

Rorschach structural summary data are presented for a group of 41 posttraumatic stress disorder (PTSD) patients who were being treated in a specialized inpatient PTSD treatment program. Results suggest that patients suffering from PTSD exhibit impaired reality-testing abilities and tend to utilize ineffective coping strategies. The group's structural summary factors are presented as incipient normative data for the Exner Comprehensive System on patients with PTSD. Implications that these protocols suggest a more severe and pervasive level of psychopathology than would be expected from theoretical descriptions of the disorder are discussed.

Adult↗
PubMed1989

A model of the pathophysiology of cerebral arteriovenous malformations by a carotid-jugular fistula in the rat.

A model of a carotid-jugular fistula in the rat was created such that the arterial feeding vessel is derived from the intracranial arterial circulation and the venous drainage communicates with a major intracranial venous drainage system. This fistula was created in 28 rats on the right side with an additional 11 rats designed as controls with a right carotid ligation and 6 rats without previous surgery. After 12 weeks convalescence, 6 rats with a carotid-jugular fistula and 6 rats without previous surgery underwent cerebral angiography. All fistulae were patent and the model was verified. All of the 33 remaining rats underwent regional cerebral blood flow (rCBF) determination by [14C]iodoantipyrine autoradiography under barbiturate anesthesia. Of the rats with the fistula, 11 had this fistula obliterated 5 min prior to rCBF determination ('closed' group) while 11 had rCBFs determined with the fistula ('open' group). The rCBF was measured from each hemisphere from 7 anatomical regions. The rCBF in the control animals ranged from a median of 82 to 112 ml/100 g/min, in the 'open fistula' group 46 to 68 ml/100 g/min, and in the 'closed' group 118 to 187 ml/100 g/min. This experimental model stimulates the pathophysiologic perturbations in the parenchyma induced by cerebral arteriovenous malformations. It supports the findings that non-infarctional hypoperfusion can result from arteriovenous malformations and that following extirpation of arteriovenous malformations hyperemia may ensue.

Animals↗
PubMed1989

The case against staged operative resection of cerebral arteriovenous malformations.

Three cases of large cerebral arteriovenous fistulae are presented in which surgical ablation was complicated by brain swelling from hyperperfusion breakthrough believed to be caused by acute intraoperative hypoperfusion superimposed on chronic preoperative hypoperfusion. On the basis of these cases, experimental data, and theoretical considerations, we seriously question the wisdom of using staged surgical resection of cerebral arteriovenous malformation to prevent complications related to alterations in cerebral hemodynamics. The reasons for this concern are: the repeated occurrence of acute-on-chronic hypoperfusion during staged resection; a lack of understanding of the time course for the correction of a disordered autoregulation; risk of hemorrhage between the initial and final resection; difficulty in assessing and substantiating flow reduction after subtotal resection; the rapidity of collateralization; the divergence of flow from large, readily accessible feeding arteries to deep penetrating vessels; and attenuation of the wall thickness in collateral vessels as a consequence of increased flow.

Adult↗
PubMed1989

The effects of hyperventilation on cerebral blood flow in the rat with an open and closed carotid-jugular fistula.

Perturbations in cerebral hemodynamics at the time of ablation of an arteriovenous shunt have been regarded as important in the pathogenesis of swelling and hemorrhage complicating resection of arteriovenous malformations (AVMs). A carotid-jugular fistula model in the rat had previously been investigated and found to simulate in part the nonhemorrhagic pathophysiology of a large cerebral arteriovenous fistula. Utilizing this model and measuring cerebral blood flow in 14 regions with a [14C]iodoantipyrine autoradiographic technique, the effects of hypocapnea on the cerebral circulation in opened and closed fistulas were investigated. Regional cerebral blood flow (rCBF) in control animals ranged from a median of 53 to 64 ml/100 g/min at a partial arterial carbon dioxide pressure (PaCO2) of 28 +/- 2 mm Hg and 85 to 112 ml/100 g/min at a PaCO2 of 40 +/- 5 mm Hg. In animals with an open carotid-jugular fistula created 12 weeks before the study, these median rCBF values at comparable PaCO2 levels ranged, respectively, from 15 to 39 ml/100 g/min and 50 to 68 ml/100 g/min (the 25th percentile for the open fistula in the hypocapneic group was 15 ml/100 g/min in 5 of the 14 regions studied). In contrast, median rCBF in the closed fistula group ranged from 73 to 100 ml/100 g/min in hypocapneic animals and from 118 to 187 ml/100 g/min in normocapneic animals. These results demonstrate the preservation of CO2 reactivity; hypoperfusion in the presence of a carotid-jugular fistula, hyperemia on fistula occlusion, and the potential to induce cerebral ischemia with hyperventilation in this model of a cerebral arteriovenous fistula.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Arterio-inferior sagittal sinus fistulae: case report.

The management of the case of a 9-year-old boy with progressive cognitive impairment due to arteriovenous fistulae at the apex of the inferior sagittal sinus is reported. This represents a unique location for an extraparenchymal deep central arteriovenous malformation. The patient underwent staged ablation of the lesion by surgery. The postoperative course was complicated by expansion of an aneurysmal vein of Galen undergoing thrombosis and hyperperfusion syndrome, but the patient ultimately made a satisfactory recovery.

Arteriovenous Fistula↗
PubMed1989

Normal perfusion pressure breakthrough complicating surgery for the vein of Galen malformation: report of three cases.

Three cases are described of infants who developed malignant brain swelling (and in one case hemorrhage) after surgery for vein of Galen malformations. The cause for the brain swelling was felt to be due to hyperperfusion, or the "normal perfusion pressure breakthrough" syndrome. Although well-described for cerebral parenchymal arteriovenous malformations, cases of this complication occurring in vein of Galen malformations have not previously been reported. It is concluded from these cases that infants with large arteriovenous shunts, as attested by cardiac failure and cerebral atrophy, have an increased risk of developing this complication.

Brain Edema↗
PubMed1989

Cerebral aneurysms in childhood and adolescence.

In this study, 24 aneurysms occurring in 23 patients under the age of 18 years (mean 12 years) are analyzed. The male:female ratio was 2.8:1, and the youngest patient was 3 months old. Mycotic lesions and those associated with other vascular malformations were excluded. Forty-two percent of the aneurysms were located in the posterior circulation, and 54% were giant aneurysms. Presenting symptoms included subarachnoid hemorrhage in 13 and mass effect in 11. Several of these aneurysms were documented to rapidly increase in size over a 3-month to 2-year period of observation. All aneurysms were surgically treated: direct clipping was performed in 14; trapping with bypass in four; trapping alone in four; and direct excision with end-to-end anastomosis in two. The postoperative results were excellent in 21 aneurysms (87%), good in two (8%), and poor in one. The pathogenesis of cerebral aneurysms is reviewed.

Adolescent↗