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A Valavanis

Publications and source records attributed to A Valavanis.

At least 37 records · Page 2Linked to original sources
PubMed1996

[Color-coded duplex ultrasonography of extracranial vascular lesions].

UNLABELLED: The diagnostic potential of color-coded duplex sonography in extracranial vascular lesions is evaluated with reference to the literature. Indications for the applications of color-coded duplex sonography comprise congenital vascular anomalies, arteriosclerotic lesions, dissections, aneurysms, arteriovenous fistulas and glomus tumors. New applications consist include monitoring after vascular interventional procedures. Color-coded duplex sonography allows recognition of congenital anatomic variants like agenesis of the internal carotid artery and variations of the origin of the vertebral artery. By superior surface delineation, characterization and quantification of plaques and stenoses are improved because of a new development in ultrasound technique. In cases of vessel dissection color-coded ultrasound is able to depict the dissection membrane, pulse synchronous flow reversal and "reentry" phenomena. Significant carotid bulb ectasia can be demonstrated and differentiated from aneurysm formation by 3D technique and angio-CT. Extracranial arteriovenous fistulas may be localized and detailed with respect to feeding arteries and draining veins. Glomus caroticum and jugular tumors are characterized by a high degree of vascularity and a position in the carotid bifurcation and within the jugular vein, respectively. The position of intravascular devices like detachable balloons and catheters was precisely demonstrated. CONCLUSION: Color-coded duplex sonography may assume a leading role in the noninvasive evaluation of extracranial vascular lesions. It provides criteria for the necessity and rational application of additional diagnostic procedures (MR, MRA, CT, DSA).

Arteriovenous Fistula↗
PubMed1996

[Inflammatory facial paralysis in MRI. An overview].

In inflammatory peripheral facial nerve palsy pathologically intense, linear and smooth enhancement of the distal intrameatal nerve segment can always be observed on T1-w- SE- MR sequences. The other nerve segments often present with a pathological enhancement as well. On T2-w- SE sequences, a thickening of the distal intrameatal nerve segment can be observed. The pathological enhancement persists over weeks and months; even in patients with complete clinical recovery, a persistent enhancement of the distal intrameatal nerve segment can be demonstrated. No correlation can be established between the intensity of the enhancement, the clinical condition and the electrophysiological data on electroneurography. The persistent enhancement of the different nerve segments is due to a long-lasting breakdown of the blood-peripheral nerve-barrier related to the process of degeneration and regeneration of the facial nerve in inflammatory palsy.

Contrast Media↗
PubMed1996

[Inflammatory diseases of the spinal cord and spinal nerve roots in the MRI].

PURPOSE: To evaluate characteristic and reliable MRI patterns of different inflammatory lesions of the spinal cord and the nerve roots in immunologically compromised and immunologically competent patients in order to be able to establish a correct diagnosis based on MRI findings. MATERIAL AND METHODS: The MRI examinations of 52 patients (27 men, 25 women, mean age 38.5 years, range 14-75 years) with proven inflammatory lesions (39 patients) or tumorous/postactinic lesions of the spinal cord (6 patients) and vascular malformations of the spinal cord (7 patients) were retrospectively analyzed. All examinations were performed on a 1.5 T MR unit, using bi- or triplanar T1-w pre- and postcontrast as well as T2-w SE sequences. Additionally, a review of the common medical literature concerning inflammatory lesions of the spinal cord was included. RESULTS: Clinical and radiological examinations allow a subdivision of inflammations of the spinal cord and the nerve roots into (meningoradiculo) myelitis and meningoradiculo (myelitis) in immunologically suppressed or competent patients. The MRI patterns of these two inflammatory subtypes vary: meningoradiculitis presents with an enhancement of the nerve roots and the leptomeninges; myelitis itself is characterized by single or multiple, diffuse or multifocal, with or without nodular, patchy or diffusely enhancing intramedullary lesions, with or without thickening of the cord and leptomeningeal inflammation. This differentiation helps to determine the underlying etiology in some of the patients. The immunologically suppressed patient suffers from viral infections (especially herpes simplex, varicella-zoster virus, cytomegalovirus), bacterinal infections (tuberculosis), but rarely from parasitic infections. The immunologically competent patient suffers from bacterial (borreliosis), but rarely viral infections, sarcoidosis and demyelinating diseases. Idiopathic myelitis is also common. CONCLUSIONS: Secondary ischemic and demyelinating processes result in a complex morphology of inflammatory lesions on MRI, and therefore the whole spectrum of demyelinating, ischemic and inflammatory lesions has to be included in the differential diagnosis. Even tumors may imitate inflammatory myelitis and radiculitis. Most commonly, meningoradiculitis can be separated from myelitis. A reliable diagnosis of a specific inflammatory lesion is difficult and is mostly achieved in patients with multiple sclerosis and in patients with HIV-associated cytomegalovirus infection.

AIDS-Related Opportunistic Infections↗
PubMed1996

Intensity of MR contrast enhancement does not correspond to clinical and electroneurographic findings in acute inflammatory facial nerve palsy.

PURPOSE: To determine the value of MR contrast enhancement in predicting the course of acute inflammatory facial nerve palsy and in selecting patients for surgical decompression. METHODS: Six patients with an acute inflammatory incomplete or complete peripheral facial nerve palsy (five idiopathic and one herpetic in origin) had repeated MR imaging studies with and without contrast enhancement, electroneurography, and clinical examinations to establish a connection between the intensity of contrast enhancement on MR images, the clinical condition, and the electrophysiological data. The examinations were performed every second day starting on the first day of admission until clinical recovery was proved by clinical deblockage (spontaneous clinical improvement). The last examination was performed 3 months after the onset of the facial nerve palsy. RESULTS: An abnormal, very intense contrast enhancement of the facial nerve was always present in the distal intrameatal and proximal tympanic segments and in the geniculate ganglion. The labyrinthine segment exhibited a mild to moderate enhancement, and the distal tympanic and mastoid segments showed a moderate to intense enhancement. The intensity of contrast enhancement did not correspond to the severity, duration, or course of the facial nerve palsy, and the electroneurographic data had no predictive value in indicating the severity of the inflammatory process. Three months after clinical recovery, a persistent and more or less unchanged or even slightly more intense contrast enhancement was observed. CONCLUSION: The long-lasting intense contrast enhancement seen in the facial nerve segments of patients who have acute peripheral inflammatory facial nerve palsy is explained by a two-phase breakdown of the blood-nerve barrier.

Adult↗
PubMed1996

The role of angiography in the evaluation of cerebral vascular malformations.

Although magnetic resonance imaging has become the modality of choice for the diagnostic evaluation of cerebral vascular malformations, cerebral angiography remains indispensable for the evaluation of cerebral arteriovenous malformations. Super-selective angiography allows detailed endovascular exploration of the various vascular elements composing cerebral arteriovenous malformations and is essential in elucidating their angioarchitecture and for treatment planning. Clinicoangioarchitectural correlations further our understanding of the natural history of cerebral arteriovenous malformations.

Brain↗
PubMed1995

The missing temporal crescent.

PURPOSE: We studied clinically the representation of the monocular temporal crescent in the human visual cortex and noted the importance of using the perimetric techniques best suited to detect this visual field defect and to study patients in whom the temporal crescent is missing. METHODS: Goldmann perimetry and high-resolution magnetic resonance imaging were performed in two patients with vascular lesions located in the anterior striate cortex. RESULTS: A monocular visual field defect, the missing temporal crescent, was found on the side contralateral to the lesion. CONCLUSIONS: The perimetric-magnetic resonance imaging correlation is in exquisite agreement with recent information about the representation of the visual field in the human primary visual cortex. Reports of this specific perimetric finding are rare, in part because of underdetection with currently used perimetric techniques that concentrate on the central 30 degrees of the visual field.

Adult↗
PubMed1995

[Quiz on an unusual orbital masquerade syndrome].

BACKGROUND: After consulting the here presented CT-images of the orbit, the question was raised whether the ocular bulbus was really enucleated or the anamnesis was wrong and a lymphoma existed in the orbit. We will therefore discuss a case of a special follow-up after an enucleation with implantation of a "Bangerter Plomb". CASE REPORT: In 1988 the patient, born on February 1, 1947, underwent an enucleation of the right eye with implantation of a "Bangerter Plomb" because of posttraumatic phthisis dolorosa. The postoperative follow up was complicated by a reactive psychopathological development with automutilation. In 1992, a Non-Hodgkin lymphoma of the mandibula was detected and treated. During the year of 1994, a painful swelling of the right orbit developed. The orbital CT suggested a recurrence of the lymphoma in the right eye, which seemed to be still in place. The biopsy however showed an abscess cavity and some parts of the Bangerter implant. CONCLUSIONS: The abscess cavity with the connected muscles and the interruption of the optic nerve which was only partially visible simulated the presence of a bulbus; the rest of the implant, on the other hand, simulated the presence of a lymphoma. The two main reasons for the infection were an early dehiscence of the wound and the automutilation. This "syndrome of masquerade" could have been detected earlier if the ophthalmologists and the neuroradiologists would have discussed the CT-images together earlier.

Abscess↗
PubMed1995

How angioarchitecture of cerebral arteriovenous malformations should influence the therapeutic considerations.

PURPOSE: To evaluate the angioarchitectural criteria of complex cerebral arteriovenous malformations (AVMs), concerning the risk of hemorrhage and therapy planing. METHODS: The magnetic resonance (MR) imaging and neuroangiographic findings of 227 AVMs (223 patients) were retrospectively evaluated. Statistical analysis was used to define the relative frequency of these lesions for hemorrhage in correlation with various parameters (i.e. age of the patient, size, location, associated aneurysms). RESULTS: Onset of symptoms was between 21 and 40 years of age in 50% of cases. The ratio of centrally to convexially located lesions was 1:2. Convexial AVMs are classified by MR imaging into sulcal and gyral, according to the arterial supply (by terminal or transit feeding arteries, respectively), as proven by super-selective neuroangiography. Central location of the AVM, size of the nidus smaller than 2 cm diameter, and presence of related aneurysms, are high risk factors for hemorrhage. AVMs with one or two draining enlarged veins, or those without reflux presented a higher incidence of hemorrhage as well. CONCLUSION: A team approach is required for the choice of the therapeutic method in patients with AVMs. Our results allow an approximate prognosis concerning the risk of hemorrhage in these patients and should be taken in consideration for the precise therapeutic planing.

Adolescent↗
PubMed1995

[Anatomy and pathology of the parotid gland. COrrelation with magnetic resonance tomography].

Due to a very complex embryological development a variety of different tissues are mixed together within the parotid gland. Secondary degenerative metaplastic and regenerative alterations result in additional tissue variety. Epithelial cells of distinct differentiation, lymphatic tissue, partly within lymph nodes, partly in clusters, sebaceous tissue, fat and peripheral nervous tissue may be the origin of a pathological neoplastic or inflammatory intraparotid lesion. MRI is an optimal tool for the delineation of the anatomy of the parotid gland and of various intraparotid lesions and often permits differentiation among malignant and benign neoplastic and inflammatory lesions. The morphology of the different pathological lesions on MRI reflects the underlying histopathology. Due to great interindividual variations in the tissue characterization of a specific intraparotid lesion, great differences in MR morphology have to be expected.

Humans↗
PubMed1994

Interventional neuroradiology of lesions of the skull base.

Preoperative embolization has been incorporated definitively into the multidisciplinary therapy strategy for lesions of the skull base. Clinical and anatomic knowledge of the pathology of the skull base, as well as experience with embolization, is the basis for therapeutic success. Clinical knowledge will lead to adequate patient selection, whereas profound anatomic knowledge and mastery of endovascular techniques will avoid predictable complications. Provided these conditions are taken into consideration, embolization of lesions of the skull base yields convincing therapeutic and technical results. Preoperative embolization of skull base tumors should not be associated with mortality or morbidity because most of these diseases are histologically benign and the interventional procedure is done as a preoperative step and not as a curative one. Major complications such as cerebral stroke, blindness, or cranial nerve palsies are results of the application of inappropriate techniques or of poor evaluation of angiographic findings, and should be avoided in the majority of cases. Minor complications are related to inadvertent occlusion of cutaneous, muscular, or osseous branches of the ECA. They are sometimes unavoidable and may include pain, skin necrosis, and trismus. Nevertheless, state-of-the-art external carotid embolization should--in skilled hands--have a permanent morbidity below 1% and no mortality.

Bone Diseases↗
PubMed1994

Idiopathic, herpetic, and HIV-associated facial nerve palsies: abnormal MR enhancement patterns.

PURPOSE: To determine specific criteria that can be used to define normal versus abnormal MR contrast enhancement of the facial nerve. METHODS: Twenty-three patients with acute unilateral inflammatory peripheral facial nerve palsy were examined on a 1.5-T MR using multiplanar T1-weighted spin-echo sequences before and after injection of gadopentetate dimeglumine. These MR patterns were compared with those of healthy control subjects. RESULTS: The normal facial nerve usually showed a mild to moderate enhancement of the geniculate ganglion and the tympanic-mastoid segment. The intracanalicular-labyrinthine segment did not enhance. All patients showed abnormal enhancement of the distal intracanalicular and the labyrinthine segment. An intense enhancement could be observed in the geniculate ganglion and the proximal tympanic segment, especially in herpetic palsy. Associated enhancement of the vestibulocochlear nerve was seen in herpetic and idiopathic palsy. Enhancement of the inner ear structures was detected only in herpetic palsy. CONCLUSIONS: Abnormal contrast enhancement of the distal intracanalicular and the labyrinthine facial nerve segment is observed in all patients and is the only diagnostically reliable MR feature proving an inflammatory facial nerve lesion. The intense enhancement of the geniculate ganglion and the proximal tympanic segment is possibly correlated with the reactivation of the latent infection in the sensory ganglion. The abnormal enhancement results from breakdown of the blood-peripheral nerve barrier and/or from venous congestion in the venous plexuses of the epi- and perineurium.

Acquired Immunodeficiency Syndrome↗
PubMed1993

[Possibilities of catheter therapy in vascular stenosis, vascular abnormalities, tumors and hemorrhages. Synopsis of an interdisciplinary colloquium].

Modern interventional catheter-technics allow amelioration of arterial blood flow by dilatation of narrowed or recanalization of closed coronary and peripheral arteries. Patients with chronic or unstable angina pectoris not responding to therapy can thus be treated successfully by percutaneous dilatation (PTCA). In peripheral occlusive disease balloon catheterization sometimes in combination with local fibrinolysis and thrombectomy may prevent amputation. On the other hand, cerebral malformations of arteries, aneurysms and tumors can be eliminated by artificial occlusion. Therapeutic embolization is also increasingly used in acute or recurrent haemorrhage in lungs, spleen and gastrointestinal tract. It may also be used as palliating therapy in malignancies. Medical indications and limitations of the various catheter techniques in cardiology, angiology, neurology and interventional radiology are discussed.

Angioplasty, Balloon↗
PubMed1993

Age distribution and iron dependency of the T2 relaxation time in the globus pallidus and putamen.

Heavily T2-weighted spin echo sequences of the brain show age-dependent low signal intensity in many extrapyramidal nuclei. Although it has been suggested that this low intensity results from non-haem iron, the specific influence of non-haem iron on the T2 relaxation time has not been quantified and remains controversial. The T2 relaxation times of the globus pallidus and putamen were measured from MRI at 1.5T in 27 healthy patients, by using a mathematical model. They were then plotted as a function of age and compared to the curve of age-dependent iron concentration determined post mortem. The curves of T2 relaxation time in the basal ganglia are congruent with published curves of iron concentration, indicating a high probability that the changes in T2 relaxation times and the low signal in the basal ganglia result from the local, age-dependent iron deposition. Individual measurements of T2 relaxation time show less variation before than after 45 years of age, indicating the influence of a second, more individual factor.

Adolescent↗
PubMed1993

[Magnetic resonance imaging in neuroradiology. Indications and applications].

On the basis of own experience with 250 MR-Angiographies and with reference to the literature the authors report on the role MR-Angiography is assuming in neuroradiological diagnostic procedures. As a noninvasive method MR-Angiography contributes to the evaluation of vessel stenosis and occlusion, venous sinus thrombosis and neurovascular compression syndromes. It supports the work-up of space-occupying lesions, as well as arteriovenous malformations and aneurysms. In addition to the diagnosis, follow-up examinations serve as a noninvasive means of therapy control particularly after interventional endovascular procedures. Knowledge of the diagnostic capabilities and limitations, the choice of the correct examination technique and modification of technical variables contribute to establish MR-Angiography as a valuable adjunct to MR imaging.

Aneurysm↗
PubMed1992

[Neuroradiology of the spinal cord].

In recent years MR has assumed a central and key role in neuroradiological evaluation of the spinal cord. Because of its noninvasiveness and high sensitivity in the detection of intramedullary lesions, it represents the method of choice today for the work-up of acute, chronic and traumatic myelopathies. The main limiting factor of MR is its rather low specificity. For this reason the clinical history as well as the neurological and laboratory findings continue to be of major importance in arriving at a definite diagnosis. The method is contraindicated in patients with pacemakers or other intracorporeal paramagnetic devices. It is relatively contraindicated in claustrophobic patients. In these cases MR should be replaced by myelography or CT-myelography. For the diagnosis of vascular diseases of the spinal cord, specifically vascular malformations and hypervascular tumors (e.g. hemangioblastoma), selective spinal angiography represents an essential adjunct to MR. Selective angiography can also be used therapeutically to treat preoperatively or definitely vascular malformations (i.e. interventional neuroradiology).

Angiography↗
PubMed1992

Central neurocytoma: histopathological variants and therapeutic approaches.

The central neurocytoma has recently been added to the differential diagnosis of intraventricular tumors. Histopathologically, this tumor is characterized by a uniform neoplastic cell population with features of neuronal differentiation. Central neurocytomas occur in young adults, develop in the area of the foramen of Monro, and are usually associated with the septum pellucidum. Initial reports appeared to indicate that these tumors are benign lesions with a favorable postoperative prognosis. The authors present clinical and neuropathological findings in a series of eight patients with central neurocytoma. An anterior transcallosal microneurosurgical approach yielded good outcomes. Postoperative radiation therapy was restricted to two patients with a malignant variant of central neurocytoma and one patient with a recurrent tumor. Observations of anaplastic variants of this neoplasm in two cases and local tumor recurrences in three indicate that the biological behavior and postoperative prognosis of central neurocytoma may not always be as favorable as previously assumed.

Adult↗
PubMed1991

Neuroradiology of central neurocytoma.

Central neurocytomas (CN) are rare, usually benign cerebral intraventricular neuroepithelial tumors, which occur in adult patients. Retrospective evaluation of the CT- and MRI-findings in eight cases as well as review of the cases reported in the literature showed that CN usually presents as a primarily slightly hyperdense and/or hyperintense mass within the body of the lateral ventricle with moderate contrast enhancement. The majority of tumors contain both multiple small cysts and calcifications and exhibit a characteristic broad based attachment to the superolateral ventricular wall. We conclude that these criteria appear to be reliable to exclude other intraventricular tumors such as astrocytoma, giant cell astrocytoma, ependymoma, subependymoma, intraventricular oligodendroglioma and meningioma. Preoperative diagnosis of CN may prove of value for planning therapy, because this tumor type seems to have a better prognosis than other intraventricular tumors.

Adult↗