Biomedical subjects

M Samii

Publications and source records attributed to M Samii.

At least 163 records · Page 9Linked to original sources

PubMed1996

The surgical treatment of Chiari I malformation.

A retrospective study was undertaken on 133 patients with a Chiari I malformation treated within the last 16 years at the Departments of Neurosurgery at the Nordstadt Hospital Hannover, Germany, and the University of California, Los Angeles, U.S.A. Ninety-seven patients presented with symptoms related to accompanying syringomyelia and 4 with associated syringobulbia. They underwent 149 surgical procedures and were followed for a mean of 39 +/- 52 months. A decompression at the foramen magnum was performed in 124 patients, while 22 of those with syringomyelia were treated by shunting (7 syringosubarachnoid shunts, 15 syringoperitoneal or -pleural shunts), and 3 by ventriculoperitoneal shunts for hydrocephalus. Except for ventriculoperitoneal shunting, at least a short-term decrease in size of an associated syrinx was observed for all procedures in the majority of cases. However, no long-term benefit was observed for syrinx shunting operations. The best clinical long-term results were obtained with decompression of the foramen magnum in patients with (86% free of a clinical recurrence) and without syringomyelia (77% free of a clinical recurrence). We advise against syrinx shunting, a large craniectomy, and obex plugging which are associated with higher recurrence rates. Instead, surgery should consist of a small craniectomy, opening of the dura, archnoid dissection to establish normal cerebrospinal fluid (CSF) outflow from the 4th ventricle, and a fascia lata dural graft.

Adult↗

PubMed1996

The neuroimaging and clinical spectrum of neurofibromatosis 2.

Neurofibromatosis 2 (NF2) is an autosomal dominant disease predisposing to multiple tumors of the central and peripheral nervous system. Bilateral vestibular schwannomas are the hallmark of the disease. To define the clinical spectrum of the disease, we performed gadolinium-enhanced magnetic resonance imaging of the brain and spine as well as neurological, dermatological, and ocular examinations in 48 patients with NF2 diagnosed with the National Institutes of Health diagnostic criteria. Patients were ascertained from patient workshops and publications and from referral as a result of vestibular schwannoma surgery. Vestibular schwannomas were found in 46 patients (96%, 43 bilateral and 3 unilateral), spinal tumors were found in 43 (90%), posterior subcapsular cataracts were found in 30 (63%), meningiomas were found in 28 (58%), and trigeminal schwannomas were found in 14 (29%). The presenting symptoms included hearing loss or tinnitus in 15 patients (31%), multiple or nonspecific symptoms in 15 (31%), skin tumors in 12 (25%), and ocular symptoms in 6 (13%). When the complete spine was imaged, spinal tumors were more common in patients with NF2 than has previously been reported. This is a noteworthy finding, because spinal tumors are a major cause of NF2 morbidity and mortality.

Adolescent↗

PubMed1996

Surgical results for meningiomas of the craniocervical junction.

OBJECTIVE: We have undertaken a retrospective analysis of 38 patients who were operated on for 40 meningiomas of the craniocervical junction between September 1977 and August 1995 to determine which factors influenced resectability, complications, and postoperative outcomes. METHODS: Radiological examinations, clinical data, and operation notes were evaluated, and additional follow-up information was obtained from outpatient examinations, telephone calls, and questionnaires. RESULTS: Four groups could be distinguished according to dural attachment as follows: 1) 15 spinocranial meningiomas originated from the spinal canal and extended intracranially; 25 craniocervical meningiomas of intracranial origin were divided into 2) meningiomas of the lower clivus (10 patients with 11 tumors), 3) lateral meningiomas (11 patients with 12 tumors), and 4) posterior meningiomas (2 patients). Standard midline or lateral suboccipital approaches with opening of the foramen magnum and laminectomy of the involved cervical segments were sufficient for the great majority of tumors. In seven instances only, drilling the posterior third of an occipital condyle was needed. Twelve of 15 spinocranial meningiomas and 13 of 25 craniocervical meningiomas could be removed totally. One patient underwent ventriculoperitoneal shunting only. With a rate of 63% of totally removed and 30% of subtotally removed meningiomas in this region, we observed clinical recurrences for two patients only. Complications were encountered in 30% of patients, predominantly with recurrent and/or infiltrative or en plaque meningiomas. Whereas motor weakness and gait ataxia tended to improve postoperatively, cranial nerve deficits usually remained unaltered. CONCLUSION: The relationship of the tumor to neighboring structures, i.e., the vertebral artery in particular, determines its resectability. We recommend using extreme caution with recurrent or en plaque meningiomas and tumors associated with extensive arachnoid scarring.

Adolescent↗

PubMed1996

Xenon/CT CBF measurements as valuable diagnostic tool in a case of bilateral occlusive cerebrovascular disease associated with intracranial aneurysm.

A patient with the coincidental occurrence of a right internal carotid artery (ICA) stenosis and asymptomatic ipsilateral infraclinoidal ICA aneurysm is presented. CBF measurements including testing of the cerebrovascular reserve capacity (CRC) demonstrated a compromise of cerebral blood flow (CBF) within the anterior circulation of the affected side. We treated the patient in one operation by aneurysm clipping and subsequent carotid endarterectomy (CEA). 10 months later she presented with an occlusion of the contralateral ICA. CBF measurements showed sufficient resting flow and CRC on both sides. One year later repeat measurements disclosed a lowered resting CBF and diminished CRC on the affected side. Extracranial/Intracranial (EC/IC) artery bypass improved both symptoms and CBF/CRC values. The authors propose to treat symptomatic ICA stenosis and concurrent silent ipsilateral intracranial aneurysms at once if the patient is eligible for aneurysm surgery. CBF measurements should be performed before surgery. In a medically compromised patient carotid endarterectomy alone appears to be justifiable. In cases of symptomatic aneurysm and concurrent ICA stenosis a CEA can be added to aneurysm clipping to improve the hemodynamic situation for a better postoperative management. Xenon/CT investigations are suitable to provide important cerebral blood flow information. Together with angiography and clinical judgment it allows to identify patients with hemodynamic insufficiency. These are suitable candidates for an operative procedure to augment cerebral blood flow and to improve symptoms.

Blood Flow Velocity↗

PubMed1996

Alteration of rCBF in skull base lesions.

Cerebral functional imaging methods provide complementary information on brain function and large vessels regulatory controls which are compromised in cranial base lesions. The presence of a skull base tumor can alter regional cerebral blood flow (rCBF) in adjacent and remote brain tissue. This report presents the results of 104 CBF studies in 66 patients with skull base lesions (aged 17-75 years). The lesions included 36 meningiomas, 21 neurinomas and 9 other tumors. Regional CBF in tumor and brain tissue was measured prior to treatment using stable xenon enhanced computed tomography (Xenon(/T). For the quantitative analysis, regions of interest were delineated on tumor regions, cerebral and cerebellar hemispheres including peritumoral regions. In order to assess the remote effect of cerebellopontine angle (CPA) tumors, the brainstem, cerebellar, and cerebral blood flow were measured in 26 cases. The average brainstem CBF for patients with good outcome was higher than the average brainstem CBF for patients with poor outcome. This indicates that CBF studies in posterior fossa can be useful in predicting the prognosis of CPA tumor patients. We report a series of 16 patients with cavernous sinus tumors in whom the internal carotid artery was affected by the tumor. In nearly all cases Xenon/CT CBF studies with acetazolamide test showed no significant difference in hemispheric perfusion and a sufficient cerebrovascular reserve capacity. Interhemispheric asymmetry was present only in one patient. These results possibly indicate that i.v. administration of acetazolamide might contribute in selecting patients with higher risk for ischemic deficits after cavernous sinus surgery. Skull base meningiomas showed very high blood flow with a wide range. Local CBF in the peripheral region of meningiomas was higher than in the central region. Blood flow values in the peritumoral areas are about 30% lower than those of the ipsilateral hemisphere. In individual cases, blood flow values in the peritumoral low-density area on CT were extremely low. It is concluded that CBF studies in skull base tumors are valuable in treatment planning. Xenon/CT can be useful additional diagnostic procedure in the evaluation of skull base surgery candidates.

Acetazolamide↗

PubMed1996

Surgical treatment of epidermoid cysts of the cerebellopontine angle.

A total of 40 patients with epidermoid cysts of the cerebellopontine angle (CPA) underwent surgery between 1980 and 1993. Total resection was achieved in 30 cases (75%); in 10 cases (25%) parts of the cyst capsule were left because they adhered to the brainstem and vascular structures of the CPA. One patient with very large bilateral epidermoid cysts, who underwent complete bilateral resection in one stage, died of pulmonary aspiration and infection. As of their latest clinical and radiological follow-up examinations (mean 5.7 years), 93% of the patients are able to lead useful lives. Three cases of cyst regrowth have been observed thus far. Modern radiological tools and microsurgery techniques have considerably improved the completeness of cyst resection and reduced postoperative mortality and morbidity rates; however, there still are some cases in which complete resection is impossible without producing severe neurological deficits.

Adult↗

PubMed1996

Meningiomas of the tentorial notch: surgical anatomy and management.

Twenty-five meningiomas located at the tentorial notch were surgically treated between 1978 and 1993 at the Neurosurgical Department of Nordstadt Hospital in Hannover, Germany. Nineteen meningiomas were classified as originating from the lateral tentorial incisura (Group I) and six were from the posteromedial tentorial incisura (Group II). Clinically, the most common symptom was trigeminal neuralgia, followed by headache. Neuroradiologically, 64% of the meningiomas were larger than 30 X 30 mm. Further evaluation revealed signs of brainstem compression in 88% of the patients. Radical surgical removal (Simpson I and II) was achieved in 88% of the cases. There was no mortality. Follow up revealed that 80% of patients were able to return to their premorbid activity. Surgical approaches to the tentorial notch included the suboccipital retrosigmoidal or the combined subtemporal-presigmoidal approach for Group I tentorial notch meningiomas; and the supracerebellar-infratentorial or the suboccipital-transtentorial approaches for Group II meningiomas. Because the best surgical approach to the tentorial incisura is still a matter of debate, the anatomy of the tentorial incisura, the clinical presentation of the patients, diagnostic indications, surgical findings, and follow up are discussed, with reference to the literature.

Adult↗

PubMed1996

[Contralateral approach to clivus tumors using the transmaxillary-transethmoid approach].

A modified transmaxillary transethmoid approach to the clivus is described. A paranasal incision is performed on the side contralateral to the major tumor extension. The approach provides preservation of the lacrimal duct, and the bony structures of the pyriform aperture. By removing the frontal process of the maxilla and if necessary the medical orbital wall, a wide access is created that can be further enlarged by dissecting the medial concha, ethmoid sinus and posterior parts of the nasal septum. Cerebrospinal fluid leakage is treated by a special technique.

Adolescent↗

PubMed1996

Microendoscopy of the internal auditory canal in vestibular schwannoma surgery.

Intraoperative microendoscopy was performed for eight patients to access the fundus of the internal auditory canal after retrosigmoid transmeatal surgery of vestibular schwannomas. The transmeatal procedure is usually limited laterally by the labyrinth block. The restricted opening of the internal auditory canal bears a potential risk of incomplete tumor resection. For eight patients with vestibular schwannomas, intraoperative microendoscopy was performed after tumor resection to expose the "blind" area of the internal auditory canal fundus. An excellent view of the fundus contents was obtained, including Cranial Nerves VII and VIII and the crista transversa. Tumor remnants were not observed in this series. Microendoscopy was shown to be an ideal adjunct to hearing-preserving transmeatal surgery of vestibular schwannomas, enabling the removal of intracanalicular tumors with direct control of the lateral intracanalicular nerve portions.

Adolescent↗

PubMed1995

Hearing preservation in acoustic tumour surgery.

900 acoustic neurinomas were removed by the suboccipital approach at Nordstadt Neurosurgical Department from 1978 to 1992 by the same surgeon (M. S.). While 247 patients were deaf on the involved side before surgery, there were 653 patients ears with some preoperative hearing. Preservation of the cochlear nerve was always attempted, and the overall-rate of hearing preservation was 38% (249 of 653), regardless of pre- and postoperative quality of hearing or of tumour sizes. In small tumour sizes below 3 cm of diameter preservation rate was 51%, in large tumours above 3 cm of diameter it was 22%. A classification system of hearing quality was made up considering pure tone audiometric hearing losses (PTA HL) at 1 to 3 kHz, and individual maximum speech discrimination scores. The usefulness of the preserved hearing is further evaluated considering the quality of hearing in the contralateral ear, and by application of other classification schemes. Presentation of the surgical strategies and their refinements by personal experience provide the base for discussion questioning whether and how further progress may still be anticipated.

Adult↗

PubMed1995

Acoustic neurinomas associated with vascular compression syndromes.

Trigeminal neuralgia and hemifacial spasm are caused by vascular compression of the cranial nerves at the brainstem in the majority of cases. Trigeminal neuralgia occurring in 3.3% of acoustic neurinomas is usually assumed to be a sign of large tumour size; if associated with small tumour size, an additional pathology, such as typical vascular compression must be suspected and has to be explored at surgery. While facial paresis will usually lead to immediate radiological diagnosis of a possible cerebellopontine angle (CPA) neoplasm, facial spasm is usually not expected to be associated with a CPA tumour. We report on clinical presentation, operative findings, surgical treatment and results in 9 cases of small acoustic neurinomas associated with trigeminal neuralgia and on 4 cases associated with hemifacial spasm. The importance of the clinical characteristics is stressed; if these are typical of a vascular compression syndrome, further exploration at the time of tumour surgery and specific treatment by vascular decompression are necessary.

Adult↗

PubMed1995

Proliferative activity of acoustic neurilemomas without neurofibromatosis determined by monoclonal antibody MIB 1.

Microscopic sections obtained from paraffin blocks of 30 consecutive neurilemomas stored in 1989 were investigated immunohistochemically with the new monoclonal antibody MIB 1 directed against recombinant parts of Ki-67 antigen. The immunohistochemical staining was carried out on dewaxed microwave-oven-processed paraffin sections of formalin-fixed tumour tissues. The labelling index (LI) obtained was below 1% in 21 cases, 1-3% in 7 cases and more than 3% in 2 cases. There was no correlation between the LI and the age of the patients or the tumour size. The major advantage of MIB 1 over previous immunohistochemical methods is its usefulness in long preserved sections which are ideal for retrospective studies.

Adult↗

PubMed1995

The comparison between the growth fraction of bilateral vestibular schwannomas in neurofibromatosis 2 (NF2) and unilateral vestibular schwannomas using the monoclonal antibody MIB 1.

Formalin-fixed paraffin sections of 55 consecutive bilateral vestibular schwannomas in 46 patients with neurofibromatosis 2 (NF2), and 50 patients with unilateral vestibular schwannomas were investigated immunohistochemically with the monoclonal antibody MIB 1 directed against recombinant parts of Ki-67 antigen. The immunohistochemical staining was carried out on dewaxed microwave oven-processed paraffin sections of formalin-fixed tumour tissues. The labelling index (LI) obtained was compared to clinical and histological findings in both groups. There was no correlation between the LI and age of the patients, tumour size, or histological type of tumour (Antoni A or B). Vestibular schwannomas in NF2 showed higher LI than unilateral vestibular schwannomas: the maximal LI found per section (LI max) ranged from 0.4 to 17.6% (mean, 2.7%) in NF2 schwannomas, and from 0 to 9% (mean, 2.2%) in unilateral schwannomas. These differences may express immunohistochemically some clinical and morphological differences between bilateral and unilateral vestibular schwannomas.

Adolescent↗

PubMed1995

Syringomyelia in association with tumours of the posterior fossa. Pathophysiological considerations, based on observations on three related cases.

In this report we describe 3 patients with syringomyelia in association with tumours of the posterior fossa. In each patient the syrinx was demonstrated on pre-operative magnetic resonance imaging (MRI). After total or partial removal of the tumour the syrinx collapsed. It is concluded that the pathogenesis of syrinx formation in this entity requires interference with normal cerebrospinal fluid (CSF) flow at the foramen magnum. We suggest that the obstruction to the flow of CSF causes alterations in the passage of extracellular fluid (ECF) in the spinal cord which lead to syringomyelia.

Adolescent↗

PubMed1995

Hearing preservation in bilateral acoustic neurinomas.

Bilateral acoustic neurinomas are found in almost all patients with neurofibromatosis 2 (NF2). With better knowledge of the disease and development of diagnostic procedures, an increasing number of patients have been detected at an early stage of the disease. Preservation of hearing in these cases has become more feasible. Between 1979 and 1992, 110 acoustic neurinomas in 74 NF2 patients have been resected in this department. All tumours but 11 were completely removed. In 11 cases deliberate subtotal tumour removal was performed: bilaterally in one deaf patient for brainstem decompression, and unilaterally in nine patients with the aim of hearing preservation. In seven of these nine cases hearing was preserved. The total rate of hearing preservation was 36%. Considering only those patients with good preoperative hearing and small tumours, the rate of hearing preservation was 58%. Facial nerve preservation was 92%. Nerve reconstructions were performed in cases of facial nerve damage, with good results in most of the cases. The importance of early detection of the disease and early removal of tumours is stressed. Surgical decision making based on the author's personal experience in dealing with these cases is discussed, and some cases are illustrated.

Adolescent↗

PubMed1995

Esthesioneuroblastomas with intracranial extension. Proliferative potential and management.

A total of 15 patients with esthesioneuroblastomas were treated between 1978 and 1992 at the Neurosurgery Department, Nordstadt Hospital, Hannover. In 9 cases, the tumors invaded the anterior cranial fossa. One patient died before any surgical intervention. Eight tumors were operated by a combined paranasal and subfrontal approach. Gross total tumor removal was achieved in all cases. Apart from anosmia, the only postoperative complication was transient mental changes in one case. Immunohistochemical analyses with MIB 1 monoclonal antibodies, directed against recombinant parts of Ki-67 antigen, were performed to estimate the proliferative potential of the esthesioneuroblastomas. Most of the tumors showed high proliferating cell indexes, which ranged from 3 to 42% (mean, 16%). The proliferating cell index with MIB 1 showed a correlation with postoperative outcome, although this was not statistically significant. Esthesioneuroblastomas can be totally removed surgically. The proliferating cell index may reflect histologically the biological behavior of tumor. Long-term follow-up is mandatory, and immunohistochemical studies may be of help in predicting outcome.

Adult↗

PubMed1995

Surgical treatment of trigeminal schwannomas.

A total of 27 patients with trigeminal schwannoma were treated between 1982 and 1992 at the Neurosurgery Department of Nordstadt Hospital. Twelve cases of solitary schwannoma without any family history or physical stigmata of neurofibromatosis were included and form the basis of this study. There were four women and eight men (mean age 44 years) in this series. Duration of symptoms ranged from 2 months to 6 years. The most frequent symptoms were either pain or numbness of the ipsilateral hemiface. The surgical approach was chosen depending on the tumor type. Tumors that belonged to Type A (five cases), which were predominantly in the middle fossa, were approached using a transsylvian method; Type B (one case), which presented predominantly in the cerebellopontine angle, was operated on via a retrosigmoid suboccipital craniectomy; Type C (five cases), which were dumbbell-shaped extending into both the middle and posterior fossa, were removed via a combined temporal craniotomy-presigmoidal method; and in Type D (one case), in which tumor was primarily extracranial with intracranial extension, an infratemporal extradural approach was undertaken. There was no operative mortality or long-term disability in this series. The follow-up period ranged from 12 to 60 months; during that time magnetic resonance imaging revealed tumor recurrence in two cases after 12 and 48 months, respectively, and these were excised again. An additional 178 cases collected from the world literature are also reviewed and analyzed.

Abducens Nerve↗

PubMed1995

Surgical treatment of jugular foramen schwannomas.

Sixteen patients with schwannomas of the jugular foramen were operated on in the Department of Neurosurgery of the Nordstadt Hospital in Hannover, Germany, between 1986 and 1992. Patients with neurofibromatosis were excluded. The records of the 16 patients were retrospectively reviewed. There were five women and 11 men (mean age 43 years) with a symptom duration ranging from 6 months to 20 years (mean 5 years). The predominant symptoms were hearing loss, hoarseness, and cerebellar symptoms. Computerized tomography (CT), magnetic resonance (MR) imaging, and angiography were performed in all 16 patients. Depending on the radiological and surgical features, the tumors were classified into four types: Type A, a tumor primarily at the cerebellopontine angle with minimal enlargement of the jugular foramen (eight cases); Type B, a tumor primarily at the jugular foramen with intracranial extension (two cases); Type C, a primarily extracranial tumor with extension into the jugular foramen (one case); and Type D, a dumbbell-shaped tumor with both intra- and extracranial components (five cases). A retromastoid suboccipital craniectomy was performed for Type A tumors, and a combined cervical-mastoidectomy for Types B, C, and D. Total tumor removal was achieved in all cases. There was no operative mortality. Postoperative complications were cerebrospinal fluid leakage in one patient and mastoiditis in two patients. The follow-up period ranged from 12 to 42 months (mean 22 months). All patients were alive at the last follow-up review, and CT and/or MR imaging showed no tumor recurrence.

Adult↗