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Biomedical subjects

Madjid Samii

Publications and source records attributed to Madjid Samii.

At least 19 recordsLinked to original sources
PubMed2007

Auditory midbrain implant: a combined approach for vestibular schwannoma surgery and device implantation.

HYPOTHESIS: The lateral suboccipital approach is a well-established route for safe removal of vestibular schwannomas in neurofibromatosis Type 2 (NF2) patients. The goal of this study was to assess if this approach can be extended to a lateral supracerebellar infratentorial approach to enable insertion of an auditory midbrain implant (AMI) penetrating array along the tonotopic gradient of the inferior colliculus central nucleus (ICC). BACKGROUND: The AMI is a new auditory prosthesis designed for penetrating stimulation of the ICC in patients with neural deafness. The initial candidates are NF2 patients who, because of the growth and/or surgical removal of bilateral acoustic neuromas, develop neural deafness and are unable to benefit from cochlear implants. The ideal surgical approach in NF2 patients must first enable safe removal of vestibular schwannomas and then provide sufficient exposure of the midbrain for AMI implantation. METHODS: This study was performed on formalin-fixed and fresh cadaver specimens. Computed tomography scan and magnetic resonance imaging were used to study the heads of the specimens and for surgical navigation. RESULTS: The lateral suboccipital craniotomy enabled sufficient exposure of the cerebellopontine angle and internal auditory canal for tumor removal. It could then be extended to a lateral supracerebellar infratentorial approach that provided good exposure of the dorsolateral aspect of the tentorial hiatus and mesencephalon for implantation of the AMI along the tonotopic gradient of the ICC. This approach did not endanger the trochlear nerve or any major midline venous structures in the quadrigeminal cistern. CONCLUSION: This modified lateral suboccipital approach ensures safe removal of large vestibular schwannomas and provides sufficient exposure of the inferior colliculus for ideal AMI implantation.

Auditory Brain Stem Implants↗
PubMed2006

Virtual reality augmentation in skull base surgery.

OBJECTIVE: Skull base anatomy is complex and subject to individual variation. Understanding the complexity of surgical anatomy is faster and easier with virtual models created from primary imaging data of the patient. This study was designed to investigate the usefulness of virtual reality in image guidance for skull base procedures. DESIGN: Primary volumetric image data from 110 patients was acquired using magnetic resonance, computed tomography (CT), and CT angiography. Pathologies included lesions in the anterior, middle, and posterior skull base. The data were transferred to an infrared-based image-guidance system for creation of a virtual operating field (VOF) with translucent surface modulation and optional "fly-through" video mode. During surgery, the target registration error for anatomical landmarks was assessed and the VOF was compared with the patient's anatomy in the operative field. RESULTS: Complex structures like the course of the sigmoid sinus, the carotid artery, and the outline of the paranasal sinuses were well visualized in the VOF and were recognized by the surgeon instantly. Perception was greatly facilitated as compared with routine mental reconstruction of triaxial images. Accurate assessment of the depth of field and very small objects was not possible in VOF images. CONCLUSION: Supported by sound anatomical knowledge, creation of a virtual operating field for a surgical approach in an individual patient offers a déjà vu experience that can enhance the capabilities of a surgical team in skull base approaches. In addition, application of this technique in image-guided procedures assists in targeting or avoiding hidden anatomical structures.

Journal Article↗
PubMed2006

Medial sphenoid wing meningiomas: clinical outcome and recurrence rate.

OBJECTIVE: To provide clinical data concerning the visual outcome and recurrence rate of medial sphenoid wing meningiomas in consideration of two different subgroups of this tumor entity. METHODS: Among 256 sphenoid wing meningiomas, there were 108 medial sphenoid wing meningiomas of globoid shape. They were classified into Group 1 (without cavernous sinus involvement) and Group 2 (with cavernous sinus involvement). En plaque meningiomas were excluded from the analysis. The charts of the patients including surgical records, discharge letters, follow-up records, and imaging studies were analyzed retrospectively. RESULTS: There were 39 Group 1 tumors and 69 Group 2 tumors. For microsurgical tumor removal, the frontolateral (15.7%) or the pterional approach (84.3%) was performed. Total resection was achieved in 92.3% of patients with Group 1 tumors and 14.5% of those with Group 2 tumors. Radiological recurrence was observed in 7.7% (Group 1 tumors) and 27.5% (Group 2 tumors). The mean follow-up time was 79.04 months (6.59 yr). Improvement of visual function (or stable visual function) was observed in 56% (44%) of patients with Group 1 tumors, in 30% (60%) with newly diagnosed Group 2 tumors, and 10% (70%) undergoing recurrent surgery for Group 2 tumors. CONCLUSION: Group 1 meningiomas present a more favorable subgroup with fortunate visual outcome. In Group 2 tumors, visual improvement was less favorable and radical removal is limited because of cavernous sinus infiltration, with consequential higher recurrence rates. Patients harboring recurrent Group 2 tumors with deteriorating visual function profit from microsurgery because vision can be preserved on the same preoperative level in the majority.

Adult↗
PubMed2006

The impact of petrosal vein preservation on postoperative auditory function in surgery of petrous apex meningiomas.

OBJECTIVE: The importance of preserving the superior petrosal vein has received increasing attention in the surgical treatment of pathologies involving the petrous apex. Recent reports have associated postoperative auditory nerve dysfunction with petrosal vein sacrifice. However, there is no systematic clinical study available thus far focusing on the postoperative auditory function after petrosal vein obliteration. METHODS: In 55 patients with meningiomas involving the petrous apex, pre- and intraoperative findings including petrosal vein sectioning were analyzed retrospectively concerning their impact on postoperative auditory function. RESULTS: The petrosal vein was preserved in 26 (47%) cases. In 27 (49%) cases, this vein was not preserved. Hearing loss occurred in 11% of all cases. In the preserved-vein group, postoperative hearing loss occurred in 3 of 26 (11%) cases and in the sacrificed-vein group in 3 of 27 (11%) cases. CONCLUSION: Sacrifice of the petrosal vein during surgery of petrous apex meningiomas seems not to have an impact on postoperative auditory function.

Adult↗
PubMed2006

Applicability of an electrosurgical device based on electromagnetics in neurosurgery.

Because of electrical and thermal spread to healthy nervous tissue, the application of electrosurgical tools in neurosurgery has specific limitations. This is true for both bipolar and monopolar devices. These limitations are not inherent to an instrument in which action is based on electromagnetic interaction with human tissue. We evaluated the indications and the clinical applicability of a new radiofrequency electrosurgical unit that works on this biophysical principle. The system was found to be a useful addition for the resection of morphologically tougher tissue with keyhole approaches in which the ultrasound aspirator cannot easily be applied.

Brain Injuries↗
PubMed2006

The endoscopic endonasal approach to the lateral recess of the sphenoid sinus via the pterygopalatine fossa: comparison of endoscopic and radiological landmarks.

OBJECTIVE: The endoscopic endonasal approach offers the opportunity to reach the pterygopalatine fossa, the lateral recess of the sphenoid sinus, and other areas of the cranial base through a minimally invasive approach. This study compares the anatomy of these areas when observed through an endoscopic endonasal view with the anatomy of the same regions as they appear in computed tomographic scans. The aim was to identify and correlate the corresponding anatomic structures, providing the surgeons with anatomic landmarks to guide them when operating in these areas through an endoscopic endonasal approach. METHODS: An anatomic dissection of six fixed cadaver heads was performed by an endoscopic endonasal approach. A step-by-step comparison of endoscopic and radiological images was made to identify the landmarks of the surgical field. RESULTS: The step-by-step comparison of endoscopic and radiological images acquired during the endoscopic endonasal approach to the lateral recess of the sphenoid sinus via the pterygopalatine fossa allowed the identification of all the relevant anatomic landmarks of the procedure. CONCLUSION: The endoscopic endonasal approach via the pterygopalatine fossa offers direct, minimally invasive access to the lateral recess of the sphenoid sinus, which can be monitored in each phase through consistent radiological imagery.

Cadaver↗
PubMed2006

Tuberculum sellae meningiomas: clinical outcome considering different surgical approaches.

OBJECTIVE: Tuberculum sellae meningiomas present a special challenge because of their proximity to arteries of the anterior circulation, anterior visual pathways, and the hypothalamus. The authors report on the clinical outcome after surgical treatment of tuberculum sellae meningiomas in our neurosurgical department. METHODS: A retrospective study was conducted analyzing the charts of the patients, including surgical records, discharge letters, histological records, follow-up records, and imaging studies. Patients with associated neurofibromatosis Type 2 were excluded from the study. RESULTS: One thousand eight hundred meningiomas were operated on between 1978 and 2002. Seventy-two of these patients had tuberculum sellae meningiomas; four had undergone previous surgical procedures in outside hospitals. Fifty-five patients were women; 17 were men. Their mean age was 54.3 years (range, 30-86 yr). All patients had visual disturbances at presentation. Tumors were operated through the bifrontal approach (n = 21, from 1978 through 1995), the pterional/frontotemporal approach (n = 21, from 1982 through 2002), and the frontolateral approach (n = 30, from 1984 through 2002). Total tumor removal was achieved in most patients (Simpson 1 + 2, 91.7%). The perioperative mortality rate was 2.8% (two out of 72 patients). Immediate postoperative improvement of visual disturbance was observed in 65% of patients. Visual improvement was dependent on the duration of preoperative visual symptoms, but not on preoperative visual acuity or tumor size. The visual improvement rate was significantly better in patients who underwent frontolateral tumor resection (77.8%) compared with those who underwent bifrontal craniotomy (46.2%). The overall recurrence rate was 2.8% (two out of 72 patients). The mean follow-up time for all patients was 4 to 238 months (mean, 45.3 mo [3.8 yr]). CONCLUSION: From 1978 through 2002, tuberculum sellae meningiomas were removed microsurgically using three different surgical approaches. Considering the operative morbidity and mortality, the frontolateral and pterional approach provided remarkable improvement compared with the bifrontal approach. These approaches allowed quick access to the tumor and were minimally invasive with less brain exposure, but still engendered high rates of total tumor removal. By comparison, the frontolateral approach provided the best results concerning visual outcome while representing the least invasive surgical approach.

Adult↗
PubMed2006

The impact of hypotension due to the trigeminocardiac reflex on auditory function in vestibular schwannoma surgery.

OBJECT: Surgical manipulation of the fifth cranial nerve during its intra- or extracranial course may lead to bradycardia or even asystole as well as arterial hypotension, a phenomenon described as the trigeminocardiac reflex (TCR). The authors studied the impact of this reflex on postoperative auditory function in patients undergoing vestibular schwannoma (VS) surgery. METHODS: One hundred patients scheduled for VS surgery were studied prospectively for parameters influencing the postoperative auditory function. The evaluation included sex, age, pre- and postoperative auditory function, preoperative mean arterial blood pressure, preoperative medical diseases or medication (for example, antiarrhythmia drugs), tumor size and localization, and the intraoperative occurrence of the TCR. The TCR, which occurred in 11% of the patients, influenced the postoperative hearing function in the patients with Hannover Class T3 and T4 VSs. With an overall hearing preservation of 47%, 11.1% of the patients in the TCR group and 51.4% of those in the non-TCR group experienced preserved hearing function postoperatively. In cases involving larger tumors (Hannover Class T3 and T4), an intraoperative TCR was associated with a significantly worse postoperative hearing function during VS surgery (p = 0.005). CONCLUSIONS: The hypotension following TCR is a negative prognostic factor for hearing preservation in patients undergoing VS surgery. Patients' knowledge of this can be increased pre- and postoperatively. Further study of this phenomenon will advance the understanding of the underlying mechanisms and may help to improve hearing preservation by controlling the occurrence of the TCR.

Adolescent↗
PubMed2006

Improved preservation of hearing and facial nerve function in vestibular schwannoma surgery via the retrosigmoid approach in a series of 200 patients.

OBJECT: The aim of this study was to evaluate and present the results of current surgical treatment of vestibular schwannomas (VSs) and to report the refinements in the operative technique. METHODS: The authors performed a retrospective study of 200 consecutive patients who had undergone VS surgery over a 3-year period. Patient records, operative reports, follow-up data, and neuroradiological findings were analyzed. The main outcome measures were magnetic resonance imaging, neurological status, patient complaints, and surgical complications. Complete tumor removal was achieved in 98% of patients. Anatomical preservation of the facial nerve was possible in 98.5% of patients. In patients treated for tumors with extension Classes T1, T2, and T3, the rate of facial nerve preservation was 100%. By the last follow-up examination, excellent or good facial nerve function had been achieved in 81% of the cases. By at least 1 year postsurgery, no patients had total facial palsy. In the patients with preserved hearing, the rate of anatomical preservation of the cochlear nerve was 84%. The overall rate of functional hearing preservation was 51%. There was no surgery-related permanent morbidity in this series of patients. Cerebrospinal fluid leakage was diagnosed in 2% of the patients. The mortality rate was 0%. CONCLUSIONS: The goal of VS treatment should be total removal in one stage and preservation of neurological function, as they determine a patient's quality of life. This goal can be safely and successfully achieved using the retrosigmoid approach.

Adolescent↗
PubMed2006

Cavernous angiomas within the internal auditory canal.

OBJECT: The aim of this study was to describe the symptomatology, radiological features, and surgical treatment of patients with cavernous angiomas within the internal auditory canal (IAC). METHODS: The authors reviewed the cases of seven patients with cavernous angiomas in the IAC that had been surgically treated in the 22-year period between 1983 and 2005. All the patients had presented with sensorineural hearing loss, and four suffered from tinnitus. Four patients also reported facial symptoms such as hemispasm or progressive palsy; one of these patients had presented with sudden facial paresis due to intrameatal tumor hemorrhage. According to computed tomography (CT) results, the lesions caused enlargement of the IAC. Interestingly, these same angiomas showed variable features on magnetic resonance (MR) imaging, making their differentiation from intrameatal vestibular schwannomas (VSs) sometimes impossible. In all patients the lesions were totally removed via the suboccipital retrosigmoid approach. They could be dissected away from the facial nerve in five cases, whereas in two cases, because of the location of the lesion, the seventh cranial nerve had to be sectioned and repaired with a sural nerve graft. Transient worsening of seventh cranial nerve symptoms occurred in two patients, with postoperative improvement in each of them. The cochlear nerve could not be functionally preserved because of its extreme adherence to the tumor, although its continuity was preserved in four patients. Complete deafness was the only postoperative complication. CONCLUSIONS: Cavernous angiomas of the IAC are very uncommon lesions that can imitate the symptoms of VSs. Although it is the most sensitive study available, MR imaging does not show sufficiently specific findings to differentiate the two lesion types. Thus, the preoperative diagnosis must be based on patient symptoms plus the CT and MR imaging features.

Adult↗
PubMed2005

The role of surgery in meningiomas involving the optic nerve sheath.

OBJECTIVE: Clinical presentation, radiological appearance and treatment options of patients with optic nerve sheath meningiomas (ONSM) vary. To provide a baseline for treatment of this tumour entity a series of 24 patients with ONSM is presented. METHOD: Clinical charts of the patients including surgical and histological records, imaging studies as well as meticulously focusing questionnaires of clinical outcome were reviewed. RESULTS: Twenty four patients with ONSM were treated at the Neurosurgical Department from 1981 to 2002. Mean age at diagnosis was 44 years (14-69) with a female:male ratio of 7:1. The preoperative duration of symptoms was negatively correlated with the preoperative visual acuity. The microsurgical approach consisted of pterional craniotomy, intra-/extradural subtotal excision of the meningioma and bony decompression of the optic canal. Surgical results showed low surgical morbidity and preserved or even improved vision in 8/16 patients (50%) all of whom had rapid visual decline preoperatively. In the long-term, visual loss occur again occurred due to recurrence in about 20% of cases. CONCLUSION: Microneurosurgery for treatment of ONSMs is still reserved for cases with intracranial extension, disfiguring proptosis and patients with rapid visual deterioration. Radiotherapy should be considered as treatment option in all other cases as it prolongs the time for functional vision in the affected eye with low morbidity.

Adolescent↗
PubMed2005

Neuronavigational neuroendoscopic surgery. Frameless free-hand maneuvering of a handy rigid-rod neuroendoscope on visualized three-dimensional computerized image guidance: trajectory to the prepontine cistern in cadaver study.

BACKGROUND: Considering the separate benefits of neuronavigation and neuroendoscopy, neuroendoscopic surgery with the aid of neuronavigation systems will play an increasingly important role in the future. Bearing this in mind, the present research project was conducted to facilitate neuronavigational neuroendoscopic surgery along the pathway to the prepontine cistern using cadaver heads. MATERIALS AND METHODS: A computer-aided, frameless image-guided stereotactic navigation system and a new type of handy rigid-rod neuroendoscope were used. The ideal entry point and the safest trajectory to the prepontine cistern through the foramen of Monro were defined in two formalin-fixed cadaver heads and clinical brain MRI data. Then, maneuvering of the neuroendoscope with the aid of the neuronavigation system was performed. RESULTS: Straight trajectories from the entry point to the prepontine cistern could be designed. For the registration accuracy of the tip of the neuroendoscope, the virtual image registered a mean error distance of 5.42 mm away from the reference point along the axis of vertical line. However, free-hand maneuvering enabled the neuroendoscope to be finely manipulated without damaging brain tissues. Neuroendoscopic anatomical views of the interpeduncular and prepontine cistern were also acquired. CONCLUSION: Interactive use of free-hand maneuvering of the handy rigid-rod neuroendoscope together with frameless neuronavigation systems plot the way to true neuronavigational neuroendoscopic surgery in a safe and reliable manner. This pairing of the most recent technological neurosurgical options with better understanding of neuroendoscopic anatomy enables the neurosurgeon to acquire broader treatment options for central nervous system diseases.

Adult↗
PubMed2005

Proliferation and progesterone receptor status in benign meningiomas are not age dependent.

BACKGROUND: Some authors have suggested that the biology of meningiomas differs according to a patient's age. Proliferation, vascularity, and hormonal status in meningiomas can be used to describe changes during aging. In the current study, proliferation activity with the Ki-67/MIB-1 antibody was evaluated by immunohistochemistry in meningioma tissue specimens from young and elderly patients. METHODS: Over the past 25 years, tissue samples from 1766 patients with meningiomas were evaluated. Of these, 588 tumor specimens from 554 patients who underwent surgery between 1990 and 2000 were evaluated immunohistochemically. The proliferation index (LI) and progesterone receptor (PR) in meningiomas were quantitatively estimated in elderly (age > or = 70 years) and young patients (age < 70 years). Patients' charts including surgical records, discharge letters, pathology reports, and imaging studies were reviewed. Correlations with histologic subtype, disease recurrence-free survival, resection grade, location, size, vascularity, and tumor calcification were calculated as well. Only patients with a well documented follow-up were included in the statistical evaluation (n = 385). RESULTS: Compared with the young group of 344 patients with meningioma (age < 70 years; mean age, 51.9 years; range, 18-69 years), the elderly population (age > or = 70 years; n = 41; mean age, 74.9 years; range, 70-88 years) showed a male-to-female ratio of 3.2: 1. Both groups had an identical median Ki-67 LI of 3.0% and a PR status of 56.1% versus 58.4 %. No statistically significant differences in disease recurrence-free survival could be found in the two groups. CONCLUSIONS: Proliferation rates and PR status in benign intracranial meningiomas did not appear to be age dependent.

Adolescent↗
PubMed2005

Evolution of vestibular schwannoma surgery: the long journey to current success.

The extraordinary improvement of patient outcome after surgical treatment for vestibular schwannomas is relatively recent and has occurred mainly over the last 30 years. The introduction of microsurgical techniques has resulted in increasing degrees of precise anatomical and functional preservation of the facial and cochlear nerves. An expanded microsurgical technique accompanied by continuous electrophysiological monitoring has resulted in marked changes in the primary goals for this surgery. Whereas in the past the primary goal of vestibular schwannoma management was to preserve the patient's life, the objective in vestibular schwannoma treatment today is to preserve neurological function. Long-term follow-up examinations show negligible recurrence rates, indicating that the aim of preservation of nerve function does not limit the completeness of tumor removal with modern neurosurgical techniques. Despite these advances in preserving the anatomical integrity of, for example, the cochlear nerve, losses of function and even deafness may occur postoperatively in some cases. Current biological and technical research in experimental and clinical settings addresses these problems. In this article, the authors report in detail the developments achieved in vestibular schwannoma surgery and the great clinicians to whom these results can be credited.

Deafness↗
PubMed2005

Fetal hydrocephalus, intrauterine diagnosis and therapy considerations: an experimental rat model.

MATERIALS AND METHODS: Fetal hydrocephalus is induced by a single intraperitoneal injection of 8 mg/kg 6-aminonikotinamide (6-AN), a niacinamide antagonist, in Sprague-Dawley rats on day 13 of gestation. Laparotomy was carried out in some rats 3, 6, 7 and 8 days after the intraperitoneal injection. The fetuses were collected by uterotomy and fixed in a formalin solution after measuring head circumference and body length for further histological investigations. The ventricular areas and volumes of the lateral ventricles were measured using a computer morphometric technique after all fetuses were serially sectioned sagittally or coronally. Furthermore, 8 maternal rats (4 treated with 6-AN and 4 controls) were used for ultrasound investigation. The fetal ventricular system and the central canal were demonstrated and compared by transabdominal ultrasound in the 6-AN and control groups. On day 19 of gestation the cerebrospinal fluid (CSF) was drained in some fetuses for 18 h through a thin micro-catheter, which was inserted into the lateral ventricle. In some other fetuses the intracranial pressure (ICP) and the intra-amniotic pressure (IAP) were measured after Doppler sonography of the cerebral blood flow (CBF). These measurements were carried out using a transuterine approach following the laparotomy. RESULTS: Hydrocephalus was produced due to the closure of all outlets of the fourth ventricle. Macrocephalus was clear on day 17 (4 days after 6-AN injection). The entire ventricular system was dilated, including the aqueduct and foramen of Monro, and cerebellar hypoplasia was revealed. CONCLUSION: Increased ICP in 6-AN fetuses was associated with decreasing CBF. The cerebral mantel was better developed after CSF drainage. The intra-amniotic pressure was increased in all pregnant rats and was either similar to or higher than ICP.

6-Aminonicotinamide↗
PubMed2005

Reliability of a new adjustable shunt device without the need for readjustment following 3-Tesla MRI.

INTRODUCTION: 3-Tesla (T) magnetic resonance imaging (MRI) offers high resolution imaging with improved signal quality. It also allows for improved functional investigations, most prominently with respect to fiber tracts and their relation to pathological lesions. Up to now, patients with adjustable shunt systems were not eligible for high field power magnetic resonance imaging. We have evaluated the effects of this technique upon a newly developed adjustable shunt valve. METHOD: Ten adjustable shunt devices were examined during routine and functional 3-T high field MRI examinations. Pressure settings were checked after 17 examinations each for all valves. There were no changes in pressure setting at all possible levels in any of the tested devices. No problems with the adjusting mechanism were observed during 340 examinations. CONCLUSION: This new shunt device offers the diagnostic benefit of high field magnetic resonance imaging in shunt-dependent patients who need an adjustable valve. The valve is not affected by higher magnetic field power and does not require readjustment of the pressure settings after MRI examination.

Brain Diseases↗
PubMed2005

A universal algorithm for an improved finite element mesh generation Mesh quality assessment in comparison to former automated mesh-generators and an analytic model.

The FE-modeling of complex anatomical structures is not solved satisfyingly so far. Voxel-based as opposed to contour-based algorithms allow an automated mesh generation based on the image data. Nonetheless their geometric precision is limited. We developed an automated mesh-generator that combines the advantages of voxel-based generation with improved representation of the geometry by displacement of nodes on the object-surface. Models of an artificial 3D-pipe-section and a skullbase were generated with different mesh-densities using the newly developed geometric, unsmoothed and smoothed voxel generators. Compared to the analytic calculation of the 3D-pipe-section model the normalized RMS error of the surface stress was 0.173-0.647 for the unsmoothed voxel models, 0.111-0.616 for the smoothed voxel models with small volume error and 0.126-0.273 for the geometric models. The highest element-energy error as a criterion for the mesh quality was 2.61x10(-2) N mm, 2.46x10(-2) N mm and 1.81x10(-2) N mm for unsmoothed, smoothed and geometric voxel models, respectively. The geometric model of the 3D-skullbase resulted in the lowest element-energy error and volume error. This algorithm also allowed the best representation of anatomical details. The presented geometric mesh-generator is universally applicable and allows an automated and accurate modeling by combining the advantages of the voxel-technique and of improved surface-modeling.

Algorithms↗