Deep learning-assisted radiomics facilitates multimodal prognostication for personalized treatment strategies in low-grade glioma.

Determining the optimal course of treatment for low grade glioma (LGG) patients is challenging and frequently reliant on subjective judgment and limited scientific evidence. Our objective was to develop a comprehensive deep learning assisted radiomics model for assessing not only overall survival in LGG, but also the likelihood of future malignancy and glioma growth velocity. Thus, we retrospectively included 349 LGG patients to develop a prediction model using clinical, anatomical, and preoperative MRI data. Before performing radiomics analysis, a U2-model for glioma segmentation was utilized to prevent bias, yielding a mean whole tumor Dice score of 0.837. Overall survival and time to malignancy were estimated using Cox proportional hazard models. In a postoperative model, we derived a C-index of 0.82 (CI 0.79-0.86) for the training cohort over 10 years and 0.74 (Cl 0.64-0.84) for the test cohort. Preoperative models showed a C-index of 0.77 (Cl 0.73-0.82) for training and 0.67 (Cl 0.57-0.80) test sets. Our findings suggest that we can reliably predict the survival of a heterogeneous population of glioma patients in both preoperative and postoperative scenarios. Further, we demonstrate the utility of radiomics in predicting biological tumor activity, such as the time to malignancy and the LGG growth rate.

Continuous intraventricular pressure monitoring for diagnosis of normal-pressure hydrocephalus.

OBJECTIVES: Normal-pressure hydrocephalus (NPH) syndrome is treatable by implantation of a cerebrospinal fluid (CSF) shunt. However, diagnosis of NPH by clinical and radiological findings alone is unreliable, and co-existing structural dementia can contribute to low success rates after shunt implantation. The aim of our study was to investigate whether long-term results after shunt implantation in NPH improve when surgical candidates are selected by continuous intraventricular pressure monitoring (CIPM). PATIENTS AND METHODS: Ninety-two consecutive patients who were admitted with suspected NPH received CIPM for 48 h including an intraventricular steady-state infusion test to determine the resistance outflow. With positive CIPM, shunt implantation was performed and the patients were prospectively followed up for 1 to 10 years (median 6.5 years). RESULTS: CIPM was negative in 37 patients. Fifty-five patients had a positive CIPM and received CSF shunt. 96.1% of them improved from gait disturbance, 77.1% from cognitive impairment and 75.7% from urinary dysfunction. Clinical improvement remained during long-term follow-up in all but 3 patients who showed a decline at 4, 5 and 7 years, respectively. CIPM-related complications (ventriculitis) occurred in only one patient. CONCLUSION: CIPM is a safe and valuable tool to establish a reliable diagnosis of NPH and to identify promising surgical candidates.

Acquired torticollis due to Grisel's syndrome: case report and follow-up of non-traumatic atlantoaxial rotatory subluxation.

Non-traumatic atlantoaxial rotatory subluxation is an uncommon entity, with inconsistent presentations. It is also known as Grisel's syndrome (GS), and most commonly follows infectious processes of the upper respiratory tract. A case is described of a non-traumatic rotatory atlantoaxial dislocation in a three-year-old boy. The patient presented with acute torticollis one week after mild upper respiratory infection. Neurological evaluation and lumbar punction were normal. After five days of intractable pain and non-reducible rotational tilt of the head to the left, CT and MR imaging were performed and showed atlantoaxial rotatory subluxation. In addition, MRI demonstrated middle ear and mastoid inflammation. Tilt reduction could be obtained through gentle skull traction under sedation and relaxation for 3 days. Antibiotic treatment was performed. The patient was then placed in a Minerva cast jacket. After seven weeks of immobilization, CT demonstrated regular atlantoaxial alignment. Follow-up after 5.5 years showed the boy neurologically intact and free of clinical complaints. Dynamic cervical radiographs confirmed that the atlantoaxial joints were stable.

[Collisiontumour composed of glioblastoma and meningioma-a case report]. / Kollisionstumor des GehirnsTumorkomponenten aus einem Glioblastom und einem Meningeom.

A 51 year old caucasian male presented with headache, facial nerve paresis and continuing contraction of the visual field. CT scan revealed a singular intracerebral contrast enhancing lesion in the left frontal lobe. Intraoperatively the tumour was well demarcated. Frozen sections showed a high grade glioma. Paraffin sections revealed, in addition to the gliomatous component, some sharply demarcated nests of meningothelial cells. Immunohistochemistry with glial fibrillary acidic protein and epithelial membrane antigen confirmed a collision tumour consisting of a glioblastoma WHO-grade IV and a meningothelial meningioma WHO-grade I. The coincidence of these two different tumours at the same time and the same location leads us to the speculation, that the collision tumour might have been caused by malignant transformation of a reactive astrogliosis surrounding the meningioma.

Epidural metastasis of a glioblastoma after stereotactic biopsy: case report.

Tumor seeding along the biopsy tract is a rare complication in stereotactic biopsy. We present the unique case of a 42-year-old male with epidural tumor seeding along the needle tract after computer tomography-guided stereotactic biopsy of a glioblastoma in the right basal ganglia. Three months after the biopsy and one week following fractionated radiation therapy, the patient died of brain edema and cardiac dilatation. Besides further tumor growth at the primary site, autopsy revealed a right frontal epidural, nodular metastatic tumor at the site of dura incision of the stereotactic biopsy. Histological examination showed a glioblastoma that spread epidurally along the needle tract. This is the first report of an epidural intracranial implantation metastasis of a glioblastoma after stereotactic biopsy.

Gamma knife radiosurgery of acoustic neurinomas.

The authors report on their series of 40 patients with 41 acoustic neurinomas (ACNs), including one patient with bilateral acoustic neurinomas suffering from neurofibromatosis type 2 (NF II) who were treated with the gamma knife unit at their institution between August 1992 and October 1995. Of these 41 tumours, 21 ACNs had been operated on before (1 to 4 times), 20 ACNs were exclusively treated by gamma knife radiosurgery (GKRS). The maximal axial tumour diameter ranged from 6 to 33 mm (median: 25 mm), the maximal transverse tumour diameter ranged from 7 mm to 36 mm (median: 16 mm). The dose distributed to the tumour margin was 10 to 17 Gy (median: 12 Gy) by enclosing the tumour with the 40% to 95% isodose line (median: 50% isodose line) and using 1 to 12 isocenters (median: 5 isocenters). Central loss of contrast enhancement was observed in 78% of the patients within six to 12 months after radiosurgery. Thirty-two patients were observed over a minimum follow up period of at least 36 months, 9 patients were lost to follow up as they died of unrelated causes or refused further check-ups. Within the follow up period of up to seven years, magnetic resonance imaging (MRI) control scans revealed the tumour diameter stable or decreased in 29 cases and increased in three tumours. Of 14 patients with useful hearing before treatment, 9 patients were examined in addition to pure tone audiogramm by measurement of brainstem auditory evoked potentials (BAEPs) one to four years after radiosurgery. None of these patients showed a postoperative loss of the cochlea function. According to slight alterations of the cochlea function (cochlea summating action potential), pure tone audiometry of those patients revealed only slight changes of the hearing level (HL) within a maximum range of +/-15 Decibel (dB). The hearing threshold improved in two, was stable in four and deteriorated in three patients, respectively. We observed postradiosurgical aggravation of a pre-existing facial weakness in two out of 13 patients, a new occurrence of facial palsy was seen in two cases (four years after treatment), one of them was previously operated on and both suffered from cystic degeneration with mass effect. Tinnitus improved in six out of 13 patients, deteriorated in two and never appeared as a new permanent sequela. Trigeminal hypaesthesia did also not appear as a new permanent symptom, improved in three out of 9, and deteriorated in one out of 9 patients. Vertigo increased in six out of 23, was stable in 8 and decreased in nine out of 23 patients each. GKRS proves to be a safe and highly satisfactory therapeutical option or addition to open surgery, especially for radiologically verified regrowing residual ACNs, but also as primary treatment in selected patients. A high rate of tumour control can be achieved with an acceptable rate of neurological deficits.

Prognostic relevance of intracytoplasmic cytokeratin pattern, hormone expression profile, and cell proliferation in pituitary adenomas of akromegalic patients.

Seventy-six pituitary adenomas of akromegalic patients were investigated to find out the prognostic relevance of the intracytoplasmic distribution of cytokeratins (CK), immunohistochemically defined hormone production profile, proliferative activity and clinical presentation. CK distribution, growth fraction (MIB1 index) and hormone production profile were analyzed by means of immunohistochemistry. Apoptotic activity was investigated by the TUNEL method. Two different CK distribution patterns were seen: a dot-like pattern in 29 cases (type 1 adenomas), and a perinuclear fibrillary pattern in 47 cases (type 2 adenomas). Type 2 adenomas showed more prominent coexpression of prolactin (p < 0.0001), luteotrophic hormone (p < 0.002), follicle-stimulating hormone (p < 0.005), thyroid-stimulating hormone (p < 0.0001), and alpha-subunit (p < 0.005), as compared to type 1 adenomas. The mean MIB1 index was significantly higher in type 1 vs. type 2 tumors (4.23%, range: 1.93% - 9.83% vs. 2.07%, range: 0.67% - 4.87%, p < 0.0001). Apoptotic activity was too low in both examined groups to be used for balancing of tumor cell turnover. Clinical analysis of patients with type 1 adenomas revealed female predominance, younger age, larger tumor size, and more frequently aggressive growth with higher incidence of suprasellar extension (p < 0.0001) and cavernous sinus infiltration (p < 0.0001), as well as larger proportions of re-operations and incomplete resections (34.5% vs. 8.51%). Additionally, the interval until re-operation was shorter in type 1 adenomas (mean: 16 months, range: 9 - 21 months vs. mean: 57 months, range: 18- 158 months). We conclude that classification of adenomas of akromegalic patients based on intracytoplasmic CK distribution, combined with examination of proliferative activity, and immunohistochemically defined hormone production profile, provides important prognostic information for the management of akromegalic patients.

An intramural macrocyst of an acoustic neurinoma rupturing after gamma knife radiosurgery: a case report.

We want to describe the rare case when an intramural macrocyst within an acoustic neurinoma (ACN) treated by gamma knife radiosurgery (GKRS) ruptured, followed by an impressive decrease of tumor volume and improvement of neurological symptoms. In a 59-year-old female patient, a large ACN with a hugh intramural macrocyst was diagnosed. As she refused open surgery, we performed GKRS covering the tumor margin and the cyst with 11 Gy. Seven months after treatment symptoms worsened slightly. Magnetic resonance imaging (MRI) revealed no significant change of tumor volume. One year after GKRS she felt a sensation behind her treated ear, followed by an immediate improvement of all her symptoms. Trigeminal hypaesthesia and vertigo disappeared, tinnitus ameliorated. A control MRI showed the cystic compartment no longer, the solid part shrunk within the following six years. Within the whole follow-up period hearing was stable. To our knowledge this is the first report of a macrocyst within an ACN to rupture after GKRS.

Intracranial hemorrhage from an aneurysm encased in a pilocytic astrocytoma--case report and review of the literature.

The authors present an unusual complication of a recurrent chiasmal/hypothalamic pilocytic astrocytoma. From his second year of life onwards, the patient was repeatedly operated on and also underwent external radiation therapy (54 Gy total dose) 1 month after the first subtotal tumor resection. Nine years after irradiation, the patient was referred to our center with a sudden onset of severe headache, vomiting and neck stiffness. Computed tomography, magnetic resonance imaging, and cerebral angiography demonstrated an intratumoral, intraventricular, and subarachnoidal hemorrhage from an anterior communicating artery aneurysm encased in the pilocytic astrocytoma. The aneurysm was clipped and the patient recovered nicely from the hemorrhage. Three years later, the patient suddenly died of cardiac failure. Autopsy disclosed vessel wall changes compatible with radiation-induced vasculopathy. In light of this finding, the importance of radiation therapy and intracranial neoplasms for aneurysm formation is discussed.

Gamma knife radiosurgery of recurrent central neurocytomas: a preliminary report.

OBJECTIVES: A series of three recurrent central neurocytomas treated by gamma knife radiosurgery (GKRS), which were initially totally resected, are described. Up to now, no reports exist on this treatment modality for this rare tumour entity. METHODS: Three male patients, aged between 20 and 25 years, presented with large intraventricular tumours. Total tumour removal was achieved by a single surgical procedure (one patient) or two operations (two patients). Neuropathological investigation showed a central neurocytoma, immunohistochemically all three tumours expressed a neuronal antigenic profile typical for neurocytomas, and the MIB-1 proliferation index ranged from 2.4% to 8.7%. Each patient experienced a tumour recurrence after 5 to 6 years. The recurrence was multifocal in two and a singular tumour mass in one patient. Gamma knife radiosurgery was performed. The tumours were enclosed within the 30% to 60% isodoseline, and delivered a tumour marginal dose of 9.6 to 16 Gy. During the follow up period, the patients were tested clinically and the volume of the tumours was measured on MRI. RESULTS: Within follow up periods of 1 to 5 years, control MRI showed a significant decrease of the tumour mass in all cases. None of the patients developed new neurological symptoms after GKRS. Two patients returned to work in their previous employment, whereas one patient remained permanently disabled due to a pre-existing visual impairment and abducens palsy. CONCLUSION: GKRS proved to be a useful tool in the treatment of recurrent central neurocytomas. Tumour control and even tumour shrinkage can be achieved with a single procedure and a low risk of morbidity.

Gamma knife radiosurgery of skull base meningiomas.

BACKGROUND: The standard surgical treatment of meningiomas is total resection of the tumour. The complete removal of skull base meningiomas can be difficult because of the proximity of cranial nerves. Stereotactic radiosurgery (SRS) is an effective therapy, either for adjuvant treatment in case of subtotal or partial tumour resection, or as solitary treatment in asymptomatic meningiomas. METHOD: Between September 1992 and October 1995. SRS using the Leksell Gamma Knife was performed on 46 patients (f:m 35:15), ranging in age from 35 to 81 years, with skull base meningiomas at the Neurosurgical Department of the University of Vienna. According to the indication of gamma knife radiosurgery (GKRS) the patients (n = 46) were divided into two subgroups. Group I (combined procedure: subtotal resection followed by GKRS as a planned procedure or because of a recurrent meningioma), group II (GKRS as the primary treatment). Histological examination of tumour tissue was available for 31 patients (67%) after surgery covering 25 benign (81%) and 6 malignant (19%) meningioma subtypes. FINDINGS: The overall tumour control rate after a mean follow-up period of 48 months (ranging from 36 to 76 months) was 96% (97.5% in benign and 83% in malignant meningiomas). Group I displayed a 96.7% tumour control rate, followed by group II with 93.3% respectively. Neurological follow-up showed an improvement in 33% stable clinical course in 58%) and a persistent deterioration of clinical symptoms in 9%. Remarkable neurological improvement after GKRS was observed in group II (47%), whereas in group I (26%) the amelioration of symptoms was less pronounced. INTERPRETATION: GKRS in meningiomas is a safe and effective treatment. A good tumour control and low morbidity rate was achieved in both groups (I, II) of our series, either as a primary or adjunctive therapeutic approach. The planned combination of microsurgery and GKRS extends the therapeutic spectrum in the treatment of meningiomas. Reduction of tumour volume, increasing the distance to the optical pathways and the knowledge of the actual growing tendency by histological evaluation of the tumour minimises the risk of morbidity and local regrowth. Small and sharply demarcated tumours are in general ideal candidates for single high dose-GKRS, even after failed surgery and radiation therapy, and in special cases also in larger tumour sizes with an adapted/reduced margin dose.

Growing blood clot mimicking an aneurysm on postoperative computerized tomography and magnetic resonance imaging studies. Case report and review of the literature.

The authors describe the case of a 15-year-old boy who underwent resection of a large left temporal tumor. During a normal postoperative course, computerized tomography (CT) scanning demonstrated a spherically hyperdense structure near the internal carotid artery, enlarging on a control CT scan. A suspected false aneurysm was confirmed on magnetic resonance imaging; angiographic studies were negative. The authors believed they were dealing with a thrombosed false aneurysm and they performed operative revision. Intraoperatively the "aneurysm" could be dissected off the internal carotid artery and no lesion of the arterial wall was obvious. Histological findings showed a fresh blood clot. This case demonstrates that a blood clot may mimic an aneurysm on CT and magnetic resonance studies, which has not been described earlier. The origin of the blood clot remains unclear.

Proliferative activity as measured by MIB-1 labeling index and long-term outcome of visual pathway astrocytomas in children.

Although most visual pathway tumors are low-grade gliomas their biologic behavior is highly unpredictable. In order to determine whether assessment of proliferative activity can assist in predicting tumor behavior, we studied the MIB-1 labeling indices (MIB-1 LIs) in surgical specimens and monitored tumor growth in 31 consecutive children operated on between 1978 and 1997. The MIB-1 LIs at diagnosis varied from 0-10.6% (mean +/- SD, 3.27 +/- 2.49%). Tumor progression occurred in 19 patients leading to death in seven, three of whom had neurofibromatosis type 1 (NF1). No association between MIB-1 LI at initial diagnosis and both progression free and overall survival was apparent. However, the MIB-1 LIs increased to 15.2% and 18% in two patients with NF1 who developed highly malignant gliomas 6 and 6.5 years after irradiation. In the remaining patients the MIB-1 LIs did not change significantly over time in a total of 17 repeat surgeries. Three patients with LIs of 6.8%, 10.6% and 8.8% are stable after 6, 4.5 and 3.5 years with partial resection, biopsy and subtotal resection, respectively, and no further therapy in the first two and chemotherapy in the latter. Three patients (10%) with LIs of 6.4%, 4.8% and 2.2% either presented with or developed leptomeningeal spread during follow-up. While MIB-1 LI does not appear to assist in clinical decision making patient numbers were too small to find out whether response to chemotherapy varies with proliferative potential.

Image-guided neurosurgery comparing a pointer device system with a navigating microscope: a retrospective analysis of 208 cases.

A retrospective analysis of neuronavigation procedures performed at the Vienna Neurosurgical Clinic was undertaken to elucidate the advantages of 2 technically different navigation systems in clinical use. In a 30-month period, 208 frameless stereotactic procedures were performed using a stereotactic microscope (MKM System, Zeiss; 92 procedures in 87 patients; 47 female, 40 male; mean age, 46 yrs) and a light emitting diode (LED) based pointer navigation device (Easy Guide Neuro (EGN), Philips; 116 procedures in 114 patients; 63 female, 51 male; mean age 46.4 yrs). The navigating microscope was exclusively used for cranial navigation, the pointer device system in 107 cases for cranial and in 9 cases for spinal navigation. Procedures were CCT-guided in 109 cases, MRI-guided in 95, and both CT/MRI guided in 4 cases. Skin fiducials were used in all these procedures. The MKM system provided coordinate-based navigation, similar to frame systems. This allowed surgical planning and performance using stereotactic coordinates for target calculation. Additionally, tumor volumes were defined by contours and projected into the ocular of the microscope, allowing guidance during targeting and resection of lesions. Both of these features proved beneficial in tumor surgery (60.8% MKM cases), cavernoma surgery (21.8% MKM cases), and epilepsy surgery (14.1% MKM cases). In contrast to the microscope, the pointer navigation system could be employed for intuitive correlation of image points with points of interest in the operating field by using a LED-equipped pointer device. This permitted image guidance during a wide spectrum of neurosurgical procedures, in tumor surgery (68.1% EGN cases), cavernoma surgery (5.1% EGN cases), epilepsy surgery (14.1% EGN cases), vascular surgery (3.4% EGN cases), spinal surgery (7.8% EGN cases), and guidance for burr holes and drainages (6.9% EGN cases), without calculating stereotactic coordinates. This analysis showed clear differences in the application of the two systems and may facilitate the decision as to which system best meets the individual demands of a neurosurgical department.

Frameless stereotactic lesion contour-guided surgery using a computer-navigated microscope.

BACKGROUND: The Zeiss MKM System is a recently developed computerized operating microscope for image-guided neurosurgery. The clinical advantages, reliability, accuracy, and limitations of this technique were investigated. METHODS: Since February 1995, 78 consecutive frameless stereotactic image-guided procedures were performed in 73 patients (30 males, 43 females; mean age, 46.9 years; range, 16-77 years) for tumor surgery (50/64.1%), cavernoma removal (16/20.5%), and functional procedures (12/15.4%). Skin markers (74 cases) or bone markers (4 cases) and a standard imaging protocol (2-mm cranial computed tomography (CCT) in 59 cases/1.5-mm magnetic resonance imaging (MRI) in 19 cases) were used. RESULTS: The main advantages were pre-operative skin incision, craniotomy and corticotomy planning, and determination of lesion boundaries. Useful registration and system reliability were noted in 97% (76/78) of the procedures. A significant improvement in registration accuracy was observed over the test period from a mean of 4.8 mm (SD = 3.36; Cases 1-25) to a mean of 2.2 mm (SD = 0.86; Cases 26-78). This resulted in an improvement in application accuracy from <5 mm in 71% (Cases 1-25) to <2 mm in 95% (Cases 26-78) of cases, and the accuracy led to successful localization of the lesion in every case. Accuracy was reliable at the beginning of every procedure, but degraded to values >5 mm by the end of the procedure in 29% (22/78) of cases. MRI cases achieved higher application accuracy values (2.1 mm mean) than CT cases (3.7 mm mean). CONCLUSIONS: The system offers a reliable alternative to frame-assisted stereotactic craniotomies in lesion targeting, but would need an intraoperative image update for resection guidance.

Frameless stereotactic guided neurosurgery: clinical experience with an infrared based pointer device navigation system.

An infrared based frameless stereotactic navigation device (Easy Guide Neuro) was investigated for its clinical applicability, registration/application accuracy and limitations in a standard operating room set-up. In a five-month period 40 frameless stereotactic procedures (23 female, 17 male, mean age 46.4, yrs range 10-83) including 36 craniotomies and 4 spinal surgery procedures were performed. Image registration, data transfer and operation planning using skin fixed fiducials (between 5-10, mean 6.6) and CCT in 12 patients/MRI in 28 patients, generally was done the day before surgery. Clinical applicability was proven in all procedures with an additional time for pre-operative imaging and system application in the OR of 50 min mean (35-120 range). A useful registration was achieved in 39/40 patients (97.5%) with a registration accuracy of 3.4 mm (range 1.8-6.7) for brain surgery cases and 14.4 mm (6.8-25) for spine cases. This resulted in intra-operative application accuracy values for brain surgery of 4.2 mm mean (range 1-12). Enhanced registration/application accuracy values over the test period from 4.2/3.8 mm mean (Cases 1-20) up to 3.2/2 mm mean (Cases 21-40) was observed. In spinal surgery an application accuracy of 11.3 mm mean (range 5-20) was found. An intra-operative re-calibration because of system-head drift was necessary in none of the patients, nevertheless, application accuracy degradation due to brain shift was detected in every case. In conclusion, the system allowed a time sufficient accurate frameless intra-operative localisation guidance in cavernoma, meningioma, glioma, and brain metastasis surgery. In spinal surgery, the application accuracy exceeded clinical usefulness due to high registration inaccuracy using skin markers.

Contour-guided brain tumor surgery using a stereotactic navigating microscope.

OBJECTIVE: The benefit of intraoperative radiological data integration in approach planning and resection of brain tumors using a computer navigating microscope (MKM Zeiss) was investigated. METHODS: Since February 1995, out of 86 MKM-guided surgical procedures, 53 contour-guided tumor cases (24 females, 29 males, mean age 51.6) including 16 metastasis, 14 glioblastomas, 10 low-grade gliomas, 6 anaplastic gliomas, 3 meningiomas and 4 others were performed. The preoperative planning was based on CT in 42 cases and Magnetic Resonance Tomography (MRT) in 11 cases using skin markers (4-9, mean 6). Neuroradiologically defined tumor contours were transferred into the ocular of the microscope and projected into the operating field during the procedure. RESULTS: The advantages of the system were: (1) preoperative approach planning; (2) minimal, accurate skin incision and craniotomy; (3) intraoperative detection of deep seated lesions or lesion components; (4) determination of lesion boundaries; (5) minimized traumatization in/near eloquent areas. Mean registration accuracy improved from 5.3 mm for the first 10 cases up to 2 mm for the last 18 cases. In glioma surgery, the system provided exact definition of radiologically planned resection borders. In meningioma surgery, it allowed a tailored craniotomy, dura opening and resection, lowering the risk of recurrence. In metastasis surgery, it provided a safe approach to deep and eloquent located lesions. CONCLUSION: Contour-guided operation planning and resection guidance using the investigated navigating microscope provides additional security to avoid some potential risks in brain tumor surgery.

Cavernous malformations: from frame-based to frameless stereotactic localization.

An exact surgical approach to cavernous malformations, in particular those located in areas of critical brain function, is important for their microsurgical resection without putting too much strain on the patient. During a two-year period, 29 cavernoma resections were performed. Stereotactic guidance was performed in 16 cases (55.2%). Nine cavernomas located in the supratentorial region were resected using the stereotactic operating microscope "MKM", which represents 21.6% of a total of 51 MKM-navigated operations; in one further case system referencing failed. The experience gathered with this frameless stereotactic system is compared to a retrospective analysis of 5 frame-based stereotactic cavernoma localizations. Frameless stereotactic localization has been shown to be sufficiently accurate but more advantageous than frame-based techniques in terms of utility, ease of integration, and detailed image-guided anatomical information. Software improvements have resulted in a high stability of the frameless stereotactic system.

Microsurgical anterior decompression and internal fixation with iliac bone graft and titanium plates for treatment of cervical intervertebral disc herniation.

42 cervical interbody fusions with iliac bone graft and titanium plate fixation were performed between October 1991 and March 1994. The mean follow up period in this study was 10.7 months. In 32 cases fusion was done for 1 and in 10 cases for 2 segments. 2 different types of plates were used. In 25 cases micro-osteosynthesis plates and screws with 2.7 mm diameter were used, and in 17 cases cervical H-plates and screws with 3.5 mm diameter. A favourable outcome was achieved in 31 of 42 cases (74%). Satisfactory pain relief was achieved in 90%. For radicular motor deficit good results were obtained in 84% and for cervical myelopathy in 54%. The 2 different types of plates showed a remarkable difference in the clinical outcome. The results were regarded favourable in 15 of 25 microplate fusions (60%) and in 16 of 17 H-plate fusions (94%). Compression of the bone graft was seen in 5 patients of the micro plate group, however, radiological signs for fusion were present in all 42 cases at follow up. Major surgical complications, damage to neural structures or neurological deterioration did not occur in this study. Plate fixation in cervical interbody fusions seems to be a safe procedure and may reduce graft related complications at the fusion site if the plates and screws are sufficiently well proportioned. A favourable impact upon the results for cervical interbody fusion might be expected and should be further investigated in a long term follow up study.