Transmuscular trocar technique - minimal access spine surgery for far lateral lumbar disc herniations

OBJECTIVE

Minimal access spine surgery (MASS) is gaining increasing importance in microsurgery of the lumbar spine. From a current prospective series we present data on MASS for far lateral lumbar disc herniations (LLDH) via a transmuscular trocar technique (T(2)). The surgical procedure and operative results are demonstrated in detail. In contrast to conventional percutaneous endoscopic techniques, T(2) allows one to operate in the typical microsurgical fashion combined with the advantages of a minimal endoscopic approach with three-dimensional visualization of the surgical target using the operating microscope.

METHODS

Microsurgery was performed through a 1.6-cm skin incision with an 11.5-mm diameter trocar that is obliquely inserted into the paraspinal muscles pointing at the lateral isthmus of the upper vertebral body. Fifteen patients were evaluated after a median follow-up period of 24 months. Overall outcome according to the modified MacNab criteria, effect of surgery on radicular pain and sensory or motor deficits, duration of surgery, complication rate, and duration of hospital stay were evaluated.

RESULTS

Good to excellent clinical outcomes were achieved in 14/15 patients. Radicular pain and motor deficits improved in all patients postoperatively, while sensory deficits recovered in 13/15 patients. The cosmetic results were excellent in all patients. No aggravation of symptoms after surgery was observed in any of the patients.

CONCLUSIONS

The T(2) technique represents an auspicious alternative to standard open microsurgery for LLDH, which allows achievement of excellent clinical and cosmetic results, preservation of segmental spine stability, and avoidance of excessive soft tissue trauma.

Delayed diagnosis of spinal dural arteriovenous fistula in the absence of pathological vessels on MRI

The authors report on a 69-year-old man presenting with progressive leg weakness and gait ataxia over two years. A central intramedullary cord lesion ranging from T8-12 on MR imaging was misdiagnosed as a low-grade glioma and a biopsy was attempted followed by temporary clinical deterioration. Selective spinal angiography revealed a spinal dural arteriovenous (AV) fistula on the left L3 nerve root sheath despite the absence of pathological vessels on MR imaging. The fistula was successfully treated by microsurgical interruption of the arterialized intradural vein. The present case should remind us to include selective spinal angiography in our diagnostic work-up in patients predisposed for spinal dural AV fistula by male sex, advanced age and clinical presentation of slowly progressive sensorimotor symptoms with myelopathy on MR imaging, even in the absence of any pathological vascular structures.

Advanced Neuronavigation in Skull Base Tumors and Vascular Lesions

OBJECTIVE

The purpose of this study was to describe the usefulness of recent advances of neuronavigational technology in the management of skull base tumors and of vascular lesions, treated via a skull base approach.

METHODS

In 16 patients (skull base meningioma n = 9, petrous apex epidermoid n = l, craniopharyngeoma n = 1, giant internal carotid artery aneurysm n = 1, basilar/vertebral artery aneurysm n = 2, brain stem cavernoma n = 2), "advanced" neuronavigation was used. In contrast to "conventional" neuronavigation, the information for the neurosurgeon was enhanced by the intraoperative screen display of 3-dimensional reconstructions of the lesion, vessels, nerves and fiber tracts at risk. The 3-dimensional reconstructions were obtained by preoperative manual or automated segmentation processes. In addition, different imaging modalities (computed tomography [CT] with magnetic resonance imaging [MRI], CT with CT angiography, T (l)- with diffusion-weighted MRI) were fused and shown on the screen.

RESULTS

In the cases of tumors, "advanced" neuronavigation facilitated the approach (n = 4), contributed to tailor the approach (n = 2) and helped to identify hidden neurovascular structures (n = 9). In the cases of aneurysms, "advanced" neuronavigation allowed us to reduce the skull base approach to the needs of safe aneurysm clipping (n = 3). In both cases of brain stem cavernoma, "advanced" neuronavigation was deemed useful for definition of the best surgical approach in relation to the pyramidal tract and brain stem nuclei.

CONCLUSION

The authors' experiences suggest that neuronavigation, which displays 3-dimensional reconstructions of lesion, vessels, nerves and fiber tracts during surgery and makes use of image fusion techniques, is an important tool in the neurosurgical management of skull base lesions.

Focused high frequency repetitive transcranial magnetic stimulation for localisation of the unexposed primary motor cortex during brain tumour surgery

OBJECTIVES

To investigate if intraoperative focused high frequency repetitive transcranial magnetic stimulation (rTMS) can localise the primary motor cortex without exposure of the cortical surface.

METHODS

A high frequency train (357 Hz) of four suprathreshold magnetic stimuli was delivered transcranially to the region of the rolandic area during brain tumour operations in 12 patients. To induce a focal magnetoelectric field, the flat figure of eight coil (outer diameter of each loop 7 cm) was used. Motor evoked potentials (MEP) were recorded in eight muscles of the upper and lower contralateral extremities. The first stimulation site was 2.5 cm behind the bregma, the second site 2 cm, and the third site 4 cm dorsal to the first stimulation site. If no MEP were obtainable, stimulation was repeated in anteroposterior direction at more laterally located sites. Using neuronavigation, each positive stimulation site was correlated with the underlying cortical anatomy.

RESULTS

Stimulation was performed at a total of 42 sites (in two patients, maximum stimulation at the three initial sites failed to evoke a motor response). In four patients, MEP were obtained only from one stimulation site. This site exactly overlayed the primary motor cortex. In eight patients, MEP could be elicited from more than one stimulation site. In seven of the eight patients, the site from which MEP with peak amplitudes were elicited, corresponded to the primary motor cortex. In total, the primary motor cortex was correctly identified on the basis of electrophysiological findings in 11 of 12 patients (92 %). In two patients, only the more lateral stimulation sites permitted MEP recording.

CONCLUSION

Intraoperative focused rTMS is highly sensitive for localisation of the primary motor cortex. Focused rTMS as a localising instrument alleviates the need of motor cortex exposure and, thereby, can contribute to minimise the surgical approach to brain tumours in the rolandic area.

Second harmonic imaging: a new ultrasound technique to assess human brain tumour perfusion

BACKGROUND

Second harmonic imaging is a new ultrasound technique that allows evaluation of brain tissue perfusion after application of an ultrasound contrast agent.

OBJECTIVE

To evaluate the potential of this technique for the assessment of abnormal echo contrast characteristics of different brain tumours.

METHODS

27 patients with brain tumours were studied. These were divided into four groups: gliomas, WHO grade III-IV (n = 6); meningiomas (n = 9); metastases (n = 5); and others (n = 7). Patients were examined by second harmonic imaging in a transverse axial insonation plane using the transtemporal approach. Following intravenous administration of 4 g (400 mg/ml) of a galactose based echo contrast agent, 62 time triggered images (one image per 2.5 seconds) were recorded and analysed off-line. Time-intensity curves of two regions of interest (tumour tissue and healthy brain tissue), including peak intensity (PI) (dB), time to peak intensity (TP) (s), and positive gradient (PG) (dB/s), as well as ratios of the peak intensities of the two regions of interest, were derived from the data and compared intraindividually and interindividually.

RESULTS

After administration of the contrast agent a marked enhancement of echo contrast was visible in the tumour tissue in all patients. Mean PI and PG were significantly higher in tumour tissue than in healthy brain parenchyma (11.8 v 5.1 dB and 0.69 v 0.16 dB/s; p < 0.001). TP did not differ significantly (37.1 v 50.2 s; p = 0.14). A tendency towards higher PI and PG as well as shorter TP was apparent in malignant gliomas. When comparing different tumour types, however, none of these variables reached significance, nor were there significant differences between malignant and benign tumours in general.

CONCLUSIONS

Second harmonic imaging not only allows identification of brain tumours, but may also help in distinguishing between different tumour types. It gives additional and alternative information about tumour perfusion. Further studies are needed to evaluate the clinical potential of this technique in investigating brain tumours-for example in follow up investigations of patients undergoing radiation or chemotherapy-especially in comparison with neuroradiological and neuropathological findings.

A case of gliosarcoma appearing as ischaemic stroke

OBJECTIVES

Ischaemic stroke attributable to malignant brain tumour is a rarely reported phenomenon and even various imaging techniques including angiography do not necessarily lead to an accurate diagnosis.

CASE DESCRIPTION

A 46-year-old, previously healthy man developed apoplectic symptoms with slight right sided hemiparesis and global aphasia. The computed tomography (CT) scan showed lesions of the left temporal lobe and the paraventricular white matter suggestive of left middle cerebral artery (MCA) infarction. Carotid angiography demonstrated compression of the M1 segment of the MCA and occlusion of temporal MCA. The patient initially refused magnetic resonance imaging (MRI) because of claustrophobia. Because of fluctuating symptoms and successive worsening of the condition over weeks an MRI scan was conducted under general anaesthesia. Beneath temporal, opercular, and subcortical infarctions it revealed a left temporal tumour. A tumour biopsy disclosed a gliosarcoma (WHO grade IV). Microscopical examination of the surgical specimen demonstrated invasion of tumour cells into the wall of a greater pre-existing blood vessel.

CONCLUSIONS

Malignant brain tumours may cause ischaemic infarction. This is a rare but important differential diagnosis for the origin of strokes. The authors describe the first case with infiltration of intracranial blood vessels by tumour cells of a gliosarcoma.

[Aneurysmal subarachnoid hemorrhage: role of computerized tomography for correct prediction of the ruptured aneurysm site]

OBJECTIVE

To investigate if the intracisternal distribution of subarachnoid hemorrhage (SAH) following aneurysm rupture allows the correct prediction of the symptomatic aneurysm site. [nl]

METHODS

Ninety-nine consecutive patients with acute SAH and angiographically proven aneurysm were included into the study. The parent vessel of the diagnosed aneurysms were the anterior communicating artery (ACoA) in 38 patients, the middle cerebral artery (MCA) in 26 patients, the internal carotid artery (ICA) in 25 patients, the pericallosal artery (A2) in 5 patients, the basilar artery (BA) in 4 patients and the vertebral artery (VA) in 1 patient. In 21 patients, an additional asymptomatic aneurysm was diagnosed. The initial computerized tomography (CT) scans of the 99 patients were given to 2 experienced vascular neurosurgeons, who were blinded for the angiography findings. The 2 investigators had to predict the site of the ruptured aneurysm. [nl]

RESULTS

Investigator 1 correctly predicted the aneurysm site in 56 (57 %), investigator 2 in 59 of the 99 patients (60 %). Investigator 1 correctly identified 81 % of the MCA aneurysms, and investigator 2 74 % of the ACoA aneurysms. However, in only 46 of the 99 patients (47 %), the aneurysm site was correctly predicted by both investigators together. [nl]

CONCLUSION

The results indicate, that the distribution of the subarachnoid blood as shown on the first CT scan after aneurysm rupture barely allows to predict the symptomatic aneurysm site. Thus, neurosurgical decision making (identification of the ruptured aneurysm in patients with multiple aneurysms; surgical exploration in patients with non-perimesencephal SAH, but negative angiography) should not rely on the first CT scan after SAH.

Influence of intraventricular hemorrhage on outcome after rupture of intracranial aneurysm

This study was performed to analyze the effect of intraventricular hemorrhage (IVH) on 14-day mortality, outcome at 6 months, and the occurrence of chronic hydrocephalus in patients with aneurysmal subarachnoid hemorrhage. Clinical grade of subarachnoid hemorrhage and the distribution of extravasated blood were evaluated in 219 patients with ruptured aneurysms. Computed tomographic scans performed within 72 h of hemorrhage were analyzed to determine the severity of intraventricular and subarachnoid hemorrhage and the volume of intracerebral hematomas. Outcome at 6 months was assessed using the Glasgow Outcome Scale. Intraventricular hemorrhage extension occurred in 109 of the 219 patients studied. Fourteen-day mortality increased from 7.3% in patients without IVH to 14.1% in those with moderate IVH (IVH score 1-6) and to 41.7% in those with more severe IVH (IVH score > 6). The corresponding figures for unfavorable outcome at 6 months are 19.8%, 30.5%, and 66.7%, respectively. According to logistic regression analyses, the severity of IVH was an independent predictor of mortality and functional outcome. The clinical outcome after aneurysm rupture is at least in part determined by the severity of IVH. Knowledge of the effect of IVH may help guide physicians in the care of patients with aneurysmal bleeding.

Bleeding from a cavernous angioma mimicking rupture of a middle cerebral artery aneurysm

Cavernous angiomas and aneurysms may both present with acute cerebral haemorrhage. We present a case in which the coexistence of an unruptured aneurysm obscured the diagnosis of cerebral haemorrhage from a cavernous angioma. Although this association was presumably coincidental, this case demonstrates that obvious pathology (an angiographically proven aneurysm at the site of haemorrhage) may reduce awareness of other, possibly more common, causes of cerebral haemorrhage.

Three-dimensional visualization of the pyramidal tract in a neuronavigation system during brain tumor surgery: first experiences and technical note

OBJECTIVE

To integrate spatial three-dimensional information concerning the pyramidal tracts into a customized system for frameless neuronavigation during brain tumor surgery.

METHODS

Four consecutive patients with intracranial tumors in eloquent areas underwent diffusion-weighted and anatomic magnetic resonance imaging studies within 48 hours before surgery. Diffusion-weighted datasets were merged with anatomic data for navigation purposes. The pyramidal tracts were segmented and reconstructed for three-dimensional visualization. The reconstruction results, together with the fused-image dataset, were available during surgery in the environment of a customized neuronavigation system.

RESULTS

In all four patients, the combination of reconstructed data and fused images was a helpful additional source of information concerning the tumor seat and topographical interaction with the pyramidal tract. In two patients, intraoperative motor cortex stimulation verified the tumor seat with regard to the precentral gyrus.

CONCLUSION

Diffusion-weighted magnetic resonance imaging allows individual estimation of large fiber tracts applicable as important information in intraoperative neuronavigation and in planning brain tumor resection. A three-dimensional representation of fibers associated with the pyramidal tract during brain tumor surgery is feasible with the presented technique and is a helpful adjunct for the neurosurgeon. The main drawbacks include the length of time required for the segmentation procedure, the lack of direct intraoperative control of the pyramidal tract position, and brain shift. However, mapping of large fiber tracts and its intraoperative use for neuronavigation have the potential to increase the safety of neurosurgical procedures and to reduce surgical morbidity.

Morphological changes following experimental intraventricular haemorrhage and intraventricular fibrinolytic treatment with recombinant tissue plasminogen activator

Intraventricular haemorrhage (IVH) occurs in up to 50% of patients with primary intracerebral haemorrhage and aneurysmal subarachnoid haemorrhage. It is a significant and independent contributor to mortality and morbidity in these intracranial haemorrhages. Using a model of isolated IVH, we assessed the morphological changes induced by intraventricular bleeding and investigated the effects of intraventricular fibrinolytic treatment following IVH. IVH was induced in 32 pigs by intraventricular infusion of 10 ml autologous blood along with thrombin. The treatment group received an intraventricular injection of 1.5 mg (1 mg/ml) tissue plasminogen activator (tPA) following the injection of blood. The placebo group received the same volume of normal saline. Morphological examinations of the brains were carried out 7 days and 6 weeks following IVH. The ventricles were incompletely filled with blood and significantly enlarged in the placebo group 7 days after the IVH. In contrast, no residual intraventricular clots were visible in the animals treated with tPA, and the diameters of the lateral ventricles had returned to normal within 7 days. Marked losses of the ependymal covering of the ventricular walls were found in the placebo-treated animals, while the ependymal layer was largely intact in the animals treated with tPA. No haemorrhages induced by tPA were observed. The results indicate that intraventricularly administered tPA significantly enhances the lysis of intraventricular blood clots, accelerates the resolution of acute posthaemorrhagic hydrocephalus, and preserves the integrity of the ependymal layer.

Subdural-atrial and subdural-peritoneal shunting in infants with chronic subdural fluid collections

BACKGROUND

In symptomatic infants with chronic subdural fluid collections a variety of treatment strategies, such as observation, repeated subdural tapping, external or internal subdural drainage, and craniotomy have been advocated. Until now, the ideal management for this etiologically heterogenous group of children seems controversial.

METHODS

The authors present their treatment with subdural-peritoneal and subdural-atrial shunts and the follow-up in 8 infants (mean age, 7 months) with bifrontal subdural hygromas and hematomas caused by different etiologic conditions.

RESULTS

Initially, all children were symptomatic, and repeated subdural taps showed no clinical and neuroradiologic benefit. Shunting resulted in disappearance of all clinical signs in all infants, with complete removal of the chronic subdural fluid collections in 6 cases and remarkable improvement in 2 cases. In all infants the shunt system was removed after disappearance of signs and decrease of fluid collections. As the only complication the shunt system had to be removed in 1 case on the fourth postoperative day because of infection without any further disadvantages. In none of the cases was a recurrence of the fluid collections seen during the follow-up.

CONCLUSION

These results suggest that in infants with symptomatic chronic subdural fluid collections who fail to respond to repeated tapping, the early placement of an unilateral subdural-peritoneal shunt with a low pressure valve represents a safe, benign, and effective treatment option.

Primary intradural pontocerebellar chordoma metastasizing in the subarachnoid spinal canal

Chordomas that are entirely extraosseous and intradural are rare. Additionally subarachnoid spinal implantation from such a cranial, intradural chordoma has never been reported before. The authors present a case of a widespread primary intradural chordoma in the basal cisterns of a 48-year-old woman which shows seeding of neoplastic cells to the spinal leptomeninges. It is concluded that also in cases of intradural and intracranial chordomas a tumor staging should include the search for spinal subarachnoid metastases.

Frameless stereotactically guided catheter placement and fibrinolytic therapy for spontaneous intracerebral hematomas: technical aspects and initial clinical results

OBJECTIVE

Frame-based stereotactic puncture and catheter placement followed by fibrinolytic therapy and drainage is one treatment option in the management of spontaneous intracerebral hemorrhage (sICH). This minimally invasive procedure could even be simplified by frameless stereotaxy. The authors present their experiences with frameless stereotactic image-guided catheter placement for lysis and drainage of sICH, with emphasis on technical aspects.

METHOD

In 27 patients with sICH, an infrared-based frameless stereotactic device was used for selecting trajectory and target point of hematoma drainage. A trajectory along the main axis of the hematoma was considered to be optimal for fibrinolytic therapy. An articulated arm served to maintain the predetermined trajectory during surgery and to guide catheter advancement. Clot lysis with recombinant tissue plasminogen activator (rt-PA) was initiated after radiological confirmation of correct catheter positioning.

RESULTS

In all cases, selection of the optimal trajectory was not restricted by the frameless stereotactic device. In 25 of the 27 patients, the catheter was placed accurately along the predetermined trajectory into the target point. In two patients, the catheter was positioned at the lateral margin of the hematoma, excluding fibrinolytic therapy in one case. In 24 of 27 patients, the mean hematoma volume could be reduced from initially 52 ml to 17 ml in an average of two days. Hematoma enlargement following rt-PA injection was observed in two patients. Further complications were culture negative pleocytosis of cerebrospinal fluid in two and meningitis in one patient.

CONCLUSION

Hematoma puncture and catheter placement for fibrinolytic therapy could be achieved with high accuracy and safety using frameless stereotaxy. This method allows unrestricted trajectory selection with catheter positioning along the main hematoma axis. Further studies are required to investigate if frameless stereotactic puncture and clot lysis could contribute to improve the outcome of patients with sICH.

Functional outcome after aneurysmal subarachnoid hemorrhage

The introduction of the operating microscope, the principle of early surgery, specialized intensive care units, the calcium antagonist nimodipine, the sophisticated pre- and postoperative management and an aggressive antiischemic pharmacological management have substantially reduced morbidity and mortality after aneurysmal subarachnoid hemorrhage (SAH). In spite of this progress, many patients after rupture and surgical repair of an intracranial aneurysm exhibit substantial cognitive deficits and emotional problems although their neurological outcome was rated as good according to the Glasgow Outcome Scale (GOS = I). Therefore, a comprehensive neuropsychological examination is called for in order to evaluate the factual functional outcome after SAH. Neither focal brain damage associated with aneurysm location nor surgery but the hemorrhage itself and related events can be regarded as the most important causal factors for the late result after SAH. In contrast to the mild permanent effects of aneurysm surgery, the initial bleeding itself seems to have substantial lasting adverse neurobehavioral effects after. In concordance with other authors our own data stress the strong predictive power of the bleeding pattern such as the presence of intraventricular and/or intracerebral blood on the functional outcome after aneurysmal SAH.

Fibrinolytic treatment of intraventricular haemorrhage preceding surgical repair of ruptured aneurysms and arteriovenous malformations

Previous studies have indicated that intraventricular administration of tissue-type plasminogen activator (TPA) might improve the prognosis of patients with intraventricular haemorrhage (IVH). In aneurysmal IVH, fibrinolytic treatment was always preceded by surgical repair of the aneurysm, since the risk of recurrent haemorrhage from a non-occluded aneurysm was estimated to be high. We reviewed a series of patients with IVH secondary to ruptured aneurysms (n = 4) or arteriovenous malformation (AVM; n = 1) who underwent emergency intraventricular administration of TPA before repair of the bleeding source. Fibrinolysis resulted in rapid decrease of haematoma volume and of ventricular dilatation, and prevented ventricular catheters from becoming obstructed. No intracranial haemorrhages or other complications occurred. The results suggest that the presence of recently ruptured aneurysms or AVM is not necessarily a contraindication for intraventricular administration of TPA. The potentially life saving benefits might outweigh the inherent risks of recurrent haemorrhage in carefully selected patients with massive IVH, in whom ventricular distension, periventricular brain compression, obstruction of CSF flow, and elevated ICP appear to be major determinants for the outcome.

Four-year experience with the routine use of the programmable Hakim valve in the management of children with hydrocephalus

OBJECTIVE

Cerebrospinal fluid (CSF) over- and underdrainage symptoms are frequent sequelae of shunt placement in patients with hydrocephalus, sometimes requiring repeated operations. To achieve more adequate CSF drainage, the non-invasively programmable Hakim valve has been developed. Because the clinical experiences with this valve so far are confined to adults, we describe our experiences with the routine use of the programmable Hakim valve in childhood hydrocephalus.

METHOD

Sixty children (mean age of 3.4 years) with hydrocephalus of various aetiologies have been shunted with the programmable Hakim valve. In the majority of cases, initial opening pressures of between 100 and 120 mm H2O were selected. The mean follow-up period was 2.1 years.

RESULTS

Thirty-three readjustment of the pressure setting of the valve were performed in 20 children because of CSF overdrainage (low intracranial pressure syndrome n = 13, slit ventricle syndrome n = 2, hygroma n = 1), CSF underdrainage (n = 3) and CSF leakage through the operation wound (n = 1). The symptoms of inadequate CSF drainage were cured in 18 of the 20 children. The necessity for valve readjustments was independent of the aetiology of the hydrocephalus. Thirty-one complications requiring repeated operation occurred during the follow-up period, accounting for an annual complication rate of 24.6%. Three complications were valve-related.

CONCLUSION

In the majority of cases, the programmable Hakim valve allows the successful management of symptoms related to CSF over- and underdrainage by non-invasive change of the initial pressure setting of the valve. Therefore, the programmable Hakim valve should be considered as an alternative to non-programmable valves of advanced design.

Surgically treated traumatic synchondrotic disruption of the odontoid process in a 15-month-old girl

A case of traumatic synchondrotic disruption in a 15-month-old girl is reported; she was treated with interlaminar wiring of C1-C2 without grafting. Reduction of the dislocation and angulation and stability were achieved without evidence of growth disturbance. However, the child's initial poor neurological status with tetraplegia below the level of C7 remained unchanged. Besides our case, there are only three other cases in the literature of young children primarily operated on for a traumatic odontoid synchondrotic disruption. Even though the dorsal interlaminar wiring of C1-C2 without grafting is an easy and safe procedure even in the very young, the optimal form of treatment for this rare injury is still unsettled.

Isolated cerebral aspergilloma--long-term survival of a renal transplant recipient

A renal transplant recipient with isolated cerebral aspergilloma 4 months after allograft transplantation is reported. On admission cerebral computed tomography showed a ring-enhancing mass in the left frontal hemisphere and aspirated purulent material revealed A. fumigatus hyphae. He was cured by short-term antifungal therapy and neurosurgical removal of the well demarcated lesion. He is still alive more than two years later and the renal transplant is well functioning. This is the first report of a renal transplant recipient with isolated cerebral aspergillosis without any relapse and only the third patient who has survived longer than 3 months. Early diagnostic procedures with rapid confirmation of aspergillus infection are pivotal for a benign clinical course.

Clinical significance of three-dimensional helical CT in neurosurgery

The authors report about a 3-years experience with helical CT and 3-D surface reconstruction applied in neurosurgical patients. All examinations were performed in addition to preexisting diagnostic CT, MRI, or angiography. The aim of this study was to assess the clinical value of this method with regard to planning of the surgical approach to anterior, middle, and posterior skull base and spinal lesions. 75 examinations of 55 patients were analysed and ranked as follows: A = examination with significant additional information for neurosurgical planning of skull base or spinal procedures or for postoperative evaluation of the neurosurgical approach, B = examination with some useful information for the neurosurgical planning or postoperative control, however, without significant advantage as compared to established diagnostic methods, C = examination without significant additional information. Classification was performed independently by two experienced surgeons. Examinations of anterior, middle, and posterior skull base lesions including cerebral aneurysms were in the majority rated as helpful and significantly informative, (A = 21, B = 24, C = 9, n = 54). Three-dimensional imaging of the spine was of clinical value only in specific cases (A = 6, B = 6, C = 9, n = 21). The authors conclude that three-dimensional imaging is a valuable diagnostic tool for pre- and postoperative imaging of tumorous and vascular lesions adjacent to the skull base, allowing for optimal surgical approaches with minimal invasiveness.

Epidural spinal infection. Variability of clinical and magnetic resonance imaging findings

STUDY DESIGN

This study evaluates the magnetic resonance characteristics of spinal epidural abscesses and their associated disc space infections.

OBJECTIVES

The results were correlated with history, clinical, and laboratory findings to provide guidelines for early and appropriate diagnosis of epidural spinal infections.

SUMMARY OF BACKGROUND DATA

Imaging signs of spinal infections have been reported before, but not with special attention to early clinical and imaging findings.

METHODS

Thirteen patients (10 men, 3 women; age range, 32-64 years) with progressive sensorimotor deficit were studied. All patients had a neurologic examination after admission and a magnetic resonance imaging scan done within the first 48 hours. In all cases, T1-weighted images before and after administration of gadolinium were obtained. T2-weighted images were acquired in eight cases as well. Ten patients subsequently underwent open surgery; in three cases, a percutaneous biopsy and drainage was performed.

RESULTS

Cervical discitis was found in five patients, and thoracic discitis was seen in another five cases. Three patients had an epidural infection without a concomitant discitis. Neurologic and clinical findings varied considerably. Despite clinical signs of spinal cord involvement, a spinal cord lesion was demonstrated only once. Signal change in T2-weighted images may be the first sign of disc space infection. Because a neurologic deficit may occur before any change is visible, follow-up examinations may be required if epidural infection is suspected on clinical grounds.

CONCLUSIONS

Magnetic resonance imaging is the appropriate method for diagnostic work-up of progressive neurologic deficit resulting from epidural infection.

A cystic lesion within the dural sinuses: a rare cause of increased intracranial pressure

We present a rare cause of intracranial hypertension in a 19-year-old woman. The torcular was obstructed by a cystic developmental lesion, thought preoperatively to be an epidermoid. The patient also had a second lesion of possibly developmental origin, a cerebral cavernous haemangioma.

Ventricular dilatation in experimental intraventricular hemorrhage in pigs. Characterization of cerebrospinal fluid dynamics and the effects of fibrinolytic treatment

BACKGROUND AND PURPOSE

Hemorrhagic ventricular dilatation (HVD) is a prominent feature of human intraventricular hemorrhage (IVH) and a strong indicator for poor outcome. We developed an IVH model to define the mechanisms responsible for HVD and to test the efficacy of intraventricular administration of tissue plasminogen activator (TPA) in the treatment of HVD.

METHODS

Isolated IVH was produced in pigs by injecting 10 mL of blood simultaneously with thrombin into the right lateral ventricle. The treatment group received 1.5 mg of TPA after induction of IVH. Intraventricular blood volume and the volume of the lateral ventricles were assessed by CT after 90 minutes, 7 days, and 42 days. Intracranial pressure, the pressure-volume index, and the resistance to outflow of cerebrospinal fluid (R(out)) were measured 30 minutes and 7 days after IVH.

RESULTS

After IVH, the volume of the lateral ventricles increased from 1.98 +/- 0.69 to 6.43 +/- 1.23 mL (P < .001). There was a linear relationship between ventricular and clot volume (P = .014). Initially, R(out) increased from 24.34 +/- 7.13 to 63.56 +/- 64.91 mm Hg/mL per minute (P < .001). After 7 days, restoration of normal cerebrospinal fluid circulation occurred, but the ventricles were still significantly enlarged (5.24 +/- 1.76 mL, P < .001) and filled with blood. Within 6 weeks, ventricular volume had returned to normal values, paralleled by complete clot resolution. Intraventricular administration of TPA significantly accelerated clot clearance and restoration of normal ventricle volume.

CONCLUSIONS

These results suggest that intraventricular bleeding may cause impairment of cerebrospinal fluid circulation but that the mass effect of clots distending the ventricle walls is the most important mechanism responsible for HVD. This model closely imitates several prominent features of human IVH and may therefore be a useful tool for preclinical assessment of the efficacy and safety of treatment with TPA.

Duplication of a vertebral artery associated with epidermoid cyst of the posterior fossa

A case of a duplication of the left vertebral artery associated with a premedullary epidermoid cyst at the level of the foramen magnum is described. The close proximity of the two malformative lesions in the present case and the overlap of the periods when such developmental abnormalities can arise suggest that they might be causally linked.

Interhemispheric approach for microsurgical removal of olfactory groove meningiomas

Eighteen consecutive patients with olfactory groove meningiomas, with diameters ranging from 1.5 to 7 cm, underwent microsurgical tumour resection using a unilateral frontal interhemispheric approach. Unilateral frontal craniotomy, superior to the frontal sinus, exposing the superior sagittal sinus was performed. The ipsilateral frontal lobe was gently retracted laterally, and the tumour resected through the gap between the falx and the medial aspect of the frontal lobe, anteriorly to the genu of the corpus callosum. Gross total tumour resection was achieved in all the patients. There was no evidence of damage to the frontal lobes, the anterior cerebral arteries or the optic system. Compared with the more commonly applied subfrontal route, the interhemispheric approach has the advantages of sparing the frontal sinuses and providing excellent overview of the dissection of the anterior cerebral arteries and the optic system, as well as for the resection of tumour invading the frontal cranial base.

[Management of craniocerebral trauma in a neurosurgery center]

Aggressive treatment of patients with severe head injury increases the chance for survival and good functional outcome in most cases. To prevent irreversible cerebral lesions, the key point of treatment is the management of intracranial hypertension caused by intracranial hematomas, brain edema and impaired circulation of cerebrospinal fluid (CSF). Therapeutic standards are surgery of traumatic hematoma, osmotherapy and mild hyperventilation for brain edema, and CSF drainage. In highly elevated intracranial pressure (ICP) administration of barbiturates and forced hyperventilation can be considered.

Microsurgical interhemispheric approach to dural arteriovenous fistulas of the floor of the anterior cranial fossa

Six patients with a dural arteriovenous fistula (DAVF) of the floor of the anterior cranial fossa underwent microsurgical treatment. Two of them were operated using a conventional frontobasal approach, and four using an interhemispheric approach. The interhemispheric approach offers the advantages of sparing the frontal sinus, minimizing frontal lobe retraction, and providing a visual angle perpendicular to the floor of the anterior fossa and an excellent view of the fistula located on the cribriform plate at the level of the foramen caecum. Using the interhemispheric route, the malformation was occluded in all the cases by dividing the vascular connection between the dura of the cribriform plate and the intradural draining vein. There were no complications related to the surgical procedure. This route avoids some disadvantages of the more frequently reported frontobasal approach. It is therefore a recommendable alternative for the management of frontal DAVFs.

Osteoplastic frontal sinusotomy and extradural microsurgical repair of frontobasal cerebrospinal fluid fistulas

The choice of the surgical approach and operative technique for the management of cerebrospinal fluid (CSF) fistulas of the anterior cranial fossa are still a controversially discussed topic. Although "extracranial" approaches through the paranasal sinuses are becoming increasingly more popular among otolaryngologists and maxillo-facial surgeons, most neurosurgeons traditionally prefer the "intracranial" repair of CSF fistulas by a craniotomy. We present an approach through the frontal sinus for the repair of dural defects behind the posterior wall of the frontal sinus and at the floor of the anterior cranial fossa. The operative procedure comprises the following main steps: 1) exposure of the anterior wall of the frontal sinus by a bicoronal incision; 2) excision of the anterior wall without frontal burr holes; 3) bilateral removal of the posterior wall of the frontal sinus; 4) extradural inspection of the dura behind the frontal sinus and above the cribriform plate, ethmoidal roof, and orbital roof bilaterally; 5) closure of dural tears by direct suture and a periosteal graft; 6) reinsertion of the anterior wall of the frontal sinus and fixation with titanium micro plates. Twenty-five patients operated upon using this technique are described. The aetiology of the frontobasal lesion was traumatic in 23, and an ethmoid carcinoma in two. In all patients, the dural fistulas were successfully repaired during the initial procedure. One patient died from sudden circulatory arrest after an uneventful postoperative course of nine days. Otherwise, there were no postoperative complications. This technique affords atraumatic extradural inspection and repair of dural fistulas bilaterally behind the frontal sinus, and above the cribriform plate and the ethmoidal and orbital roofs with none or minimal brain retraction. It therefore allows early repair of CSF fistulas also in patients with severe brain injury. Although we consider the extradural closure of fistulas the method of choice, this approach also allows for a combined extradural-intradural procedure, thus enabling the surgeon to treat associated intradural pathologies, such as traumatic lesions or tumours of the frontal cranial base.

PET-study of intracranial meningiomas: correlation with histopathology, cellularity and proliferation rate

The glucose metabolism of 62 meningiomas was measured by fluorine -18-2-fluorodeoxyglucose (FDG) PET and correlated with proliferation rate (Ki-67 index) and tumor cellularity. The mean metabolic rate (MRGlu) for meningiomas was 0.26 +/- 0.13 mikromol/g/min (range 0.08-0.62 mikromol/g/min). The relative tumor FDG-uptake (Q-MRGlu) (tumor/contralateral cortex) of all meningiomas was calculated with 0.73 +/- 0.37 (0.24-1.79). Differences of Q-MRGlu were significant between the groups with high vs. low cellularity (p < 0.01), increased vs. normal proliferation rate (p < 0.025) and low (WHO grade I) vs. higher (WHO grades II, III) graded tumors. In recurrent meningiomas (14 tumors) the glucose metabolism was not increased. The data show that 18 FDG-PET is suitable to serve as non-invasive predictor of tumor growth characteristics in meningiomas.

Hemangioblastomas of the spinal cord and the brainstem: diagnostic and therapeutic features

Hemangioblastomas of the spinal cord and the brainstem make up 4% of all spinal tumors and are less common than cerebellar hemangioblastomas. CT and MRI are essential for preoperative diagnosis. Nevertheless, cerebral and spinal angiography are also mandatory, since they allow a detailed study of the vascular situation, which is decisive for exact planning of a surgical strategy. The purpose of this study was to evaluate the diagnostic and therapeutic factors which influence surgical morbidity and postoperative outcome. Twelve patients harbouring spinal(8 cases) or medullary (4 cases) hemangioblastomas, all symptomatic with sensorimotor deficits corresponding to the level of the lesion were evaluated. All patients were treated in our department between December 1989 and September 1994. Complete resection of the lesion was achieved in each case. Postoperatively, none of the patients showed deterioration. Nine patients had immediate postoperative improvement of neurological signs and symptoms; in three patients the initial neurological deficits remained unchanged during the in-patient period. Late postoperative outcome demonstrated a clear improvement; in only one patient was there no change of the clinical signs, while in the other 11 patients a significant improvement of pre-existing neurological deficits was experienced. We conclude that microsurgical resection of spinal and medullary hemangioblastomas with low morbidity is feasible.

Microsurgical management of ventral and ventrolateral foramen magnum meningiomas

The authors report their experiences gained from 19 patients with ventral or ventrolateral foramen magnum meningiomas operated on via the dorsolateral, suboccipital transcondylar access route. It is emphasized that the microsurgical management of these lesions includes two important aspects which increase the safety of the procedure: a meticulous preoperative planning based on the microanatomical details of each patient, as well as an individualized tailoring of the surgical approach. There were no deaths, and, in the past 5 years, no neurological complications in this series. Gross total removal of the tumour was achieved in each case. It is concluded that microsurgical removal of ventral or ventrolateral foramen magnum meningiomas with this technique constitutes a safe and recommendable procedure.

Planning and surgical strategies for early management of vertebral artery and vertebrobasilar junction aneurysms

Selection of the approach and technique for surgical repair of aneurysm of the vertebrobasilar artery system is mainly based on angiographic features. This report emphasizes that planning the surgical procedure should also include preoperative evaluation of the individual skull base configuration, as well as the relationship between aneurysm site and surrounding bony structures. These features are evaluated on thin slice CT scans using bone tissue algorithms and are particularly important for adequate exposure of distal vertebral artery (VA) or midline aneurysms, because these cases require drilling of the jugular tubercle. For the use of lateral approaches, the surgeon must be familiar with the extradural and intradural anatomy of the foramen magnum region and may rely on at least five anatomical landmarks for orientation during surgery: 1) the dural entrance of the vertebral artery; 2) the posterior condylar emissary vein; 3) the medial rim of the distal sigmoid sinus; 4) the hypoglossal canal; 5) the jugular tubercle. To increase the safety of the procedure, the authors recommend an individualized tailoring of the surgical approach according to the variable morphological situation of each patient.

Ultrasound-guided craniotomy for minimally invasive exposure of cerebral convexity lesions

The authors describe a method of real-time ultrasound-guided craniotomy for an approach to cerebral convexity lesions. During surgery, a specially designed high frequency (7.5 MHz) sector probe with a thin (11 mm), extended tip is used to image the cerebral lesion through a single burr-hole. The distance between burr-hole and lesion and the direction of the target are then determined from the ultrasound images, and craniotomy is completed with the aid of these parameters. Errors in the preoperative planning of the approach, which might result in incorrect placement of the craniotomy, can easily be recognized and corrected at an early stage of the operation, before the craniotomy has been completed. This technique greatly improves the accuracy in placing craniotomy flaps. Since the risk of misplacing the craniotomy is virtually eliminated in lesions which are identifiable on ultrasound images, the technique allows the surgeon to keep the skull opening as limited as possible.

Lysis of basal ganglia haematoma with recombinant tissue plasminogen activator (rtPA) after stereotactic aspiration: initial results

In a series of 10 patients with stereotactically treated basal ganglia haematoma rtPA was used to dissolve remaining clots. Pre-operative haematoma volume ranged between 39 and 111 cm3 (average 56 cm3). Stereotactic aspiration alone yielded an average volume reduction of 60% (range 23 to 78%). Haematoma cavity was instillated with rtPA repeatedly beginning 24 hours after the stereotactic intervention. At the end of rtPA therapy between 2 and 4 days after onset of the haemorrhage 67 to 92% (average 84%) of the initial haematoma was removed in all patients. More than 80% of the pre-operative clot could be removed in 8 out of 10 patients between day 2 and 4. There were no signs of rtPA related toxicity. At the end of the follow-up period (between 4 and 17 months--mean 8 months) 6 patients were awake, oriented and with a residual hemiparesis able to live in their familiar environment. It is concluded that local rtPA instillation is an effective additional treatment to further resolution of deep seated intracerebral haematomas after stereotactic aspiration.

Three-dimensional spiral CT for neurosurgical planning

We carried out 22 examinations to determine the value of three-dimensional (3D) volumetric CT (spiral CT) for planning neurosurgical procedures. All examinations were carried out on a of the first generation spiral CT. A tube model was used to investigate the influence of different parameter settings. Bolus injection of nonionic contrast medium was used when vessels or strongly enhancing tumours were to be delineated. 3D reconstructions were carried out using the integrated 3D software of the scanner. We found a table feed of 3 mm/s with a slice thickness of 2 mm and an increment of 1 mm to be suitable for most purposes. For larger regions of interest a table feed of 5 mm was the maximum which could be used without blurring of the 3D images. Particular advantages of 3D reconstructed spiral scanning were seen in the planning of approaches to the lower clivus, acquired or congenital bony abnormalities and when the relationship between vessels, tumour and bone was important.

Bilateral chronic subdural haematomas following traumatic cerebrospinal fluid leakage into the thoracic epidural space

This report describes a patient who developed bilateral chronic subdural haematomas after a stab injury to the thoracic meninges causing prolonged cerebrospinal fluid leakage into the epidural space. Diagnostic findings and therapeutic management are presented and possible pathogenic mechanisms are discussed. This case suggests that patients who have symptoms or signs of increased intracranial pressure after a penetrating spinal injury should be studied for subdural haematoma.

Effect of recombinant tissue plasminogen activator on clot lysis and ventricular dilatation in the treatment of severe intraventricular haemorrhage

Twelve patients with severe intraventricular haemorrhage (IVH) underwent intraventricular thrombolysis with recombinant tissue plasminogen activator (rtPA). External ventricular drainage was performed in all patients within 24 hours of haemorrhage. Fibrinolytic therapy was started within 24 hours from the onset of symptoms in ten cases, and in two further cases after 48 hours and 5 days, respectively. Two to 5 mg of rtPA were injected via the ventricular catheter into one or both lateral ventricles. The injection was repeated at intervals ranging from 6 to 24 hours until CT scans demonstrated a substantial reduction of intraventricular blood. The total rtPA doses per patient ranged from 3 to 31 mg. CT scans showed a marked reduction of intraventricular blood and normalization of ventricular size within 24 to 48 hours from the beginning of the fibrinolytic therapy. Rapid reduction of elevated intracranial pressure by continuous diversion of cerebrospinal fluid could be achieved in all patients, because the ventricular catheters never became obstructed by clotted blood during the fibrinolytic therapy. During the period of treatment, the level of consciousness, as classified according to the Glasgow Coma Scale, improved from a mean value of 7 to 12. One fatal case of meningitis most probably due to the ventriculostomy was the only complication related to the treatment. This method of treatment might improve the prognosis in patients in whom a large intraventricular haematoma volume, ventricular dilatation, and impaired cerebrospinal fluid circulation are major determinants for the outcome.

[Diagnosis of complications of ventriculo-peritoneal and ventriculo-atrial shunts]

The value of imaging (cranial CT, cranial and abdominal sonography, plain film surveys) was examined retrospectively in 28 shunted children in whom 82 instances of suspected dysfunction arose. There were 23 obstructions, 12 dislocations, 1 disconnection, 6 infections, 3 overdrainages and 5 slit ventricle syndromes. Impaired absorption with ascites, a peritoneal liquor cyst and a seroma occurred in the peritoneal part of the shunt. Progressive dilatation of the ventricle system shown by CCT (89%) or ultrasound was the most sensitive sign of high-pressure hydrocephalus. Periventricular hypodensity and flattening of the gyri (15%) were found less often. An examination strategy in suspected shunt dysfunction is suggested on the basis of these findings.

Neurofibromatosis 2: a clinically and genetically heterogeneous disease? Report on 10 sporadic cases

Clinical and genetic data of 10 patients with neurofibromatosis 2 (NF-2) are presented. Interestingly, no family history of neurofibromatosis was detectable in any of them, which indicates that these are sporadic cases of NF-2, most likely due to a new mutational event. According to our own results and the data in the literature, sporadic cases of NF-2 are clinically characterized by a high incidence of multiple meningiomas and spinal tumors in addition to the bilateral occurrence of acoustic neurinomas. The clinical heterogeneity of NF-2 is pointed out and the possible existence of different forms of this disease is discussed.

CT-guided stereotactic fibrinolysis of spontaneous and hypertensive cerebellar hemorrhage: long-term results

The surgical indication for spontaneous cerebellar hemorrhage is not as controversial as the operative management of intracranial hemorrhage. Timing of the operation is crucial: intervening too early can produce an additional strain on the patient and an increased risk, while waiting too long to evacuate the hematoma can be fatal. This dilemma may be a factor in the relatively high mortality and morbidity rates following both operative and conservative treatment that have been reported in the literature (42.5% and 30%, respectively). In long-term studies on 14 patients, the authors have shown that stereotactic puncture and fibrinolysis for cerebellar hemorrhage is a valuable alternative to treatments used currently. The method consists of computerized tomography (CT)-guided stereotactic puncture and partial evacuation of the hematoma. After fibrinolysis with urokinase, the residual hematoma can be completely evacuated via a catheter introduced into the cavity of the hematoma. Only one of the 14 patients died in the direct postoperative phase; the remaining patients were enjoying a good to very good quality of life 6 months after the acute event. Two patients subsequently died as a result of pneumonia and cerebral infarction, respectively; both conditions were unrelated to the hemorrhage. The authors conclude that the CT-guided stereotactic method is simple, effective, and safe, and can be applied to patients of any age.

Chromosome abnormalities in multiple meningiomas of a child

We report the cytogenetic findings in two meningiomas from a child presenting with multiple meningiomas. In contrast to the chromosomal profile of adult meningiomas, both tumors studied revealed excess of chromosomes in addition to monosomy 22. This difference is remarkable considering several reports indicating that childhood meningiomas behave differently and have a worse prognosis than those in adults.

Intracranial calcified deposits in neurofibromatosis type 2. A CT study of 11 cases

CT examinations of 11 consecutive patients with neurofibromatosis type 2 (NF-2) revealed non-tumoral intracranial calcified deposits in seven cases. Abnormal calcification of the choroid plexus was found in six cases. Calcification in the cerebellar hemispheres was observed in four cases. In two cases nodular calcifications on the surface of the cerebral hemispheres were detected. Our findings and the data in the literature show that non-tumoral calcifications of different locations can be regarded as part of the NF-2 syndrome.

Cytogenetic and in situ DNA-hybridization studies in intracranial tumors of a patient with central neurofibromatosis

We have studied a meningioma and an acoustic neurinoma of a patient with central neurofibromatosis. In the meningioma cells, one chromosome 22 was replaced by an almost metacentric, bisatellited marker chromosome that appeared monocentric after CBG-staining. In situ hybridization with a chromosome 22 centromere specific DNA probe (p22hom48.4) revealed specific signals in the pericentromeric region of the marker chromosome, indicating the presence of at least the short arm and the centromere of chromosome 22. The pericentromeric localization of the hybridization signals suggest the marker consists of an isoformation of the short arm of chromosome 22, resulting in a monosomy for the long arm of chromosome 22. In contrast to these findings in meningioma cells, no chromosomal abnormality could be detected in acoustic neurinoma cells. Our findings provide further evidence that loss of genetic material on the long arm of chromosome 22 is associated with the development of central neurofibromatosis.

Downbeat nystagmus indicates cerebellar or brain-stem lesions in vitamin B12 deficiency

Two cases of vitamin B12 deficiency caused by gastric atrophy are described. Together with the neuropsychiatric features usually associated with this condition, a downbeat nystagmus syndrome was observed. It is concluded that vitamin B12 deficiency may also result in lesions to those cerebellar or brain-stem structures that are generally assumed to cause downbeat nystagmus.

The role of fixation and visual attention in the occurrence of express saccades in man

The differential influence of fixation and directed visual attention on reaction times of goal-directed saccades and especially on the occurrence of express saccades was investigated. In all the experiments the subjects were instructed first to keep their direction of gaze at the center of a translucent screen with or without a central fixation point. When a new stimulus appeared, the subjects had to look at it as soon as possible. In some control experiments the subjects had to direct their gaze to the screen center and simultaneously direct their attention to a peripheral light spot before the target for the saccade appeared. Many express saccades occurred when either active fixation of a central fixation point or attention directed to a peripheral visual target (regardless of its position) was interrupted 200 ms before the target for the saccade appeared. Express saccades were almost completely abolished in the presence of fixation and/or directed visual attention at the moment in which the saccade target appeared. We conclude that express saccades occur if visual attention has already been released at the moment when the target for the saccade appears. This disengagement needs some time which adds to the reaction time.