Functional and Diffusion-Weighted Magnetic Resonance Imaging for Visualization of the Postthalamic Visual Fiber Tracts and the Visual Cortex

Diffusion-weighted magnetic resonance imaging (MRI) offers the possibility to study the course of the cerebral white matter tracts whereas functional MRI (fMRI) provides information about the specific functions of cortical areas. We evaluated the combination of fMRI and diffusion-weighted MRI to detect cortical visual areas with their corresponding visual fiber tracts in 15 healthy controls (age: 23 - 53 years, male : female = 8 : 7). We demonstrated activation within the primary visual cortex and white matter bundles connecting the lateral geniculate body and the striate cortex in all subjects investigated. Additional activation could be appreciated in some subjects within the lateral geniculate bodies (n = 2) and the motion-sensitive area V5 (n = 3). The combination of diffusion-weighted and functional imaging allows visualization of the origin, direction and functionality of large white matter tracts. This will prove helpful for imaging structural connectivity within the brain during functional imaging. Moreover, this technique might provide important information for neurosurgical patients presenting with space-occupying lesions close to the cortical and subcortical visual system since this technique can -- in contrast to diffusion tensor imaging -- easily be adopted into a neuronavigation system and can be performed on all MR scanners capable of diffusion-weighted imaging without specific post-processing programs.

Rückenmarkskompression durch eine zervikale osteokartilaginäre Exostose: Operationsstrategische Aspekte

AIM

The authors present the therapeutic management of a 12-year-old boy with known hereditary multiple exostosis syndrome (HME), who developed spinal cord compression symptoms caused by an exostosis of the C2 lamina. A perinatal brain lesion with tetraparesis delayed the recognition of the spinal cord compression substantially, which resulted in an extensive spur-like growth of the exostosis.

METHOD

In comparison with already published cases, this growth pattern was rather unique and required consideration on the best surgical management. We decided to monitor the spinal cord function from positioning of the patient to skin closure and to modify the surgical steps of the laminectomy with initial lateral cutting of both hemilaminae.

RESULTS

Electrophysiological monitoring helped to avoid spinal cord compression by inadequate head anteflexion during positioning. Lateral cutting of the hemilaminae C2 resulted in spontaneous extrusion of the exostosis with immediate improvement of the electrophysiological findings. The boy experienced a prompt improvement of his neurological deficits.

CONCLUSION

The good surgical and clinical result confirm the value of the applied management concept.

Course of brain shift during microsurgical resection of supratentorial cerebral lesions: limits of conventional neuronavigation

BACKGROUND

The authors have conducted a prospective study to evaluate the amount and course of brain shift during microsurgical removal of supratentorial cerebral lesions, and to assess factors which potentially influence these shifts.

METHOD

In 61 patients the displacement of 2-3 cortical landmarks on the cerebral surface was dynamically quantified during surgery, i.e. during dissection of the tumour at the estimated half-time of surgery, and at the end of microsurgical removal of the cerebral lesion using the neuronavigation system EasyGuide Neuro. In 14 of these patients the displacement of a subcortical landmark was additionally analysed. Age of the patients, preoperative midline shift, location of the lesion, lesion volume, depth of the lesion below the cortical surface, presence or absence of oedema, and size of the craniotomy were analysed for potential influence on the amount of brain shift. Correlations were analysed for all patients together and for the subgroups of vault meningiomas (n=10), gliomas (n=30), and nonglial intra-axial lesions (n=21).

FINDINGS

The mean displacement of the cortical landmarks ranged between 0.8 and 14.3 mm (mean: 6.1 mm, standard deviation: 3.4 mm) during surgery (10-210 minutes [mean: 50.7 minutes, standard deviation: 34.5 minutes] after dura opening) and between 2.4 and 15.2 mm (mean: 6.6 mm, standard deviation: 3.2 mm) at the end of microsurgical removal of the tumourous cerebral lesions (20-375 minutes [mean: 107.2 minutes, standard deviation: 65.6 minutes] after dura opening). Significant correlations (p<0.01) for the entire patient group were found between brain shift and tumour volume, midline shift, and size of the craniotomy, respectively. For the subgroup of vault meningiomas a significant correlation (p<0.01) between brain shift and patient age was found. For the subgroup of gliomas a significant correlation (p<0.01) between brain shift and tumour volume, midline shift and size of the craniotomy, respectively, was found. For the subgroup of nonglial intra-axial lesions a significant correlation (p<0.01) between brain shift and midline shift and between brain shift and size of the craniotomy was found. The quantity of shared common variance ranged between 10-50%. Performing a discriminant analysis, lesion volume was the only certain factor influencing brain shift intra-operatively as well as at the end of lesion removal. 58.5% of the extent of brain shift could be correctly classified by the tumour volume as the only discriminating variable during dissection of the tumour and at the end of surgery. Comparing superficial with subcortical brain shift over the same time period, a mean superficial shift of 4.6 mm (1.6-10.8 mm, standard deviation: 2.8 mm) and a mean subcortical shift of 3.5 mm (1.0-7.7 mm, standard deviation: 2.3 mm) was found. A highly significant Spearman correlation (Rho:.97, p<0.001) between superficial and subcortical brain shift emerged. Shifting of superficial landmarks exceeded shifting of subcortical structures in all patients.

CONCLUSIONS

The data demonstrate the dynamics of brain shift and the limits of conventional neuronavigation and add additional support for the unavoidable inaccuracy of contemporary neuronavigational systems once the cranium is opened. Brain shift leads to a significant loss of reliability of neuronavigation systems during microsurgical removal of intracranial lesions and there are differences of the course and the amount of brain shift in relation to special subgroups of supratentorial cerebral lesions. However, because of the heterogeneous nature of lesions neurosurgeons have to remove, the modest quantity of shared common variance, and the differences between superficial and subcortical brain shift, it seems unlikely that the amount and course of brain shift become exactly predictable pre-operatively. Only an intra-operative update of image data should have the capacity to overcome this fundamental problem of modern neuronavigation.

Haemorrhagic tracheal necrosis as a lethal complication of an aneurysm model in rabbits via endoluminal incubation with elastase

BACKGROUND

We describe a lethal complication of an aneurysm model in rabbits for saccular aneurysmal creation via endoluminal incubation with elastase.

METHOD

In 24 anaesthetized female New Zealand White rabbits, the right common carotid artery (CCA) was ligated distally to the arteriotomy. A 4F sheath was then placed retrograde into the CCA, and its origin was occluded endoluminally using a 2F Fogarty balloon. Elastase was incubated above the balloon in the separated vessel lumen for the duration of 20 minutes. Two weeks later, digital subtraction angiography was performed for aneurysm control. Two animals were then sacrificed and the aneurysm studied on histology. All animals that died within the experiment were examined post-mortem.

FINDINGS

Following this protocol, an aneurysm with a mean size of 7.6 x 3.2 mm could be created in 11 out of 24 animals. 9 out of 13 animals with lethal outcome died from haemorrhagic necrosis of the trachea with subsequent pulmonary complications. DSA releaved an arterial branch originating from the proximal CCA in a near 90 degree-angle aiming at the trachea.

INTERPRETATION

The endoluminal incubation with elastase is suitable for aneurysm creation of reproducible size that are suited to test new endovascular devices such as stents and new coils. One should always be aware of an arterial branch of the CCA supplying the trachea. In case of elastase instillation into this branch, lethal haemorrhagic necrosis of the trachea occurs. Bearing this complication in mind, we have experienced a minimal loss of animals in subsequent studies.

[Diffusion Weighted Imaging Combined with Intraoperative 3D-Ultrasound and fMRI for the Resection of an Optic Radiation Cavernoma]

A 17-year-old patient with a symptomatic cavernoma of the optic radiation underwent surgery supported by functional magnetic resonance imaging (fMRI), diffusion weighted magnetic resonance imaging (DWI) and navigated 3D-ultrasound. The primary visual cortex was visualized with fMRI. The optic radiation was delineated by means of DWI. The diffusion weigthed images were used for 3-dimensional reconstruction of the optic radiation. During surgery, the information of the localisation of functional brain regions were used together with the 3D-ultrasound, enabling the surgeon to remove the cavernoma without morbidity. This is the first report of the combined use of fMRI, fiber tract imaging and 3D-ultrasound for the safe resection of an optic radiation lesion.

Microsurgical Therapy of Symptomatic Lumbar Juxta Facet Cysts

OBJECTIVE

Symptomatic lumbar juxta facet cysts (ganglion and synovial cysts) (JFC) are uncommon lesions of the spine, causing radiculopathy and low back pain. The authors present their experiences with microsurgically treated JFC. This rare pathology is discussed with special focus on therapeutic concepts and long-term outcome.

METHOD

The records of 27 patients with symptomatic lumbar JFC were retrospectively reviewed. The clinical data and diagnostic procedures were evaluated. The patient age ranged from 38 to 83 years (mean 61 years). Treatment consisted exclusively of microsurgical excision of the cysts after partial hemilaminectomy. The early surgical results were evaluated 6 weeks after surgery. For assessment of late surgical results (mean follow-up period 70 months), the Finneson and Cooper outcome scale was used.

RESULTS

After 6 weeks, the preoperative symptoms were improved in 25 patients (93 %). Long-time follow-up was available in 23 patients. Good (pain improved and able to function well) to excellent (pain free and able to function well) results were still found in 83 % of the patients. With exception of 2 small asymptomatic dural tears and a slight temporary increase of the preoperative paresis, no surgical complications were encountered. One JFC recurred after 4 months and required re-operation with finally good outcome.

CONCLUSION

Adequate and definitive treatment in symptomatic JFC consists in microsurgical resection. A partial hemilaminectomy is sufficient for surgical exposure. Excellent long-term outcome can be achieved. Recurrences and surgical complications are rare.

MRI and intraoperative findings in cavernous haemangiomas of the spinal cord

More sensitive imaging techniques, such as MRI, have led to an increase in the number of reported cases of spinal cord cavernous haemangioma (SCCH). Complete surgical resection has been performed with good outcomes. However, operative findings do not always confirm preoperative MRI as to the size and site (superficial or deep) of the lesion. We evaluated whether MRI can be used to predict whether or not SCCH reach the surface of the spinal cord, since this has an impact on surgical strategy. We reviewed the preoperative MRI, case-notes and video recordings of 12 patients who underwent surgery, at which five superficial and seven deep-seated lesions were identified. T1-weighted images correctly indicated the site of the lesion in ten, T2-weighted images in only eight. One deep lesion was thought to be superficial on both T1- and T2-weighted images. Intravenous contrast medium was not helpful in diagnosis or localisation. In no case was a surgically proven superficial lesion interpreted as deep in the spinal cord.

Recurrent intracranial sarcoma mimicking chronic subdural haematoma

Primary sarcomas of the central nervous system and their coincidence with a subdural haematoma are each rare. We describe an unusual case of unsuspected dural spreading of a recurrent spindle cell sarcoma concealed in a chronic subdural haematoma, which occurred months after microsurgical resection and external radiation of a temporal parenchymatous sarcoma.

Measurement of motor evoked potentials following repetitive magnetic motor cortex stimulation during isoflurane or propofol anaesthesia

BACKGROUND

Isoflurane and propofol reduce the recordability of compound muscle action potentials (CMAP) following single transcranial magnetic stimulation of the motor cortex (sTCMS). Repetition of the magnetic stimulus (repetitive transcranial magnetic stimulation, rTCMS) might allow the inhibition caused by anaesthesia with isoflurane or propofol to be overcome.

METHODS

We applied rTCMS (four stimuli; inter-stimulus intervals of 3, 4, 5 ms (333, 250, 200 Hz), output 2.5 Tesla) in 27 patients and recorded CMAP from the hypothenar and anterior tibial muscle. Anaesthesia was maintained with fentanyl 0.5-1 microg kg(-1) x h(-1) and either isoflurane 1.2% (10 patients) or propofol 5 mg kg(-1) x h(-1) with nitrous oxide 60% in oxygen (17 patients).

RESULTS

No CMAP were detected during isoflurane anaesthesia. During propofol anaesthesia 333 Hz, four-pulse magnetic stimulation evoked CMAP in the hypothenar muscle in 75%, and in the anterior tibial muscle in 65% of the patients. Less response was obtained with 250 and 200 Hz stimulation.

CONCLUSIONS

In most patients, rTCMS can overcome suppression of CMAP during propofol/nitrous oxide anaesthesia, but not during isoflurane anaesthesia. A train of four magnetic stimuli at a frequency of 333 Hz is most effective in evoking potentials from the upper and lower limb muscles. The authors conclude that rTCMS can be used for evaluation of the descending motor pathways during anaesthesia.

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.

Pituitary deficiency following aneurysmal subarachnoid haemorrhage

OBJECTIVE

To investigate the incidence and severity of pituitary insufficiency after aneurysmal subarachnoid haemorrhage.

METHODS

Pituitary function was tested in a series of patients more than 12 months but less than 60 months after aneurysmal subarachnoid haemorrhage using a combined TRH-LHRH-arginine test and the insulin tolerance test, to elucidate possible deficits in the gonadotrophic, somatotrophic, thyreotrophic, and corticotrophic hormonal axes.

RESULTS

Of 21 patients screened, nine (43%) showed deficiencies of at least one pituitary hormone axis. Four patients had corticotrophin deficiency, one had partial growth hormone deficiency, two had severe growth hormone deficiency, and two had severe growth hormone deficiency plus corticotrophin deficiency.

CONCLUSIONS

Persistent pituitary dysfunction may be more common after aneurysmal subarachnoid haemorrhage than has so far been recognised and warrants further investigation, given the possibility that some health and neurobehavioural problems in these patients could result from hormone deficiency.

Endovascular treatment of experimentally induced aneurysms in rabbits using stents: a feasibility study

Although Guglielmi detachable coil (GDC) systems have been generally accepted for treatment of intracranial aneurysms, primary stenting of aneurysms using porous stents or implantation of coils after stent placement remains experimental. Testing of these new methods requires an animal model which imitates human aneurysms in size, configuration and neck morphology. We assessed in detail the technical requirements of and steps for transfemoral stent treatment of experimentally induced aneurysms at the top of the brachiocephalic trunk in rabbits. We created aneurysms in ten rabbits by distal ligation and intraluminal digestion of the right common carotid artery with elastase. We treated five animals with porous stents alone, and five with stents plus coiling via the meshes of the stent, which permitted dense packing of coils. No complications related to the procedures occurred. In all animals, even in those treated solely with porous stents, total occlusion of the aneurysm was achieved. Our animal model can be suitable for testing the biocompatibility and occlusion rate of new methods and devices for the treatment of experimental aneurysms.

Experience with a new concept to lower non-infectious complications in infants with programmable shunts

In neonates and infants less than 1 year of age who are treated with a ventriculo-peritoneal shunt, non-infectious complications are almost as frequent and dangerous as infectious complications. While the incidence of infections can be reduced, using perioperative antibiotics, special surgical techniques and postoperative care non-infectious complications such as wound break-down, cerebrospinal fluid (CSF) fistula and subcutaneous CSF collection are preventable, but seem difficult to manage, especially in the group of patients at a susceptible age. The authors present their experience with the programmable Hakim valve in 40 neonates and infants less than 1 year of age, who were treated with de novo implantation of a ventriculo-peritoneal shunt due to various pathologies. The uneventful wound healing during the first weeks after shunt implantation, avoiding the above mentioned non-infectious complications, was supported by initial, temporary overdrainage and readjustment of the programmable valve after completed wound healing. All patients tolerated this procedure well and showed no pathological signs or symptoms of overdrainage like premature closure of cranial sutures, clinical low-pressure syndrome, slit ventricle syndrome (SVS), subdural fluid collection or brain collapse during an average follow-up period of 2.6 years (2 - 65 months). Infectious and other mechanical, non-infectious complications were analysed as well during the follow-up period. These results suggest that an initial, temporary overdrainage in infants and neonates with shunted hydrocephalus may contribute to further lower the incidence of non-infectious complications like wound break-down, CSF-fistula or subcutaneous CSF accumulation, without negative side effects. This technique could be a valuable option in the regimen of shunt-treatment of this age group in order to optimise the overall success rate and lower the general complication rate.

Extended pterional orbital decompression in severe orbital cellulitis

BACKGROUND

Bacterial orbital cellulitis is a relatively uncommon infective process, which can threaten the function of orbital structures. Apart from antibiotic therapy, sinus surgery with or without abscess drainage via an orbito-otorhinolaryngological approach might be necessary.

CASE DESCRIPTION

We present three cases of severe orbital cellulitis, leading to increasing loss of vision, proptosis, afferent pupillary disturbances and restriction of extra-ocular movements, despite antibiotic therapy. After extended pterional orbital decompression and reducing the orbital pressure by removal of the lateral and superolateral orbital walls, all patients showed distinct improvement of initial symptoms, without any complications related to the operation.

INTERPRETATION

Extended pterional orbital decompression represents an effective treatment alternative and supplement in cases of a severe, threat to ocular function due to orbital cellulitis, where acute reduction of pressure on orbital, neural and vascular structures is intended.

[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.

Endovascular treatment of experimental aneurysms in rabbits using Guglielmi detachable coils -- a feasibility study

The Guglielmi detachable coil (GDC) has been generally accepted for treatment of intracranial aneurysms. Preclinical testing of new coil developments requires animal models of aneurysms which imitate human aneurysms in size, configuration and neck morphology. We assessed in detail the technical requirements and steps for transfemoral treatment of experimentally induced aneurysms at the top of the brachiocephalic trunk (TBC) in rabbits. We created aneurysms in five rabbits by distal ligation and intraluminal incubation of the right common carotid artery with elastase. All animals were treated successfully 2-3 weeks after induction of the aneurysm, with dense packing of the coils. No complications related to the procedures occurred. The study demonstrates that our animal model can be a suitable method for testing the biocompatibility and occlusion rate of new embolic materials.

Incidence of cerebrospinal fluid leak after microsurgical removal of vestibular schwannomas

OBJECTIVES

Cerebrospinal fluid (CSF) leak still remains an unresolved problem after microsurgical removal of vestibular schwannomas (VS).

METHODS

14 (6%) Cases of cerebrospinal fluid rhinorrhea and 3 cases with subcutaneous retro-auricular CSF collection, occurring in a series of 224 patients operated on by the senior author (JMG) on VS between 1989-2000 via the suboccipital retrosigmoidal approach were studied retrospectively. Prophylaxis of CSF leak was usually attempted by packing the unroofed posterior wall of internal acoustic meatus with muscle. The mastoid air cells were packed first with collagen then with muscle and bone dust.

RESULTS

All CSF leaks were diagnosed within 2-7 days after surgery. We found no relation to tumour size. Treatment was initiated in all patients with continuous external lumbar cerebrospinal fluid drainage (CELCFD) for 7 days. In 11 cases with CSF rhinorrhea and all cases with retro-auricular CSF collection, the CSF leak was stopped. However, in 3 cases the CSF leak persisted despite the lumbar drain. These patients were operated on again with sealing the IAM and the mastoid cells again with muscle and collagen. No recurrence of CSF leak was noted after the second operation. There was no case of late onset CSF leak during the follow-up of one year.

CONCLUSION

Although CSF leak is a common complication (6%) after vestibular schwannoma removal, aggressive treatment is required only in a few cases (1%). Most of the cases are successfully treated by (CELCFD). The suboccipital approach offers an advantage of opening only a part of mastoid air cells, which are in our opinion the second most common site of CSF leakage.

Prognostic factors for patients with microsurgically resected brain metastases

BACKGROUND

With the advent of new therapies for metastatic carcinoma to the brain, patterns of intracranial disease and factors influencing survival become important considerations when examining treatment options. This study was conducted at a single institution to determine prognostic factors for tumor response and patient survival after microsurgical resection of brain metastases.

PATIENTS AND METHODS

187 consecutive patients who underwent microsurgical resection of brain metastases between July 1989 and September 1996 were retrospectively reviewed and statistically analyzed. The primary cancers included lung cancer (85), gastrointestinal cancer (20), renal cell cancer (19), breast cancer (17), malignant melanoma (8) and 38 cases of various other carcinomas or of unknown primary site. 111 patients received whole-brain radiation therapy (WBRT) with a mean dose of 32 Gy after tumor resection. The influence of number, size, and localization of brain metastases as well as histology of the primary tumor, preoperative performance status, presence of extracranial systemic disease, time course and adjuvant radiation therapy were statistically evaluated (uni- and multivariate) as prognostic factors for survival.

RESULTS

Early postoperative Karnofsky score was improved in 59%, unchanged in 32% and worse in 9% of patients. Median survival time (MST) was 9.8 months (range 1 day-5.3 years). The most important parameter showing a significant influence on survival time was the histology of the primary tumor, with prediction of a bad outcome especially for patients with metastases from renal-cell cancer and malignant melanomas. Patients with breast cancer showed longer survival than patients with other primary cancers. Furthermore, survival varied significantly depending on location of brain metastases, performance status at time of craniotomy and duration of symptoms. None of the other studied variables gained prognostic significance.

CONCLUSION

Microsurgical resection of one or more brain metastases followed by WBRT still is a useful and efficient treatment in a carefully selected patient group to prolong median survival and improve or stabilize the performance status. Among the factors determining the survival times in this patient group, histology of the primary tumor is most important, together with preoperative Karnofsky score, location of metastasis and preoperative duration of symptoms.

Functional MRI and 18F FDG-positron emission tomography for presurgical planning: comparison with electrical cortical stimulation

BACKGROUND

In patients with mass lesions near "eloquent" cortical areas different preoperative mapping techniques can be used. Two of the most widely used approaches include positron emission tomography (PET) and functional MRI (fMRI). We employed both methods in the same patients undergoing presurgical evaluation and compared the results to those obtained by direct electrical cortical stimulation (DECS).

METHOD

22 patients with tumours of different aetiology near the central region were investigated. FMRI was performed using a T2(*)-weighted gradient-echo BOLD sequence at 1.5 T, PET was performed after injection of 122-301 MBq (18)F-Fluorodeoxyglucose (18-FDG) under rest and activation conditions. DECS was performed in all patients with recordings of muscles primarily involved in the investigated tasks.

FINDINGS

In 19 patients all three modalities could be compared, 1 patient demonstrated discordance between fMRI and PET with DECS speaking in favour of fMRI, 6 patients had neighbouring results of PET and fMRI (between 1-2 cm distance), 12 patients had overlapping results.

INTERPRETATION

The high incidence of neighbouring results is presumably related to fMRI specific artefacts. Advantages of fMRI are: Higher spatial and temporal resolution, more and different functional runs, shorter examination time, wider availability, longitudinal examinations, non-invasiveness and cost-effectiveness, easy registration to anatomical images. Advantages of PET are: higher signal-to-noise ratio, lesser susceptibility to artefacts (motion, draining veins), evaluation of tumour metabolism. It is our opinion that the neurosurgeon has to decide on a case-by-case basis which study suits his specific needs in the presurgical evaluation of his patient.

Factors related to the magnitude of T2* MR signal changes during functional imaging

Our aim was to determine whether age, sex, the degree of weakness, anticonvulsants, the histology of the underlying lesion(s), the presence of oedema or the distance of the lesion from the motor region have an impact on the blood oxygenation level-dependent (BOLD) signal strength and therefore on the validity of functional MRI (fMRI). We studied 98 patients with masses near the central region imaged for surgical planning at 1.5 tesla, employing a BOLD sequence during a motor task. We calculated percentage signal change in the primary motor cortex between rest and activation and carried out multiple linear regression to examine the impact of the above factors on signal strength. Using a stepwise analysis strategy, the distance of the lesion from the motor region had the strongest influence (r=0.653, P<0.001). The factor with largest uncorrelated additional impact on signal change was the presence of oedema. Both predictors together formed a highly significant multiple r=0.739 ( P<0.001). No other predictive factor was identified (all P>0.20). Disturbances of cerebral blood flow and metabolism induced by the tumour were presumed to be the causes of a decrease in signal in the adjacent cortex.

Occurrence and therapy of space-occupying cystic lesions after brain tumor surgery

OBJECTIVES

Space-occupying cystic lesions may develop in a variable time after resection of particular intracranial tumors, representing a small amount of complications of these procedures. We present our experience with the development and operative treatment of such postoperative cystic lesions in order to identify possible risk factors and to optimize the treatment.

METHODS

The records and neuroradiological findings of patients, operated on either gliomas and meningeomas or craniopharyngeomas, who developed symptomatic cystic lesions in the former tumor resection area during the last ten years, were analyzed.

RESULTS

31 patients (2.5%) out of a total of 1240 corresponding tumor operations were identified. The mean age among the 20 female and 11 male patients was 47 years (12-74 years). In 17 patients (55%) the cystic lesion occured within 6 months after tumor resection (mean 5.6 weeks) and in 14 patients (45%) later than 6 months postoperatively (mean 3.6 years). 22 patients (71%) had malignant tumors and 16 patients (52%) had previous radiation therapy. 14 patients (45%) had more than one tumor resection at the same location and one patient had a postoperative meningitis as predisposing factor for the cyst-formation. All patients profited of the various definitive treatment modalities: repetitive percutaneous puncture/external drainage (5 patients), craniotomy for cyst-resection/-fenestration without (5 patients) and with Rickham-catheter implantation (10 patients), endoscopic cyst-fenestration with Rickham-catheter implantation (3 patients) and implantation of cysto-atrial or cysto-peritoneal shunts (8 patients).

CONCLUSIONS

Symptomatic cystic lesions developing after brain tumor resection may occur as early - (5.6 weeks) or as late - (3.6 years) complications and though predisposing factors, like malignant primary tumor, preceding radiation therapy and multiple tumor resections can be identified, the reason for their occurrence remains unclear. A variety of effective therapy options is applicable but should consider the patients condition and prognosis.

[Pterional orbital decompression in traumatic orbital hematomas]

The results are presented for pterional orbital decompression in 12 patients with symptomatic traumatic retrobulbar hematoma after various traumatic mechanisms. Pre- and postoperative course, neuroradiological findings, additional brain or facial injuries as well as outcome of eye function are analyzed in detail. Mean time delay between trauma and decompression was 56 h (2.4 days), with a wide range from 2 h to 15 days. Preoperative exophthalmos and pupillary disturbances as well as restrictions of extraocular movements decreased in all patients after orbital decompression and removal of the retrobulbar hematoma if the bleeding was localized. Visual acuity remained normal or showed significant improvement in seven patients, four of whom experienced complete recovery. In three patients the eye remained amaurotic. No complications related to the operation were seen. The pterional orbital decompression described here represents an effective alternative approach for patients with sight-threatening retrobulbar hematoma, especially in cases where it is necessary to gain space for the orbit in addition to evacuating space-occupying blood or bone clots and treating neighbouring lesions. Immediate detection and adequate treatment of orbital hematomas is mandatory to achieve an acceptable outcome of eye function.

What is the ideal initial valve pressure setting in neonates with ventriculoperitoneal shunts?

In order to determine the optimal valve pressure setting during the first weeks in neonates after implantation of programmable Hakim valves and to analyze the benefits and possible side effects of a new treatment protocol in this age group, we performed this prospective study. In 20 consecutive newborns less than 5 weeks of age with hydrocephalus due to various etiologies, a ventriculoperitoneal shunt with a programmable Hakim valve at an extremely low initial valve pressure setting of 30-40 mm H(2)O was implanted. This "overdrainage" was maintained, monitored by regular clinical examination and transcranial ultrasonographic imaging, until the wound healing was uneventfully completed and the permanent valve pressure setting of 100-120 mm H(2)O was chosen. In this age group, which is prone to specific noninfectious shunt complications like wound breakdown, cerebrospinal fluid (CSF) fistula and subcutaneous CSF collections, none of these complications were seen, nor were there any persisting overdrainage phenomena on transcranial ultrasonography. Initial, temporary "overdrainage" represents a simple, useful and risk-free therapy in neonates with programmable shunts which might lower the incidence of typical noninfectious complications in this age group.