Tissue Characterization of Intracranial Tumors by MR Imaging

The main purpose of this in vivo study was to provide a detailed description of the T1- and T2-relaxation processes in intracranial tumors at 1.5 T. A total of 100 patients were investigated. Optimal experimental conditions were carefully observed, including the use of long TR values. T1 determination was based on a partial saturation inversion recovery sequence covering 12 or 6 data points. T2 determination involved a multiple spin echo sequence with 32 echoes. Calculations included biexponential analysis of the 12-point T1 data and all T2 data obtained. The results were evaluated in accordance with histopathology. The T1- and the T2-relaxation times of the prevailing tumor types were significantly different (p < 0.0005). However, biologic scatter and overlap between tumor types were considerable. In particular, no discrimination between benign and malignant tumor growth was possible. Biexponential evaluation did not increase the specificity, although a biexponential relaxation behavior was recognized in 37% of the T2 curves. The results indicate that tissue heterogeneity is responsible for most of the scatter in the relaxation times. It is concluded that tissue characterization by MR imaging, based solely on relaxation time measurements, seems to be of no value in the differentiation of intracranial tumors.

Increased Self-Diffusion of Brain Water in Hydrocephalus Measured MR Imaging

We used MR imaging to measure the apparent brain water self-diffusion in 5 patients with normal pressure hydrocephalus (NPH), in 2 patients with high pressure hydrocephalus (HPH), and in 8 age-matched controls. In all patients with NPH significant elevations of the apparent diffusion coefficients (ADC) of brain water were found within periventricular white matter, in the corpus callosum, in the internal capsule, within cortical gray matter, and in cerebrospinal fluid, whereas normal ADCs were found within the basal ganglia. In 2 patients with HPH elevated ADCs were found most prominently within white matter, and in one patient reexamined one year after surgery, ADCs were unchanged in nearly all brain regions. The increased ADC values in hydrocephalus patients may be caused by factors such as changes in myelin-associated bound water, increased Virchow-Robin spaces, and increased extracellular brain water fraction. For further studies of brain water diffusion in hydrocephalus patients, echo-planar imaging techniques with imaging times of a few seconds may be valuable.

Ophthalmologic prognosis in benign intracranial hypertension

In a prospective study twenty patients with benign intracranial hypertension, 15 females and five males with mean age 34 years (range 12-61 years), were followed up from 12 to 61 months (mean 22 months). Initially all patients showed marked papilledema, normal visual acuity, considerable enlargement of the blind spot area, and significantly delayed pattern reversal visual evoked potentials. During medical treatment eleven patients showed within 3-6 months a rapidly regression and normalization of papilledema, blind spot area, and visual evoked potentials. Eight patients continued in showing papilledema including disc gliosis, enlargement of blind spot area, and pathological visual evoked potentials. One patient developed optic nerve atrophy. The results indicated that repeated examinations of visual evoked potentials, when suspect of threatening visual loss has come up (papilledema, increased blind spot area, and field defects), might increase the change of diagnose of an optic nerve atrophy as early as possible.

Idiopathic normal-pressure hydrocephalus: clinical comorbidity correlated with cerebral biopsy findings and outcome of cerebrospinal fluid shunting

OBJECTIVES

To elucidate the importance of clinically diagnosed cerebral comorbidity in idiopathic normal-pressure hydrocephalus (INPH) and its effect on improvement after shunt surgery as well as concordance with parenchymal pathological changes described in frontal cerebral biopsy specimens.

METHODS

In 28 consecutive patients diagnosed with INPH and shunted according to clinical, radiological and cerebrospinal fluid dynamic criteria, concomitant disorders were carefully registered, with special emphasis on cerebrovascular disease (CVD) and possible Alzheimer's disease. During shunt surgery, a frontal cerebral biopsy specimen was obtained and subsequently analysed for pathological changes.

RESULTS

One or several concurrent disorders were present in 89% of the patients, most often CVD (n = 17) and possible Alzheimer's disease (n = 12), of which eight patients presented both, diagnosed according to the criteria of the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association. The shunt success rate was 33%. A clear tendency towards increasing prevalence of CVD or Alzheimer's disease was found in the subgroups with no improvement or clinical deterioration compared with the patients improving after shunt surgery. The presence of CVD tended towards an unfavourable shunt outcome. The pathological parenchymal changes reflected the clinical diagnoses of comorbidity, and were described in about half of the biopsy specimens, with Alzheimer's disease (n = 7) and vascular changes (n = 7) being the most common findings. However, no significant correlation was found with the clinical diagnoses of Alzheimer's disease and CVD. The presence of cerebral comorbidity, whether diagnosed clinically or by brain biopsy, did not preclude clinical improvement after shunt operation.

CONCLUSIONS

A high prevalence of CVD and Alzheimer's disease was found in patients shunted for INPH, which was reflected, although less commonly, by similar neuropathological biopsy findings. No significant correlation was found between the presence of comorbidity and shunt outcome. The findings support the perception of INPH as a multiaetiological clinical entity, possibly overlapping pathophysiologically with CVD and Alzheimer's disease.

Increasing incidence of childhood tumours of the central nervous system in Denmark, 1980-1996

The registered incidence rate of childhood central nervous system (CNS) tumours has increased in several countries. It is uncertain whether these increases are biologically real or owing to improved diagnostic methods. We explored the medical records of 626 CNS tumours diagnosed in Danish children between 1980 and 1996. Population-based registers were used to extract data on mortality and background population. Temporal patterns were analysed by regression techniques. Most tumours were verified by computed tomography (78%) or magnetic resonance imaging (14%). Overall, the incidence rate increased by 2.9% per year (95% confidence interval (CI): 1.3;4.5) and the mortality rate increased by 1.4% per year (95% CI: −0.4;3.3). Among children aged 0–4 years, the survival rate after diagnosis remained almost unchanged, whereas among children aged 5–14 years, the 10-year survival rate improved from 59 to 74%. These data suggest that the incidence rate of CNS tumours among Danish children has truly increased, although alternative explanations cannot be excluded.

What is new about idiopathic intracranial hypertension? An updated review of mechanism and treatment

Idiopathic intracranial hypertension (IIH) is the syndrome of raised intracranial pressure without clinical, laboratory or radiological evidence of intracranial pathology. IIH is a relatively rare disease but rapidly increasing incidence is reported due to a global increasing incidence of obesity. Disease course is generally said to be self-limiting within a few months. However, some patients experience a disabling condition of chronic severe headache and visual disturbances for years that limit their capacity to work. Permanent visual defects are serious and not infrequent complications. The pathophysiology of IIH is still not fully understood. Advances in neuroimaging techniques have facilitated the exclusion of associated conditions that may mimic IIH. No causal treatment is yet known for IIH and existing treatment is symptomatic and rarely sufficient. The aim of this review is to provide an updated overview of this potentially disabling disease which may show a future escalating incidence due to obesity. Theories of pathogenesis, diagnostic criteria and treatment strategies are discussed.

Intraventricular or lumbar infusion test in adult communicating hydrocephalus? Practical consequences and clinical outcome of shunt operation

BACKGROUND

To investigate the therapeutic consequences of restricting the CSF dynamic evaluation to a lumbar infusion test (LIT), as opposed to our formerly applied intraventricular assessment (VIT), in patients with communicating hydrocephalus (CH).

METHOD

All patients over 18 years of age referred with clinical and radiological indication of treatment-requiring secondary CH (n = 50) or idiopathic normal-pressure hydrocephalus (INPH, n = 33) were subjected to a LIT. Subsequently, a combination of the results of the LIT (mainly the resistance to CSF outflow) and the clinical presentation determined whether to proceed with (a) VIT before a decision about shunt surgery, (b) shunt surgery or (c) no further diagnostic investigation or surgery.

FINDINGS

In 88 percent of the patients with secondary CH and 80 percent of the patients with INPH the decision on shunt surgery was made after performing exclusively a LIT. The shunting success rate was 90 percent in patients with secondary CH and 82 percent in patients with INPH, which however in the latter group decreased to 76 percent, when including the patients undergoing an additional VIT. The achieved shunt success rates are equal or better, compared to the results from previous studies using intraventricular assessment.

CONCLUSIONS

LIT and VIT are equally reliable for selecting shunt responsive patients with CH, using clinical improvement rate as the main criterion for comparison. The practical and economic consequences are substantial: the LIT can be performed in an outpatient setting, whereas VIT necessitates hospitalisation for 1-2 days including occupation of the neurosurgical theatre and postoperative neuro-intensive monitoring.

Shunting to the sagittal sinus

OBJECTIVES

To develop a shunt that drains CSF from the ventricles to the sagittal sinus under normal-physiological conditions. This shunting principle will not lead to any over-drainage, and a large proportion of the known shunt-complications will be avoided.

METHODS

On the basis of the normal values for ICP, resistance to outflow and the production rate of CSF we have developed a shunt that drains CSF to the sagittal sinus and restores normal condition for the CSF dynamics. The shunt consists of two unidirectional valves, a pre-chamber, a resistance tube made of titanium, and a titanium tube leading CSF into the sagittal sinus. The shunt has been tested in 18 patients. Observation time ranged from 2 to 430 days, mean time 54 days.

RESULTS

The first results from the use of the new shunt are very promising. It has an immediate effect on the clinical symptoms, it restores CSF dynamics (investigated with the shunt inserted) and the size of the ventricles is only gradually diminished. Slit ventricles have not yet been observed. In all patients the symptoms of hydrocephalus were relieved. No occlusion or thrombosis of the sagittal sinus have been observed. This is in agreement with the reports in the literature of shunting to the sagittal sinus, where 99 cases have been presented with an observation period of up to 6 years. The shunt has proven easy and safe to implant.

CONCLUSIONS

Shunting to the sagittal sinus has proven easy and safe with regard to short term results. By using a dedicated shunt that drains at normal physiological parameters for the CSF dynamics any over-drainage is avoided, and it may be expected that the complication rate will be substantially smaller than with existing shunting systems.

Idiopathic normal-pressure hydrocephalus: evaluation and findings in a multidisciplinary memory clinic

The diagnostic evaluation of patients with possible idiopathic normal-pressure hydrocephalus (INPH) is traditionally performed in the settings of either neurological, neurosurgical or psychiatric departments. The diagnostic procedure and findings in 71 consecutive patients referred with a clinical and radiological suspicion of INPH to our out-patient multidisciplinary memory clinic are evaluated. Primary diagnoses and potential concomitant disorders considered of secondary importance for the symptomatologies were established. Abnormal hydrodynamics, demonstrated by intraventricular pressure monitoring and infusion test were mandatory for the diagnosis of INPH. Mean age was 68 years and mean Mini-Mental State Examination (MMSE) score was 22. DSM IV criteria of dementia were fulfilled in 42%. In half of the referred patients (n=36), the suspicion of INPH was already disproved subsequently to the evaluation programme performed in the outpatient clinic. The main primary diagnosis was cerebrovascular disease (CVD) comprising 27% (n=19) of the referrals, whereas INPH was diagnosed in only 20% (n=14). Shunt improvement rate was 72%. The remaining patients were diagnosed as having one of 26 different conditions. A multiplicity of disorders mimics the INPH syndrome, with CVD being the primary differential diagnosis. Evaluating patients with possible INPH in an outpatient multidisciplinary memory clinic is an effective and rational diagnostic approach.

Shunting effects in patients with idiopathic normal pressure hydrocephalus; correlation with cerebral and leptomeningeal biopsy findings

Normal Pressure Hydrocephalus (NPH) is a potentially treatable syndrome with abnormal cerebrospinal fluid dynamics. Meningeal fibrosis and/or obliteration of the subarachnoid space have been suggested as one of the patho-anatomical substrates. However, other types of adult onset dementia, predominantly Alzheimer's disease and Vascular Dementia, may mimic the clinical NPH characteristics. The purpose of the present study was to correlate cerebral parenchymal and leptomeningeal biopsy findings to the clinical outcome after CSF shunting in a prospective group of idiopathic NPH (INPH) patients. The study comprises 27 patients with INPH, diagnosed and shunted according to generally accepted clinical, imaging and hydrodynamic criteria. In all patients a frontal leptomeningeal and brain biopsy was obtained prior to the shunt insertion. Degenerative cerebral changes, most often Alzheimer (6 cases) or vascular changes (7 cases) were described in 14 out of 27 biopsies. Arachnoid fibrosis was found in 9 of the 18 biopsies containing arachnoid tissue. Overall, nine patients (33%) improved, of whom 6 presented Alzheimer or vascular changes in their biopsies. No correlation was found between clinical outcome and the presence or absence of degenerative cerebral changes and/or arachnoid fibrosis. However, a tendency towards higher improvement rates was noted in the subgroups presenting degenerative cerebral changes or arachnoid fibrosis. The results suggest that no constant morphological element exists in the syndrome of INPH. Various aetiologies may be involved in the pathogenesis and possibly in some cases co-existing: Patients may also improve by shunting despite the presence of degenerative cerebral parenchymal changes.

Thoracic disc herniation. Unilateral transpedicular approach in 35 consecutive patients

BACKGROUND

Thoracic disc herniation is uncommon and surgery for thoracic disc herniation represents less than 1-2% of operations for disc disease. However, there is no consensus on the best approach and reports are based on small series.

METHODS

A consecutive series of 35 thoracic disc herniations (25 in women and 10 in men) were treated between 1991 and 1996 using the transpedicular approach and followed in a prospective study. All patients had a preoperative MRI examination. The mean age was 51 years. The T6-7 and T7-8 level were the most frequent localization. The interval between onset of symptoms and operation ranged from 6 weeks to 4 years with a mean of 18 months. Presenting symptoms on admission was radiculopathy in 12 patients and myelopathy in 23 patients. Severe urinary symptoms were found in 2 patients, moderate symptoms in 9 patients, mild symptoms in 3 patients and 21 patient had no urinary symptoms.

RESULTS

One patient was paraplegic immediately after surgery and she made no further improvement. A good result was found in 15 patients, a fair result was found in a further 11 patients but in 8 patients the outcome was unchanged with no effect of a reoperation in two cases. No clinical or radiographic features of instability were found. The postoperative course was uneventful, except in one patient with a wound abscess leading to discitis.

CONCLUSIONS

The transpedicular approach can be an effective and safe method of surgical decompression in carefully selected patients.

Childhood medulloblastoma in Denmark 1960-1984. A population-based retrospective study

Medulloblastoma is a common paediatric brain tumour, located in the cerebellum and in the IV ventricle, surpassed in frequency only by astrocytomas. 180 children below the age of 15 with a medulloblastoma of the posterior fossa were treated in Denmark in the 25-year period from 1960 to 1984 and followed up until the end of 1996, or until death. During the 25 years they accounted for 20% of all intracranial tumours in children in Denmark. All tumours were histologically verified. The mean annual incidence was 6.4x10(-6), decreasing slightly with a factor of 0.12x10(-6) per year. The male/female ratio was 2.1 - twice that of the background population of children (1.05). The 5-year survival rate following diagnosis, surgery and radiotherapy was 23%, and the 25-year survival rate was 16%. The 5-year survival rate was 8% in the first 5-year period of 1960-1964, increasing to 36% in the last period 1980-1984. Presumably the increase in survival depends on many factors, e.g. improved diagnostic methods and neuroanaesthesia, better operative technique (microscope), improvements in radiotherapy and the introduction of chemotherapy. The best predictive factors of a good prognosis were preoperative CSF shunting, radical tumour removal and complete radiotherapy, i.e. irradiation of the brain, tumour bed and spinal cord. The survival rate in the last five-year period was seven times higher than the survival rate found in a comparable Danish study from the years 1935-1959. Most of the children followed Collins law of risk index. The results of treatment in children with medulloblastoma remain unsatisfactory. Accordingly, participation in international prospective studies of multimodal treatment should be encouraged, possibly using chemotherapy prior to surgery.

A comparison between ventriculo-peritoneal and ventriculo-atrial cerebrospinal fluid shunts in relation to rate of revision and durability

Results of 884 first-time shunts inserted in the time period from 1958 to 1989 are retrospectively evaluated, 1) to perform a durability analysis of a shunt based on Kaplan-Meyer method, 2) to compare the rate of revision for ventriculo-atrial (VA) and ventriculo-peritoneal (VP) shunts, 3) to compare the durability of a VA shunt with a VP shunt and 4) to do a stratified durability analysis comparing the VA and VP shunts in relation to the following background variables: shunt type, time period and age of the patient. Furthermore the specific complications related to VA and VP shunts are identified based on findings in the literature. Overall one-year shunt durability is 57% and five-year shunt durability is 37%. The median shunt durability is 1.68 years. Revision rate is 51% for VA shunts and 38.5% for VP (p < 0.05). Shunt durability is longer for VP shunts though the difference is not significant (p < 0.1). By use of stratified analysis of shunt durability no differences however are found between the two shunting methods. Hence the apparent difference in revision rate between VA and VP shunts seems secondary to variations in follow-up time and variations in background variables. To supplement our statistical analysis we have performed a literature study to look at the specific complications associated with VA and VP shunts. It seems as if the specific complications in relation to the VA shunting method are more severe than in relation to the VP shunting method.

Age dependency of resistance to cerebrospinal fluid outflow

OBJECT

Resistance to cerebrospinal fluid (CSF) outflow (Rout)is an important parameter in assessing the need for CSF shunt placement in patients with hydrocephalus. The normal lower limit of Rout has been estimated on the basis of the clinical effect of shunt placement in patients with varying values of Rout and in young healthy volunteers. The lack of clinical effect from CSF shunts in some elderly patients, despite elevated Rout,suggests that the normal value of Rout increases with age and may be higher in elderly persons. The aim of the present study was to examine the relationship between Rout and age in patients without known CSF dynamic disturbances.

METHOD

Fifty-two patients ranging from 20 to 88 years of age and with no known CSF dynamic disorders were examined. The Rout was measured using a lumbar computerized infusion test. The correlation between Rout and age was analyzed by performing linear regression. The Rout increased significantly with patient age. The Rout in a patient in the eighth decade will be approximately 5 mm Hg/ml/minute higher than in a young patient.

CONCLUSIONS

The present study shows a small but critical increase in Rout with increased patient age. A notable residual variation was present and borderline values of Rout should be regarded and used with caution.

Epidemiology and prognosis in children treated for intracranial tumours in Denmark 1960-1984

A total of 911 Danish children under 15 years of age were treated for an intracranial tumour in the 25-five year period 1960-1984. All cases were followed up to the end of 1994 or to emigration or death if one of these came sooner. The mean annual incidence was 32.5 per million children with a slight increase over the 25 years. The male/female ratio was 1.15 and close to the M/F ratio for the entire Danish population of children. Of the tumours, 46% were located in the supratentorial and 54% in the infratentorial compartment, and 94% were verified histologically. In order of frequency the most common types were astrocytomas (all grades, 35%), medulloblastomas (20%), ependymomas (14%), and craniopharyngiomas (5%). Total removal of the tumour was performed in 277 and partial removal, including biopsy, in 490 children. In 57 patients a shunt operation only was performed, and 87 children did not have an operation or died before the correct diagnosis was established. Radiotherapy was administered in 55%. The outcome depended on extent of removal, radiation, location and histology of the tumour. Most (784 or 86%) of the children survived more than 1 month after diagnosis or operation, and 353 children (39% of the whole series, 47% of those alive more than 1 month after diagnosis) were alive at follow-up. Of the survivors 29% had a tumour in the supratentorial midline, 26% one in the lateral part of the supratentorial area, 31% a cerebellar tumour and 13% a IV ventricle tumour. It was possible for 66% of the survivors with supratentorial and 90% of those with infratentorial tumours to lead a normal life. The long-term prognosis was especially good for children with cerebellar and supratentorial astrocytomas and optic chiasma tumours. Children with juvenile cerebellar astrocytoma had the best prognosis: 90% were alive at the end of the follow-up period, as against 20% of those with medulloblastoma and 6% of those with glioblastoma. A comparison of the data from the present series and from a similar Danish series of intracranial tumours in 533 children seen in the years 1935-1959 shows no significant differences in location or histology, a slight increase in annual incidence, and improved survival rates during the 50 years in question.

[Frequency of infections after shunting of hydrocephalus. An analysis of 884 shunts]

Postoperative infections are major complications to cerebrospinal fluid (CSF) shunting in the treatment of hydrocephalus and other conditions with impeded CSF transportation. In a retrospective study 884 first-time shunts inserted in the years 1958-1989 are investigated. Infection rate is studied including influence of following variables: time period, age of patient, education of neurosurgeon, length and time of operation and placement of the distal drain. Overall infection rate for all implanted CSF shunts is 7.4% (5.7-9.3%) and acute rate of infection is 6.2% (4.6-7.9%). Rate of infection is virtually constant for all variables except education of the neurosurgeon. Neurosurgical trainees have significantly higher infection rates. Use of prophylactic antibiotics is still controversial No prospective, double blinded studies including sufficient number of patients to evaluate this issue exist today. Meta-analysis studies conclude that use of prophylactic antibiotics is associated with a significant reduction in subsequent CSF shunt infection. We recommend that shunt implantation primarily be performed by highly trained neurosurgeons and that there should be increased supervision during CSF shunt operations performed by neurosurgical trainees.

Frontal brain and leptomeningeal biopsy specimens correlated with cerebrospinal fluid outflow resistance and B-wave activity in patients suspected of normal-pressure hydrocephalus

OBJECTIVE

Normal-pressure hydrocephalus (NPH) is a potentially treatable syndrome with abnormal cerebrospinal fluid dynamics. Meningeal fibrosis and/or obliteration of the subarachnoid space has been suggested as the pathoanatomic basis. The purpose of the present study was to investigate whether meningeal fibrosis causes increased resistance to cerebrospinal fluid outflow (R(out)) and/or increased B-wave activity and whether pathological changes in the brain parenchyma after brain compliance, causing increased B-wave activity.

METHODS

The study involved a group of 38 consecutively studied patients with clinical and radiological evidence of idiopathic NPH, for whom a frontal brain biopsy was obtained. For 29 patients, hydrodynamic criteria of NPH were fulfilled and a ventriculoperitoneal shunt was performed.

RESULTS

Meningeal fibrosis was found in 12 of 25 biopsies containing arachnoid tissue, but no correlation with R(out) or B-waves was found. Pathological parenchymal changes, most often Alzheimer's disease (10 cases) or vascular changes (10 cases), were found in 21 biopsies, but no correlation with B-waves or R(out) was found.

CONCLUSION

The results suggest that leptomeningeal fibrosis is not the only pathoanatomic basis of increased R(out) and/or B-wave activity in patients with NPH and that various degenerative changes in the parenchyma may be responsible for the altered cerebrospinal fluid dynamics characteristic of NPH.

Prognostic factors in oligodendrogliomas

An outcome analysis was performed on 96 patients with pure cerebral oligodendrogliomas operated in the 30-year period 1962 to 1991. The most important predictive prognostic factors were youth and no neurological deficit, demonstrated as a median survival for the group younger than 20 years of 17.5 years and for the group older than 60 years of 13 months. The group without neurological deficits had a 5-years survival of 43 per cent while the group with deficits had a 5-years survival of 5 per cent. The 5-years survival for oligodendroglioma of grade II was 46 per cent and for grade III 10 per cent. We found no effect of radiotherapy on survival, neither in the whole material or in any subgroup.

How many neurosurgeons do we want to educate in Europe annually? The Danish proposal

The neurosurgical population consists of professors, consultants, specialised senior registrars, and doctors in training (senior registrars, trainees and young doctors to be educated as neurosurgeons). Knowing number and size of the neurosurgical departments in each European country, the number of staff members, the politics of retirement (age, educational level) and the age of every neurosurgeon it is possible to calculate the exact number of trainees needed per year to maintain a state of balance in every single European country. With Denmark as a model we based our assessments partly on a simple calculation model of the exact annual number of neurosurgical trainees or senior registrars and partly used an actuary flow model for calculation. In Denmark with 5 neurosurgical departments, 5.2 mill. population and a retirement age of 70, we have an average of 1-2 newcomers per year and maintain a bulk of 10 senior registrars in education. Thus there will be a balance between intake of newcomers and retirement, of course with some unknown factors as unforeseen dismissal or resignation, death rate among neurosurgeons and transfer to private practice.

[Diagnostic imaging in suspected lumbar disk prolapse. A controlled comparison of myelography, CT and magnetic resonance imaging]

Eighty patients with monoradicular sciatica were examined by myelography, computed tomography (CT) and magnetic resonance imaging (MRI) and all had subsequent surgery. The images were evaluated by a decision-analytic regret function. The largest amount of diagnostic information was gained from CT followed by MRI and myelography. Myelography was not significantly informative. The results suggest that CT or MRI should be the first choice examination in patients with suspected lumbar disc herniation.

Measurement of blood flow in the superior sagittal sinus in healthy volunteers, and in patients with normal pressure hydrocephalus and idiopathic intracranial hypertension with phase-contrast cine MR imaging

PURPOSE

To measure blood flow and velocity in the superior sagittal ++sinus.

MATERIAL AND METHODS

MR velocity mapping was used to examine 14 healthy volunteers, 15 patients with normal pressure hydrocephalus (NPH), 3 patients with high pressure hydrocephalus (HPH), and 11 patients with idiopathic intracranial hypertension (IIH).

RESULTS

Mean blood flow was 443 ml/min in healthy volunteers with a tendency towards reduced blood flow with increasing age. In NPH patients significantly lower superior sagittal sinus blood flow values were found, but this difference was no longer significant when patients and controls were matched for age. In HPH and IIH patients blood flow and velocity were within the normal range. In one patient with thrombosis of the superior sagittal sinus the blood flow was reduced to 40 ml/min.

CONCLUSION

MR velocity mapping methods may be of value in the assessment of blood flow in the dural sinuses in various pathologies resulting in dural sinus occlusion, such as dural sinus thrombosis, and for following the progress of these patients while undergoing treatment.

[Percutaneous lumbar diskectomy]

The results after percutaneous lumbar discectomy were evaluated in 52 patients with low back pain corresponding to the L5 or S1 root. All patients were examined with a median follow-up time of 14 weeks. The patients were divided in two groups. Group 1: patients with an obvious indication for surgery (29 patients) and group 2: patients with a relative indication for surgery (23 patients). The follow-up results for patients in group 1 were comparable with the results after conventional discectomy. The results concerning follow-up low back pain in groups 1 and 2 were good or excellent in 69% and 43% of the patients respectively. The corresponding results for sciatica were 69% and 65% respectively. It is concluded that percutaneous lumbar discectomy is a possible alternative to conventional discectomy in selected patients.

Heterogeneous cerebral glucose metabolism in normal pressure hydrocephalus

The regional cerebral metabolic rate for glucose (rCMRglu) has never been investigated in large consecutive groups of patients with normal pressure hydrocephalus (NPH), a potentially treatable form of dementia with an unpredictable outcome after shunt surgery. Using PET and 18F-2-fluorodeoxyglucose, rCMRglu was studied in 18 patients who fulfilled hydrodynamic criteria for NPH and in whom a biopsy of the frontal cortex was obtained. When compared with an age matched group of 11 healthy subjects, the patients with NPH showed a significant rCMRglu reduction in all cortical and subcortical regions of interest. Individual metabolic patterns, however, disclosed a large topographical heterogeneity. Furthermore, histopathological examination identified Alzheimer's disease or cerebrovascular disease in six cases, and no parenchymal disease or non-specific degenerative processes in the remaining 12. After separating the patients according to the histological diagnosis, the rCMRglu patterns were still heterogeneous, the abnormalities ranging from focal to diffuse in both subgroups. After shunt operation, 11 patients did not improve or worsened clinically. Six patients improved; of those, two had Alzheimer changes and two cerebrovascular changes in their biopsy. The metabolic pattern of these six patients did not differ from the rest of the NPH group. The results indicate that the NPH syndrome may be non-specifically associated with different degenerative disorders. The metabolic heterogeneity, together with the heterogeneous histopathological findings, indicate the necessity of reevaluating the pathogenesis of the NPH syndrome, and may account for the high variability in the success rate of shunt surgery series.

[Primary intracranial and intraspinal neoplasms in Denmark 1943-1987]

This is a descriptive study of primary intracranial and intraspinal tumours notified to the national Danish Cancer Registry during the years 1943-1987. A total of 19,317 cases of benign and malignant neoplasms were included over these 45 years with a doubling of the age-standardized incidence rates for both men and women from start till end of the registration period. The trend was mainly explained by markedly increasing rates in the age groups 60 years or above at diagnosis. Approximately some 74% of tumours were derived from the brain tissues and 19% from the intracranial and intraspinal meninges. Meningiomas predominate among women with a male:female ratio of 0.5, while tumours of the brain tissues predominate among men (ratio 1.3). Meningiomas are more frequently encountered as a chance finding at autopsy compared to other types of intracranial and intraspinal tumours. The above-mentioned increase in age-specific incidence is due mainly to improved diagnostic capabilities over the period and a subsequent decrease in the underreporting of these tumour types.

Frequency and causes of shunt revisions in different cerebrospinal fluid shunt types

Shunt complications and revisions are common in hydrocephalic patients treated with a ventriculo-atrial or a ventriculo-peritoneal shunt. The reported revision rate differs very much but the rate of revision is close to 50% in many papers. Data from 884 hydrocephalic patients treated with various shunt types in the period 1958-1989 were recorded retrospectively in order to evaluate the frequency of revision for various shunt types and secondly to analyse the specific reasons for the shunt revisions. The rate of shunt revision was 45%. The Pudenz shunt was revised more often (62%) than the remaining shunt types. The Hakim and the Orbis-Sigma shunts had fewer revisions (35% and 27%, respectively) than the other observed shunt types. A defect of or an obstruction in the ventricular catheters was a frequent cause of revision followed by a defect or an obstruction of the distal catheter, a displacement of the distal catheter and an acute infection. Because of the higher rate of revision for the Pudenz shunt the rate of the above mentioned specific complications is also higher in most of the subgroups for that specific shunt type. Driven by these experiences it is reasonable to seek to develop and introduce new shunt types in an attempt to reduce the complication rate.

Risk of infection after cerebrospinal fluid shunt: an analysis of 884 first-time shunts

Postoperative infections are major complications of cerebrospinal fluid (CSF) shunting in the treatment of hydrocephalus and other conditions with obstructed CSF circulation. In a retrospective study 884 first-time shunted patients with hydrocephalus operated on in the years 1958-1989 were investigated with special reference to the infection rate and to the influence of the following variables: time period, age of the patient, education of the neurosurgeon, length and time of the operation and the exact placement of the distal drain. The overall infection rate for all implanted CSF shunts was 7.4% (5.7-9.3%) and the acute rate of infection was 6.2% (4.6-7.9%). The rate of infection was virtually constant for all variables with the exception of the education of the neurosurgeon. Neurosurgical trainees particularly had a significantly higher rate of infection. Shunt infection is still a major complication. The infection rate has not declined in recent decades. It is not possible to relate any main cause to the infection rate. The literature recommends removal of the infected shunt combined with antibiotics. The use of prophylactic antibiotics is still controversial. No prospective, double-blind studies, including a sufficiently large number of patients to evaluate this issue, exist today.

The effect of nimodipine on autoregulation of cerebral blood flow after subarachnoid haemorrhage in rat

Disturbance of the autoregulation of the cerebral blood flow (CBF) is frequently seen following subarachnoid haemorrhage (SAH) and is possibly partly caused by cerebral ischaemia. It is well-known, that the calcium channel blocker nimodipine reduces the incidence of cerebral infarction and ischaemic dysfunction after SAH. The aim of the present study was to investigate the effect of nimodipine on autoregulation of CBF in an experimental model of SAH. The autoregulation was investigated in 10 control rats with SAH and in 10 nimodipine treated rats with SAH by serial measurements of CBF using a 133Xenon intracarotid injection method during controlled blood pressure manipulations. In the control rats the autoregulation was severely disturbed, no plateau was found where CBF was independent of changes in the arterial blood pressure (MABP). In rats treated with intravenous nimodipine (0.03 mg/kg body weight/h), CBF was 33.0% higher and MABP 5.3% higher compared with the controls. CBF was found constant in the MABP interval between 60 and 100 mmHg which indicates, that nimodipine improves the autoregulation of CBF after SAH.

A controlled comparison of myelography, computed tomography, and magnetic resonance imaging in clinically suspected lumbar disc herniation

STUDY DESIGN

A controlled prospective blinded study.

OBJECTIVES

To compare the diagnostic power of myelography, computed tomography and magnetic resonance imaging in the diagnosis of low lumbar disc herniation.

METHODS

Eighty patients with monoradicular sciatica were examined by myelography, computed tomography, and magnetic resonance imaging, and all underwent subsequent surgery. The images were evaluated twice in a blinded fashion, and the diagnostic power of the modalities was expressed by a decision-analytic regret function.

RESULTS

In 57 patients (71%) a disc herniation at the expected level was disclosed at surgery. The largest amount of diagnostic information was gained from computed tomography, followed by magnetic resonance imaging and myelography. Both computed tomography and magnetic resonance imaging were significantly informative, whereas this was not the case for myelography.

CONCLUSION

The results indicate that computed tomography or magnetic resonance imaging should be the first choice for imaging in patients with suspected lumbar disc herniation.

Increased brain water self-diffusion in patients with idiopathic intracranial hypertension

PURPOSE

To investigate changes in brain water diffusion in patients with idiopathic intracranial hypertension.

METHODS

A motion-compensated MR pulse sequence was used to create diffusion maps of the apparent diffusion coefficient (ADC) in 12 patients fulfilling conventional diagnostic criteria for idiopathic intracranial hypertension and in 12 healthy volunteers.

RESULTS

A significantly larger ADC was found within subcortical white matter in the patient group (mean, 1.16 x 10(-9) m2/s) than in the control group (mean, 0.75 x 10(-9) m2/s), whereas no significant differences were found within cortical gray matter, the basal nuclei, the internal capsule, or the corpus callosum. Four of 7 patients with increased ADC in subcortical white matter also had increased ADC within gray matter.

CONCLUSION

Measurement of diffusion coefficients in vivo demonstrated increased local water mobility within subcortical white matter in 7 patients with idiopathic intracranial hypertension that otherwise appeared normal on conventional MR imaging. Further studies are necessary to assess the clinical significance of these observations.

Increased self-diffusion of brain water in hydrocephalus measured by MR imaging

We used MR imaging to measure the apparent brain water self-diffusion in 5 patients with normal pressure hydrocephalus (NPH), in 2 patients with high pressure hydrocephalus (HPH), and in 8 age-matched controls. In all patients with NPH significant elevations of the apparent diffusion coefficients (ADC) of brain water were found within periventricular white matter, in the corpus callosum, in the internal capsule, within cortical gray matter, and in cerebrospinal fluid, whereas normal ADCs were found within the basal ganglia. In 2 patients with HPH elevated ADCs were found most prominently within white matter, and in one patient reexamined one year after surgery, ADCs were unchanged in nearly all brain regions. The increased ADC values in hydrocephalus patients may be caused by factors such as changes in myelin-associated bound water, increased Virchow-Robin spaces, and increased extracellular brain water fraction. For further studies of brain water diffusion in hydrocephalus patients, echo-planar imaging techniques with imaging times of a few seconds may be valuable.

Assessment of CSF dynamics and venous flow in the superior sagittal sinus by MRI in idiopathic intracranial hypertension: a preliminary study

A velocity-sensitive magnetic resonance imaging (MRI) phase-mapping method was used for non-invasive study of cerebrospinal fluid (CSF) flow in the cerebral aqueduct, for indirect calculation of supratentorial CSF production, and for measurement of blood flow in the superior sagittal sinus (SSS). We examined 12 patients with idiopathic intracranial hypertension (IIH; pseudotumour cerebri), and 10 healthy volunteers. The peak caudal and rostral CSF flow in the aqueduct during the cardiac cycle did not differ significantly between the patients and the volunteers. A significant correlation was found between the CSF volume flow amplitude and the resistance to cerebrospinal fluid outflow in the patients (p < 0.05). The calculated mean supratentorial CSF production rate was 0.79 ml/min in the patients and 0.70 ml/min in the controls, but this difference was not statistically significant. However, the MRI measurements suggested CSF hypersecretion in three patients, whereas increased transependymal passage of CSF could have been the cause of negative calculated CSF production rates in two others. A tendency towards lower mean blood flow in the SSS (mean 345 ml/min) in the patients than in the controls (mean 457 ml/min) was found, and in two patients showed very low values. We showed that MRI phase-mapping may be used to study the relative importance of the pathophysiological factors thought to play a role in the development of IIH.

Cerebrospinal fluid flow and production in patients with normal pressure hydrocephalus studied by MRI

An interleaved velocity-sensitised fast low-angle shot pulse sequence was used to study cerebrospinal fluid (CSF) flow in the cerebral aqueduct, and supratentorial CSF production in 9 patients with normal pressure hydrocephalus (NPH) and 9 healthy volunteers. The peak aqueduct CSF flow, both caudal and rostral, was significantly increased in patients with NPH. No significant difference in the supratentorial CSF production rate was found between patients (mean 0.60 +/- 0.59 ml/min) and healthy volunteers (mean 0.68 +/- 0.31 ml/min). Our method may be useful for investigation and monitoring of patients with NPH before and after ventriculoperitoneal shunt operations.

Brain biopsy in AIDS. Diagnostic value and consequence

Nineteen male patients with AIDS were investigated by biopsy of brain lesions. Six patients had progressive multiple leucoencephalopathy and no specific treatment was given. Toxoplasmosis (two patients), bacterial abscesses (two cases), viral encephalitis (two patients) and only gliosis (two cases) accounted for almost half of the cases. A fungal infection, a lymphoma and a sarcoma-like tumour were found in three patients. In two patients the biopsy was not diagnostic: one had only necrosis and one had normal findings. The biopsy findings gave reason for modifying the treatment in only three cases. The mean survival rate was relatively short, only 76 days with a range from 1 to 1041 days. Two patients were in a very bad clinical condition at the time of biopsy and one died of a haemorrhagic complication due to the biopsy. In ten cases an autopsy was carried out. In five cases there was agreement between the biopsy and autopsy findings. In the other five cases the autopsy findings differed widely. In our experience we can recommend cerebral biopsy in patients with AIDS only after treatment for toxoplasmosis and mainly to estimate the prognosis.

The effect of tirilazad mesylate (U74006F) on cerebral oxygen consumption, and reactivity of cerebral blood flow to carbon dioxide in healthy volunteers

BACKGROUND

The 21-aminosteroids are a series of compounds designed to inhibit lipid peroxidation in the cell, and, as such, may have cerebral protective effects. The current study was performed to evaluate the effect of a 21-aminosteroid, tirilazad mesylate (U74006F), on cerebral blood flow, metabolism, and carbon dioxide reactivity.

METHODS

Using a double-blind study design, eight volunteers received tirilazad mesylate, and eight others received only vehicle. The cerebral blood flow was measured by single photon emission computerized tomography using 133Xe inhalation in the resting condition at the beginning of the study and after infusion of tirilazad mesylate (1.5 mg/kg) or vehicle. Cerebral oxygen metabolism was calculated from the cerebral blood flow and the measured cerebral arteriovenous oxygen content difference. After both of the above cerebral blood flow measurements, arterial carbon dioxide tension was decreased by voluntary hyperventilation, and, later, increased by breathing an air/carbon dioxide mixture. The relative changes in cerebral blood flow induced by the PaCO2 variations were estimated from the changes in the arteriovenous oxygen content difference.

RESULTS

Blood pressure, pulse rate, and PaCO2 were similar before and after the infusion of tirilazad mesylate in both groups, and there was no difference between the groups. The cerebral blood flow and oxygen metabolism did not change after the tirilazad mesylate infusion. The slope of the regression line of relative change of estimated cerebral blood flow and PaCO2 (regression coefficients in both groups, > 0.90) was unchanged after infusion.

CONCLUSIONS

Tirilazad mesylate has no effect on cerebral blood flow, cerebral oxygen metabolism, or reactivity of cerebral blood flow to carbon dioxide in healthy volunteers.