Diagnostic value of electrophysiological tests in patients with sciatica.

OBJECTIVES: To assess the diagnostic value of electrophysiological tests in patients with sciatica. MATERIALS AND METHODS: The diagnostic value of electrophysiological tests were evaluated in 25 patients with monoradicular sciatica. The electrophysiological study included dermatomal somatosensory evoked potentials, electromyography, F-wave latencies, H-reflexes and motor and sensory nerve conduction determinations. The results of the electrophysiological examinations were evaluated blindly, and the test results were analysed separately by a receiver operating characteristic (ROC) analysis. Furthermore, the 5 modalities were evaluated jointly and analysed by a decision-analytic regret function. RESULTS: A high predictive value was found for the H-reflex examination, but low for the other modalities. When the 5 modalities were evaluated jointly, a non-significant decrease in expected regret from the pre-test situation of 0.96 to a value of 0.93 in post-test situation was revealed. CONCLUSION: Electrophysiological testing is not sufficient as stand-alone examination in patients with sciatica.

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.

[Frequency of infections after shunting of hydrocephalus. An analysis of 884 shunts]. / Infektionsfrekvens ved ventilbehandling af hydrocephalus. En opgørelse af 884 ventiler.

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.

[Diagnostic imaging in suspected lumbar disk prolapse. A controlled comparison of myelography, CT and magnetic resonance imaging]. / Billeddiagnostik ved mistanke om lumbal diskusprolaps. En kontrolleret sammenligning af myelografi, CT og magnetisk resonans-billeddannelse.

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.

[Percutaneous lumbar diskectomy]. / Perkutan lumbal diskektomi.

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.

Contrast enhanced computed tomography and magnetic resonance imaging in the diagnosis of recurrent disc herniation.

A positive result of re-operation in patients with recurrent symptoms after lumbar disc surgery is likely only if a new disc herniation is present. An improved ability to differentiate between recurrent disc herniation and scar tissue by contrast enhanced CT and MRI is suggested in earlier studies. In a prospective study 29 patients were selected for operation for suspected recurrent disc herniation. The inclusion of the patients was based on clinical symptoms and signs and myelography or non-enhanced CT. All patients were examined by CT and MRI both with and without intravenous contrast pre-operatively. The examinations were evaluated blind on a five point scale and statistical analysed by a regret function. Intravenous contrast improved the diagnostic power of both CT and MRI. MRI was superior to CT in both non-enhanced and enhanced examinations. MRI with intravenous contrast enhancement is proposed as the primary examination in patients with suspected recurrent disc herniation.

A critical assessment of clinical diagnosis of disc herniation in patients with monoradicular sciatica.

The diagnostic power or clinical parameters in the diagnosis of lumbar disc herniation in patients with monoradicular pain was evaluated in a prospective study with a 100% verification of the diagnosis. Eighty patients with monoradicular pain corresponding to the fifth lumbar or the first sacral nerve root were included. Pre-operatively a number of clinical parameters were recorded and compared to the intra-operative finding of a disc herniation. The parameters were analysed by receiver operating characteristic (ROC) curves. Results from the available literature were analysed by ROC curves for comparison. In 76% of the cases a disc herniation was discovered. The level of the disc herniation was correctly predicted in 93% of these cases by the location of the pain alone or supplemented by neurological signs. Apart from radicularly distributed pain, all parameters in the present study and in the literature had no or low diagnostic accuracy. Thus, in patients with monoradicular sciatica further clinical parameters do not add to the diagnosis of lumbar disc herniation.

Distinction between homozygous and heterozygous subjects with hereditary haemochromatosis using iron status markers and receiver operating characteristic (ROC) analysis.

The purpose of the present study was: 1) to evaluate which of the four iron status markers (serum iron, serum transferrin, serum transferrin saturation, serum ferritin) displayed the highest discriminatory potential in the distinction between homozygous patients with hereditary haemochromatosis and heterozygous relatives, 2) to suggest optimum cut-off values for these iron status markers, and 3) to demonstrate how these cut-off values change if the expected utility from a correct diagnosis is incorporated into the analysis. The patients and relatives were found by a nation-wide epidemiological survey. The study population consisted of 162 patients with clinically overt hereditary haemochromatosis and 84 asymptomatic heterozygous relatives. The statistical evaluation was performed using receiver operating characteristic (ROC) curve analysis. The diagnostic power of the iron markers is expressed as the area under the ROC curve. The optimum cut-off value is at the point where the slope of the ROC curve is equal to one. Changes in the optimum cut-off value at varying expected utility from a correct classification was estimated by changing the scaling of the ROC diagram. Serum iron and serum transferrin had the smallest area under the ROC curve, and were both unsuitable as discriminators. Near complete discrimination was obtained with serum transferrin saturation and serum ferritin concentrations, displaying the largest area under the ROC curve (0.991 and 0.998). The optimum threshold value for transferrin saturation was 61%, and for serum ferritin concentration 800 micrograms/l. The transferrin saturation level reflects the presence of the haemochromatosis allele, whereas the serum ferritin concentration indicates the degree of iron overload.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Patient attitudes to myelography, computed tomography and magnetic resonance imaging when examined for suspected lumbar disc herniation.

In reports of diagnostic methods in disorders of the spine focus is centred on diagnostic resolution, while psychological effects and patients' discomfort are often disregarded. To get a comprehensive picture of the appropriateness of a new technology the latter factors need to be explored and included in an assessment. In a prospective study, eight patients with signs of lumbar disc herniation underwent myelography, computed tomography and magnetic resonance imaging. A structured patient interview on attitudes to these technologies was carried out after all three examinations had been carried out. Myelography was most often reported painful and unpleasant among the three modalities. Discomfort due to magnetic resonance imaging stem from the narrow calibre of the machine and the noise. In computed tomography immobilization was the main reason for discomfort. Altogether most patients preferred computed tomography. In view of the fact that myelography must be considered as diagnostically inferior to the other two examinations, the reported discomfort from myelography indicates that computed tomography and magnetic resonance imaging should be the primary examinations for patients with lumbar disc herniation.

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.

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.

Computerized infusion test compared to steady pressure constant infusion test in measurement of resistance to CSF outflow.

Resistance to cerebro-spinal fluid outflow is together with intracranial pressure the most important parameter in the investigation of patients with disturbances of CSF dynamics. The methods for determination of resistance are either unreliable or too time-consuming for routine clinical use, which has limited the popularity of this kind of measurement. In this paper a method for computerized acquisition and processing of an infusion test is described. A good correlation to a standard technique is documented.

Diagnostic imaging in fracture of lumbar vertebral ring apophyses.

The findings at plain radiography, myelography, CT, and MR imaging in 3 cases of fracture of the lumbar vertebral ring apophysis are presented. Familiarity with this entity is important in evaluating low back pain in children and young adults. Conventional radiographs and/or MR imaging may suggest ring apophysis fracture; CT will confirm and classify the diagnosis.

Intracranial pressure and cerebrospinal fluid outflow conductance in healthy subjects.

Conductance of cerebrospinal fluid (CSF) outflow (Cout) is an important parameter to be considered in patients with CSF circulation abnormalities. In patients with normal-pressure hydrocephalus it is the single most important parameter in determining if the patient needs CSF shunting. The lower normal limit for Cout has been estimated from the effect of shunting in patients with normal-pressure hydrocephalus, from patients retrospectively reevaluated after recovering from illness, and from patients with known abnormalities in the brain or the CSF system. The true value of Cout in normal individuals, however, has hitherto not been reported. In the present study, Cout has been measured by a lumbar infusion test in eight young volunteers with no suspicion of disease. The mean intracranial pressure (ICP) was 11 mm Hg and a linear relationship was found between CSF absorption and ICP. The mean Cout was 0.11 ml/min/mm Hg and the lower 95% confidence level was 0.10 ml/min/mm Hg. These values are in accordance with those obtained from previous studies.

Fracture of the lumbar vertebral ring apophysis imitating disc herniation.

Three cases of fracture of the lumbar ring apophysis representing type I, II, and III are described in detail and the natural history of these fractures is discussed. The symptoms of apophyseal fractures are usually low back pain, sciatica, tension signs, and neurological deficits, thus imitating the symptoms of lumbar disc herniation. Plain radiography and magnetic resonance are often inconclusive and computed tomography is essential for the true diagnosis. An explanation of the different types of fractures, based on the osteogenesis of the human vertebra, is proposed. Recognition of these fractures is essential for proper planing of surgery, and apophyseal ring fractures must be suspected when children and young adults show signs of lumbar disc herniation.

[ROC-curve analysis. A statistical method for the evaluation of diagnostic tests]. / ROC-kurveanalyse. En statistisk metode til evaluering af diagnostiske test.

Receiver operating characteristic (ROC)-curves are a statistical method which may be employed inter alii for assessing a diagnostic test. These have been employed particularly in radiology but have also been employed for assessing laboratory tests and obstetric estiamation scales. The method is based on an analysis of nosological probabilities for varying limits of decision thresholds. ROC-curves may be employed for data on ratio/interval scales and data on rank scales. Parametric and non-parametric methods are available for obtaining a single quantitative measurement for the entire ROC-curve and to carry out significance tests between several ROC-curves.

Magnetic resonance imaging, computed tomography, and myelography in the diagnosis of recurrent lumbar disc herniation.

Thirteen patients with recurrent symptoms after lumbar discectomy were evaluated. All the patients were enrolled in the study on the basis of clinical symptoms and signs only. The patients were examined with MRI, CT, and myelography in order to compare a) the clinical findings with the imaging investigations, b) the predictive value of the different investigations, and c) the clinical and investigative results with the operative findings. All patients were operated upon according to the clinical findings, and the surgical results were used as the final diagnosis. In six patients a new disc herniation was detected. In the remaining cases surgery revealed either scar tissue or nothing to explain the recurrence of the symptoms. The three imaging modalities were analysed by receiver operating characteristic (ROC) curves. The areas under the ROC curves were 0.68 for MRI, 0.83 for CT, and 0.43 for myelography. The difference in areas between CT and myelography was significant (p less than 0.05). The results indicate that CT has the highest predictive value for demonstrating the recurrence of a lumbar disc herniation.