Psychosocial and pharmacologic interventions for methamphetamine addiction: protocol for a scoping review of the literature

BACKGROUND

Methamphetamine use and harms are rising rapidly. Management of patients with methamphetamine use disorder (MUD) and problematic methamphetamine use (PMU) is challenging, with no clearly established best approach; both psychosocial and pharmacologic interventions have been described. Furthermore, given the diversity of individuals that use methamphetamines, there is a need to assess evidence for treatments for subgroups including youths; gay, bisexual, and other men who have sex with men; individuals with mental health comorbidities; and individuals in correction services. Establishing awareness of the messages regarding treatment from recent clinical practice guidelines (CPG) in the field is also of value. The first study objective will be to establish a greater understanding of the methods, populations, and findings of controlled studies for psychosocial and pharmacologic treatments for MUD and PMU. Investigation of this information can help establish the potential for advanced syntheses of the evidence (such as network meta-analysis) to compare therapies for this condition and to identify gaps related to key populations where more primary research is needed. Summarizing the recommendations regarding treatment of MUD/PMU from recent CPGs and systematic reviews will be an important secondary objective.

METHODS

A scoping review will be performed. Using the OVID platform, MEDLINE, Embase, PsycINFO, and relevant Cochrane databases from EBM Reviews will be searched (from databases' inception onwards). Eligibility criteria will include individuals described as having MUD or PMU, with designs of interest including randomized trials, non-randomized trials, and controlled cohort studies with three or more months of follow-up; systematic reviews and CPGs will also be sought. Two reviewers (with support from automation tools) will independently screen all citations, full-text articles, and chart data. Different approaches to handling and summarizing the data will be implemented for each type of study design. Tables and graphics will be used to map evidence sources and identify evidence gaps.

DISCUSSION

This research will enhance awareness of evidence addressing the effects of psychosocial and pharmacologic interventions for MUD/PMU overall and in sub-populations, both in terms of recent CPGs/reviews and primary studies; inspection of the latter will also help establish the feasibility of future syntheses to compare treatments, such as network meta-analysis. SYSTEMATIC REVIEW PROTOCOL REGISTRATION: Open Science Framework ( https://osf.io/9wy8p ).

Case-Based Explanation for Medical Diagnostic Programs, with an Example from Gynaecology

One of the most accountable methods of providing machine assistance in medical diagnosis is to retrieve and display similar previously diagnosed cases from a database. In practice, however, classifying cases according to the diagnoses of their nearest neighbours is often significantly less accurate than other statistical classifiers. In this paper the transparency of the nearest neighbours method is combined with the accuracy of another statistical method. This is achieved by using the other statistical method to define a measure of similarity between the presentations of two cases. The diagnosis of abdominal pain of suspected gynaecological origin is used as a case study to evaluate this method. Bayes’ theorem, with the usual assumption of conditional independence, is used to define a metric on cases. This new metric was found to correspond as well as Hamming distance to the clinical notion of “similarity” between cases, while significantly increasing accuracy to that of the Bayes’ method itself.

Risk factors for mortality in smear-negative tuberculosis suspects: a cohort study in Harare, Zimbabwe

OBJECTIVE

To investigate mortality rates and risk factors for death among smear-negative tuberculosis (TB) suspects.

DESIGN

Cohort study nested within a cluster-randomised trial of community-based active case finding. Smear-negative TB suspects were followed for 12 months, with home tracing where necessary. We calculated mortality rates and used regression analysis to investigate the relationship between clinical characteristics and death.

RESULTS

Between February 2006 and June 2007, 1195 smear-negative TB suspects were followed for 1136.8 person-years. Human immunodeficiency virus (HIV) prevalence was 63.3%. During follow-up, 139 participants died (11.6%) and mortality rates remained high throughout; 119 (16.5%) HIV-positive individuals and 13 (3.1%) HIV-negative individuals died (HR = 5.8, 95%CI 3.3-10.4, P < 0.001). Advanced immunosuppression was the main risk factor for death among HIV-positive participants, with CD4 count < 50 cells/μ l associated with a 13-fold increased risk of death. Antiretroviral treatment (ART) was initiated by only 106 (14.7%), with long delays in accessing care.

CONCLUSION

HIV-positive smear-negative TB suspects are at high and sustained risk of death. Current guidelines for the management of HIV-infected TB suspects are limited, and this study adds to evidence that specific policies are required to promote earlier HIV and TB diagnosis and reduce delays in ART initiation.

Epigenetic regulation of the MGMT and hMSH6 DNA repair genes in cells resistant to methylating agents

We investigated the relationship between DNA cytosine methylation and the expression of two genes associated with resistance to DNA methylation damage. Variants of RajiMex- cells acquired resistance to N-methyl-N-nitrosourea by either reactivating a previously silent O6-methylguanine-DNA methyltransferase (MGMT) gene or by repressing the hMSH6 mismatch repair gene. DNA sequencing and measurements of mRNA and enzyme levels revealed that MGMT activity was not correlated with methylation of the core MGMT promoter. Treatment with the demethylating agent 5-azadeoxycytidine reduced MGMT mRNA and enzyme levels, indicating that methylation of some nonpromoter sequences may be required for MGMT gene expression. In contrast, both hMSH6 mRNA and protein levels were increased by 5-azadeoxycytidine treatment of an N-methyl-N-nitrosourea-resistant variant that did not express detectable hMSH6, which implies that this gene was transcriptionally silenced by cytosine methylation. This could be substantiated by in vitro modification of the CpG sites in the hMSH6 promoter with restriction methylase M.SssI, which abolished the transcription of a reporter gene under its control in a transient transfection assay. Taken together, our data show that treatment with chemical methylating agents alters gene expression patterns through increased CpG methylation of genomic DNA, and thereby permits the emergence and selection of clones that are resistant to these agents due to increased repair or tolerance of O6-methylguanine.

The cytotoxicity of DNA carboxymethylation and methylation by the model carboxymethylating agent azaserine in human cells

Carboxymethylating agents are potential sources of endogenous DNA damage that have been proposed as possible contributors to gastrointestinal carcinogenesis. The cytotoxicity of the model DNA carboxymethylating agent azaserine was investigated in human cells. Expression of the DNA repair enzyme O(6)-methylguanine-DNA methyltransferase (MGMT) did not affect sensitivity to the drug in two related Raji Burkitt's lymphoma cell lines. DNA mismatch repair-defective variants of Raji cells which display increased tolerance to DNA methylation damage were not selectively resistant to azaserine. Complementary results were obtained with a second carboxymethylating agent, potassium diazoacetate. In contrast, lymphoblastoid cell lines representative of each of the xeroderma pigmentosum complementation groups, including the variant, were all significantly more sensitive to azaserine than nucleotide excision repair-proficient cells. The hypersensitivity of XP cells was not due to systematic differences in the concentrations of intracellular thiol compounds or related thiol metabolizing enzymes. The data indicate that of the two types of potentially lethal DNA damage which azaserine introduces, carboxymethylated bases and O(6)-methylguanine, the former are repaired by nucleotide excision repair and are a more significant contributor to azaserine lethality in human cells.

Frameshift mismatch recognition by the human MutS alpha complex

DNA mismatch binding by an extensively purified hMutS alpha mismatch recognition complex was investigated using a bandshift assay. The complex bound to G. T mispairs and to looped structures containing an unpaired single or two adjacent bases. A CA loop was preferentially recognised if the unpaired bases formed part of a repeated sequence. In general, single base loops were also more favourably recognised by hMutS alpha when present in monotonic runs of two to five. In one series of substrates, based on a known hotspot for frameshift mutations in the hypoxanthine-guanine phosphoribosyltransferase gene, in which different length G, A, C or T tracts were flanked by closely similar sequences, an A loop was bound preferentially in the absence of adjacent As and a C loop in the absence of adjacent Cs. This preferential binding was influenced by the base immediately 5' to the loop. Thus, while repeated regions generally favour recognition of single base loops by hMutS alpha, other factors related to local sequence may influence this interaction.

Mismatch repair defects and O6-methylguanine-DNA methyltransferase expression in acquired resistance to methylating agents in human cells

Fifteen variants with >/=30-fold resistance to N-methyl-N-nitrosourea were isolated from the Burkitt's lymphoma Raji cell line. Eight had received a single treatment with a highly cytotoxic dose. The remainder, including the previously described RajiF12 cell line, arose following multiple exposures to initially moderate but escalating doses. Surprisingly, methylation resistance arose in three clones by reactivation of a previously silent O6-methylguanine-DNA methyltransferase gene. Five clones, including RajiF12, displayed the microsatellite instability and increased spontaneous mutation rates at the hypoxanthine-guanine phosphoribosyltransferase locus, consistent with deficiencies in mismatch repair. Defects in either the hMutSalpha or hMutLalpha mismatch repair complexes were identified in extracts of these resistant clones by in vitro complementation using extracts from colorectal carcinoma cell lines. Defects in hMutLalpha were confirmed by Western blot analysis. Remarkably, five methylation-resistant clones in which mismatch repair defects were demonstrated by biochemical assays did not exhibit significant microsatellite instability.

Processing of O6-methylguanine by mismatch correction in human cell extracts

Human cell extracts perform an aberrant form of DNA synthesis on methylated plasmids [1], which represents processing of O6-methylguanine (O6-meG). Here, we show that extracts of colorectal carcinoma cells with defects in the mismatch repair proteins that normally correct replication errors do not carry out this synthesis. hMSH2-defective LoVo cell extracts (hMSH for human MutS homologue) performed O6-meG-dependent DNA synthesis only after the addition of the purified hMutS alpha mismatch recognition complex. Processing of O6-meG by mismatch correction requires PCNA and therefore probably DNA polymerase delta and/or epsilon. Mismatch repair-defective cells withstand O6-meG in their DNA [2], making them tolerant to methylating agents. Methylation-tolerant HeLaMR clones, with a mutator phenotype and a defect in either mismatch recognition or correction in vitro, also performed little O6-meG-dependent DNA synthesis. Assays of pairwise combinations of tolerant and colorectal carcinoma cell extracts identified hMLH1 as the missing mismatch repair function in a group of tolerant clones. The absence of processing by extracts of methylation-tolerant cells provides the first biochemical evidence that lethality of DNA O6-meG derives from its interaction with mismatch repair.

hMSH2-independent DNA mismatch recognition by human proteins

Two distinct mismatch binding activities are detected using bandshift assays with human cell extracts and DNA with mispairs at defined positions. One requires hMSH2 protein and is absent from extracts of LoVo cells, which contain a partial deletion of the hMSH2 gene. The second activity is independent of hMSH2 and is present at normal levels in LoVo and three other cell lines, which are defective in in vitro hMSH2-dependent binding. The two mismatch recognition activities are distinguished by their sensitivity to polycations and can be resolved by chromatography on MonoQ. hMSH2-independent activity has been purified extensively from wild-type cells and from a cell line deficient in hMSH2-dependent binding. The purified material preferentially recognizes A-C, some pyrimidine-pyrimidine mismatches, and certain slipped mispaired structures. Binding exhibits some sequence preferences. The similar properties of the two mismatch binding activities suggest that they both contribute to mismatch repair.

Case-based explanation for medical diagnostic programs, with an example from gynaecology

One of the most accountable methods of providing machine assistance in medical diagnosis is to retrieve and display similar previously diagnosed cases from a database. In practice, however, classifying cases according to the diagnoses of their nearest neighbours is often significantly less accurate than other statistical classifiers. In this paper the transparency of the nearest neighbours method is combined with the accuracy of another statistical method. This is achieved by using the other statistical method to define a measure of similarity between the presentations of two cases. The diagnosis of abdominal pain of suspected gynaecological origin is used as a case study to evaluate this method. Bayes' theorem, with the usual assumption of conditional independence, is used to define a metric on cases. This new metric was found to correspond as well as Hamming distance to the clinical notion of "similarity" between cases, while significantly increasing accuracy to that of the Bayes' method itself.

Diffuse brain swelling after head injury: more often malignant in adults than children?

A series of 118 patients with diffuse traumatic brain swelling was studied retrospectively in order to compare the clinical findings in children with those in adults, and to determine the occurrence of neurological deterioration and outcome. The computerized tomography (CT) picture of absent third ventricle and basal cisterns was used to identify the cases. Although this condition has been associated with children, we found the same number of children and adults (59 cases each). Secondary deterioration (decline in consciousness, the development of new focal neurological signs, or an increase in intracranial pressure) occurred in 40% of cases and was more common in adults than children. Features that were significantly associated with deterioration were the presence of prolonged coma (> 1 hour) after the injury, CT signs of diffuse axonal injury or subarachnoid hemorrhage, or a recorded episode of hypotension. A moderate or good recovery at 6 months was achieved by 70 patients (59%), but 45 patients had a poor outcome (severe disability in nine, vegetative state in three, and death in 33) and this was often a consequence of secondary deterioration. In three patients, the outcome was not known. The combination of a severe initial injury, secondary insult, and diffuse swelling is associated with a poor outlook, particularly in adults. The CT appearance of diffuse swelling may develop more readily in children because of the lack of cerebrospinal fluid available for displacement. In children, diffuse swelling may have a relatively benign course unless there is a severe primary injury or a secondary hypotensive insult.

The design and construction of a medical simulation model

This paper describes the design, construction and validation of a probabilistic simulation model of patients who present with abdominal pain. The model incorporates text-book medical knowledge, clinical judgment, and statistics collected from real cases. The knowledge representation combines techniques of Bayesian network modelling with ideas of logistic discrimination. The model is shown to generate convincing, realistic cases; large numbers of artificial cases with no missing observations can be generated quickly. This should make the model a useful tool for investigating factors which limit achievable computer accuracy in the diagnosis of abdominal pain.

Surfactant proteins A (SP-A) and D (SP-D): levels in human amniotic fluid and localization in the fetal membranes

Surfactant proteins A (SP-A) and D (SP-D) are major proteins, in the lung, which are composed of collagenous and globular domains. They show an overall similarity to the serum complement protein Clq, which is involved in the initiation of antibody-dependent defence mechanisms. Both SP-A and SP-D were detected, immunochemically, in amniotic fluid as early as 26 weeks gestation and, as expected, SP-A levels rose sharply from 32 weeks towards term. By contrast, SP-D levels in the same samples rose only moderately. Immunochemistry of paraffin sections of fetal membranes, revealed the presence of both SP-A and SP-D in the amniotic epithelium and chorio-decidual layers. SP-A and SP-D are both lectins and therefore they may play a role in the antibody-independent recognition and clearance of pathogens in the amniotic fluid.

A probabilistic rule-based expert system

This paper explores a medical expert system combining techniques of Bayesian network modelling with ideas of weighted inference rules. The weights of the individual rules can be estimated objectively from a training set of actual cases; and they can be used in a Monte Carlo stimulation to estimate objectively conditional probabilities of diagnosis given particular combinations of symptoms. The paper describes and evaluates a medical expert system built according to this design. The diagnostic accuracy of the program was found to be similar to that obtained through the usual application of Bayes theorem with the assumption of conditional independence of symptoms given disease, even though the Bayesian classifier has more than 70 times as many numerical parameters. The method may be promising in cases where small training sets do not permit accurate estimation of large numbers of parameters.

O6-methylguanine residues elicit DNA repair synthesis by human cell extracts

We have investigated the processing of O6-methylguanine (O6-MeGua) in plasmid DNA by extracts of human cells defective in O6-MeGua-DNA methyltransferase. Cell extracts of HeLaMR cells performed viral T antigen-independent DNA synthesis on plasmids that had been treated with low concentrations of methylating agents. The in vitro DNA synthesis was non-semiconservative and depended on the presence of O6-MeGua in the substrate. The involvement of DNA polymerase delta or epsilon and proliferating cell nuclear antigen but not single-strand binding protein was indicated by partial fractionation, inhibitor, and antibody studies. Processing of O6-MeGua is not via the UV nucleotide excision repair pathway since additional component(s) are apparently required to perform repair synthesis on the methylated substrate. This is the first direct demonstration of DNA repair synthesis provoked by O6-MeGua in DNA. Since O6-MeGua is not excised from DNA by Mex- cells, it represents a novel type of processing of the methylated base that may be involved in its cytotoxicity.

Indications for and accuracy of magnetic resonance imaging and computed tomography in orbital disease

All patients referred for orbital imaging to the neuroradiology department of the Institute of Neurological Sciences in Glasgow over a three year period were enrolled in the study and were scheduled to undergo both magnetic resonance imaging and computed tomography. A total of 101 of the 110 referred patients were deemed suitable for analysis. Details of key presenting symptoms, signs, and a pre-imaging diagnosis were recorded prospectively. A final diagnosis was obtained by histology in 65% of cases with an orbital abnormality, by a minimum of one year of clinical review in 19.5%, by response to antibiotic or steroid therapy in 8.5%, or by conclusive investigations such as carotid angiography in in 7% of patients, 29% of the patients had no detectable orbital disease despite a minimum one years' follow-up, and so were regarded as a "normal" group. The images were interpreted prospectively by separate masked observers. The diagnostic accuracies of the two techniques were compared to the final diagnosis. The two imaging methods were shown to be comparable in overall diagnostic accuracy, with a small and statistically non-significant advantage held by magnetic resonance imaging. Interpretation of the two investigations gave more accurate information in different types of disease.

Fibrous dysplasia of the skull: disease activity in relation to age

Eighteen of 19 patients with histologically confirmed fibrous dysplasia of the skull seen at the Institute of Neurological Sciences, Glasgow, in the past 20 years have been reviewed and recent radiographs obtained. Sex, age at presentation and at follow-up were recorded, in addition to the site, type and extent of cranial involvement. The findings have been related to disease activity and progression. In comparison with other reports we found the proportion of patients with activity in adulthood to be relatively high (37%). Overall, there was an equal sex distribution, but of seven patients presenting as adults, six were female as were six of seven patients with evidence of disease activity in adulthood.

MRI in the management of suspected cervical spondylotic myelopathy

One hundred and two patients with suspected cervical spondylotic myelopathy were prospectively investigated using MRI as the initial imaging technique. The aim was to discover if clinicians could manage patients with MRI alone, or if they would find a second investigation necessary. Eighty two patients were managed using MRI alone, 34 of whom were treated surgically. Twenty patients had a second investigation: a myelogram in 18 and a CT myelogram in two. This was performed in nine patients to exclude structural pathology in the thoracic or lumbar region (which was not examined with MRI), and in 11 to obtain more specific information about the cervical region. Only five of these 20 patients had surgical treatment. The diagnosis changed after the second investigation in four patients, but management was not influenced in any of these. MRI is a satisfactory alternative to myelography for most patients with suspected cervical spondylotic myelopathy.

Gadolinium DTPA enhanced magnetic resonance imaging in acute head injury

We studied the effect of contrast enhancement on magnetic resonance imaging (Gadolinium DTPA Magnetic Resonance) in 10 patients with a recent head injury. The use of contrast did not increase the number of traumatic lesions identified and we did not detect evidence of altered blood brain barrier permeability in any of the 7 patients, who had a total of 27 lesions, imaged between one and 4 days after injury. Enhancement was found in each of 3 patients imaged 6 or more days after injury. These findings suggest that traumatic cortical and intraparenchymal lesions are not associated with increased cerebrovascular permeability within the first 96 hours of a head injury.

The value of pre-operative embolisation of meningioma estimated subjectively and objectively

In a personal series a comparison has been made of the subjective and objective assessments of benefit between a group of patients in whom preoperative embolisation for meningioma was performed and a group, referred during the same timescale, in whom embolisation was either not possible or not appropriate. Preoperative difficulty with bleeding was experienced in 25% of the embolisation group and in 62% of the non-embolised group. Blood replacement overall was less in the embolised patients. Surgical complications occurred in 21% of those embolised but in 54% of those in whom embolisation had not been performed. At follow-up the outcome was rated as good in 79% in the embolisation group as opposed to 58% in the non-embolised group. Preoperative embolisation was therefore beneficial.

Supplementary CT temporal lobe cuts confer no worthwhile benefit

The value of angled temporal lobe cuts as a supplement to conventional head computed tomography (CT) has been assessed by comparing the diagnostic yield of standard axial and specific temporal lobe images (TLCT) in 62 patients with temporal lobe epilepsy and 87 with Alzheimer-type senile dementia. Fewer than one patient in six had structural abnormality in the temporal lobe most readily demonstrated by axial CT. Five patients with epilepsy and ten with dementia had changes demonstrated only by TLCT, reported on by one or other of a pair of observers. However such changes were of dubious clinical relevance, or arose as a result of artefact. In one patient with epilepsy and underlying neoplasm, axial CT was positive and TLCT false-negative. The routine addition of temporal lobe cuts to a conventional axial examination confers no added benefit to justify the prolonged examination time and increased radiation dose to the lens of the eye.

Regulation of O6-methylguanine-DNA methyltransferase expression in the Burkitt's lymphoma cell line Raji

We have investigated the expression of the DNA-repair enzyme O6-methylguanine-DNA methyltransferase in the Burkitt's lymphoma cell line Raji. An existing mutant Raji cell line which lacks thymidine kinase activity had previously been shown to be Mex- and to no longer express O6-methylguanine-DNA methyltransferase. We report here that in addition to the methyltransferase and thymidine kinase, a third enzyme with an unrelated function, galactokinase, is also not expressed in Raji cells. The control of thymidine kinase expression is post-transcriptional and it is possible that galactokinase and methyltransferase can share a common post-transcriptional regulation with thymidine kinase.

CT scanning and surgical treatment of 1551 head injured patients admitted to a regional neurosurgical unit

Computed tomographic (CT) scans of 1551 recently head injured patients transferred to a regional neurosurgical unit (NSU) were reviewed. Some 90% of first scans were done outside normal working hours. More than a third of first scans were normal including a fifth of the patients who were in deep coma. Haematoma was found in 50%, contusion 28%, shearing injuries 13% and general swelling in 9%. In 22% the first scan led to urgent surgical evacuation of an intracranial haematoma. More than one scan was done in 41% of patients and more than two in 10%, making 2608 scans in all. Repeat scans were more often done when the first scan was abnormal. In only five of 554 patients (1%) whose first scan had been normal were contusions or haematomas seen on subsequent scans, and in none of these was surgery required. Of 997 patients whose first scan had been abnormal a new lesion (contusion, haematoma and/or infarction) was seen on a subsequent scan in 103 cases (10%). Surgery was required (for the first time), in 57 patients whose abnormal first scans had not indicated the necessity for surgery at that time. The implications of these and other findings for the scanning of recently head injured patients in general hospitals, as scanners become more widely available, are discussed in our accompanying paper on p. 88.

Implications of scanning recently head injured patients in general hospitals

Increasing availability of computed tomography (CT) in general hospitals makes it appropriate to scan certain categories of acutely head injured patients in these hospitals. Policies should be devised locally indicating which types of patient should be scanned there, and what circumstances require transfer to the neurosurgical unit (NSU). Consideration must be given to the implications for training, staffing and other CT scanner commitments. The paper discusses these issues in the light of a study of the CT scans and surgical treatment of 1551 patients admitted to an NSU over a five year period, and provides models for discussion.

Non-invasive radiological investigation for oculomotor palsy

An application of computed tomography (CT) is described in which multiplanar high resolution images of the terminal carotid and basilar arteries are obtained. This has been applied in a series of 32 patients with IIIrd nerve palsy in whom the underlying pathology was thought to be a posterior communicating artery aneurysm. The results of the CT were compared with conventional angiography. Seventeen aneurysms were detected in 13 patients by CT and all were confirmed by angiography. Vessels considered to be normal on CT were confirmed to be normal by angiography. This CT technique is a simple non invasive first line investigation for IIIrd nerve palsy with the ability to exclude or predict an aneurysm.

Cerebral radiation necrosis complicating stereotactic radiosurgery for arteriovenous malformation

A patient presented with symptoms and signs of raised intracranial pressure and increasing focal deficit 13 months after stereotactic radiosurgical treatment of an arteriovenous malformation (AVM). Computed Tomography (CT) showed a mass lesion at the site of the previous abnormality typical of radiation necrosis, but with features identical to those of a malignant neoplasm. Biopsy confirmed cerebral radiation necrosis. The radiation dose was 25 Gray to the periphery of two overlapping 14 mm collimator fields, delivered in a single dose. Treatment with steroids led to improvement in the symptoms and signs of raised intracranial pressure, but not the focal deficit. Radiation necrosis is a consequence of the large doses required to obliterate AVMs and is a limiting factor in their treatment. It is important for clinicians referring patients for stereotactic radiosurgery to be aware of this complication, and to be able to recognise and treat it.

Coregulation of the human O6-methylguanine-DNA methyltransferase with two unrelated genes that are closely linked

The loss of expression of the enzyme O6-methylguanine-DNA methyltransferase (the Mex- phenotype), which often results from cellular transformation, confers hypersensitivity to alkylating agents. We have observed two unrelated examples in which human cell lines have undergone a spontaneous alteration in their Mex phenotype during propagation in vitro. The change was reversible and was not the result of mutation. In both cases a loss of methyltransferase expression was accompanied by a simultaneous loss of expression of two metabolically unrelated enzymes: thymidine kinase and galactokinase. "Reversion" to methyltransferase expression was accompanied by simultaneous reexpression of both kinase activities. A third example of this coordinate gene regulation was seen with the Burkitt's lymphoma cell line Raji which expresses methyltransferase, thymidine kinase, and galactokinase at high levels. A thymidine kinase- Raji cell line derived by bromodeoxyuridine mutagenesis that is also Mex- was found to be galactokinase-. It appears that methyltransferase expression may in some instances be coordinately regulated with the tk and glk loci which are closely linked on human chromosome 17.

CT, MR and SPECT imaging in temporal lobe epilepsy

Cranial computed tomography (CT) with modified temporal lobe technique, 0.15T magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT) were carried out on 30 patients with intractable temporal lobe epilepsy. Lateralising abnormalities were detected in 21/30 patients overall. Specific lesions were detected by CT in one patient and by MRI in seven patients (in one case bilateral). In addition CT detected asymmetry of the sylvian fissures or temporal horns in 10 patients, and MRI in eight patients. SPECT detected lateralising abnormalities in 19 patients (in five cases bilateral). It is concluded that low field MRI is superior to modified CT in demonstrating subtle structural lesions of the temporal lobe. Functional scanning with SPECT supports the evidence of origin of an epileptic focus in a substantial proportion of cases and may improve the selection of patients for surgery.

Gadolinium-DTPA enhanced magnetic resonance imaging in human head injury

We used low field magnetic resonance imaging and Gadolinium-DTPA to study 10 recently head injured patients. On the pre-contrast images we identified 36 abnormalities in 9 of the 10 patients. After contrast enhancement was seen in 9 of these lesions in 3 patients imaged 5-6 days after injury. Altered blood brain barrier permeability to gadolinium was not seen in 6 patients studied within 4 days of trauma. We did not identify any lesions with gadolinium that were not present on the pre-contrast images. We do not think that the routine use of contrast in head injury is justified since clinically important lesions will be present on routine sequences. However the use of gadolinium may provide information about the nature and timing of the underlying pathophysiological changes. In human head injury cytotoxic oedema occurs early and vasogenic oedema does not occur until 5-6 days after injury.

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Images

Pituitary microadenomas. Does Gadolinium enhance their demonstration?

Ten patients with biochemical evidence of a hormonally active pituitary adenoma were examined by dynamic contrast enhanced computed tomography (CT) and then by pre and post Gadolinium-DTPA (Gd-DTPA) enhanced magnetic resonance imaging (MRI). Excluding one false positive case, CT and unenhanced MRI were comparable in the detection of microadenoma. Post Gd-DTPA examination gave more clear evidence of the actual adenoma in two patients and aided in the demonstration of a third. However, in two others all imaging techniques failed to demonstrate the microadenoma subsequently found at surgery. On the post enhancement MRI it was easier to assess the relationship of a tumour to the cavernous sinus and to visualise the relationships of the parasellar carotid arteries.

Comparison of magnetic resonance imaging and computed tomography in suspected lesions in the posterior cranial fossa

OBJECTIVE

To compare computed tomography and magnetic resonance imaging in investigating patients suspected of having a lesion in the posterior cranial fossa.

DESIGN

Randomised allocation of newly referred patients to undergo either computed tomography or magnetic resonance imaging; the alternative investigation was performed subsequently only in response to a request from the referring doctor.

SETTING

A regional neuroscience centre serving 2.7 million.

PATIENTS

1020 Patients recruited between April 1986 and December 1987, all suspected by neurologists, neurosurgeons, or other specialists of having a lesion in the posterior fossa and referred for neuroradiology. The groups allocated to undergo computed tomography or magnetic resonance imaging were well matched in distributions of age, sex, specialty of referring doctor, investigation as an inpatient or an outpatient, suspected site of lesion, and presumed disease process; the referring doctor's confidence in the initial clinical diagnosis was also similar.

INTERVENTIONS

After the patients had been imaged by either computed tomography or magnetic resonance (using a resistive magnet of 0.15 T) doctors were given the radiologist's report and a form asking if they considered that imaging with the alternative technique was necessary and, if so, why; it also asked for their current diagnoses and their confidence in them.

MAIN OUTCOME MEASURES

Number of requests for the alternative method of investigation. Assessment of characteristics of patients for whom further imaging was requested and lesions that were suspected initially and how the results of the second imaging affected clinicians' and radiologists' opinions.

RESULTS

Ninety three of the 501 patients who initially underwent computed tomography were referred subsequently for magnetic resonance imaging whereas only 28 of the 493 patients who initially underwent magnetic resonance imaging were referred subsequently for computed tomography. Over the study the number of patients referred for magnetic resonance imaging after computed tomography increased but requests for computed tomography after magnetic resonance imaging decreased. The reason that clinicians gave most commonly for requesting further imaging by magnetic resonance was that the results of the initial computed tomography failed to exclude their suspected diagnosis (64 patients). This was less common in patients investigated initially by magnetic resonance imaging (eight patients). Management of 28 patients (6%) imaged initially with computed tomography and 12 patients (2%) imaged initially with magnetic resonance was changed on the basis of the results of the alternative imaging.

CONCLUSIONS

Magnetic resonance imaging provided doctors with the information required to manage patients suspected of having a lesion in the posterior fossa more commonly than computed tomography, but computed tomography alone was satisfactory in 80% of cases...

Delayed deterioration in patients with traumatic frontal contusions

The clinical course of 18 head injured patients in whom CT had shown frontal contusions without diffuse brain injury or intracranial haematoma was reviewed. All 10 patients with unilateral frontal contusion made a good recovery. Only two of five patients with limited bilateral frontal contusions made a good recovery. Two of three patients with extensive bilateral frontal contusions deteriorated more than 24 hours after injury, and one died. Delayed deterioration is an important complication of extensive traumatic bifrontal contusions.

Diagnosis and management of delayed traumatic intracerebral haematomas

In a retrospective study of 888 consecutive patients with traumatic intracranial haematomas, we identified 23 (2.6%) who had developed a delayed intracerebral haematoma after admission to hospital. The initial CT scan within 48 h of injury had been abnormal in all 23 cases; a haematoma had been evacuated in eight (35%) and intracranial pressure (ICP) had been monitored in 14 (61%). A delayed intracerebral haematoma had been diagnosed by repeat CT scan between 4 h and 10 days later, and nine of these had been evacuated on clinical grounds. Patients with persistently elevated ICP were rescanned more quickly than those who deteriorated clinically or failed to improve. Seven patients (30%) died, and the main cause of death was severe primary brain damage. Overall outcome was better in this series than in other reported series of delayed haematomas. We conclude that delayed haematomas occur only when the initial CT scan has been abnormal, and that clinically important ones are uncommon. ICP monitoring offers earlier diagnosis, but it remains to be established that this affects outcome.

Can computed tomography be relied upon to detect skull fractures?

Skull fractures were detected on plain films in 63 of 100 consecutive head-injured patients admitted to a neurosurgical unit. On routine computed tomographic (CT) lateral scout films, only 58% of lateral fractures were detected and there was a false positive rate of 12%. None of the anterior or posterior fractures was seen. On the routine axial CT cuts only 22.5% of fractures were detected. When examined at bone window settings, 76% of vertical and 37.5% of oblique linear fractures were detected but none of the horizontal fractures. All comminuted and depressed fractures were demonstrated when the axial cuts were examined at bone window settings and in all but one case by the scanogram and at routine brain window settings. Basal fracture extent was better shown by axial CT than on plain films, especially at bone window settings. Recommendations are made regarding the use of CT in the detection of skull fractures.

CT demonstration of a 5th ventricle--a finding to KO boxers?

The reported prevalence of 5th ventricles based on air studies varies from 1-12% and ranges up to 60% as an autopsy finding. The prevalence of what is usually an incidental anomaly has not been determined by computed tomography (CT). 5th ventricles are however known to be more common in brain damaged boxers and with the introduction of compulsory CT scanning for certain boxers it is necessary to know what significance to attach to the finding of a cavum in these individuals. To ascertain the prevalence and morphology of 5th ventricles as detected by CT in the population, a thousand consecutive scans were analysed for the presence or absence of a 5th ventricle and other associated midline developmental abnormalities and correlations made with any pathology found. A 5th ventricle was present in 5.5% of the group and in most cases was less than 3 mm wide. An apparent association with other pathology was found only in patients under the age of 15. A 6th ventricle was found in 0.5% while a cavum velum interpositum was present in 9.5%. The isolated finding of a small 5th ventricle on the CT scan of a young active boxer almost certainly represents a persistent congenital anomaly of no significance.

Magnetic resonance imaging of acute subarachnoid hemorrhage

The feasibility, safety, and diagnostic value of magnetic resonance (MR) imaging versus computerized tomography (CT) scanning were compared in 30 patients with clinical evidence of subarachnoid hemorrhage. Subarachnoid blood was identified more often and more information was available about the site and source of the hemorrhage on MR imaging than on CT. Magnetic resonance imaging could be used safely both before and after the operation, provided that nonferromagnetic clips were used and that comprehensive monitoring and cardiorespiratory support were available. Postoperative studies showed that artifacts from metallic implants and from patient movement caused less image degradation on MR images than on CT scans.

Rhino-orbital-cerebral mucormycosis--a clinico-pathological report of two cases

Rhino-orbital-cerebral mucormycosis is an acute fungal infection of the oropharynx, paranasal sinuses, orbit and intracranial structures. It is rare, occurring mainly in diabetics in ketoacidosis. The clinical presentation is highly suggestive of the diagnosis. Current treatment has resulted in a greatly improved prognosis for survival and clinical awareness of this disease is important for early initiation of treatment with optimal effect. A clinico-pathological report of two cases is presented.

Invasive v non-invasive assessment of the carotid arteries prior to trans-sphenoidal surgery

Imaging studies in 47 patients who were to undergo trans-sphenoidal surgery were analysed with reference to the vascular structures in the parasellar region. The results of cavernous sinography, dynamic contrast enhanced Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) showed good correlation with each other and with the appearances found at operation. CT and MRI, both non-invasive investigations, are therefore reliable preliminary screening methods for identifying the small proportion of patients on whom other imaging techniques need to be performed.

Syringomyelia: cyst measurement by magnetic resonance imaging and comparison with symptoms, signs and disability

The severity and distribution of symptoms and signs in patients with syringomyelia is considered to be dependent on the longitudinal and transverse dimensions of the syrinx and it is thought that clinical examination can identify the extent of the cyst. Magnetic resonance imaging has made the anatomical localisation of intramedullary spinal lesions more exact and probably more specific than previous methods of investigation. Syrinx length, diameters, cyst:cord and cord:canal ratios have been studied in 12 patients with syringomyelia to assess whether the dimensions of the syrinx relate to the clinical findings. The length of syrinx appeared to be related to cyst diameter, cyst:cord and cord:canal ratios. Patients with a small syrinx tended to have a small cyst diameter, and small cyst:cord and cord:canal ratios. No significant relationship was found between muscle wasting or weakness, distribution of sensory loss, degree of disability or distress and the dimensions of the syrinx. These findings should be borne in mind when surgical management is being considered.

Do cerebral arteriovenous malformations increase in size?

Six patients are reported with cerebral arteriovenous malformations which have enlarged over follow up periods of from 4 to 20 years. The frequency of spontaneous enlargement is estimated to range from 0.2% to 2.8% per annum. This rate of enlargement should be considered when treatment options are reviewed in individual patients, and should be added to the risk of haemorrhage.

The prophylactic use of phenytoin during iopamidol contrast studies of the subarachnoid space

Contrast examinations of the subarachnoid space are associated with side effects including convulsions. Attention has been given to the prophylactic use of anticonvulsants. We describe a simple oral regimen using the established anticonvulsant phenytoin that can be administered to short-stay patients and that achieves effective serum and CSF concentrations. A preliminary account of this work was presented to the British Pharmacological Society in January 1984 in London.