Assessing the risk of stroke from neck manipulation: a systematic review.

BACKGROUND: Strokes, typically involving vertebral artery dissection, can follow cervical spinal manipulative therapy, and these types of stroke occur rarely. There is disagreement about whether a strong association between neck manipulation and stroke exists. An earlier systematic review found two relevant studies of association that used controls, which also discussed the limitations of the two papers. Our systematic review updates the earlier review, and aims to determine whether conclusive evidence of a strong association exists. METHODS: PRISMA guidelines for systematic reviews were followed, and the literature was searched using a strategy that included the terms 'neck manipulation' and 'stroke' from the PubMed, Embase, CINAHL Plus and AMED databases. Citations were included if they met criteria such as being case-control studies, and dealt with neck manipulation and/or neck movement/positioning. Papers were scored for their quality, using similar criteria to the earlier review. For individual criteria, each study was assigned a full positive score if the criterion was satisfied completely. RESULTS: Four case-control studies and one case-control study, which included a case- crossover design, met the selection criteria, but all of them had at least three items in the quality assessment that failed to be completely positive. Two studies were assessed to be the most robustly designed, one indicating a strong association between stroke and various intensities of neck movement, including manipulation, and the other suggesting a much reduced relative association when using primary care practitioners' visits as controls. However, potential biases and confounders render the results inconclusive. CONCLUSION: Conclusive evidence is lacking for a strong association between neck manipulation and stroke, but is also absent for no association. Future studies of association will need to minimise potential biases and confounders, and ideally have sufficient numbers of cases to allow subgroup analysis for different types of neck manipulation and neck movement.

Vertebral arteries and neck rotation: Doppler velocimeter interexaminer reliability.

The purpose of this study was to test the interexaminer reliability of Doppler ultrasound (US) velocimeter examination of vertebral arteries during contralateral cervical rotation. Vertebral arteries from 20 adults were insonated using a bidirectional Doppler velocimeter at the suboccipital portal (standard technique) and C2 transverse process level (new technique) during contralateral cervical rotation. The data obtained by two examiners, regarding persistence or major reduction in Doppler signals, were compared. There was 93% agreement between the data from the two examiners, and the kappa score was 0.78 at p = 0.05. These results provide evidence to support the interexaminer reliability of bidirectional Doppler velocimeter examination for the purpose of assessing the effects of contralateral rotation on vertebral artery blood flow.

Vertebral arteries and neck rotation: Doppler velocimeter and duplex results compared.

The purpose of this study was to test the validity of Doppler ultrasound (US) velocimeter examination of vertebral arteries during contralateral (to the opposite side) cervical rotation. Vertebral arteries from 20 subjects were insonated using a bidirectional Doppler velocimeter at the suboccipital portal (standard technique) and C2 transverse process level (new technique) during contralateral cervical rotation. The results, regarding persistence or major reduction in Doppler signals, were then compared with those from a colour-flow duplex US scanner using the same procedure. There was complete agreement between the combined suboccipital and C2 velocimeter results and those from the duplex scanner (k = 1.00 at p = 0.01): both sensitivity (n = 5) and specificity (n = 34) were 100%. This study provides evidence to support the validity of bidirectional Doppler velocimeter examination, by an experienced examiner, for the purpose of assessing the effects of contralateral rotation on vertebral artery blood flow.

Doppler studies comparing the effects of cervical rotation and lateral flexion on vertebral artery blood flow.

OBJECTIVE: To determine the effects of cervical contralateral rotation and cervical contralateral lateral flexion on vertebral artery blood flow velocity. DESIGN AND SETTING: A prospective study was performed at a private chiropractic clinic. PATIENTS: One hundred forty-eight patients had their vertebral arteries insonated as part of the premanipulative screening procedure. INTERVENTION: The vertebral arteries were insonated using a Doppler ultrasound velocimeter in the neutral position, during cervical contralateral rotation to the end range and during contralateral lateral flexion to the end range. MAIN OUTCOME MEASURES: Persistence or loss of Doppler signals from the vertebral arteries during neck movement was recorded. RESULTS: Of 280 vertebral arteries able to be insonated, 5% (0 < 5% < 9% at p = .99 confidence interval) had Doppler signals that stopped during contralateral rotation. Doppler signals from all 187 vertebral arteries tested during lateral flexion persisted, whereas 6 (3.2%) of this group of arteries had signals that ceased during contralateral rotation. CONCLUSION: Vertebral artery Doppler signals from patients can be greatly reduced or extinguished during contralateral cervical rotation. However, this is an unusual finding. The same phenomenon was not observed during contralateral cervical lateral flexion, which suggests that there may be less mechanical stress placed on the vertebral artery during lateral flexion.

Are the effects of local joint movement on blood flow limited to the vertebral and internal carotid arteries? Doppler studies of the ulnar artery.

OBJECTIVE: To determine what effect wrist extension has on ulnar artery blood flow. DESIGN AND SETTING: This is a descriptive study performed at a private chiropractic clinic. SUBJECT SELECTION: Sixty-three ulnar arteries were examined from thirty-two volunteers, 15 men and 17 women, whose ages ranged from 21-75 yr. Only wrists that were asymptomatic and freely mobile were candidates for ulnar artery examination. INTERVENTION: The arteries were insonated approximately 2 cm proximal to the pisiform bone using a continuous-wave Doppler flow meter in the neutral position and during passive wrist extension to the limit with the fingers straightened. MAIN OUTCOME MEASURES: The persistence or loss of Doppler signals. RESULTS: Doppler signals from 83% (0.99 confidence interval: 68% < p < 93%) of arteries stopped. In 4% of vessels, the signals were markedly reduced; in 13%, they remained apparently unchanged. CONCLUSION: Blood flow in ulnar arteries can be severely restricted during wrist extension. By using Doppler ultrasound, the ulnar artery may provide a good model of local joint movement effects on arterial blood flow.

The aconitase of Escherichia coli: purification of the enzyme and molecular cloning and map location of the gene (acn).

The aconitase of Escherichia coli was purified to homogeneity, albeit in low yield (0.6%). It was shown to be a monomeric protein of Mr 95,000 or 97,500 by gel filtration and SDS-PAGE analysis, respectively. The N-terminal amino acid sequence resembled that of the Bacillus subtilis enzyme (citB product), but the similarity at the DNA level was insufficient to allow detection of the E. coli acn gene using a 456 bp citB probe. Phages containing the acn gene were isolated from a lambda-E. coli gene bank by immunoscreening with an antiserum raised against purified bacterial enzyme. The acn gene was located at 28 min (1350 kb) in the physical map of the E. coli chromosome by probing Southern blots with a fragment of the gene. Attempts to locate the gene using the same procedure with oligonucleotide probes encoding segments of the N-terminal amino acid sequence were complicated by the lack of probe specificity and an inaccuracy in the physical map of Kohara et al. (Cell 50, 495-508, 1987). Aconitase specific activity was amplified some 20-200-fold in cultures transformed with pGS447, a derivative of pUC119 containing the acn gene, and an apparent four-fold activation-deactivation of the phagemid-encoded enzyme was observed in late exponential phase. The aconitase antiserum cross-reacted with both the porcine and Salmonella typhimurium (Mr 120,000) enzymes.

Radiation protection aspects of repairing a highly contaminated tritium cold box.

Radiation protection aspects of modifying a system exposed to tritium gas are discussed. This paper includes a brief discussion of the tritium gas and tritium surface contamination hazards associated with a facility designed to detritiate heavy water. Also described are the protective equipment, dosimetry, instrumentation, contamination control, and decontamination procedures used during welding of tubes that have been exposed to almost pure tritium gas. Absorption of the tritium gas on materials resulted in exposures to high peak concentrations of tritium oxide and high levels of tritium surface contamination (TSC).

Effects of idazoxan on catecholamine systems in rat brain.

Experiments have been performed to assess the potency of idazoxan (RX 781094) at alpha and beta-adrenoceptors and dopamine receptors and on catecholamine uptake processes in rat brain. The effects of idazoxan on the turnover rates of noradrenaline and dopamine have been determined. Radioligand binding studies with cerebral cortex membranes have demonstrated that idazoxan exhibits 46-fold selectivity for alpha 2-adrenoceptors labelled by (3H)-idazoxan (Mean Ki +/- S.E.M. = 3.1 +/- 0.4 nM) compared with alpha 1-adrenoceptors labelled by (3H)-prazosin (Mean Ki +/- S.E.M. = 142 +/- 27 nM). Under the same conditions, yohimbine showed 6-fold selectivity for alpha 2-adrenoceptors. Idazoxan had low affinity for beta-adrenoceptors labelled by (3H)-dihydroalprenolol (IC50 value greater than 10 microM), for dopamine receptors labelled by (3H)-domperidone (IC50 value greater than 20 microM), for the (3H)-noradrenaline uptake site in rat hypothalamus (IC50 = 31 microM) and for the (3H)-dopamine uptake site in rat striatum (IC50 value approximately 800 microM). In rats treated with alpha-methyl-p-tyrosine, idazoxan (10-80 mg/kg, po) produced a marked increase (63% at 10, 217% at 20 mg/kg, po) in the apparent rate of turnover of noradrenaline in rat cortex/striatum, without affecting the rate of turnover of dopamine. This was in contrast to yohimbine (5-20 mg/kg, po) which increased the turnover rates of both catecholamines. In the absence of alpha-methyl-p-tyrosine, idazoxan (5-40 mg/kg, po) produced a dose related increase in the MHPG concentration and a small (20-30%) reduction in the steady state concentration of NA; the duration of the reduction was dose-related. DA steady state concentrations were unaffected. Idazoxan is a new selective alpha 2-adrenoceptor antagonist which should prove a valuable investigative tool in neurochemical studies and which may be a useful clinical agent in the management of the affective disorders.

Effect of metronidazole on the C3H/HeJ mouse and growth of the C3HBA mammary adenocarcinoma.

Metronidazole (0.6 mg/gm) was injected intraperitoneally at 12 hour intervals for 10 days into C3H/HeJ mice with established C3HBA mammary adenocarcinomas. Tumor growth, total white cell count and body weight were decreased by 3 days. Heart rate and rectal temperature were depressed most following the initial injections but were less depressed by 10 days. Hemoglobin and hematocrit were not changed. Plasma assays of total protein, uric acid, bilirubin, alkaline phosphatase and calcium were not affected. It was not possible to separate the tumors treated with metronidazole from control tumors, based on cellular differences. Blood vessels in most of the tumors in the drug treated animals were larger and appeared engorged with blood.