Are all spinal segments equal: intrinsic membrane properties of superficial dorsal horn neurons in the developing and mature mouse spinal cord

Neurons in the superficial dorsal horn (SDH; laminae I-II) of the spinal cord process nociceptive information from skin, muscle, joints and viscera. Most of what we know about the intrinsic properties of SDH neurons comes from studies in lumbar segments of the cord even though clinical evidence suggests nociceptive signals from viscera and head and neck tissues are processed differently. This ‘lumbar-centric' view of spinal pain processing mechanisms also applies to developing SDH neurons. Here we ask whether the intrinsic membrane properties of SDH neurons differ across spinal cord segments in both the developing and mature spinal cord. Whole cell recordings were made from SDH neurons in slices of upper cervical (C2-4), thoracic (T8-10) and lumbar (L3-5) segments in neonatal (P0-5) and adult (P24-45) mice. Neuronal input resistance (R(IN)), resting membrane potential, AP amplitude, half-width and AHP amplitude were similar across spinal cord regions in both neonates and adults (∼100 neurons for each region and age). In contrast, these intrinsic membrane properties differed dramatically between neonates and adults. Five types of AP discharge were observed during depolarizing current injection. In neonates, single spiking dominated (∼40%) and the proportions of each discharge category did not differ across spinal regions. In adults, initial bursting dominated in each spinal region, but was significantly more prevalent in rostral segments (49% of neurons in C2-4 vs. 29% in L3-5). During development the dominant AP discharge pattern changed from single spiking to initial bursting. The rapid A-type potassium current (I(Ar)) dominated in neonates and adults, but its prevalence decreased (∼80% vs. ∼50% of neurons) in all regions during development. I(Ar) steady state inactivation and activation also changed in upper cervical and lumbar regions during development. Together, our data show the intrinsic properties of SDH neurons are generally conserved in the three spinal cord regions examined in both neonate and adult mice. We propose the conserved intrinsic membrane properties of SDH neurons along the length of the spinal cord cannot explain the marked differences in pain experienced in the limbs, viscera, and head and neck.

Weight changes in breast cancer survivors who received adjuvant antiestrogen therapy

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Background: Antiestrogen therapy has dramatically improved breast cancer survival rates but weight gain may be problematic. Studies evaluating antiestrogen therapy-related weight gain have yielded mixed results. Our primary objective was to evaluate weight changes in female breast cancer survivors (BCS) who received adjuvant anti-estrogen therapy for stage 0-III breast cancer. Methods: A retrospective chart review was conducted to evaluate weight changes in female chemo naive BCS receiving anti-estrogen therapy. Weights at initiation of hormonal therapy and at 6, 12, 24, and 36 months of follow-up were recorded. Median weight changes were calculated and were compared with Wilcoxon's signed rank test or the Kurskall-Wallis test. Results: A total of 622 women were included. The majority were white (77%), had stage I disease (78%), and were postmenopausal (82%). The median age at diagnosis was 59 years (range, 26–87). Median weight at initiation of hormonal therapy among premenopausal women was 65 kg (range 45.4–122.9). Median weight gain in this group was 0.4 kg (p = 0.009), 0.7 kg (p = 0.013), 1.9 kg (p = 0.0001), and 2.4 kg (p < 0.0001) at 6, 12, 24, and 36 months respectively. Among post-menopausal women, median weight at initiation of therapy was 71.7 kg (range 41.5–152.0) and median weight gain was 0.5 kg (p < 0.0001), 1 kg (p < 0.0001), 0.85 kg (p = 0.001), and 0.85 kg (p = 0.004) at 6, 12, 24, and 36 months respectively. Premenopausal patients had significantly more weight gain at 24 (p = 0.041) and 36 months (p = 0.005), as compared to postmenopausal patients. Among premenopausal women, 110/111 were treated with tamoxifen. Among post-menopausal women (n = 510), hormonal therapy was as follows: unknown n = 28 patients, tamoxifen n = 312, and AI n = 170. Overall, BCS treated with tamoxifen vs an AI had significantly more weight gain at 24 (p = 0.003) and 36 months (p = 0.009). Conclusions: Premenopausal patients are at higher risk for weight gain than postmenopausal patients. Further prospective research is warranted examining weight gain as a long-term side effect of anti-estrogen therapy in BCS.

No significant financial relationships to disclose.

Prognostic role of cardiac troponin I after percutaneous coronary intervention in stable coronary disease

OBJECTIVE

To assess the role of cardiac troponin I (cTnI) in predicting outcome after percutaneous coronary intervention (PCI).

METHODS AND RESULTS

cTnI was measured immediately before and at 6, 14, and 24 hours after PCI in 316 consecutive patients with stable symptoms and native coronary artery disease. The study end point was the occurrence of major adverse cardiac events (MACE) at 30 days and at 18 months after PCI: death, Q wave myocardial infarction (MI), or repeat revascularisation in hospital. Postprocedural cTnI increased in 31% of patients. The cumulative MACE rate at 18 months was 25% (17.7% due to repeat PCI procedures). There was a significant association between postprocedural cTnI increase and death, Q wave MI, or both (odds ratio (OR) 3.28, 95% confidence interval (CI) 1.7 to 6.4, p = 0.01). Post-PCI cTnI increase had a positive predictive value (PPV) for adverse events at 18 months of 0.47 and a negative predictive value (NPV) of 0.96 (OR 18.9, 95% CI 9.7 to 37, p < 0.0001). The presence of both a postprocedural cTnI rise and a procedural angiographic complication gave a PPV for adverse events of 0.69 and an NPV of 0.92 (OR 22.6, 95% CI 2.6 to 68.6, p = 0.0005).

CONCLUSIONS

cTnI increased post-procedurally in one third of this stable patient population undergoing elective PCI and was independently and significantly predictive of an increased risk of adverse events at 18 months, predominantly in the form of repeat PCI.

A comparison of three screw types for unicortical fixation in the lateral mass of the cervical spine

STUDY DESIGN

In vitro comparison of three different screws for unicortical fixation in lateral masses of the cervical spine.

OBJECTIVES

To compare the axial load-to-failure of cervical lateral mass screws and their revision screws in a cadaveric model.

SUMMARY OF BACKGROUND DATA

Lateral mass screws are used for posterior fixation of the cervical spine. Risks to neurovascular structures have led many surgeons to advocate unicortical application of these screws, although fixation strength may vary with screw design.

METHODS

Screws from three posterior cervical fixation systems were used: Axis, Starlock/Cervifix, and Summit. Tested were 3.5-mm cancellous screws, along with revision screws for each system. The C3-C6 vertebrae from three cadaveric specimens were fixed with screws inserted into the lateral masses at a depth of 10 mm with 30 degrees cephalad and 20 degrees lateral angulation. Coaxial pullout force was recorded for each primary and revision screw.

RESULTS

Axial load-to-failure (mean +/- SD) of the screws was 459 +/- 60 N for Axis screws, 423 +/- 78 N for Starlock screws, and 319 +/- 97 N for Summit screws. The Axis and Starlock screws were significantly stronger than Summit screws (P = 0.017 and P = 0.067, respectively). The load-to-failure of revision screws was much lower than that of primary screws (Axis 54%, Starlock 56%, Summit 63% of the primary screw), without significant difference between screw types.

CONCLUSIONS

The Axis and Starlock screws resisted significantly greater axial load-to-failure than did the Summit screws. For all three systems, the revision screws could not restore the load-to-failure of the primary screw in this model. The tested unicortical screws had a consistently higher load-to-failure than those previously tested under similar conditions, suggesting that currently available screws may be superior to those previously tested.

Comparison of cardiac troponin T and I and CK-MB for the detection of minor myocardial damage during interventional cardiac procedures

A number of cardiac interventional procedures are available for the treatment of angina, including percutaneous transluminal coronary angioplasty (PTCA), stent insertion and rotational atherectomy (RA). Variable degrees of myocardial cell injury during PTCA and stent insertion have been observed, based on rises in creatine kinase MB isoenzyme (CK-MB) and cardiac troponin T (cTnT) 6-24 h post-procedure. As there are many variations in technique within each procedure it would be helpful to be able to determine objectively the degree of myocardial damage in order to optimize technique. We measured CK-MB, cTnT and cardiac troponin I (cTnI) to ascertain which is the most sensitive marker for minor myocardial damage in this setting. Blood samples were taken both before and 6, 14 and 24h after the procedure in 109 patients (77 men) with angina, 42 of whom had unstable angina. Of the 109 patients, 86 had a stent inserted (21 as a primary stent), nine had PTCA, eight had RA and six intracoronary brachytherapy. Using the manufacturers' recommended cut-offs--CK-MB 4 microg/L, cTnI and cTnT 0.1 microg/L--five patients were excluded from further analysis as all three markers were raised pre-procedure. Post procedure all three markers were in agreement for 68 patients (44 all normal, 24 all raised). Overall, CK-MB was raised in 28 patients, cTnT in 38 and cTnI in 58. In 19 patients CK-MB and cTnT were normal, but cTnI was raised (15 between 0.11 and 0.30 microg/L). cTnI was the most sensitive indicator of minor myocardial damage, but at the recommended cut-off of 0.1 microg/L may be overly sensitive. We await the results of our follow-up study to determine the clinical implications of these small rises in cTnI.

Occult ligamentous injury of the cervical spine

Evaluating the cervical spine for injury is an essential part of the assessment of a traumatized patient. Clinical examination and radiographs are the traditional techniques used for this evaluation. Often, however, a reliable clinical examination is not possible because of head injury, altered mental status, or "distracting" injuries. In such cases, cervical spine injury that is not apparent on radiographs may be missed. This case report illustrates a purely ligamentous cervical spine injury resulting in cervical instability. We describe our method of screening for and evaluating these types of injuries using physician-controlled stretch, flexion, and extension examination under fluoroscopy.

Brainwashing and battering fatigue. Psychological abuse in domestic violence

Intimate partner violence occurs often in the United States; it involves an interrelated combination of physical, sexual, and psychological abuse, usually directed against women. The psychological aspect deserves special attention because victims who lose their independence, self-esteem, and dignity tend to remain in abusive situations. The abuse is perpetrated by a domestic partner to maintain power and control in the relationship. To assert control, the abuser uses "brainwashing tactics" similar to those used on prisoners of war, hostages, or members of a cult. Common features of brainwashing include isolation, humiliation, accusation, and unpredictable attacks. The abusive environment produces real and anticipated fear, which contributes to the battered woman's belief that her situation is hopeless and that she must depend on her abuser. She develops coping strategies to deal with her oppressive environment, but eventually exhibits symptoms of "battering fatigue," similar to the battle fatigue of soldiers in combat who, like battered women, live in fear of being killed or severely injured. Recognizing the state of mind of these women can help us understand why it is difficult for them to flee their traumatic environment and why they may resort to suicide or homicide. For healthcare providers to screen and treat their patients adequately, it is imperative that they appreciate the complex and devastating psychological aspects of domestic violence.

Risk of cancer of the breast after legal abortion during first trimester: a Swedish register study

An increase in induced abortions in Sweden has been accompanied by an increase in the incidence of breast cancer of about 40% in women aged 20-44. To assess whether the apparent risk is real the risk of breast cancer was investigated in practically all Swedish women with a history of a legal abortion in the first trimester before the age of 30 during 1966-74 (n = 49,000). The cohort was followed up in the Swedish cancer register to identify cases of breast cancer diagnosed more than five years after the abortion until the end of 1984. The number of observed cases of breast cancer was 65 compared with an expected number of 84.5, estimated from the contemporary Swedish population with due consideration to age, giving a relative risk of 0.8 (95% confidence interval 0.58 to 0.99). Contrary to most earlier reports, this study did not indicate any overall increased risk of breast cancer after an induced abortion in the first trimester in young women.