The refractory period of transmission is impaired in axonal Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is classified as acute motor axonal neuropathy (AMAN) or acute inflammatory demyelinating polyneuropathy (AIDP). Motor nerve conduction block is frequently found in both subtypes of GBS. To compare patterns of conduction block and the safety factor for impulse transmission in AMAN and AIDP, pairs of supramaximal stimuli at intervals of 1-5 ms were delivered to stimulate the median nerve at the wrist. At the 2- and 3-ms intervals, compound muscle action potentials (CMAPs) to the second stimulus were significantly smaller in AMAN patients (n = 7) than in normal subjects (n = 10) and AIDP patients (n = 6). Over 4 weeks from onset, the amplitude of both conditioned and unconditioned CMAPs returned toward normal, consistent with improvement in the safety factor for impulse transmission. The refractory period of transmission is impaired in AMAN, and the site of transmission failure is likely to be the motor nerve terminals. In addition to axonal degeneration, the critically but reversibly reduced safety factor is important in the pathophysiology of AMAN, and consistent with the rapid resolution of distal conduction block often seen in AMAN patients.     

Cerebral blood flow and vasodilatory capacity in anemia secondary to chronic renal failure

BACKGROUND: Our previous study reported that cerebral oxygen extraction fraction (OEF) increased in hemodialysis patients with anemia. The increased OEF suggests that the cerebral vasodilatory capacity might be impaired in these patients. To clarify this issue, we measured the CO2 response in patients with anemia secondary to chronic renal failure (CRF) using positron emission tomography (PET). METHODS: Ten anemic patients with CRF (6 females and 4 males) and 6 age-matched normal controls were studied. The underlying diseases of CRF were glomerulonephritis in 8 patients, systemic lupus erythematosus (SLE) in one patient, and hypertension in one patient; in this cohort, 5 patients were on hemodialysis treatment and the remaining 5 patients were in a pre-hemodialysis state. The cerebral blood flow (CBF) was measured by the O-15 H2O bolus injection method with each patient in a resting state and during 5% CO2 inhalation. The CO2 response was estimated as the percentage change of CBF per 1 mm Hg change of PaCO2. RESULTS: The CO2 response was significantly attenuated in anemic patients with CRF in comparison to the normal controls, and it inversely correlated with the severity of anemia. There was no significant difference in the CO2 response between the hemodialysis and pre-hemodialysis patients. The CO2 response significantly correlated with CBF and the cerebral metabolic rate for oxygen (CMRO2) at rest, however, it did not correlate with OEF and cerebral blood volume (CBV). CONCLUSIONS: The present study revealed the existence of a reduced cerebral vasodilatory capacity in anemic patients with CRF, suggesting that chronic hypoxic brain damage might play a role in the impaired cerebrovascular response to CO2.     

Right atrial lipoma with calcification in ascending aorta; report of a case

A 67-year-old male was diagnosed to have a right atrial tumor by echocardiography incidentally. Computed tomography (CT) indicated a mass which showed very low radiodensity and magnetic resonance imaging (MRI) [T1-weighted] showed the high signal intensity of tumor. We could predict the mass as lipoma. Tumor removal was performed under cardio-pulmonary bypass and under ventricular fibrillation because of the calcification in ascending aorta. Microscopically the tumor was consisted of mature adipose tissue. The postoperative course was uneventful. Cardiac lipomas are rare tumors. CT and MRI are better investigations for preoperative diagnosis. After surgical excision the prognosis is excellent.     

Distribution patterns of demyelination correlate with clinical profiles in chronic inflammatory demyelinating polyneuropathy.

BACKGROUND: Chronic inflammatory demyelinating polyneuropathy (CIDP) is a heterogeneous disorder having a wide clinical range, and is characterised by multifocal demyelination that can involve the distal nerve terminals, intermediate nerve segments, and nerve roots. OBJECTIVE: To investigate whether the distribution patterns of demyelination along the course of the nerve correlate with clinical profiles in patients with CIDP. METHODS: Motor nerve conduction studies were carried out on 42 consecutive patients. According to the physiological criteria for demyelination, the presence of a demyelinative lesion was determined in the distal nerve segments (distal pattern) or intermediate nerve segments (intermediate pattern), or in both (diffuse pattern). The serum concentration of tumour necrosis factor (TNF)-alpha was measured by immunoassay. RESULTS: Patients were classified as having a distal (n=10), intermediate (n=13), or diffuse (n=15) pattern, or were unclassified (n=4). Patients with the distal or diffuse pattern had common clinical features such as subacute onset, symmetric symptoms, and weakness involving proximal as well as distal muscles. Patients with the distal pattern had a good response to treatment and a monophasic remitting course, but the diffuse pattern was associated with a treatment dependent relapsing course, reflecting longer disease activity. The serum TNF-alpha concentrations increased only in the "diffuse" subgroup of patients, and this might be associated with breakdown of the blood-nerve barrier and therefore, involvement of the intermediate segments. The intermediate pattern was characterised by a chronic course, asymmetric symptoms, less severe disability, and refractoriness to treatments. CONCLUSIONS: CIDP consists of subtypes with varying predilections for lesions along the course of the nerve. The distribution patterns of conduction abnormalities may be useful in the prediction of outcome of patients with CIDP.     

Abnormalities of axonal excitability are not generalized in early multifocal motor neuropathy

The clinical and neurophysiological features of multifocal motor neuropathy (MMN) indicate selective involvement of motor axons, but pathological abnormalities in sensory axons suggest a more widespread disease process. The present study was undertaken to determine whether the focal abnormalities are associated with widespread subclinical abnormalities in motor axons. Threshold tracking was used to measure excitability properties (stimulus-response curves, strength-duration properties, recovery cycle, and threshold electrotonus) of the median nerve in five patients with MMN with lesions proximal to the site of testing. Patients were compared with 25 healthy controls. The changes in excitability indices were similar to those in controls, and in one patient there was no alteration after treatment with intravenous gammaglobulin. In this patient, indices of axonal excitability were also measured before, during, and after ischemia of the arm for 10 min. Again no differences were detected. This study provides no evidence for a generalized subclinical abnormality in MMN, at least when disease duration is less than 6 years.     

Increased occupancy of dopamine receptors in human striatum during cue-elicited cocaine craving.

In all, 19 research subjects, with current histories of frequent cocaine use, were exposed to cocaine-related cues to elicit drug craving. We measured the change of occupancy of dopamine at D2-like receptors with positron emission tomography (PET) and inferred a change of intrasynaptic dopamine (endogenous dopamine release), based on the displacement of radiotracer [(11)C]raclopride. Receptor occupancy by dopamine increased significantly in putamen of participants who reported cue-elicited craving compared to those who did not. Further, the intensity of craving was positively correlated with the increase in dopamine receptor occupancy in the putamen. These results provide direct evidence that occupancy of dopamine receptors in human dorsal striatum increased in proportion to subjective craving, presumably because of increased release of intrasynaptic dopamine.     

Nuclear medicine for general radiologists: clinical application of brain SPECT

Brain SPECT studies are used to evaluate the cerebral hemodynamic changes in cerebrovascular diseases and other neuro-psychiatric disorders. I-123 and Tc-99m labeled radiopharmaceuticals widely used for brain perfusion SPECT studies include I-123 IMP, Tc-99m HMPAO, and Tc-99m ECD. I-123 IMP is suitable for the quantitative evaluation of cerebral blood flow, while Tc-99m HMPAO and Tc-99m ECD have problems owing to the non-linearity between cerebral radioactivity and cerebral blood flow. In addition, Tc-99m ECD does not show cerebral blood flow in the subacute phase of cerebral infarct or other conditions. Thus, it is important to consider the characteristics of radiopharmaceuticals and the clinical aspect of brain lesions in the interpretation of brain perfusion SPECT images. In this review, some useful information on brain perfusion SPECT is presented mainly as it relates to the cerebrovascular diseases.     

Effect of mental stress on left ventricular ejection fraction and its relationship to the severity of coronary artery disease

To evaluate the relationship between the mental stress-induced decrease in left ventricular ejection fraction (LVEF) and the severity of exercise-induced ischaemia, 20 patients with stable coronary artery disease (CAD) underwent radionuclide ventriculography during mental stress testing and stress myocardial perfusion single-photon emission tomography (SPET). We also examined whether changes in haemodynamic and neurohormonal parameters are related to changes in LVEF during mental stress. The LVEF decreased from 54.8% +/- 17.7% to 49.8% +/- 16.2% with mental stress (P < 0.0005). Ten of the 20 patients (50.0%) had a > or = 5% decrease in LVEF The remaining ten patients had no or a <5% decrease in LVEF There was a significant correlation between the change in LVEF during mental stress and the size of the reversible defect on stress myocardial perfusion SPET (r = -0.80, P < 0.0005), with close regional correspondence (75% identical). This correlation was less strong in the 12 patients with a total defect score at rest of <10 (r = -0.69, P = 0.014) than in the eight patients with a total defect score at rest of > or = 10 (r = -0.94, P = 0.001). The changes in blood pressure and heart rate were not significantly correlated with the change in LVEF, but the percent change in adrenaline concentration correlated with the change in LVEE It is suggested that mental stress impairs systolic function by inducing transient myocardial ischaemia. The effect of neurohormonal responses during mental stress on LV systolic function may also be important in patients with CAD.     

The stem cell factor/c-kit receptor pathway enhances proliferation and invasion of pancreatic cancer cells

Background  

The transmembrane protein c-kit is a receptor tyrosine kinase (KIT) and KIT is expressed in solid tumors and hematological malignancies such as gastrointestinal stromal tumor (GIST), small-cell lung cancer and chronic myelogenous leukemia (CML). KIT plays a critical role in cell proliferation and differentiation and represents a logical therapeutic target in GIST and CML. In pancreatic cancer, c-kit expression has been observed by immunohistochemical techniques. In this study, we examined the influence of c-kit expression on proliferation and invasion using five pancreatic cancer cell lines. In addition, the inhibitory effect of imatinib mesylate on stem cell factor (SCF)-induced proliferation and invasion was evaluated. Finally, we also analyzed KIT and SCF expression in pancreatic cancer tissues using immunohistochemistry and correlated the results with clinical features.