Gadolinium Enhancement of Atherosclerotic Plaque in the Middle Cerebral Artery: Relation to Symptoms and Degree of Stenosis

BACKGROUND AND PURPOSE:High-resolution MR imaging can depict intracranial arterial atherosclerotic plaques. Our aim was to evaluate the relationship between the degree of enhancement of MCA plaques on contrast-enhanced high-resolution MR imaging and ischemic stroke and stenosis severity.MATERIALS AND METHODS:This study enrolled 36 patients diagnosed with moderate-to-severe atherosclerotic MCA stenosis. A contrast-enhanced T1-weighted volume isotropic turbo spin-echo acquisition sequence was acquired for assessing plaque enhancement. Plaque-to-CSF contrast ratio was calculated after the signal intensity of plaques at the stenotic segment was measured. Univariate comparison and multivariate logistic regression analyses were performed for symptomatic and asymptomatic groups to assess the relationship between symptomatic stenosis and independent variables, including plaque-to-CSF contrast ratio, degree of stenosis, and clinical risk factors. Plaque-to-CSF contrast ratio was compared between the moderate and severe stenosis groups.RESULTS:Twenty-one patients had symptomatic MCA stenosis, and 15 had asymptomatic stenosis. The plaque-to-CSF contrast ratio was significantly higher in the symptomatic group than in the asymptomatic group (63.6 ± 10.6% versus 54.1 ± 13.5%, respectively; P < .05). The degree of stenosis also differed significantly between the 2 groups (P < .05). Multivariate analysis revealed that the degree of stenosis was the only independent predictor of ischemic stroke symptoms. The plaque-to-CSF contrast ratio of severe stenosis was significantly higher than that of moderate stenosis (66.8 ± 8.7% versus 55.9 ± 12.8%, respectively; P < .05).CONCLUSIONS:Plaque enhancement was significantly higher in patients with symptomatic plaques and may have been affected by the degree of stenosis. A difference in plaque enhancement according to the degree of stenosis has implications for understanding the development of intracranial atherosclerotic plaques.

Intracranial atherosclerotic disease (ICAD) is now considered the most common cause of ischemic stroke worldwide.^1,2 It is a challenge for many clinicians to assess vulnerable regions of intracranial artery stenosis by using in vivo methods. As a result, there has been a recent increase in interest in techniques to depict the state of the intracranial artery wall by using high-resolution MR imaging (HR-MRI) with a high magnetic field.Inflammation increases vulnerability to plaque rupture by facilitating neovascularization within the plaque and increasing endothelial permeability. Strong contrast enhancement of arterial plaques on MR imaging suggests the presence of a vascular supply and increased endothelial permeability, which facilitate the entry of contrast agents from the blood plasma.^3–6 Several studies have shown that gadolinium (Gd) enhancement of extracranial carotid plaques on MR imaging is associated with plaque neovascularization or increased levels of serum inflammatory markers such as C-reactive protein.^7–10 An association between carotid plaque enhancement and clinical symptoms has been observed in several recent investigations by using Gd-enhanced MR imaging.^9,11In contrast to the numerous investigations that have been performed on the carotid artery, only a few studies performed on a small number of patients have focused on the clinical significance of Gd enhancement of plaques in the setting of ICAD.^12–14 These studies identified a significant association between plaque enhancement on ICAD and ischemic events. However, there is some debate about whether contrast enhancement is a good predictor of intracranial stenosis in ischemic stroke. Klein et al¹⁵ expressed doubt about the relationship between plaque enhancement and stroke because they found stationary enhancement of basilar plaques regardless of the time elapsed after an acute event.Several factors are known to be related to ischemic stroke in the territory of the stenotic segment.^16,17 In particular, the severity of stenosis is a strong predictor of subsequent stroke in the territory of the symptomatic stenotic artery. To assess whether Gd enhancement of plaques at the stenotic segment is valuable as a predictor of ischemic stroke, an unbiased assessment of the influence of other independent factors, including the degree of stenosis, should be undertaken. Thus, the purpose of this study was to evaluate whether Gd enhancement of plaques in ICAD is associated with clinical symptoms, independent of other predictive factors for ischemic stroke risk.     

Value of Perfusion Weighted Magnetic Resonance Imaging in the Diagnosis of Supratentorial Anaplastic Astrocytoma

We report perfusion weighted imaging (PWI) findings of nonenhanced anaplastic astrocytoma in a 30-year-old woman. Brain magnetic resonance imaging showed a nonenhanced brain tumor with mild peritumoral edema on the right medial frontal lobe and right genu of corpus callosum, suggesting a low-grade glioma. However, PWI showed increased relative cerebral blood volume, relative cerebral blood flow, and permeability of nonenhanced brain tumor compared with contralateral normal brain parenchyma, suggesting a high-grade glioma. After surgery, final histopathological analysis revealed World Health Organization grade III anaplastic astrocytoma. This case demonstrates the importance of PWI for preoperative evaluation of nonenhanced brain tumors.     

Water-deprivation-induced expression of neuronal nitric oxide synthase in the hypothalamic paraventricular nucleus of rat

This study was conducted to define the molecular mechanism by which dehydration induces expression of neuronal nitric oxide synthase (nNOS) in the hypothalamic paraventricular nucleus (PVN). Rats were deprived from water for 48 hr and then sacrificed immediately or 1 hr after ad libitum access to water. Another group of rats had free access to food and water and was included as euhydrate control group. The PVN sections fixed with 4% paraformaldehyde were processed for nNOS immunohistochemistry and NADPH-diaphorase (NADPH-d)/pCREB or NADPH-d/c-Fos double staining. nNOS-ir neurons significantly increased with water deprivation and decreased with rehydration, both in the posterior magnocellular (pM)- and the medial parvocellular (mP)-PVN. Most NADPH-d histostained neurons in the PVN appeared to exhibit pCREB-ir as well. Water deprivation markedly increased, and rehydration decreased, NADPH-d/pCREB neurons both in the pM- and in the mP-PVN. Gel shift assay demonstrated that dehydration may promote CREB binding to nNOS promoter in the PVN neurons. Significant amounts of NADPH-d-stained neurons in the PVN of water-deprived rats (67-68% in both the mP and the pM) exhibited c-Fos-ir. NADPH-d/c-Fos neurons in the pM-PVN were increased by water deprivation but not changed by rehydration. NADPH-d/c-Fos double-stained neurons in the mP-PVN did not significantly change depending on different water conditions. These results suggest that pCREB may play a role in dehydration-induced nNOS gene expression in the PVN neurons, and c-Fos might not be implicated in the regulatory pathway.     

Surgical Outcome of Spinal Cord Hemangioblastomas

Objective

Spinal cord hemangioblastomas are rare tumors. Despite their benign, slow-growing nature, they can cause severe neurological consequences. The purpose of this study was to evaluate variable factors, including clinical features, tumor findings, the extent of resection, and its recurrence or progression, which determine postoperative functional outcomes.

Methods

This study included sixteen patients at our institute who underwent microsurgical resection for sporadic spinal intramedullary hemangioblastomas and spinal intramedullary hemangioblastomas associated with von Hippel-Lindau (VHL) disease, between June 2003 and March 2012.

Results

A total of 30 operations were performed. Total resection (TR) of the tumor was achieved in 10 patients, and subtotal resection (STR) was achieved in 6. Postoperatively, the initial presenting symptoms were improved in 18.7% of the patients and were unchanged in 56.3%, but 25% were worse. Stable postoperative neurological functions were found in 83% of patients with preoperative McCormick grade I, and TR was achieved in 75% of these patients. In the STR group, poorer neurological status was observed in one patient, despite multiple operations. There were no poorer outcomes in the four cases of VHL disease. Various factors were analyzed, but only a correlation between the pre- and postoperative neurological status was verified in the TR-group patients.

Conclusion

Preoperative focal neurological impairment and meticulous microsurgical manipulation may be predictors of favorable outcomes for solitary hemangioblastomas. In addition, the preservation of function is more important than the extent of resection in VHL disease.     

A Clinical,Microbiological, and Histopathologic Study of Trichostasis Spinulosa

Trichostasis spinulosa (TSS) is a relatively common follicular disorder that can occur on the face and trunk, especially in the interscapular area. Its cause remains unclear. We examined clinically 30 patients with TSS and follicular materials extracted from each patient were examined microscopically. Bacterial culture and skin biopsy were done in 12 and 10 patients, respectively. Periodic acid Schiff (PAS) and Brown-Brenn Gram stain were used for detection of pityrosporum (malassezia) and bacteria. The interscapular area (14/30), nose (8/30), and cheek (4/30) were common sites of TSS. Pityrosporum and bacteria in the extracted follicular material were found at the rates of 82.6% and 73.3%, respectively. In histologic examination, follicular hyperkeratosis and numerous vellus hairs enveloped within keratotic sheath were common features. Pityrosporum and bacteria were found at the rate of 70% in biopsied specimens on PAS and Brown-Brenn Gram stain. In bacterial culture, Propionibacterium acne was most commonly identified in 75% (9 out of 12 patients). Pityrosporum and bacteria, especially Propionibacterium acne, were commonly found in the extracted follicular material and biopsied specimens. Thus, they may be related to the induction of follicular hyperkeratosis with retention of vellus hairs, and we suggest that these microorganisms may be one of the possible etiologic factors of TSS.     

Fasting-induced down-regulation of NADPH-diaphorase in the magnocellular PVN of rats

In this study, we examined if glucocorticoids are required for the fasting-induced decrease of neuronal nitric oxide synthase (nNOS) in the magnocellular division of the paraventricular nucleus (PVN). Rats were adrenalectomized, subjected to 48 h of food deprivation with/without dexamethasone (5 mg/ kg, 4 subcutaneous injections with 12 h intervals), and the brain slices were processed for NADPH-diaphorase (NADPH- d) staining, a histochemical marker for nNOS in neuronal cells. In food deprived adrenalectomized rats, but not in free fed intact rats, dexamethasone significantly decreased NADPH-d staining in the magnocellular PVN. We previously reported that food deprivation decreases nNOS in the magnocellular PVN of intact rats. Thus, the present results together with our previous report suggest that although glucocorticoids are required for fasting-induced nNOS down-regulation in the magnocellular PVN, glucocorticoids may not be directly involved and some other molecular signals produced by food deprivation may play a pivotal role over glucocorticoid in the regulatory pathway for nNOS expression in this brain region.     

Effects of dextromethorphan on nocturnal behavior and brain c-Fos expression in adolescent rats.

Dextromethorphan, an antitussive widely available over-the-counter, is abused, mostly by teenagers at high doses. In our previous report, a high dose of dextromethorphan activated the midbrain dopamine neurons of adolescent rats. In the present study, we performed c-Fos immunohistochemistry in the dopaminergic terminal regions of adolescent rat brain after the intraperitoneal administration of dextromethorphan at different doses (0, 10, 20, and 40 mg/kg), and also examined the effects on nocturnal behavior. The results showed that dextromethorphan increased c-Fos expression dose dependently in the anterior cingulate cortex, caudate putamen, nucleus accumbens, and central amygdala. Significant ataxia occurred and both locomotor and rearing activity decreased immediately after the dextromethorphan injection. We conclude that the neurons in the reward pathway of the adolescent rat brain appear to be activated by a single injection of dextromethorphan, and that activation of this pathway by dextromethorphan may correlate with the behavioral effects and abuse potential of the drug.     

Magnetic resonance findings in two episodes of repeated cerebral fat embolisms in a patient with autologous fat injection into the face

We report magnetic resonance image (MRI) and magnetic resonance spectroscopy (MRS) findings in a patient of cerebral fat embolism (CFE) occurred in a 26-year-old woman after an autologous fat injection into the face. After initial neurologic symptom onset, MRI and MRS data were obtained two times to investigate repeated CFE. We obtained the MRS data in the two different time intervals and two different echo times to compare the lesions with normal brain parenchyma. The results of MRS data showed that a decrease in N-acetyl-aspartate, an increase in lactate and a very high early peak of free lipids between 0.9 and 1.4 ppm were obtained at the acute infarcted lesion as compared with normal brain parenchyma. In addition, these findings were more clearly detected on short echo time spectrum rather than long spectrum. A close relationship between the clinical manifestations and MRI and MRS findings of the brain can helpful to distinguish CFE with other conditions and to evaluate the cause materials of infarctions rather than conventional MRI or diffusion-weighted imaging.     

Clinical course of incidental syringomyelia without predisposing pathologies

Although the widespread use of MRI has facilitated the diagnosis of subclinical syringomyelia, little information has been established regarding its natural course. To elucidate the clinical course and treatment strategy of incidental syringomyelia without predisposing pathologies, we retrospectively reviewed the clinical course of 12 adult patients with incidental syringomyelia. No patients had any predisposing pathology, including Chiari malformation or spinal cord tumor. Using the medical records and MRI, we analyzed the neurological and radiological features of each patient. After a mean of 39.9 months follow-up, no patient developed neurological deterioration. Although one patient had radiological progression without neurological deterioration, 11 patients (91.7%) had no change on MRI. Additionally, all patients experienced a favorable clinical course without surgery. These results indicate that, for patients with incidental syringomyelia without predisposing pathology, close observation rather than surgery can be recommended.