Spine stabilization is a risk factor for the development of pelvic iliac vein lesions.

BACKGROUND: Open lumbar spine stabilization surgery often requires mobilization of the left and right common iliac veins (CIVs) and the placement of plates and screws that can impinge on them. We reviewed our venography experience of the past 3 years to determine whether there is an association between spine stabilization surgery and the development of symptomatic iliac vein outflow lesions. METHODS: A retrospective chart review of prospectively collected data from our electronic medical record system was performed to identify patients who underwent venography with or without venous stenting and had a history of previous lumbar spine stabilization. Patients' demographics, medical comorbidities, venograms, and intravascular ultrasound (IVUS) data were collected and analyzed. The senior author reviewed all venograms and IVUS images of patients with previous spine stabilization procedures. RESULTS: From January 2014 to April 2018, venography was performed in 1713 limbs in 1245 patients at the Center for Vascular Medicine. Of the 1245 patients, 18 patients had a history of lumbar spine stabilization procedures: five anterior-posterior and 13 posterior. Nine had single-level and eight had two- or three-level fusions. All 18 patients demonstrated pelvic lesions. These included 1 left CIV aneurysm, 5 left CIV stenoses, 3 bilateral CIV stenoses, 2 left CIV and inferior vena cava occlusions, and 2 external iliac vein stenoses. The aneurysm patient was treated with anticoagulation, 8 patients underwent stenting, 1 patient refused stenting because of relocation to another country, 1 inferior vena cava-CIV occlusion could not be crossed, fear of dislodging a thrombus and the proximity to a protruding posteriorly placed screw prevented stenting in 2 patients, and 4 patients had a venoplasty alone because of undersizing of a stenosis or missed lesions with IVUS after review by a blinded reviewer. Lesions in anterior lumbar interbody fusion patients were extremely stenotic, required predilation, and resulted in a residual stenosis requiring venoplasty at a second setting in one patient. CONCLUSIONS: Lumbar spine stabilization surgery may be a risk factor for development of symptomatic venous outflow obstruction lesions. During venography and stenting in patients with anterior lumbar interbody fusion approaches, significant scarring may be encountered, resulting in a residual stenosis after stent placement. Predilation venoplasty, before stent deployment, is recommended to prevent stent migration. Furthermore, a history of spine stabilization surgery in patients presenting with pelvic symptoms, lower extremity pain or swelling, or post-thrombotic symptoms should prompt consideration of a pelvic venous duplex ultrasound examination to determine whether an iliac venous outflow lesion is present.

Acute onset of upbeat nystagmus, exotropia, and internuclear ophthalmoplegia--a tell-tale of ponto-mesencephalic infarct.

Two patients were assessed for acute onset of diplopia. Clinical examination revealed upbeat nystagmus, exotropia, and internuclear ophthalmoplegia (INO). Both patients had vascular risk factors; acute ischemic stroke affecting ponto-mesencephalic junction was suspected. Magnetic resonance imaging confirmed strategic location of the acute infarct affecting the medial longitudinal fasciculus, adjacent occulomotor nuclei, and paramedian tract. We propose that constellation of acute onset of upbeat nystagmus, INO, and exotropia in patients with vascular risk factors might be unequivocal manifestation of the ponto-mesencephalic stroke.

Chaos game representation of human pallidal spike trains.

Many studies have demonstrated the presence of scale invariance and long-range correlation in animal and human neuronal spike trains. The methodologies to extract the fractal or scale-invariant properties, however, do not address the issue as to the existence within the train of fine temporal structures embedded in the global fractal organisation. The present study addresses this question in human spike trains by the chaos game representation (CGR) approach, a graphical analysis with which specific temporal sequences reveal themselves as geometric structures in the graphical representation. The neuronal spike train data were obtained from patients whilst undergoing pallidotomy. Using this approach, we observed highly structured regions in the representation, indicating the presence of specific preferred sequences of interspike intervals within the train. Furthermore, we observed that for a given spike train, the higher the magnitude of its scaling exponent, the more pronounced the geometric patterns in the representation and, hence, higher probability of occurrence of specific subsequences. Given its ability to detect and specify in detail the preferred sequences of interspike intervals, we believe that CGR is a useful adjunct to the existing set of methodologies for spike train analysis.

Feed-forward excitation of striatal neuron activity by frontal cortical activation of nitric oxide signaling in vivo.

The gaseous neurotransmitter nitric oxide plays an important role in the modulation of corticostriatal synaptic transmission. This study examined the impact of frontal cortex stimulation on striatal nitric oxide efflux and neuron activity in urethane-anesthetized rats using amperometric microsensor and single-unit extracellular recordings, respectively. Systemic administration of the neuronal nitric oxide synthase inhibitor 7-nitroindazole decreased spontaneous spike activity without affecting activity evoked by single-pulse stimulation of the ipsilateral cortex. Train (30 Hz) stimulation of the contralateral frontal cortex transiently increased nitric oxide efflux in a robust and reproducible manner. Evoked nitric oxide efflux was attenuated by systemic administration of 7-nitroindazole and the non-selective nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester. Train stimulation of the contralateral cortex, in a manner identical to that used to evoke nitric oxide efflux, had variable effects on spike activity assessed during the train stimulation trial, but induced a short-term depression of cortically evoked activity in the first post-train stimulation trial. Interestingly, 7-nitroindazole potently decreased cortically evoked activity recorded during the train stimulation trial. Moreover, the short-term depression of spike activity induced by train stimulation was enhanced following pretreatment with 7-nitroindazole and attenuated after systemic administration of the dopamine D2 receptor antagonist eticlopride. These results demonstrate that robust activation of frontal cortical afferents in the intact animal activates a powerful nitric oxide-mediated feed-forward excitation which partially offsets concurrent D2 receptor-mediated short-term inhibitory influences on striatal neuron activity. Thus, nitric oxide signaling is likely to play an important role in the integration of corticostriatal sensorimotor information in striatal networks.