Horner's syndrome: A complication of experimental carotid artery surgery in rats

Duplicated Vagus Nerve in Adolescence: Case Report and Review of Literature

BACKGROUND

Vagus nerve stimulation (VNS) has become an increasingly popular procedure for the treatment of epilepsy and depression. Significant complications or side effects associated with VNS surgery may result from either the inadvertent direct injury to the vagus nerve as part of the surgical approach, placement of the electrode, or the concomitant stimulation of vagal efferent fibers. To mitigate these effects, the recognition of anatomic variants that may place the nerve at increased risk is necessary.

CASE DESCRIPTION

During microsurgical dissection of the carotid sheath for the implantation of a vagus nerve stimulator in a 17-year-old male patient with refractory epilepsy, additional nonidentified nerve tissue was found running parallel to the vagus nerve. These fibers were two thirds of the thickness of the vagus nerve and ran medial to it, from the most superior to the most inferior aspect of the carotid sheath dissection, found at a distance of at least 4 cm in a craniocaudal direction. This duplicated nerve did not appear to branch from the vagal trunk nor exit the sheath but rather paralleled the course of the vagus nerve. The parallel course and the proximity of the unidentified nerve make this structure likely to be a duplicated vagus nerve.

CONCLUSIONS

This is the first reported case of cervical vagus nerve duplication presented in the literature. Surgeons performing VNS implantations should be cognizant of this potential anomaly in order to avoid inadvertent injury to the nerve.

Carotid-Jugular Fistula Model to Study Systemic Effects and Fistula-Related Microcirculatory Changes

BACKGROUND

Arteriovenous fistulae impair the distal circulation, but their effects at the microcirculatory level are not well understood. This study presents the carotid-jugular fistula (CJF) as a model to evaluate fistula-related microcirculatory and systemic changes.

MATERIALS AND METHODS

Female Wistar rats were anesthetized and divided into a fistula group (FG, n = 10) and a sham group (SG, n = 6). End-to-end anastomosis was performed between the right carotid artery and the jugular vein in the FG. The hemodynamic status was followed for 6 weeks. On the sixth postoperative week, liver and kidney microcirculation was measured using laser Doppler; then microcirculatory changes were assessed after occlusion of the carotid artery. At the end of the experiment, histological samples were taken and the weights of the organs were measured.

RESULTS

The heart rate and systolic blood pressure decreased significantly due to the CJF. Laser Doppler showed a reduction in liver blood flow units (BFU) in the FG in comparison with the SG (p = 0.01), and they increased (p < 0.01) after occlusion of the fistula. Kidney BFU showed slight changes only. The comparative morphological study revealed significant increases in heart weight (p < 0.001) and left ventricular hypertrophy (p = 0.008) in the FG.

CONCLUSION

Beside hemodynamic and morphologic changes, a CJF causes a deterioration in the microcirculation of the liver rather than of the kidney, but occlusion of the CJF immediately reverses these changes.

A Retrospective Study of Horner Syndrome in Australian Wild Birds, 2010-2016

Horner syndrome was identified in 25 of 30 777 avian admissions to Currumbin Wildlife Hospital during 2010-2016. Unilateral ptosis and erection of facial feathers were distinct findings on physical examination and consistent across 9 species. Affected birds were biased toward adults (64%) suffering traumatic injuries (88%). Concurrent injuries requiring treatment were present in 38% of cases, and 76% had additional neurologic deficits. Prognosis for release was poor, with an overall success rate of 32%. Resolution of clinical signs increased to 44% with higher doses of meloxicam and required an average hospitalization of 22 days (range, 3-78 days). Further investigation of the underlying causes of Horner syndrome in birds to provide treatment and prognostic guidelines is warranted.

Dystrophin Distribution and Expression in Human and Experimental Temporal Lobe Epilepsy

OBJECTIVE

Dystrophin is part of a protein complex that connects the cytoskeleton to the extracellular matrix. In addition to its role in muscle tissue, it functions as an anchoring protein within the central nervous system such as in hippocampus and cerebellum. Its presence in the latter regions is illustrated by the cognitive problems seen in Duchenne Muscular Dystrophy (DMD). Since epilepsy is also supposed to constitute a comorbidity of DMD, it is hypothesized that dystrophin plays a role in neuronal excitability. Here, we aimed to study brain dystrophin distribution and expression in both, human and experimental temporal lobe epilepsy (TLE).

METHOD

Regional and cellular dystrophin distribution was evaluated in both human and rat hippocampi and in rat cerebellar tissue by immunofluorescent colocalization with neuronal (NeuN and calbindin) and glial (GFAP) markers. In addition, hippocampal dystrophin levels were estimated by Western blot analysis in biopsies from TLE patients, post-mortem controls, amygdala kindled (AK)-, and control rats.

RESULTS

Dystrophin was expressed in all hippocampal pyramidal subfields and in the molecular-, Purkinje-, and granular cell layer of the cerebellum. In these regions it colocalized with GFAP, suggesting expression in astrocytes such as Bergmann glia (BG) and velate protoplasmic astrocytes. In rat hippocampus and cerebellum there were neither differences in dystrophin positive cell types, nor in the regional dystrophin distribution between AK and control animals. Quantitatively, hippocampal full-length dystrophin (Dp427) levels were about 60% higher in human TLE patients than in post-mortem controls (p < 0.05), whereas the level of the shorter Dp71 isoform did not differ. In contrast, AK animals showed similar dystrophin levels as controls.

CONCLUSION

Dystrophin is ubiquitously expressed by astrocytes in the human and rat hippocampus and in the rat cerebellum. Hippocampal full-length dystrophin (Dp427) levels are upregulated in human TLE, but not in AK rats, possibly indicating a compensatory mechanism in the chronic epileptic human brain.

Neuroendocrine homeostasis after vagus nerve stimulation in rats

BACKGROUND

The vagus nerve is important in maintaining HPA axis and sympatho-adrenal system (SAS) homeostasis, however little is known about the effect of vagus nerve stimulation (VNS), as used therapeutically, on these functions. Accordingly, the effect of VNS on plasma indices of HPA axis (ACTH, corticosterone), and SAS (norepinephrine, epinephrine) function were evaluated in rats.

METHODS

Male rats, on day-0 (D0), underwent surgeries for implantation of catheters into the right jugular vein and programmable (VNP) or non-programmable (VND) neurocybernetic devices encircling the left cervical vagus. On D7, after a blood sample, the device in VNP rats was programmed to deliver 500 μs width, 0.25 mA current pulses at 20 Hz ('on' 30s, 'off' 5 min) followed by timed blood samples during the next 90 min. In acute studies, VNS was stopped at 60 min and the rats were perfused at 90 min to evaluate neuronal Fos immunoreactivity (Fos-IR). In chronic studies, the probe remained active. In these rats, the HPA axis response to airpuff-startle stressor (D17) and anterior pituitary CRF-receptor binding (D26) were evaluated.

RESULTS

During acute VNS, plasma indices of HPA axis and SAS activity, as well as Fos-IR activation pattern in brain regions known to increase after stress, were not different between VND and VNP rats. During chronic VNS, stress-induced HPA axis responses exhibited a tendency toward faster recovery to baseline in VNP rats.

CONCLUSIONS

Therapeutic VNS is not a stressor and does not compromise HPA axis or SAS homeostasis. Chronic VNS may facilitate development of efficient feedback mechanisms.

Rat vagus nerve stimulation model of seizure suppression: nNOS and ΔFos B changes in the brainstem

Vagus nerve stimulation (VNS) is a moderately effective treatment for intractable epilepsy. However, the mechanism of action is poorly understood. The effect of left VNS in amygdala kindled rats was investigated by studying changes in nNOS and ΔFos B expression in primary and secondary vagus nerve projection nuclei: the nucleus of the solitary tract (NTS), dorsal motor nucleus of the vagus nerve (DMV), parabrachial nucleus (PBN) and locus coeruleus (LC). Rats were fully kindled by stimulation of the amygdala. Subsequently, when the fully kindled state was reached and then maintained for ten days, rats received a single 3-min train of VNS starting 1min prior to the kindling stimulus and lasting for 2min afterwards. In control animals the vagus nerve was not stimulated. Animals were sacrificed 48h later. The brainstems were stained for neuronal nitric oxide synthase (nNOS) and ΔFos B. VNS decreased seizure duration with more than 25% in 21% of rats. No VNS associated changes in nNOS immunoreactivity were observed in the NTS and no changes in ΔFos B were observed in the NTS, PBN, or LC. High nNOS immunopositive cell densities of >300cells/mm(2) were significantly more frequent in the left DMV than in the right (χ(2)(1)=26.2, p<0.01), independent of whether the vagus nerve was stimulated. We conclude that the observed nNOS immunoreactivity in the DMV suggests surgery-induced axonal damage. A 3-min train of VNS in fully kindled rats does not affect ΔFos B expression in primary and secondary projection nuclei of the vagus nerve.

Animal models for vagus nerve stimulation in epilepsy

Vagus nerve stimulation (VNS) is a moderately effective adjunctive treatment for patients suffering from medically refractory epilepsy and is explored as a treatment option for several other disorders. The present review provides a critical appraisal of the studies on VNS in animal models of seizures and epilepsy. So far, these studies mostly applied short-term VNS in seizure models, demonstrating that VNS can suppress and prevent seizures and affect epileptogenesis. However, the mechanism of action is still largely unknown. Moreover, studies with a clinically more relevant setup where VNS is chronically applied in epilepsy models are scarce. Future directions for research and the application of this technology in animal models of epilepsy are discussed.