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Jin Guo-Xin and Wang Huan

OBJECT

Atlantoaxial instability often requires surgery, and the current methods for fixation pose some risk to vascular and neurological tissues. Thus, new effective and safer methods are needed for salvage operations. This study sought to assess unilateral C-1 posterior arch screws (PASs) and C-2 laminar screws (LSs) combined with 1-side C1–2 pedicle screws (PSs) for posterior C1–2 fixation using biomechanical testing with bilateral C1–2 PSs in a cadaveric model.

METHODS

Six fresh ligamentous human cervical spines were evaluated for their biomechanics. The cadaveric specimens were tested in their intact condition, stabilization after injury, and after injury at 1.5 Nm of pure moment in 6 directions. The 3 groups tested were bilateral C1–2 PSs (Group A); left side C1–2 PSs with an ipsilateral C-1 PAS + C-2 laminar screw (Group B); and left side C1–2 PSs with a contralateral C-1 PAS + C-2 LS (Group C). During the testing, angular motion was measured using a motion capture platform. Data were recorded, and statistical analyses were performed.

RESULTS

Biomechanical testing showed that there was no significant difference among the stabilities of these fixation systems in flexion-extension and rotation control. In left lateral bending, the bilateral C1–2 PS group decreased flexibility by 71.9% compared with the intact condition, the unilateral C1–2 PS and ipsilateral PAS+LS group decreased flexibility by 77.6%, and the unilateral C1–2 PS and contralateral PAS+LS group by 70.0%. Each method significantly decreased C1–2 movements in right lateral bending compared with the intact condition, and the bilateral C1–2 PS system was more stable than the C1–2 PS and contralateral PAS+LS system (p = 0.036).

CONCLUSIONS

A unilateral C-1 PAS + C-2 LS combined with 1-side C-1 PSs provided the same acute stability as the PS, and no statistically significant difference in acute stability was found between the 2 screw techniques. These methods may constitute an alternative method for posterior atlantoaxial fixation.

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Tao Hong, Yang Wang, Hai-tao Wang and Huan Wang

Object

The gap junction is important in the propagation of dilation/constriction signals along vessels for coordinated behavior in control of vascular tone. The authors hypothesized that gap junctions might play a role in cerebral vasospasm following subarachnoid hemorrhage (SAH). The aims of the present study were to investigate the role of gap junctions and to observe the potential therapeutic efficacy of gap junction blockers in cerebral vasospasm in vitro and in vivo.

Methods

For the in vitro investigation, the effect of heptanol on the oxyhemoglobin (HbO2)-induced contraction of isolated rabbit basilar arteries (BAs) was observed by using an isometric tension-recording method. For the in vivo experiments, the potential therapeutic efficacy of heptanol and carbenoxolone was surveyed after it was given intravenously in the rabbit double-hemorrhage model. Light microscopy was performed to assess the morphological changes in the arteries examined.

Results

For the in vitro method, heptanol significantly inhibited the sustained contraction induced both by HbO2 and K+ in the BA rings. The magnitude of the heptanol-induced relaxation was dose dependent. The inhibitory effect of heptanol on the K+-induced vasoconstriction was weaker than that on the HbO2-induced constriction. After arterial rings were pretreated for 10 minutes, heptanol significantly decreased their responses to the HbO2-induced contraction. For the in vivo method, heptanol and carbenoxolone significantly decreased the narrowing of BAs when given intravenously in the rabbit double-hemorrhage model. In both treated groups, the diameters of the arteries had not changed significantly on Day 7 compared with those of the arteries in the SAH + vehicle and the SAH-only group.

Conclusions

Heptanol and carbenoxolone significantly inhibited the experimental cerebral vasospasm both in vitro and in vivo. Blockage of gap junctions is a probable candidate for a new approach in the treatment of cerebral vasospasm. Gap junctions may play a pathophysiological role in cerebral vasospasm.

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Huan Wang and Darren B. Orbach

✓Intracranial aneurysms in young infants are extremely rare, with few published reports on the etiology, evaluation, treatment strategies, and follow-up of this condition in this population. The authors report the case of a traumatic dissecting aneurysm at the vertebrobasilar junction (VBJ) in a 3-month-old infant caused by nonaccidental trauma. Therapeutic occlusion of the VBJ was contemplated, but coil embolization of the main aneurysm sac proved feasible, and anticoagulation and antiplatelet agents were initiated. The patient made a full neurological recovery, and follow-up studies demonstrated stable aneurysm occlusion. Management and follow-up strategies for this challenging condition are discussed.

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Carlo Bortolotti, Huan Wang, Kenneth Fraser and Giuseppe Lanzino

✓ The etiopathogenesis of traumatic spinal subdural hematoma (SSH) is uncertain. Unlike the supratentorial subdural space, no bridging veins traverse the spinal subdural space. The authors describe a case of subacute SSH that occurred after spontaneous resolution of traumatic intracranial SDH and suggest a causal relationship between the two.

A 23-year-old woman suffered an acute intracranial SDH after a snowboarding accident. There was no clinical or radiological evidence of spine injury. Conservative management of the supratentorial SDH resulted in spontaneous radiologically documented resolution with redistribution of blood in the subdural space.

Four days after the injury, the patient started noticing new onset of mild low-back pain. The pain progressively worsened. Magnetic resonance imaging of the lumbosacral spine 10 days after the original injury revealed a large L4—S2 SDH. Ten days after the original injury, bilateral L5—S1 laminotomy and drainage of the subacute spinal SDH were performed. The patient experienced immediate pain relief.

The authors hypothesize that in some cases spinal SDH may be related to redistribution of blood from the supratentorial subdural space.

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Bonnie H. Wang, Seong-Jin Moon, Huan Wang and William C. Olivero

Isolated unilateral temporalis muscle hypertrophy is an extremely rare cause of swelling in the temple region, with only 7 cases reported in the literature. The authors report the eighth case of this unique occurrence in a 17-year-old boy and review the current literature.

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Huan Wang, Giuseppe Lanzino, Kenneth Fraser, Patrick Tracy and David Wang

Object. The prognosis of patients with acute symptomatic cervical internal carotid artery (ICA) occlusion is generally considered to be poor. Traditionally, such patients are not considered eligible for urgent thrombolytic/endovascular treatment. Since 1998, an aggressive therapeutic approach with endovascular treatment has been adopted at the authors' institution. In this report they assess whether aggressive treatment of ICA occlusion is appropriate.

Methods. The clinical characteristics and outcome of six consecutive patients treated urgently with an endovascular approach between 1998 and 2001 are reviewed and summarized.

Recanalization was accomplished in all patients. At a mean follow-up period of 8 months (range 2–14 months), five of six patients had good or excellent outcomes (modified Rankin Scale [mRS] Score 0–1) and one had a poor outcome (mRS Score 4).

Conclusions. With recent advancements in thrombolytic and endovascular treatments, an aggressive endovascular approach in patients with acute symptomatic cervical ICA occlusion may be successful. Further clinical data are required to determine the optimal endovascular approach in these patients.

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Huan Wang, Albert K. Oh and Darren B. Orbach

Patients with the congenital neurocutaneous disorder PHACES are at a markedly increased risk of ischemic infarction during childhood. Although intracranial arterial anomalies have been well described, venous abnormalities have not been documented. The authors report on a unique case of a 3-month-old girl with PHACES and a skull base osteodural arteriovenous fistula. A separate arteriovenous shunt at T-5 may also have been present. Imaging findings and treatment strategies are discussed.

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Huan Wang, Robert J. Spinner and Anthony J. Windebank

Object

Contralateral C-7 nerve transfer has been used clinically for more than 20 years. The increased interest in studies of transfer effectiveness at different target muscles, posttransfer cocontraction, and brain plasticity has prompted the need for an animal model. In addition to the conventional electrophysiological, histomorphometric, and biomechanical evaluation modalities, quantitative functional and behavioral evaluation will be crucial in applying this kind of model. The aim of this study was to establish a C-7 transection animal model and quantify the changes in upper-limb joint movement and muscle power.

Methods

A C-7 nerve transection model was created in Sprague-Dawley rats, the brachial plexus of which resembles the human brachial plexus. The impact of C-7 transection on donor limb function—namely, strength, movement, and coordination—was evaluated in 6 rats. Muscle strength (power reported in g) was measured as a grasping task. The active range of motion (ROM; angle reported in °) of the elbow, wrist, and metacarpophalangeal joints was quantified by computerized video motion analysis. Antiresistance coordinated movement (speed reported in seconds) was assessed by the vertical rope-climbing test. These tests were carried out before surgery and at 2, 4, 6, 8, 10, 14, 21, and 28 days after C-7 transection. Repeated-measures 1-way analysis of variance was applied for statistical analysis. When the overall probability value was < 0.05, the Dunnett multiple-comparison posttest was used to compare postoperative values with preoperative baseline values.

Results

Immediately after C-7 transection, the mean ± SD grip strength declined from 378.50 ± 20.55 g to 297.77 ± 15.04 g. Active elbow extension was impaired, as shown by a significant decrease of the elbow extension angle. The speed of vertical rope climbing was also reduced. Elbow flexion, wrist flexion and extension, and metacarpophalangeal joint flexion and extension were not impaired. Fast recovery of motor function was observed thereafter. Grip strength, range of active elbow extension, and speed of rope climbing returned to baseline values at postoperative Days 4, 8, and 8, respectively.

Conclusions

The ROM and muscle strength of the upper limb in rats can be measured quantitatively in studies that simulate clinical situations. Application of these functional evaluation modalities in a C-7 nerve transection rat model confirmed that transection of C-7 causes only temporary functional dysfunction to the donor limb. The results obtained in this animal model mimic those seen in humans who undergo contralateral C-7 nerve harvesting.

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Erratum

Conversion of external ventricular drains to ventriculoperitoneal shunts after aneurysmal subarachnoid hemorrhage: effects of site and protein/red blood cell counts on shunt infection and malfunction

Stylianos Rammos, Jeffrey Klopfenstein, Lori Augspurger, Huan Wang and Jennifer Poston