Tonically Active cAMP-Dependent Signaling in the Ventrolateral Medulla Regulates Sympathetic and Cardiac Vagal Outflows.

The ventrolateral medulla contains presympathetic and vagal preganglionic neurons that control vasomotor and cardiac vagal tone, respectively. G protein-coupled receptors influence the activity of these neurons. Gα s activates adenylyl cyclases, which drive cyclic adenosine monophosphate (cAMP)-dependent targets: protein kinase A (PKA), the exchange protein activated by cAMP (EPAC), and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. The aim was to determine the cardiovascular effects of activating and inhibiting these targets at presympathetic and cardiac vagal preganglionic neurons. Urethane-anesthetized rats were instrumented to measure splanchnic sympathetic nerve activity (sSNA), arterial pressure (AP), heart rate (HR), as well as baroreceptor and somatosympathetic reflex function, or were spinally transected and instrumented to measure HR, AP, and cardiac baroreflex function. All drugs were injected bilaterally. In the rostral ventrolateral medulla (RVLM), Sp-cAMPs and 8-Br-cAMP, which activate PKA, as well as 8-pCPT, which activates EPAC, increased sSNA, AP, and HR. Sp-cAMPs also facilitated the reflexes tested. Sp-cAMPs also increased cardiac vagal drive and facilitated cardiac baroreflex sensitivity. Blockade of PKA, using Rp-cAMPs or H-89 in the RVLM, increased sSNA, AP, and HR and increased HR when cardiac vagal preganglionic neurons were targeted. Brefeldin A, which inhibits EPAC, and ZD7288, which inhibits HCN channels, each alone had no effect. Cumulative, sequential blockade of all three inhibitors resulted in sympathoinhibition. The major findings indicate that Gα s-linked receptors in the ventral medulla can be recruited to drive both sympathetic and parasympathetic outflows and that tonically active PKA-dependent signaling contributes to the maintenance of both sympathetic vasomotor and cardiac vagal tone.

Outcomes after decompressive laminectomy for lumbar spinal stenosis: comparison between minimally invasive unilateral laminectomy for bilateral decompression and open laminectomy: clinical article.

OBJECT: The development of minimally invasive surgical techniques is driven by the quest for better patient outcomes. There is some evidence for the use of minimally invasive surgery for degenerative lumbar spine stenosis (LSS), but there are currently no studies comparing outcomes with matched controls. The object of this study was to compare outcomes following minimally invasive unilateral laminectomy for bilateral decompression (ULBD) to a standard "open" laminectomy for LSS. METHODS: The authors conducted a prospective, 1:1 randomized trial comparing ULBD to open laminectomy for degenerative LSS. The study enrolled 79 patients between 2007 and 2009, and adequate data for analysis were available in 54 patients (27 in each arm of the study). Patient demographic characteristics and clinical characteristics were recorded and clinical outcomes were obtained using pre- and postoperative Oswestry Disability Index (ODI) scores, visual analog scale (VAS) scores for leg pain, patient satisfaction index scores, and postoperative 12-Item Short Form Health Survey (SF-12) scores. RESULTS: Significant improvements were observed in ODI and VAS scores for both open and ULBD interventions (p < 0.001 for both groups using either score). In addition, the ULBD-treated patients had a significantly better mean improvement in the VAS scores (p = 0.013) but not the ODI scores (p = 0.055) compared with patients in the open-surgery group. ULBD-treated patients had a significantly shorter length of postoperative hospital stay (55.1 vs. 100.8 hours, p = 0.0041) and time to mobilization (15.6 vs. 33.3 hours, p < 0.001) and were more likely to not use opioids for postoperative pain (51.9% vs. 15.4%, p = 0.046). CONCLUSIONS: Based on short-term follow-up, microscopic ULBD is as effective as open decompression in improving function (ODI score), with the additional benefits of a significantly greater decrease in pain (VAS score), postoperative recovery time, time to mobilization, and opioid use.

Complications with K-wire insertion for percutaneous pedicle screws.

STUDY DESIGN: Retrospective study. OBJECTIVE: To determine the risk profile and complications associated with anterior vertebral body breach by Kirschner (K)-wire during percutaneous pedicle screw insertion. SUMMARY OF BACKGROUND DATA: Percutaneous techniques and indications are rapidly expanding with numerous studies now supporting the use of percutaneous pedicle screw stabilization as an adjunct for multiple pathologies such as degenerative, tumor, and trauma. With regards to complication rates, little has been documented. MATERIALS AND METHODS: A total of 525 consecutive percutaneous pedicle screws were retrospectively reviewed and the rate of anterior vertebral body breach was recorded, including any potential adverse clinical outcomes. RESULTS: Of 525 percutaneous pedicle screw insertions, there were 7 anterior breaches recorded. We rated the breaches as a minor breach (<5 mm; n=3), moderate breach (5-25 mm; n=2), and major breach (>25 mm; n=2). Two patients had a postoperative ileus with a retroperitoneal hematoma on postoperative computed tomography scan. No patient required reoperation or blood transfusion. CONCLUSIONS: The indications for minimally invasive spinal fusion have expanded to include conditions such as degenerative, trauma, deformity, infection, and neoplasia. Although the rate of anterior K-wire breach is low, the technique requires the acquisition of a new set of skills including the safe passage of a K-wire, and knowledge of potential complications that may ensue.

An unusual case of a pituitary fossa aspergilloma in an immunocompetent patient mimicking infiltrative tumour.

Sellar aspergillosis is a rare infection commonly mistaken for a pituitary tumour. We present a rare case of pituitary fossa Aspergillus fumigatus mycetoma in an immunocompetent 90-year-old female, who presented with headaches. Magnetic resonance imaging scans demonstrated an enhancing pituitary fossa mass that appeared to infiltrate the sphenoid sinus, suggestive of an invasive tumour. Stereotactic trans-sphenoidal resection confirmed localized A. fumigatus infection. The abscess was debrided and the dura was left intact. Her headaches resolved post-operatively and she was treated with voriconazole. This indicates that aspergilloma should be considered as a differential for an unexplained pituitary lesion even in elderly immunocompetent patients.

Herniation of an enlarged middle cerebral artery through a temporal bone defect in association with an arteriovenous malformation.

We present a previously undescribed variant of the middle cerebral artery (MCA) protruding through a defect in the temporal bone, associated with a large arteriovenous malformation (AVM). The patient, a 59-year-old male, presented with a large right frontoparietal AVM with feeding aneurysms and a recent haemorrhage. Preoperative imaging demonstrated a tortuous right MCA feeder abutting the anterosuperior temporal bone in the region of the pterion. An associated temporal bone defect was visible. The patient underwent a pterional craniotomy for surgical clipping of aneurysms associated with the AVM. On reflection of the temporalis muscle, the MCA branch was transected as it coursed through a defect in the temporal bone. This patient demonstrates that the MCA may deviate from its usual anatomy and herniate through a defect in the skull. Because a pterional craniotomy is such a common surgical approach, knowledge and anticipation of such anatomic variants are essential to avoid catastrophic vascular injury during surgery.

Retrospective computed tomography scan analysis of percutaneously inserted pedicle screws for posterior transpedicular stabilization of the thoracic and lumbar spine: accuracy and complication rates.

STUDY DESIGN: Retrospective clinical data analysis. OBJECTIVE: To investigate the misplacement rate and related clinical complications of percutaneous pedicle screw insertion in the thoracic and lumbar spine. SUMMARY OF BACKGROUND DATA: Percutaneous insertion of cannulated pedicle screws has been developed as a minimally invasive alternative to the open technique during instrumented fusion procedures of the thoraco-lumbar spine. The reported rate of screw misplacement using open techniques is well described, however data is lacking on the exact failure rate of the percutaneous technique. METHODS: A total of 424 percutaneously inserted pedicle screws from 2007 to 2010 were analyzed in 88 patients, from a single surgeon series (RJM). Axial reformatted computer tomographic images were examined by 2 independent observers and individual and consensus interpretation was obtained for each screw position. A simple grading system was used for assessment of screw accuracy--Grade 0: screw within cortex of pedicle; Grade 1: screw thread breach of wall of pedicle <2 mm; Grade 2: significant breach >2 mm with no neurological compromise; Grade 3: complication including pedicle fracture, anterior breach with neuro-vascular compromise, and lateral or medial breach with neurological sequelae. RESULTS: The indications for percutaneous pedicle screw insertion include: degenerative (78%), trauma (13%), tumour (8%), and infection (1%). Pedicle screws were inserted into level T4 to S1. The most common levels performed include L4 and L5 with the most common indication for surgery being an L4/5 spondylolisthesis. 383 out of 424 screws (90.3%) were placed in the cortical shell of the pedicle (Grade 0). Forty-one screws (9.7%) were misplaced from T4 to S1. Of these, the majority were Grade 1 pedicle violations (24 screws; 5.7%), with 15 Grade 2 violations (3.5%) and 2 Grade 3 violations (0.5%). Of the 2 Grade 3 pedicle violations, both were pedicle fractures but only 1 had associated neurological deficit (L4 radiculopathy postoperatively). CONCLUSION: Percutaneous insertion of cannulated pedicle screws in the thoracic and lumbar spine is an acceptable technique with a low complication rate in experienced hands. The overall rate of perforation is below the higher rates reported in the literature for the open technique. Complication rates including pedicle fracture were low.