Utility of MRI in surgical planning for parasagittal meningiomas.

BACKGROUND: Surgical resection is the standard treatment for parasagittal meningioma (PSM), but complete resection may be challenging due to superior sagittal sinus (SSS) involvement. The SSS may be partially or completely obstructed, and collateral veins are commonly present. Thus, knowing the status of the SSS in PSM cases prior to treatment is essential to a successful outcome. MRI is utilized prior to surgery in order to determine SSS status and to check for presence of collateral veins. The objective of this study is to evaluate the reliability of MRI in predicting both SSS involvement and presence of collateral veins in subsequent comparison to actual intra-operative findings, and to report on complications and outcomes. METHODS: 27 patients were retrospectively analyzed for this study. A blinded radiologist reviewed all pre-operative images, noting SSS status and collateral vein presence. Intraoperative findings were obtained from hospital records to similarly categorize SSS status and collateral vein presence. RESULTS: Sensitivity of the MRI to SSS status was found to be 100% and specificity was 93%. However, sensitivity and specificity of MRI to collateral vein presence was only 40% and 78.6%, respectively. Complications were experienced by 22% of patients, the majority neurologic in nature. CONCLUSION: MRI accurately predicted SSS occlusion status, but was less consistent in identification of collateral veins. These findings suggest MRI should be used with caution prior to PSM resection surgery particularly with regards to the presence of collateral veins which may complicate resection.

Intraoperative electrophysiological monitoring for C1-2 spinal cord stimulation.

OBJECTIVE This study is a retrospective case series involving C1-2 spinal cord stimulation in patients with complex regional pain syndrome (CRPS) under general endotracheal anesthesia. Currently, C1-2 paddle lead placement is an accepted practice, which provides effective cervical stimulation to ameliorate upper-extremity and sometimes lower-extremity symptoms experienced by patients with CRPS. However, this technique must be performed under general endotracheal anesthesia rather than in an awake or semiconscious state due to intraoperative safety concerns and patient comfort. The authors aim to provide additional data to support the following novel technique: the use of somatosensory evoked potential (SSEP) diminution data to assist with proper midline placement of C1-2 leads under general anesthesia. METHODS SSEP median nerve (MN) and posterior tibial nerve (PTN) data were collected from 6 patients undergoing placement of C1-2 leads under general anesthesia. Fluoroscopy was used as an initial guide for proper anatomical midline placement. This was followed by the activation of the spinal cord stimulator and simultaneous collection of primarily MN SSEPs as well as PTN SSEPs for physiological midline placement. Unilateral and bilateral reductions in SSEPs assisted with the correct lateralization of the lead to ensure effective postoperative coverage according to the patient's individual preoperative symptoms. RESULTS Six patients were monitored using SSEPs and repeatable, reliable MN and PTN baseline responses were obtained from all. A reduction in amplitude ranging from 5% to 87% was observed, confirming inhibition of dorsal column conduction, and an average pain relief of 63% at short-term and 64% at long-term follow-up was recorded with 6 of 6 and 5 of 6 patients responding, respectively. CONCLUSIONS Intraoperative SSEP collision study testing appears to be a safe technique to monitor placement of C1-2 paddle leads intraoperatively under general anesthesia.

The use of macroelectrodes in recording cellular spiking activity.

Microelectrode recording (MER) is an important navigational and investigational tool, specifically with regard to deep brain stimulation (DBS) surgery. MER is often utilized when targeting the subthalamic nucleus (STN) and other deep brain nuclei in the management of Parkinson's disease (PD), tremor, dystonia and other emerging applications. Microelectrodes are used to detect and measure cellular spiking activity while macroelectrodes are considered more suitable for measuring the collective sum of slow potentials from multiple cells near the electrode, the local field potential (LFP). Precisely how the characteristics of an electrode affect the data recorded is still unclear. Technical idiosyncrasies of some surgical cases allowed serendipitous data collection from a 250 to 6000 Hz bandpassed macroelectrode recording during DBS implantation for PD. Simultaneous recording from both a microelectrode and macroelectrode were compared along the same surgical trajectory. Audio, normalized root mean square of the recorded signal, and power spectrograms were used to analyze the data. The analyses demonstrate similar results in detecting cellular spiking activity when recording with macroelectrodes compared with microelectrodes. This has important implications for the standardization of recording electrophysiological data as well as for the development of next generation closed-loop deep brain stimulation systems.

Laminectomy, durotomy, and piotomy effects on spinal cord intramedullary pressure in severe cervical and thoracic kyphotic deformity: a cadaveric study.

OBJECT: Previous studies have shown that cervical and thoracic kyphotic deformity increases spinal cord intramedullary pressure (IMP). Using a cadaveric model, the authors investigated whether posterior decompression can adequately decrease elevated IMP in severe cervical and thoracic kyphotic deformities. METHODS: Using an established cadaveric model, a kyphotic deformity was created in 16 fresh human cadavers (8 cervical and 8 thoracic). A single-level rostral laminotomy and durotomy were performed to place intraparenchymal pressure monitors in the spinal cord at C-2, C4-5, and C-7 in the cervical study group and at T4-5, T7-8, and T11-12 in the thoracic study group. Intramedullary pressure was recorded at maximal kyphosis. Posterior laminar, dural, and pial decompressions were performed while IMP was monitored. In 2 additional cadavers (1 cervical and 1 thoracic), a kyphotic deformity was created and then corrected. RESULTS: The creation of the cervical and thoracic kyphotic deformities resulted in significant increases in IMP. The mean increase in cervical and thoracic IMP (change in IMP [ΔIMP]) for all monitored levels was 37.8 ± 7.9 and 46.4 ± 6.4 mm Hg, respectively. After laminectomies were performed, the mean cervical and thoracic IMP was reduced by 22.5% and 18.5%, respectively. After midsagittal durotomies were performed, the mean cervical and thoracic IMP was reduced by 62.8% and 69.9%, respectively. After midsagittal piotomies were performed, the mean cervical and thoracic IMP was reduced by 91.3% and 105.9%, respectively. In 2 cadavers in which a kyphotic deformity was created and then corrected, the ΔIMP increased with the creation of the deformity and returned to zero at all levels when the deformity was corrected. CONCLUSIONS: In this cadaveric study, laminar decompression reduced ΔIMP by approximately 15%-25%, while correction of the kyphotic deformity returned ΔIMP to zero. This study helps explain the pathophysiology of myelopathy in kyphotic deformity and the failure of laminectomy alone for cervical and thoracic kyphotic deformities with myelopathy. In addition, the study emphasizes the need for correction of deformity during operative treatment of kyphotic deformity, the need for maintaining adequate intraoperative blood pressure during operative treatment, and the higher risk of spinal cord injury associated with operative treatment of kyphotic deformity.

Subepyndemal hemangioblastomas of the cervicomedullary junction: lessons learned in the management of two cases.

OBJECTIVE: This retrospective case series analyzes two cases of hemangioblastomas in the cervicomedullary junction. METHODS: A survey of the pediatric staff and of the operative reports from medical records with a review of the literature and medical records of patients with the condition was conducted. RESULTS: Two patients were successfully treated surgically. CONCLUSION: Surgery is the treatment of choice for hemangioblastomas of the cervicomedullary junction. Careful monitoring for unique complications, treatment of the tumor as a vascular malformation, and screening for von Hippel Lindau must all be employed to safely care for this challenging group of patients.

Carbon monoxide as an attenuator of vasoconstriction in piglet cerebral arterioles.

Carbon monoxide (CO) is an endogenous dilator in the newborn cerebral circulation. The present study addressed the hypothesis that endogenous CO attenuates pial arteriolar vasoconstriction caused by hypocapnia, platelet activating factor, and elevated blood pressure. Experiments used anesthetized piglets with implanted, closed cranial windows. Topical application of a metal porphyrin inhibitor of heme oxygenase was used to inhibit production of CO. Chromium mesopophyrin increased vasoconstriction in response to hypocapnia. The constrictor response to a topical stimulus, platelet activating factor, was also increased by application of chromium mesoporphyrin. Inhibition of heme oxygenase did not constrict pial arterioles in normotensive newborn pigs (mean arterial pressure of about 70 mmHg), but did constrict pial arterioles of piglets with experimentally induced increases in arterial pressure (mean arterial pressure greater than 90 mmHg). In fact, pial arterioles of normotensive piglets transiently dilated to chromium mesoporphyrin, whereas those of hypertensive piglets progressively constricted during 10 min of chromium mesoporphyrin treatment. Therefore, inhibition of heme oxygenase augments cerebral vasoconstriction in response to several very different constrictor stimuli. These data suggest endogenous CO attenuates vasoconstrictor responses in the newborn cerebral circulation.