Effects of thigh extension on the position of the femoral nerve: application to prone lateral transpsoas approaches to the lumbar spine

Some authors have suggested that thigh extension during the prone lateral transpsoas approach to the lumbar spine provides the theoretical advantage of providing posterior shift of the psoas muscle and plexus and is responsible for its lower rates of nerve injury. We aimed to elucidate the effects of surgical positioning on the femoral nerve within the psoas muscle via a cadaveric study. In the supine position, 10 fresh frozen adult cadavers had a metal wire secured to the pelvic segment of the femoral nerve and then extended proximally along with its L2 contribution. Fluoroscopy was then used to identify the wires on the femoral nerves in a neutral position and with the thigh extended and flexed by 25 and 45°. Additionally, a lateral incision was made in the anterolateral abdominal wall to mimic a lateral transpsoas approach to the lumbar spine, and measurements were made of the amount of movement in the vertical plane of the femoral nerve from neutral to then 25 and 45° of thigh flexion and extension. On fluoroscopy, the femoral nerves moved posteriorly at a mean of 10.1 mm with thigh extension. Femoral nerve movement could not be detected at any degree of this range of flexion of the thigh. Extension of the thigh to about 30° can move the femoral nerve farther away from the dissection plane by approximately one centimeter. This hip extension not only places the femoral nerve in a more advantageous position for lateral lumbar interbody fusion procedures but also helps to promote accentuation of lumbar lordosis.

Seizure outcomes after stereotactic radiosurgery for the treatment of cerebral arteriovenous malformations

OBJECTIVE

Patients with cerebral arteriovenous malformations (AVMs) commonly present with seizure. Seizure outcomes in patients treated with stereotactic radiosurgery (SRS) are poorly defined. A case series of patients with cerebral AVMs treated with SRS is presented to evaluate long-term seizure outcome.

METHODS

A retrospective review of the medical record was performed, identifying 204 consecutive patients with AVMs treated with SRS between January 1991 and June 2012. Clinical and radiographic data were evaluated. Seizure outcome was measured using the Engel Epilepsy Surgery Outcome Scale. Mean duration of follow-up was 37.1 months (SD 38.3 months) with a minimum follow-up period of 1 month.

RESULTS

Of the 204 patients with cerebral AVMs treated with SRS, 78 patients (38.2%) presented with seizures and 49 of those patients were treated with antiepileptic drugs (AEDs). Following SRS, 63 (80.8%) of the 78 patients who had had seizures prior to SRS were seizure-free at a mean follow-up time of 37.2 months (SD 41.3 months). Of the 49 patients who had been treated with AEDs, 17 were still taking AEDs at last follow-up. Of the 126 patients who did not present with seizures prior to treatment with SRS, only 5 patients (4.0%) had seizures in the post-SRS period. There was no significant correlation between post-SRS seizure status and patient demographic features, comorbidities, AVM characteristics, history of operative intervention, pre- or posttreatment hemorrhage, or radiographic degree of AVM resolution.

CONCLUSIONS

Stereotactic radiosurgery for treatment of cerebral AVMs is effective at providing long-term control of seizures. A substantial number of patients who were treated with SRS were not only seizure free at their last follow-up, but had been successfully weaned from antiepileptic medications.

The nonsurgical nature of patients with subarachnoid or intraparenchymal hemorrhage associated with mild traumatic brain injury

OBJECT

Mild traumatic brain injury (mTBI), as defined by Glasgow Coma Scale (GCS) score of 13 or higher, is a common problem in the United States and worldwide, estimated to affect more than 1 million patients yearly. When associated with intracranial hemorrhage, it is a common reason for neurosurgical consultation and transfer to tertiary care centers. The authors set out to investigate the clinical implications of subarachnoid hemorrhage (SAH) and/or intraparenchymal hemorrhage (IPH) associated with mTBI in hopes of standardization of mTBI clinical care and optimization of resource allocation.

METHODS

The authors performed a retrospective review of 500 consecutively treated patients with mTBI and SAH and/or IPH admitted to a Level I trauma center in Alabama between May 2003 and May 2013. They performed a review of medical records to confirm the diagnosis, determine neurological condition at admission, and assess for episodes of neurological decline or brain injury–related complications including altered mental status, seizures, and hyponatremia.

RESULTS

Of the 500 patients for whom data were reviewed, 304 (60.8%) were male and 196 (39.2%) were female. Average age was 46.3 years. Overall, 63 patients (12.6%) had isolated IPH, 411 (82.2%) had isolated SAH, and 26 (5.2%) had radiographic evidence of both IPH and SAH. One hundred forty-five patients (29%) were transferred an average distance of 64.5 miles. The authors identified no patients who experienced neurological worsening during their hospital course. Two patients experienced hyponatremia that required treatment with sodium supplementation.

CONCLUSIONS

Patients with the constellation of SAH and/or IPH and mTBI do not require neurosurgical consultation, and these findings should not be used as the sole criteria to justify transfer to tertiary referral centers.

Validation and modification of a predictive model of postresection hydrocephalus in pediatric patients with posterior fossa tumors

OBJECT

Postresection hydrocephalus is observed in approximately 30% of pediatric patients with posterior fossa tumors. However, which patients will develop postresection hydrocephalus is not known. The Canadian Preoperative Prediction Rule for Hydrocephalus (CPPRH) was developed in an attempt to identify this subset of patients, allowing for the optimization of their care. The authors sought to validate and critically appraise the CPPRH.

METHODS

The authors conducted a retrospective chart review of 99 consecutive pediatric patients who presented between 2002 and 2010 with posterior fossa tumors and who subsequently underwent resection. The data were then analyzed using bivariate and multivariate analyses, and a modified CPPRH (mCPPRH) was applied.

RESULTS

Seventy-six patients were evaluated. Four variables were found to be significant in predicting postresection hydrocephalus: age younger than 2 years, moderate/severe hydrocephalus, preoperative tumor diagnosis, and transependymal edema. The mCPPRH produced observed likelihood ratios of 0.737 (95% CI 0.526-1.032) and 4.688 (95% CI 1.421-15.463) for low- and high-risk groups, respectively.

CONCLUSIONS

The mCPPRH utilizes readily obtainable and reliable preoperative variables that together stratify children with posterior fossa tumors into high- and low-risk categories for the development of postresection hydrocephalus. This new predictive model will aid patient counseling and tailor the intensity of postoperative clinical and radiographic monitoring for hydrocephalus, as well as provide evidence-based guidance for the use of prophylactic CSF diversion.