Alexander K. Powers

Abnormal white matter integrity related to head impact exposure in a season of high school varsity football.

The aim of this study was to determine whether the cumulative effects of head impacts from a season of high school football produce magnetic resonance imaging (MRI) measureable changes in the brain in the absence of clinically diagnosed concussion. Players from a local high school football team were instrumented with the Head Impact Telemetry System (HITS™) during all practices and games. All players received pre- and postseason MRI, including diffusion tensor imaging (DTI). Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) was also conducted. Total impacts and risk-weighted cumulative exposure (RWE), including linear (RWELinear), rotational (RWERotational), and combined components (RWECP), were computed from the sensor data. Fractional, linear, planar, and spherical anisotropies (FA, CL, CP, and CS, respectively), as well as mean diffusivity (MD), were used to determine total number of abnormal white matter voxels defined as 2 standard deviations above or below the group mean. Delta (post-preseason) ImPACT scores for each individual were computed and compared to the DTI measures using Spearmans rank correlation coefficient. None of the players analyzed experienced clinical concussion (N=24). Regression analysis revealed a statistically significant linear relationship between RWECP and FA. Secondary analyses demonstrated additional statistically significant linear associations between RWE (RWECP and RWELinear) and all DTI measures. There was also a strong correlation between DTI measures and change in Verbal Memory subscore of the ImPACT. We demonstrate that a single season of football can produce brain MRI changes in the absence of clinical concussion. Similar brain MRI changes have been previously associated with mild traumatic brain injury.

Hemispherotomy: efficacy and analysis of seizure recurrence

OBJECT Hemispherotomy generally is performed in hemiparetic patients with severe, intractable epilepsy arising from one cerebral hemisphere. In this study, the authors evaluate the efficacy of hemispherotomy and present an analysis of the factors influencing seizure recurrence following the operation. METHODS The authors performed a retrospective review of 49 patients (ages 0.2-20.5 years) who underwent functional hemispherotomy at their institution. The first 14 cases were traditional functional hemispherotomies, and included temporal lobectomy, while the latter 35 were performed using a modified periinsular technique that the authors adopted in 2003. RESULTS Thirty-eight of the 49 patients (77.6%) were seizure free at the termination of the study (mean follow-up 28.6 months). Of the 11 patients who were not seizure free, all had significant improvement in seizure frequency, with 6 patients (12.2%) achieving Engel Class II outcome and 5 patients (10.2%) achieving Engel Class III. There were no cases of Engel Class IV outcome. The effect of hemispherotomy was durable over time with no significant change in Engel class over the postoperative follow-up period. There was no statistical difference in outcome between surgery types. Analysis of factors contributing to seizure recurrence after hemispherotomy revealed no statistically significant predictors of treatment failure, although bilateral electrographic abnormalities on the preoperative electroencephalogram demonstrated a trend toward a worse outcome. CONCLUSIONS In the present study, hemispherotomy resulted in freedom from seizures in nearly 78% of patients; worthwhile improvement was demonstrated in all patients. The seizure reduction observed after hemispherotomy was durable over time, with only rare late failure. Bilateral electrographic abnormalities may be predictive of posthemispherotomy recurrent seizures.

A review of surgical intervention in the setting of traumatic central cord syndrome

BACKGROUND CONTEXT Surgical treatment in the setting of central cord syndrome (CCS) has become safer since Schneiders original description. It is generally accepted that a decompressive surgical intervention is a valid treatment option in a patient with CCS and radiographic evidence of spinal cord compression. The optimal timing of surgical intervention for CCS remains controversial. PURPOSE To review a single institutions experience managing CCS, with particular emphasis on surgical versus medical management, timing of surgery, neurologic outcomes, hospital length of stay, and complications. STUDY DESIGN Retrospective review. PATIENT SAMPLE One hundred twenty-six patients diagnosed with CCS were treated at Wake Forest University Baptist Medical Center between June 1985 and September 2006. OUTCOME MEASURES Neurological outcomes were measured using the Frankel grading scale. Other outcome measures included hospital and intensive care unit (ICU) length of stay and complication profiles. METHODS A retrospective chart review was performed on patients admitted to Wake Forest University Baptist Medical Center with the diagnosis of traumatic central cord injury from June 1985 to September 2006 with institutional review board approval. Neurologic status was recorded on presentation and at maximum follow-up using the Frankel classification. The surgical cohort was stratified into three subgroups with regard to the timing of surgical intervention after injury: surgery less than 24 hours after injury, surgery greater than 24 hours after injury but during the initial admission, and delayed operative intervention on a second hospital admission. Other variables collected included ICU and hospital length of stay and complication profiles. Data analyses were performed using SPSS (SPSS, Chicago, IL, USA) and Excel 2002 (Microsoft, Seattle, WA, USA). RESULTS A total of 126 patients treated for CCS were reviewed. Sixty-seven patients received surgery compared with 59 patients managed nonoperatively. Of those managed operatively, 16 patients received surgery within 24 hours of the time of injury. There were 34 patients who received surgery greater than 24 hours after the time of injury but during their initial admission with a mean time to surgery of 6.4 days (5-52 days). There were 17 patients who received their operation on a second hospital admission with a mean time interval of 137 days between injury and surgery (3-209). Mean follow-up was 32 months (1-210 months). An improvement in Frankel grade was seen in the overall operative cohort compared with those patients who received medical management alone. No statistically significant difference in neurologic outcome using Frankel grades was identified between the surgical subgroups with regard to timing of surgery. A trend toward decreased length of stay was seen in the surgical subgroup that received surgery during their initial admission. No statistically significant difference was identified between complication rates for the operative and nonoperative groups; however, a trend toward fewer complications and deaths was seen in those who received surgery in the first 24 hours or during the initial hospitalization. CONCLUSIONS Surgical treatment in the setting of CCS has become safer since Schneiders original description. Acknowledging its numerous limitations, this retrospective study supports surgical intervention in the setting of CCS as a safe effective management option. Improved Frankel grades were identified in those patients managed surgically compared with those receiving medical management alone. The data further shed light on the safety and potential benefits of early operative intervention for acute CCS compared with delayed surgical treatment. A prospective randomized controlled trial is needed to definitively compare surgical versus medical management and/or early versus delayed surgical treatment in the setting of traumatic CCS.

Complete versus anterior two-thirds corpus callosotomy in children: analysis of outcome

OBJECT The goal of this study was to evaluate the efficacy of anterior versus complete sectioning of the corpus callosum in children suffering from medically refractory epilepsy. The authors report seizure outcome in patients who underwent anterior two-thirds or complete corpus callosotomy (CC) during the period 1995-2008 at St. Louis Childrens Hospital. METHODS The medical records of 27 children and adolescents with a minimum follow-up of 6 months were retrospectively evaluated with respect to seizure status, anticonvulsant outcomes, and subjective results. Preoperatively, patients suffered from a variety of seizure types that occurred daily, weekly, or episodically. The male/female ratio was 19:8, and patients ranged in age between 3 and 19 years (mean 9.93 years). Seizure outcome, parental assessment of daily function, and changes in the number of prescribed antiepileptic drugs were all assessed. RESULTS Fifteen patients underwent an initial anterior two-thirds CC, and 12 underwent a complete CC. Of the 15 patients who underwent an anterior CC, 7 went on to receive a posterior CC. Seizure control was superior in children undergoing a complete CC (91%, Class I-III) versus an anterior two-thirds CC (75%, Class I-III). Seizure types most affected by CC included atonic, myoclonic, and absence. The number of postoperative antiepileptic drugs did not significantly change following CC in either the anterior only or complete groups. One patient experienced a transient disconnection syndrome that resolved within 4 weeks, and 4 patients experienced mild hemiparesis and speech delays that resolved with therapy. Three patients experienced surgical complications requiring a second operation. The overall daily function and attentiveness of the patients improved. CONCLUSIONS A complete CC should be considered as the initial procedure in lower-functioning children afflicted by absence, atonic, or myoclonic seizures. Severely affected higher-functioning children may also benefit from a complete CC, without clinically significant disconnection syndromes. A completion posterior CC may benefit patients in whom a prior anterior CC has failed.

Simplified harvest of autologous pericranium for duraplasty in Chiari malformation Type I. Technical note.

The authors describe a method of harvesting autologous pericranium for duraplasty in patients with Chiari malformation Type I (CM-I) that avoids excessive exposure or a second incision. Nonautologous dural grafts have been associated with numerous complications including hemorrhage, bacteria and virus transmission, fatal Creutzfeldt-Jakob disease transmission, foreign body reaction, systemic immune response, excessive scarring, slower healing, premature graft dissolution, and wound dehiscence. Autogenous tissues have the advantage of being nonimmunogenic, nontoxic, readily available, and inexpensive. Pericranium is a preferred substrate because it is flexible, strong, and easily sutured for a watertight closure. Current literature supports the use of autogenous pericranium for dural grafting in CM-I procedures, but has heretofore failed to provide a method of harvest that avoids the complications associated with a larger exposure or second incision. The authors offer a simple alternative technique for using local pericranium in duraplasty for CM-I or other posterior fossa abnormalities.

Palliative hemispherotomy in children with bilateral seizure onset.

OBJECT Intractable epilepsy is a significant burden on families and on the cognitive development and quality of life (QOL) of patients. Periinsular hemispherotomy (PIH) for medically intractable epilepsy can benefit patients who qualify for this procedure. The ideal hemispherotomy candidate has ipsilateral ictal and interictal epileptiform activity, unilateral MR imaging abnormalities, contralateral hemiplegia, and a normal contralateral hemisphere. However, certain patients present with a mixed picture of bilateral electroencephalography (EEG) findings and severe intractable epilepsy, prompting consideration of a more aggressive treatment approach. This report introduces the possibility of surgery for patients who normally would not meet criteria for this treatment modality. METHODS In this retrospective chart review, the authors report on 7 patients with bilateral seizure onset noted on routine or video-EEG monitoring. A QOL phone questionnaire, based on the Quality of Life in Childhood Epilepsy tool, was administered to a parent. The authors reviewed each patients chart for surgical complications, changes in examination, QOL, limited neuropsychological outcomes, and seizure outcomes. They also investigated each chart for MR imaging and EEG findings as well as the patients epilepsy clinic notes for seizure semiology and frequency. RESULTS All patients enjoyed a decrease in seizure frequency and a subjective increase in QOL after PIH. Five patients (71%) achieved Engel Class I or II seizure control. The mean follow-up was 3.64 years (2-5.3 years). One patient is now off all antiseizure medication. No patient had a decrement in Full Scale IQ on postsurgical testing, and 2 (28.5%) of 7 individuals had increased adaptive and social functioning. Postsurgical examination changes included hemiplegia and homonymous hemianopia. CONCLUSIONS Hemispherotomy in patients with intractable epilepsy is generally reserved for individuals with unilateral epileptiform abnormalities or lesions on MR imaging. Seven patients in this study benefited from surgery despite bilateral seizure onset with improvement in seizure control and overall QOL. Thus, bilateral ictal onset does not necessarily preclude consideration for hemispherotomy in selected patients with severe medically refractory epilepsy.

Vacuum-assisted closure for complex cranial wounds involving the loss of dura mater

The aim in this study was to describe the safety and efficacy of vacuum-assisted closure (VAC) in patients with complex cranial wounds with extensive scalp, bone, and dural defects who were not candidates for immediate free tissue transfer. Five patients (4 men and 1 woman) ages 24-73 years with complex cranial wounds were treated with VAC at Wake Forest Baptist Medical Center. Etiologies included trauma, squamous cell carcinoma, and malignant meningioma. Cutaneous wound defects measured as large as 15 cm in diameter. Four of the 5 patients had open skull defects with concomitant dural defects, and 1 patient had dural dehiscence. After surgical debridement, all 5 patients were treated with the direct application of a VAC device to a reapproximated dura mater (1 patient), to a pericranial flap (1 patient), or to a regenerative tissue matrix overlying CNS tissue (3 patients). In all cases involving open cranial wounds, the VAC device promoted granulation tissue formation over the dural substitute, prevented CSF leakage, and kept the wounds free from local infection. The duration of VAC therapy ranged from 16 to 91 days. Although VAC therapy was intended as a temporary measure until these patients could be stabilized for larger tissue transfer procedures or they succumbed to their primary pathology, 1 patient had a successful skin graft following VAC therapy. Hydrocephalus requiring shunt placement developed in 2 patients during VAC therapy. The VAC dressings applied to a tissue matrix or other barrier over brain tissue in extensive cranial wounds are safe and well tolerated, providing a functional barrier and preventing infection.

Concussions: What a neurosurgeon should know about current scientific evidence and management strategies

Background: There has been a tremendous amount of interest focused on the topic of concussions over the past few decades. Neurosurgeons are frequently consulted to manage patients with mild traumatic brain injuries (mTBI) that have radiographic evidence of cerebral injury. These injuries share significant overlap with concussions, injuries that typically do not reveal radiographic evidence of structural injury, in the realms of epidemiology, pathophysiology, outcomes, and management. Further, neurosurgeons often manage patients with extracranial injuries that have concomitant concussions. In these cases, neurosurgeons are often the only “concussion experts” that patients encounter. Results: The literature has been reviewed and data have been synthesized on the topic including sections on historical background, epidemiology, pathophysiology, diagnostic advances, clinical sequelae, and treatment suggestions, with neurosurgeons as the intended target audience. Conclusions: Neurosurgeons should have a fundamental knowledge of the scientific evidence that has developed regarding concussions and be prepared to guide patients with treatment plans.

Estimation of skull table thickness with clinical CT and validation with microCT

Brain injuries resulting from motor vehicle crashes (MVC) are extremely common yet the details of the mechanism of injury remain to be well characterized. Skull deformation is believed to be a contributing factor to some types of traumatic brain injury (TBI). Understanding biomechanical contributors to skull deformation would provide further insight into the mechanism of head injury resulting from blunt trauma. In particular, skull thickness is thought be a very important factor governing deformation of the skull and its propensity for fracture. Current computed tomography (CT) technology is limited in its ability to accurately measure cortical thickness using standard techniques. A method to evaluate cortical thickness using cortical density measured from CT data has been developed previously. This effort validates this technique for measurement of skull table thickness in clinical head CT scans using two postmortem human specimens. Bone samples were harvested from the skulls of two cadavers and scanned with microCT to evaluate the accuracy of the estimated cortical thickness measured from clinical CT. Clinical scans were collected at 0.488 and 0.625 mm in plane resolution with 0.625 mm thickness. The overall cortical thickness error was determined to be 0.078 ± 0.58 mm for cortical samples thinner than 4 mm. It was determined that 91.3% of these differences fell within the scanner resolution. Color maps of clinical CT thickness estimations are comparable to color maps of microCT thickness measurements, indicating good quantitative agreement. These data confirm that the cortical density algorithm successfully estimates skull table thickness from clinical CT scans. The application of this technique to clinical CT scans enables evaluation of cortical thickness in population‐based studies.

Motor vehicle crash-related subdural hematoma from real-world head impact data

Abstract Approximately 1,700,000 people sustain a traumatic brain injury (TBI) each year and motor vehicle crashes (MVCs) are a leading cause of hospitalization from TBI. Acute subdural hematoma (SDH) is a common intracranial injury that occurs in MVCs associated with high mortality and morbidity rates. In this study, SDH volume and midline shift have been analyzed in order to better understand occupant injury by correlating them to crash and occupant parameters. Fifty-seven head computed tomography (CT) scans were selected from the Crash Injury Research Engineering Network (CIREN) with Abbreviated Injury Scale (AIS) level 3+ SDH. Semi-automated methods were used to isolate the intracranial volume. SDH and additional occupant intracranial injuries were segmented across axial CT images, providing a total SDH injury volume. SDH volume was correlated to crash parameters and occupant characteristics. Results show a positive correlation between SDH volume and crash severity in near-side and frontal crashes. Additionally, the location of the resulting hemorrhage varied by crash type. Those with greater SDH volumes had significantly lower Glasgow Coma Scale (GCS) scores at the crash site in near-side crashes. Age and fracture type were found to be significant contributors to SDH volume. This study is a volumetric analysis of real world brain injuries and known MVC impacts. The results of this study demonstrate a relationship among SDH volume, crash mechanics, and occupant characteristics that provide a better understanding of the injury mechanisms of MVC-associated TBI.