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Michael S. Turner

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Michael F. O'Brien, David Peterson and H. Alan Crockard

✓ Extreme-lateral lumbar disc herniations present a surgical challenge because the conventional posterior approach requires bone resection for complete visualization of the pathology. The authors have identified constant anatomical landmarks in cadaveric dissections that facilitate access to the intervertebral foramen when combined with a posterolateral approach, as described by Watkins, for lumbar spinal fusion. The authors describe a technique that allows rapid localization and safe excision of these extreme-lateral lumbar disc herniations without the need for bone resection.

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Stephen M. Pirris, Eric W. Nottmeier, Sherri Kimes, Michael O'Brien and Gazanfar Rahmathulla

Object

Considerable biological research has been performed to aid bone healing in conjunction with lumbar fusion surgery. Iliac crest autograft is often considered the gold standard because it has the vital properties of being osteoconductive, osteoinductive, and osteogenic. However, graft site pain has been widely reported as the most common donor site morbidity. Autograft site pain has led many companies to develop an abundance of bone graft extenders, which have limited proof of efficacy. During the surgical consent process, many patients ask surgeons to avoid harvesting autograft because of the reported pain complications. The authors sought to study postoperative graft site pain by simply asking patients whether they knew which iliac crest was grafted when a single skin incision was made for the fusion operation.

Methods

Twenty-five patients underwent iliac crest autografting with allograft reconstruction during instrumented lumbar fusion surgery. In all patients the autograft was harvested through the same skin incision but with a separate fascial incision. At various points postoperatively, the patients were asked if they could tell which iliac crest had been harvested, and if so, how much pain did it cause (10-point Numeric Rating Scale).

Results

Most patients (64%) could not correctly determine which iliac crest had been harvested. Of the 9 patients who correctly identified the side of the autograft, 7 were only able to guess. The 2 patients who confidently identified the side of grafting had no pain at rest and mild pain with activity. One patient who incorrectly guessed the side of autografting did have significant sacroiliac joint degenerative pain bilaterally.

Conclusions

Results of this study indicate the inability of patients to clearly define their graft site after iliac crest autograft harvest with allograft reconstruction of the bony defect unless they have a separate skin incision. This simple, easily reproducible pilot study can be expanded into a larger, multiinstitutional investigation to provide more definitive answers regarding the ideal, safe, and cost-effective bone graft material to be used in spinal fusions.

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Ian McCarthy, Michael O'Brien, Christopher Ames, Chessie Robinson, Thomas Errico, David W. Polly Jr. and Richard Hostin

Object

Incremental cost-effectiveness analysis is critical to the efficient allocation of health care resources; however, the incremental cost-effectiveness ratio (ICER) of surgical versus nonsurgical treatment for adult spinal deformity (ASD) has eluded the literature, due in part to inherent empirical difficulties when comparing surgical and nonsurgical patients. Using observed preoperative health-related quality of life (HRQOL) for patients who later underwent surgery, this study builds a statistical model to predict hypothetical quality-adjusted life years (QALYs) without surgical treatment. The analysis compares predicted QALYs to observed postoperative QALYs and forms the resulting ICER.

Methods

This was a single-center (Baylor Scoliosis Center) retrospective analysis of consecutive patients undergoing primary surgery for ASD. Total costs (expressed in 2010 dollars) incurred by the hospital for each episode of surgical care were collected from administrative data and QALYs were calculated from the 6-dimensional Short-Form Health Survey, each discounted at 3.5% per year. Regression analysis was used to predict hypothetical QALYs without surgery based on preoperative longitudinal data for 124 crossover surgical patients with similar diagnoses, baseline HRQOL, age, and sex compared with the surgical cohort. Results were projected through 10-year follow-up, and the cost-effectiveness acceptability curve (CEAC) was estimated using nonparametric bootstrap methods.

Results

Three-year follow-up was available for 120 (66%) of 181 eligible patients, who were predominantly female (89%) with average age of 50. With discounting, total costs averaged $125,407, including readmissions, with average QALYs of 1.93 at 3-year follow-up. Average QALYs without surgery were predicted to be 1.6 after 3 years. At 3- and 5-year follow-up, the ICER was $375,000 and $198,000, respectively. Projecting through 10-year follow-up, the ICER was $80,000. The 10-year CEAC revealed a 40% probability that the ICER was $80,000 or less, a 90% probability that the ICER was $90,000 or less, and a 100% probability that the ICER was less than $100,000.

Conclusions

Based on the WHO's suggested upper threshold for cost-effectiveness (3 times per capita GDP, or $140,000 in 2010 dollars), the analysis reveals that surgical treatment for ASD is cost-effective after a 10-year period based on predicted deterioration in HRQOL without surgery. The ICER well exceeds the WHO threshold at earlier follow-up intervals, highlighting the importance of the durability of surgical treatment in assessing the value of surgical intervention. Due to the study's methodology, the results are dependent on the predicted deterioration in HRQOL without surgery. As such, the results may not extend to patients whose HRQOL would remain steady without surgery. Future research should therefore pursue a direct comparison of QALYs for surgical and nonsurgical patients to better understand the cost-effectiveness of surgery for the average ASD patient.

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Kristian Aquilina, Donncha F. O’Brien, Michael A. Farrell and Ciaran Bolger

✓The authors report on the case of a craniopharyngioma arising in the cerebellopontine angle (CPA) in a patient with Gardner syndrome. Although familial adenomatous polyposis (FAP) is associated with intracranial neoplasms, the current case is only the third reported craniopharyngioma in a patient with Gardner syndrome. Two of these tumors, including that of the current case, originated in the CPA, an unusual location for craniopharyngiomas. The literature concerning FAP and its associations with intracranial neoplasia, as well as the pathogenesis of craniopharyngiomas in the posterior fossa, is discussed.

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Laura A. Snyder, Harry Shufflebarger, Michael F. O'Brien, Harjot Thind, Nicholas Theodore and Udaya K. Kakarla

Object

Isthmic spondylolysis can significantly decrease functional abilities, especially in adolescent athletes. Although treatment can range from observation to surgery, direct screw placement through the fractured pars, or Buck's procedure, may be a more minimally invasive procedure than the more common pedicle screw-hook construct.

Methods

Review of surgical databases identified 16 consecutive patients treated with Buck's procedure from 2004 to 2010. Twelve patients were treated at Miami Children's Hospital and 4 at Barrow Neurological Institute. Demographics and clinical and radiographic outcomes were recorded and analyzed retrospectively.

Results

The 16 patients had a median age of 16 years, and 14 were 20 years or younger at the time of treatment. Symptoms included axial back pain in 100% of patients with concomitant radiculopathy in 38%. Pars defects were bilateral in 81% and unilateral in 19% for a total of 29 pars defects treated using Buck's procedure. Autograft or allograft augmented with recombinant human bone morphogenetic protein as well as postoperative bracing was used in all cases. Postoperatively, symptoms resolved completely or partially in 15 patients (94%). Of 29 pars defects, healing was observed in 26 (89.6%) prior to 1 revision surgery, and an overall fusion rate of 97% was observed at last radiological follow-up. There were no implant failures. All 8 athletes in this group had returned to play at last follow-up.

Conclusions

Direct screw repair of the pars interarticularis defect as described in this series may provide a more minimally invasive treatment of adolescent patients with satisfactory clinical and radiological outcomes, including return to play of adolescent athletes.

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Michael A. Murphy, Terence J. O'Brien, Kevin Morris and Mark J. Cook

Object. The aim of this study was to review seizure outcome, imaging modalities used, and complications following surgery in patients with epilepsy who had undergone multimodality image-guided surgery at our institution.

Methods. Data from patients with epilepsy who had undergone surgery between April 1999 and October 2001 were reviewed. During this time period, 116 operations were performed in 109 patients with medically refractory epilepsy. Among these patients, 22 were selected to undergo multimodality image-guided surgery primarily on the basis of whether they had no lesion visible on conventional magnetic resonance (MR) imaging sequences, multiple lesions, or one very large lesion that could not be completely resected without the risk of significant postoperative morbidity. A fourth group of patients in whom there was a single lesion in the eloquent cortex, a location associated with a significant risk of postoperative morbidity, was also included in the analysis. This latter group was assessed with the aid of intracranial grid electrodes that were coregistered to the MR image and were used intraoperatively to minimize electrode position error. Other imaging modalities used included positron emission tomography (PET), fluid-attenuated inversion recovery (FLAIR) MR imaging, and subtracted ictal–interictal single-photon positron emission computerized tomography (SPECT) coregistered with MR imaging (SISCOM). After coregistration, images were then downloaded onto an image-guided surgical system and the epileptogenic area was then resected.

The mean patient age was 33 years (range 17–46 years), and there was a mean follow up of 27 months (range 14–41 months). Multimodality coregistrations used were as follows: nine PET scans, seven subdural electrode grids, four SISCOM studies, one FLAIR MR image, and one combined PET/subdural grid. Seizure outcome was excellent in 17 patients (77%) and not excellent in five (23%), or favorable in 19 (86%) and unfavorable in three (14%). Six patients (27%) had a transient neurological deficit, one patient (5%) a permanent major deficit, and three patients (15%) a permanent minor deficit. Five patients (24%) had a transient psychiatric problem postoperatively.

Conclusions. Multimodality image-guided surgery offers a new perspective in surgery for epilepsy. Functional imaging modalities previously lateralized and often localized a seizure focus, but did not provide enough anatomical information to resect the epileptogenic zone confidently and safely. The coregistration of these modalities to a volumetric MR image and their incorporation into an image-guided system has allowed surgeons to offer surgery to patients who may not previously have been considered eligible, with outcomes comparable to those in patients with more straightforward lesional epilepsy.

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Joseph R. O'Brien and William D. Smith

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Ross P. Carne, Terence J. O'Brien, Christine J. Kilpatrick, Lachlan R. MacGregor, Rodney J. Hicks, Michael A. Murphy, Stephen C. Bowden, Andrew H. Kaye and Mark J. Cook

Abstract

Object. The syndrome of medial temporal lobe epilepsy (MTLE) may occur in patients in whom magnetic resonance (MR) images demonstrate normal findings. In these patients, there is no evidence of hippocampal sclerosis on neuroimaging, and histopathological examination of the resected hippocampus does not reveal significant neuron loss. In this paper the authors describe the distinct clinical features of this MTLE subtype, referred to as paradoxical temporal lobe epilepsy (PTLE).

Methods. The authors selected 12 consecutive patients with preoperative findings consistent with MTLE in whom MR imaging did not demonstrate any hippocampal abnormality. Onset of hippocampal seizure was confirmed by long-term intracranial monitoring. There were six female and six male patients with a mean age of 32 ± 11 years (mean ± standard deviation [SD]) at presentation. These patients' seizure histories, available hippocampal volumetric measurements, and hippocampal cell densities in different subfields were reviewed. Sharp electrode recordings from dentate granule cells that had been maintained in hippocampal slices provided a measure of excitation and inhibition in the tissue. We compared these data with those of a cohort of 50 randomly selected patients who underwent anteromedial temporal resection for medial temporal sclerosis (MTS) during the same time period (1987–1999). The durations of follow up (means ± SDs) for the PTLE and MTS groups were 51 ± 59 months and 88 ± 44 months, respectively.

A history of febrile seizure was present less frequently in the PTLE group (8%) than in the MTS group (34%). Other risk factors for epilepsy such as trauma, meningoencephalitis, or perinatal injuries were present more frequently in the PTLE group (50%) than in the MTS cohort (36%). In patients in the PTLE group the first seizure occurred later in life (mean age at seizure onset 14 years in the PTLE group compared with 9 years in the MTS group, p = 0.09).

Ten patients (83%) in the PTLE cohort and 23 patients (46%) in the MTLE cohort had secondary generalization of their seizures. Among patients with PTLE, volumetric measurements (five patients) and randomized blinded visual inspection (seven patients) of the bilateral hippocampi revealed no atrophy and no increased T2 signal change on preoperative MR images. All patients with PTLE underwent anteromedial temporal resection (amygdalohippocampectomy, in five patients on the left side and in seven on the right side). Electrophysiological studies of hippocampal slices demonstrated that dentate granule cells from patients with PTLE were significantly less excitable than those from patients with MTS. The mean pyramidal cell loss in the CA1 subfield in patients in the PTLE group was 20% (range 0–59%) and that in patients in the MTS group was 75% (range 41–90%) (p < 0.001). Maximal neuron loss (mean loss 38%) occurred in the CA4 region in six patients with PTLE (end folium sclerosis). At the last follow-up examination, six patients (50%) in the PTLE group were seizure free compared with 38 patients (76%) in the MTS group.

Conclusions. Clinical PTLE is a distinct syndrome with clinical features and surgical outcomes different from those of MTS.

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Blake C. Phillips, Michael Gelsomino, Ambre' L. Pownall, Eylem Ocal, Horace J. Spencer, Mark S. O'Brien and Gregory W. Albert

Object

Many patients with myelomeningocele (MMC) develop hydrocephalus, and most will undergo CSF diversion. The goal of this retrospective study was to determine whether there was a change in the shunt rate over the 7 consecutive years of the study. The authors will also identify the criteria used to determine the need for shunt placement.

Methods

During a 7-year period, 73 patients underwent MMC closure at Arkansas Children's Hospital. The shunt rate for each year was calculated. Clinical characteristics were evaluated, including apneic and bradycardic spells, CSF leak, level of the MMC, head circumference, and rate of head growth. In addition, radiological images were reviewed, and the frontooccipital horn ratio (FOHR), ventricular index (VI), and thalamooccipital distance (TOD) were calculated. Comparisons were made between those patients who underwent shunt placement and those who did not.

Results

One patient was excluded due to death in the perinatal period. Of the 72 remaining patients, 54 (75%) underwent placement of a ventriculoperitoneal shunt. This rate did not change significantly over time. Between the cohorts with and without a shunt there was no significant difference in age, sex, or race. There was no significant difference in apneic episodes or bradycardic episodes. There was a statistically significant difference in fontanelle characteristics, head circumference at birth, and rate of head growth. Patients who required CSF diversion had a mean head growth of 0.32 cm/day compared with those who did not receive a shunt (0.13 cm/day; p < 0.05). All radiological parameters were found to be statistically significant.

Conclusions

In this study, several classic indicators of hydrocephalus in the neonate were not found to be significantly associated with the need for CSF diversion. Fontanelle characteristics, head circumference at birth, and head growth velocity were associated with the need for shunt placement. Imaging information including the VI, TOD, and FOHR are statistically significant measures to evaluate prior to placement of a ventriculoperitoneal shunt. The optimal patient with MMC for CSF diversion will have full to tense fontanelle, increasing head circumference of more than 3 mm/day, and radiological evidence of an elevated VI, TOD, and/or FOHR.