Short-term and long-term outcomes of minimally invasive and open transforaminal lumbar interbody fusions: is there a difference?

OBJECT: Previous studies comparing minimally invasive transforaminal lumbar interbody fusion (MITLIF) with open TLIF have demonstrated that MITLIF reduces blood loss and decreases postoperative pain while preserving fusion rates and reducing complications. In this study, the authors wanted to compare outcomes of MITLIF with those of open TLIF to determine whether MITLIF also improves postoperative functional mobility and decreases the usage of pain medication. METHODS: In total, 75 consecutive patients who underwent either single-level open TLIF or MITLIF at the University of California, San Francisco, between 2006 and 2011 were included, and patients were followed up for an average of 5.05 years. Fifty patients underwent MITLIF and 25 underwent open TLIF. Primary outcomes included administration of morphine-equivalent narcotics and functional status on postoperative Day 1. Secondary outcomes included operative characteristics, complications, long-term fusion rates, and visual analog scale (VAS) scores. RESULTS: No statistically significant differences in age, sex, body mass index (BMI), level of disease, or surgical indication were detected between the open TLIF and MITLIF groups. Similarly, preoperative medication usage did not significantly differ between these groups. Intraoperatively, compared with TLIF, MITLIF resulted in decreased lengths of operation, lower blood loss, and fewer complications (p < 0.05). Total administration of morphine-equivalent pain medication in the hospital also tended to be lower in the MITLIF than in the TLIF group. Functional assessment by physical therapy on postoperative Day 1 demonstrated higher function in the MITLIF patients for transfer-related tasks, ambulatory ability, and distance walked than in the TLIF patients (p < 0.05). This translated to shorter inpatient hospitalizations (6.05 vs 4.8 days for open TLIF vs MITLIF patients, respectively, p = 0.006) and an average cost reduction of $3885 per MITLIF patient. Long-term fusion rates were 92% in the MITLIF group and 100% in the open TLIF group (p = 0.09). Preoperative VAS pain scores were 7.1 for the MITLIF patients and 7.6 for the TLIF patients (p = 0.26). At the last follow-up, the reported VAS pain score was 2.9 in the MITLIF patients and 3.5 in the open TLIF patients, but this difference was not statistically significant (p = 0.25). There was also no statistically significant difference in the degree change in this score (p = 0.44). CONCLUSIONS: The MITLIF approach achieves improved functional mobility, decreases the usage of postoperative pain medication, and significantly reduces cost compared with open TLIF while preserving long-term fusion rates. To the authors' knowledge, this is the first study comparing the postoperative usage of pain medication between treatments in the postoperative period before discharge.

Mini-open removal of intradural spinal tumor.

Minimally invasive surgical (MIS) approaches have gained popularity in many surgical fields. Potential advantages to a minimally invasive, spinal intradural approach include decreased operative blood loss, shorter hospitalization, and less post-operative pain. Potential disadvantages include longer operative times, decreased exposure, and difficulty closing the dura. Prior case series from our group and others have demonstrated successful tumor resections using MIS techniques without increased complications. In this 3D video, we demonstrate the key steps in our mini-open, transpinous approach for the resection of an intradural, extramedullary lumbar schwannoma. This operation is performed through a midline incision confined to one or two levels. The spinous process is removed. The paraspinal muscles are spread using a series of sequentially larger tubular dilators, and the first dilator is placed in the space previously occupied by the target level spinous process. The expandable tube retractor is then placed over the largest dilator and docked into place over the target laminae. The expandable tubular retractor is 6 centimeters in depth and 2.5 centimeters in width before expansion and is adjustable to 9 centimeters in depth and 4-5 centimeters in diameter which allows removal of intradural lesions confined to one or two spinal segments. The video can be found here: http://youtu.be/l_C4VruKYng .

Incidence and management of venous air embolisms during awake deep brain stimulation surgery in a large clinical series.

BACKGROUND/AIMS: Venous air embolism (VAE) is a potential complication during neurosurgical procedures, particularly in the sitting position. The diagnosis and management of VAE in patients undergoing awake deep brain stimulation (DBS) lead implantation in the sitting position are underreported. METHODS: We performed a retrospective chart review of 467 consecutive DBS surgeries at the University of California, San Francisco. Data was collected for patient demographics, diagnosis, intraoperative events, and postoperative course. RESULTS: Six cases of clinically diagnosed VAE were found, amounting to a total incidence of 1.3% per procedure. We did not observe a statistical association with patient age, diagnosis, or DBS target. The most common symptoms of intraoperative VAE were coughing, oxygen desaturation, and hypotension. In all cases, VAE was treated by copious irrigation of the surgical field and lowering the patient's head. In 4 cases, DBS implantation was abandoned because of ongoing symptoms of VAE. The respiratory outcome in all patients was good after several days of close observation. CONCLUSION: The incidence of VAE during DBS procedures is small, but prompt recognition and management of VAE are critical to avoid further associated complications.

Management of medically refractory trigeminal neuralgia in patients with multiple sclerosis.

OBJECT: Trigeminal neuralgia (TN) is a painful disorder that frequently causes lancinating, electrical shock-like pain in the trigeminal distribution. Common surgical treatments include microvascular decompression (MVD), radiosurgery, and radiofrequency ablation, and complete pain relief is generally achieved with a single treatment in 70 to 85% of cases for all modalities. In a subset of patients with multiple sclerosis (MS), however, the rates of surgical treatment failure and the need for additional procedures are significantly increased compared with those in patients without MS. In this study the authors report their experience with a cohort of 11 patients with TN who also had MS, and assess the efficacy of MVD, gamma knife surgery (GKS), and radiofrequency ablation in achieving complete or partial long-term pain relief. METHODS: Eleven patients with TN and MS who were treated by the senior author (N.B.) at the University of California, San Francisco were included in this study. All patients underwent GKS and/or radiofrequency ablation, and four received MVD. A detailed clinical history and intraoperative findings were recorded for each patient and frequent follow-up evaluations were performed, with a mean follow-up duration of 40.6 months (range 1-96 months). Pain was assessed for each patient by using the Barrow Neurological Institute scale (Scores I-V). CONCLUSIONS: Achieving complete pain relief in patients with TN and MS required significantly more treatments compared with all other patients with TN who did not have MS (p = 0.004). Even when compared with a group of 32 patients who had highly refractory TN, the cohort with MS required significantly more treatments (p = 0.05). Radiosurgery proved to be an effective procedure and resulted in fewer retreatments and longer pain-free intervals compared with MVD or radiofrequency ablation.

Recurrent or refractory trigeminal neuralgia after microvascular decompression, radiofrequency ablation, or radiosurgery.

OBJECT: Trigeminal neuralgia (TN) is characterized by paroxysmal lancinating pain in the trigeminal nerve distribution. When TN is refractory to medical management, patients are referred for microvascular decompression (MVD), radiofrequency ablation, or radiosurgery. After the initial treatment, patients may have refractory or recurrent symptoms requiring retreatment. The purpose of this study was to determine what factors are associated with the need for retreatment and which modality is most effective. METHODS: To define this population further, the authors evaluated a cohort of patients who required retreatment for TN. The mean follow-up periods were 51 months from the first treatment and 23 months from the last one, and these were comparable among treatment groups. CONCLUSIONS: Trigeminal neuralgia can recur after neurosurgical treatment. In this study the authors demonstrate that the number of patients requiring retreatment is not negligible. Lower retreatment rates were seen in patients who initially underwent radiosurgery, compared with those in whom MVD or radiofrequency ablation were performed. Radiosurgery was more likely to be the final treatment for recurrent TN regardless of the initial treatment. After retreatment, the majority of patients attained complete or very good pain relief. Pain relief after retreatment correlates with postoperative facial numbness.

A predictive algorithm for evaluating elevated serum prolactin in patients with a sellar mass.

Hyperprolactinemia occurs in patients with a prolactinoma and in those with a sellar mass compressing the pituitary stalk. Distinguishing these two diagnostic possibilities guides treatment with dopamine agonist therapy or surgical resection. We aimed to identify a simple, predictive algorithm to aid in the diagnosis of prolactinoma in patients with an elevated serum prolactin and a sellar mass. A case-control analysis of pathologically confirmed prolactinomas and non-endocrine secreting controls from the University of California, San Francisco was performed. From 2001 to 2011, this resulted in 177 patients with prolactinomas and 87 controls. Univariate and classification and regression tree (CART) analysis determined the significance of demographic variables, patient symptoms, laboratory values, and radiographic findings in distinguishing pathology. Additionally, a subset of patients with mildly elevated serum prolactin (25-125 ng/ml) was independently analyzed. Prolactinomas had a mean pre-operative prolactin of 858 ng/ml versus 17.57 ng/ml in controls (p<0.01). One hundred and two (62.6%) of the prolactinomas were macroadenomas (size >10mm) compared to 74 (92.5%) of the controls (p<0.01). CART analysis identified preoperative prolactin (>41.5 ng/ml), age (<40.5 years), and size (<17 mm) as being predictive of prolactinoma with a misclassification rate of 7.9% (21/264). Similar analysis on the subset of patients with mildly elevated serum prolactin (<125 ng/ml) identified size (<2.5 cm) and pre-operative prolactin (>40 ng/ml) as key variables. These two factors correctly predicted 98.6% (69/70) of cases. Our model correctly classifies most patients with elevated serum prolactin and identifies those patients most amenable to surgical treatment.

A review of percutaneous treatments for trigeminal neuralgia.

BACKGROUND: Common treatments for trigeminal neuralgia include percutaneous techniques, microvascular decompression, and Gamma Knife radiosurgery. Although microvascular decompression is considered the gold standard for treatment, percutaneous techniques remain an effective option for select patients. OBJECTIVE: To review the historical development, advantages, and limitations of the most common percutaneous procedures for trigeminal neuralgia: balloon compression (BC), glycerol rhizotomy (GR), and radiofrequency thermocoagulation (RF). METHODS: Publications reporting clinical outcomes after BC, GR, and RF were reviewed and included. Operative technique was based on the experience of the primary surgeon and senior author. RESULTS: All 3 percutaneous techniques (BC, GR, and RF) provide effective pain relief but differ in method and specificity of nerve injury. BC selectively injures larger pain fibers while sparing small fibers and does not require an awake, cooperative patient. Pain control rates up to 91% at 6 months and 66% at 3 years have been reported. RF allows somatotopic nerve mapping and selective division lesioning and provides pain relief in up to 97% of patients initially and 58% at 5 years. Multiple treatments improve outcomes but carry significant morbidity risk. GR offers similar pain-free outcomes of 90% at 6 months and 54% at 3 years but with higher complication rates (25% vs. 16%) compared with BC. Advantages of percutaneous techniques include shorter procedure duration, minimal anesthesia risk, and in the case of GR and RF, immediate patient feedback. CONCLUSION: Percutaneous treatments for trigeminal neuralgia remain safe, simple, and effective for achieving good pain control while minimizing procedural risk.

Targeted reduction in neurosurgical laboratory utilization: resident-led effort at a single academic institution.

OBJECT: Given economic limitations and burgeoning health care costs, there is a need to minimize unnecessary diagnostic laboratory tests. METHODS: The authors studied whether a financial incentive program for trainees could lead to fewer unnecessary laboratory tests in neurosurgical patients in a large, 600-bed academic hospital setting. The authors identified 5 laboratory tests that ranked in the top 13 of the most frequently ordered during the 2010-2011 fiscal year, yet were least likely to be abnormal or influence patient management. RESULTS: In a single year of study, there was a 47% reduction in testing of serum total calcium, ionized calcium, chloride, magnesium, and phosphorus. This reduction led to a savings of $1.7 million in billable charges to health care payers and $75,000 of direct costs to the medical center. In addition, there were no significant negative changes in the quality of care delivered, as recorded in a number of metrics, showing that this cost savings did not negatively impact patient care. CONCLUSIONS: Engaging physician trainees in quality improvement can be successfully achieved by financial incentives. Through the resident-led quality improvement incentive program, neurosurgical trainees successfully reduced unnecessary laboratory tests, resulting in significant cost savings to both the medical center and the health care system. Similar programs that engage trainees could improve the value of care being provided at other academic medical centers.

Tau reduction diminishes spatial learning and memory deficits after mild repetitive traumatic brain injury in mice.

OBJECTIVE: Because reduction of the microtubule-associated protein Tau has beneficial effects in mouse models of Alzheimer's disease and epilepsy, we wanted to determine whether this strategy can also improve the outcome of mild traumatic brain injury (TBI). METHODS: We adapted a mild frontal impact model of TBI for wildtype C57Bl/6J mice and characterized the behavioral deficits it causes in these animals. The Barnes maze, Y maze, contextual and cued fear conditioning, elevated plus maze, open field, balance beam, and forced swim test were used to assess different behavioral functions. Magnetic resonance imaging (MRI, 7 Tesla) and histological analysis of brain sections were used to look for neuropathological alterations. We also compared the functional effects of this TBI model and of controlled cortical impact in mice with two, one or no Tau alleles. RESULTS: Repeated (2-hit), but not single (1-hit), mild frontal impact impaired spatial learning and memory in wildtype mice as determined by testing of mice in the Barnes maze one month after the injury. Locomotor activity, anxiety, depression and fear related behaviors did not differ between injured and sham-injured mice. MRI imaging did not reveal focal injury or mass lesions shortly after the injury. Complete ablation or partial reduction of tau prevented deficits in spatial learning and memory after repeated mild frontal impact. Complete tau ablation also showed a trend towards protection after a single controlled cortical impact. Complete or partial reduction of tau also reduced the level of axonopathy in the corpus callosum after repeated mild frontal impact. INTERPRETATION: Tau promotes or enables the development of learning and memory deficits and of axonopathy after mild TBI, and tau reduction counteracts these adverse effects.

Intraoperative changes in transcranial motor evoked potentials and somatosensory evoked potentials predicting outcome in children with intramedullary spinal cord tumors.

OBJECT: Intraoperative dorsal column mapping, transcranial motor evoked potentials (TcMEPs), and somatosensory evoked potentials (SSEPs) have been used in adults to assist with the resection of intramedullary spinal cord tumors (IMSCTs) and to predict postoperative motor deficits. The authors sought to determine whether changes in MEP and SSEP waveforms would similarly predict postoperative motor deficits in children. METHODS: The authors reviewed charts and intraoperative records for children who had undergone resection for IMSCTs as well as dorsal column mapping and TcMEP and SSEP monitoring. Motor evoked potential data were supplemented with electromyography data obtained using a Kartush microstimulator (Medtronic Inc.). Motor strength was graded using the Medical Research Council (MRC) scale during the preoperative, immediate postoperative, and follow-up periods. Reductions in SSEPs were documented after mechanical traction, in response to maneuvers with the cavitational ultrasonic surgical aspirator (CUSA), or both. RESULTS: Data from 12 patients were analyzed. Three lesions were encountered in the cervical and 7 in the thoracic spinal cord. Two patients had lesions of the cervicomedullary junction and upper spinal cord. Intraoperative MEP changes were noted in half of the patients. In these cases, normal polyphasic signals converted to biphasic signals, and these changes correlated with a loss of 1-2 grades in motor strength. One patient lost MEP signals completely and recovered strength to MRC Grade 4/5. The 2 patients with high cervical lesions showed neither intraoperative MEP changes nor motor deficits postoperatively. Dorsal columns were mapped in 7 patients, and the midline was determined accurately in all 7. Somatosensory evoked potentials were decreased in 7 patients. Two patients each had 2 SSEP decreases in response to traction intraoperatively but had no new sensory findings postoperatively. Another 2 patients had 3 traction-related SSEP decreases intraoperatively, and both had new postoperative sensory deficits that resolved. One additional patient had a CUSA-related SSEP decrease intraoperatively, which resolved postoperatively, and the last patient had 3 traction-related sensory deficits and a CUSA-related sensory deficit postoperatively, none of which resolved. CONCLUSIONS: Intraoperative TcMEPs and SSEPs can predict the degree of postoperative motor deficit in pediatric patients undergoing IMSCT resection. This technique, combined with dorsal column mapping, is particularly useful in resecting lesions of the upper cervical cord, which are generally considered to be high risk in this population. Furthermore, the spinal cord appears to be less tolerant of repeated intraoperative SSEP decreases, with 3 successive insults most likely to yield postoperative sensory deficits. Changes in TcMEPs and SSEP waveforms can signal the need to guard against excessive manipulation thereby increasing the safety of tumor resection.

Delayed acute spinal cord injury following intracranial gunshot trauma: case report.

The authors report the case of a patient who presented with a hoarse voice and left hemiparesis following a gunshot injury with trajectory entering the left scapula, traversing the suboccipital bone, and coming to rest in the right lateral medullary cistern. Following recovery from the hemiparesis, abrupt quadriparesis occurred coincident with fall of the bullet into the anterior spinal canal. The bullet was retrieved following a C-2 and C-3 laminectomy, and postoperative MR imaging confirmed signal change in the cord at the level where the bullet had lodged. The patient then made a good neurological recovery. Bullets can fall from the posterior fossa with sufficient momentum to cause an acute spinal cord injury. Consideration for craniotomy and bullet retrieval should be given to large bullets lying in the CSF spaces of the posterior fossa as they pose risk for acute spinal cord injury.

Association of morbidity with extent of resection and cavernous sinus invasion in sphenoid wing meningiomas.

Sphenoid wing meningiomas (SWMs) typically are histologically benign, insidious lesions, but the propensity of these tumors for local invasion makes disease control very challenging. In this review, we assess whether the degree of resection and extent of cavernous sinus invasion affects morbidity, mortality, and recurrence in patients with SWM. A comprehensive search of the English-language literature was performed. Patients were stratified according to extent of resection and extent of cavernous sinus invasion, and tumor recurrence rate, morbidity, and mortality were analyzed. A total of 23 studies and 131 patients were included. Overall recurrence and surgical mortality rate were 11% and 2%, respectively (average follow-up = 65 months). Cranial nerve III palsy was significantly associated with incompletely versus completely resected SWMs (7 to 0%) as well as meningiomas with cavernous sinus invasion versus no sinus invasion (14 vs. 0%). No significant difference in tumor recurrence rate was noted between these groups. In conclusion, complete excision of SWMs is always recommended whenever possible, but surgeons should acknowledge that there is nonetheless a chance of recurrence and should weigh this against the risk of causing cranial nerve injuries.

Collagen VI protects neurons against Abeta toxicity.

Amyloid-beta (Abeta) peptides, widely presumed to cause Alzheimer's disease, increased mouse neuronal expression of collagen VI through a mechanism involving transforming growth factor signaling. Reduction of collagen VI augmented Abeta neurotoxicity, whereas treatment of neurons with soluble collagen VI blocked the association of Abeta oligomers with neurons, enhanced Abeta aggregation and prevented neurotoxicity. These results identify collagen VI as an important component of the neuronal injury response and demonstrate its neuroprotective potential.