Motion Detection and Correction for Frame-Based Stereotactic Localization.

Frame-based stereotactic localization is an important step for targeting during a surgical procedure. The motion may cause artifacts in this step reducing the accuracy of surgical targeting. While modeling of motion in real-life scenarios may be difficult, herein we analyzed the case where motion was suspected to impact the localization step. In this case, a scan with and without motion was performed with a 3N localizer, allowing for a thorough analysis. Pseudo-bending of straight rods was seen when analyzing the data. This pseudo-bending appears to occur because head-frame motion during imaging acquisition decreases the accuracy of the subsequent reconstruction, which depends on Digital Imaging and Communications in Medicine (DICOM) metadata to specify the slice-to-slice location that assumes embedded object stability. Comparison of single-slice and multi-slice stereotactic localization allowed for comparative errors for each slice in a volume. This comparative error demonstrated low error when the patient was under general anesthesia and presumed not to have moved, whereas a higher error was present during the scan with motion. Pseudo-bending can be corrected by using only localizer fiducial-based information to reorient the pixels in the volume, thus creating a reoriented localizer scan. Finally, targeting demonstrated a low error of 0.1 mm (+/- 0.1 mm) using this reoriented localizer scan, signifying that this method could be used to improve or recover from motion problems. Finally, it is concluded that stability and elimination of motion for all images utilized for stereotactic surgery are critical to ensure the best possible accuracy for the procedure.

Biplanar X-Ray Methods for Stereotactic Intraoperative Localization in Deep Brain Stimulation Surgery.

BACKGROUND: Efficacy in deep brain stimulation (DBS) is dependent on precise positioning of electrodes within the brain. Intraoperative fluoroscopy, computed tomography (CT), or magnetic resonance imaging are used for stereotactic intraoperative localization (StIL), but the utility of biplanar X-ray has not been evaluated in detail. OBJECTIVE: To determine if analysis of orthogonal biplanar X-rays using graphical analysis (GA), ray tracing (RT), and/or perspective projection (PP) can be utilized for StIL. METHODS: A review of electrode tip positions comparing postoperative CT to X-ray methods was performed for DBS operations containing orthogonal biplanar X-ray with referential spheres and pins. RESULTS: Euclidean (Re) errors for final DBS electrode position on intraoperative X-rays vs postoperative CT using GA, RT, and PP methods averaged 1.58 mm (±0.75), 0.74 mm (±0.45), and 1.07 mm (±0.64), respectively (n = 56). GA was more accurate with a ventriculogram. RT and PP predicted positions that correlated with third ventricular structures on ventriculogram cases. RT was the most stable but required knowledge of the geometric setup. PP was more flexible than RT but required well-distributed reference points. A single case using the O-arm demonstrated Re errors of 0.43 mm and 0.28 mm for RT and PP, respectively. In addition, these techniques could also be used to calculate directional electrode rotation. CONCLUSION: GA, RT, and PP can be employed for precise StIL during DBS using orthogonal biplanar X-ray. These methods may be generalized to other stereotactic procedures or instances of biplanar imaging such as angiograms, radiosurgery, or injection therapeutics.

Trigeminal and sphenopalatine ganglion stimulation for intractable craniofacial pain--case series and literature review.

INTRODUCTION: Facial pain is often debilitating and can be characterized by a sharp, stabbing, burning, aching, and dysesthetic sensation. Specifically, trigeminal neuropathic pain (TNP), anesthesia dolorosa, and persistent idiopathic facial pain (PIFP) are difficult diseases to treat, can be quite debilitating and an effective, enduring treatment remains elusive. METHODS: We retrospectively reviewed our early experience with stimulation involving the trigeminal and sphenopalatine ganglion stimulation for TNP, anesthesia dolorosa, and PIFP between 2010-2014 to assess the feasibility of implanting at these ganglionic sites. Seven patients received either trigeminal and/or sphenopalatine ganglion stimulation with or without peripheral nerve stimulation, having failed multiple alternative modalities of treatment. The treatments were tailored on the physical location of pain to ensure regional coverage with the stimulation. RESULTS: Fluoroscopy or frameless stereotaxy was utilized to place the sphenopalatine and/or trigeminal ganglion stimulator. All patients were initially trialed before implantation. Trial leads implanted in the pterygopalatine fossa near the sphenopalatine ganglion were implanted via transpterygoid (lateral-medial, infrazygomatic) approach. Trial leads were implanted in the trigeminal ganglion via percutaneous Hartel approach, all of which resulted in masseter contraction. Patients who developed clinically significant pain improvement underwent implantation. The trigeminal ganglion stimulation permanent implants involved placing a grid electrode over Meckel's cave via subtemporal craniotomy, which offered a greater ability to stimulate subdivisions of the trigeminal nerve, without muscular (V3) side effects. Two of the seven overall patients did not respond well to the trial and were not implanted. Five patients reported pain relief with up to 24-month follow-up. Several of the sphenopalatine ganglion stimulation patients had pain relief without any paresthesias. There were no electrode migrations or post-surgical complications. CONCLUSIONS: Refractory facial pain may respond positively to ganglionic forms of stimulation. It appears safe and durable to implant electrodes in the pterygopalatine fossa via a lateral transpterygoid approach. Also, implantation of an electrode grid overlying Meckel's cave appears to be a feasible alternative to the Hartel approach. Further investigation is needed to evaluate the usefulness of these approaches for various facial pain conditions.

Acute Ischemic Stroke During Deep Brain Stimulation Surgery of Globus Pallidus Internus: Report of 5 Cases.

BACKGROUND: Cerebrovascular accident (CVA) is a potentially devastating complication of deep brain stimulation (DBS) surgery. Although there are substantial data reporting the incidence and cause of hemorrhagic CVA, reports of acute ischemic infarctions during DBS implantation surgery are rare. OBJECTIVE: To present a series of 5 patients who experienced clinically significant ischemic CVA during microelectrode-guided globus pallidus internus (GPi) DBS, and evaluate the potential risk factors and mechanisms. METHODS: A retrospective analysis of GPi DBS surgeries performed between June 2010 and February 2015 at UCLA Medical Center and June 2010 and February 2014 at Cedars-Sinai Medical Centers was performed to identify stroke risk factors. Statistical analysis was performed, comparing the stroke group with all patients undergoing GPi DBS. RESULTS: All 5 patients developed acute onset of lethargy, dysarthria, and contralateral facial and/or hemibody weakness intraoperatively. Computed tomographic scans in all cases were negative for hemorrhage. Magnetic resonance images obtained in 3 patients revealed infarction in the posterior limb of the internal capsule. During the time period analyzed, a total of 234 GPi leads were placed in 129 patients, yielding a 2.14% rate of ischemic stroke per lead. No statistically significant risk factors were identified in the stroke group. Given the variability of symptom onset during surgery, the mechanism is not clear, but it could be related to compression, compromise, or vasospasm of lenticulostriate arteries and/or anterior choroidal branches near the GPi target. CONCLUSION: Ischemic stroke in GPi DBS is a significant complication for clinicians to be aware of and discuss with their patients preoperatively.

Effect of Cranial Window Diameter During Deep Brain Stimulation Surgery on Volume of Pneumocephalus.

OBJECTIVE: Successful deep brain stimulation (DBS) surgery necessitates high accuracy in targeting specific intracranial nuclei. Brain shift due to pneumocephalus can contribute to decreased accuracy. Larger burr holes and dural openings may increase pneumocephalus volume due to a greater degree of communication between the subdural space and extracranial air. The aim of this study is to determine if there is a statistically and clinically significant difference in postoperative pneumocephalus volume related to burr hole and durotomy size. MATERIALS AND METHODS: DBS electrodes were surgically implanted through either large (14 mm) burr holes or small (4 mm) twist drill holes. Immediate postoperative computerized tomography (CT) scans of 165 electrode implantations in 85 patients from 2010 to 2013 were retrospectively analyzed. Student's t-test and Mann-Whitney U-test were employed with a threshold of significance set at p ≤ 0.05. RESULTS: No significant difference in pneumocephalus was identified between patients who had implantation of DBS electrodes through 4 mm twist drill holes (N = 71 hemispheres, 12.84 ± 9.79 cm(3) ) and those with large 14 mm burr holes (N = 87, 11.70 ± 7.46 cm(3) , p = 0.42). Volume of pneumocephalus did not correlate with duration of surgery or patient age. The groups did not differ significantly with respect to other aspects of surgical implantation technique or surgical duration. CONCLUSION: While identifying factors that may reduce pneumocephalus volume may be critical to improving stereotactic accuracy and targeting, the current results suggest that burr hole size may not alter the degree of brain shift.

Minimally invasive palliative resection of lumbar epidural metastasis.

Spinal metastatic lesions are the most common tumors encountered by spinal surgeons. As with procedures for degenerative disease, minimally invsive surgery techniques have been applied to minimize muscle and soft tissue destruction in procedures for tumor resection. Here, we present a 23-year-old female with radiculopathy and foot drop secondary to nerve root compression by epidural metastases from Ewing's sarcoma. This patient had a history of previous resection and instrumentation as well as multiple rounds of chemotherapy and radiation that failed to control her disease. The patient presented with three weeks of radicular pain and foot drop that was continuing to worsen at the time of her operation. The decision was therefore made to perform a palliative resection and decompression for relief of her progressive symptoms. In this video, we demonstrate a palliative tumor debulking and nerve root decompression utilizing an MIS approach. The video can be found here: http://youtu.be/tq4kbvKTebI.

Minimally invasive surgical decompression for lumbar spinal metastases.

BACKGROUND: The risk of significant morbidity and mortality often outweighs the benefit of surgical resection as palliative treatment for patients with high systemic disease burden, poor cardiopulmonary status, and previous spinal surgeries. Minimally invasive surgical (MIS) approaches to decompressing metastatic epidural cord compression (MECC) can address these issues and thereby make palliation a feasible option for these patients. CASE DESCRIPTION: We present the cases of three consecutively collected patients with severe neurological compromise secondary to lumbar epidural metastases who underwent MIS decompression and achieved improved functional outcome and quality of life. The first patient is a 23-year-old female with metastatic Ewing's sarcoma who presented with 2 weeks of a right foot drop and radiculopathic pain. The next case is that of a 71-year-old male with metastatic prostate cancer who presented with significant radiculopathic L5-S1 pain and severe motor deficits in his lower extremities. The last case is that of a 73-year-old male with metastatic hepatocellular carcinoma who presented with worsening left leg weakness, paresthesia, and dysethesia. Postoperatively, each patient experienced significant improvement and almost complete enduring return of function, strength, and resolution of pain. CONCLUSION: We demonstrate that MIS approaches to spinal decompression as palliative treatment for metastatic disease is a viable treatment in patients with a focal symptomatic lesion and comes with the benefits of decreased surgical morbidity inherent to the minimally invasive approach as well as excellent functional outcomes.

Hearing preservation after LINAC radiosurgery and LINAC radiotherapy for vestibular schwannoma.

Linear accelerators (LINAC) can deliver both radiosurgery and fractionated radiotherapy. In this systematic analysis, we compare hearing preservation in patients with vestibular schwannomas (VS) treated with either LINAC-based radiotherapy (SRT) or LINAC-based radiosurgery (SRS), with an emphasis on the prognostic implications of tumor size and patient age. A total of 400 patients met our criteria for LINAC SRS, with an average hearing preservation rate of 66.3%. Patients with smaller tumors (<3.0 cm(3)) treated with SRS had similar hearing preservation rates to those with larger tumors. However, younger patients (<55 years) demonstrated improved hearing preservation compared to older patients (≥55 years). When comparing LINAC SRS to LINAC SRT directly, hearing preservation was similar in patients with smaller tumors. However, patients with larger tumors (≥3.0cm(3)) who received SRT had higher hearing preservation rates than those who received SRS. A total of 629 patients met our criteria for LINAC SRT, with an average hearing preservation rate of 75.3%. Patients with larger tumors who received SRT had better hearing outcomes than those with smaller tumors, while there was no significant difference in hearing preservation in younger patients compared to older patients. When comparing LINAC SRS to LINAC SRT directly, younger patients had similar hearing preservation rates. However, older patients who received SRT had improved hearing preservation compared to those who received SRS. In a direct comparison of average hearing preservation, patients who received SRT had higher hearing preservation rates than those who underwent SRS. Prospective studies will be needed to further characterize radiation dose and other variables.

Surgical approaches to tinnitus treatment: A review and novel approaches.

BACKGROUND: Tinnitus, a profoundly widespread auditory disorder, is characterized by the perception of sound in the absence of external stimulation. The aim of this work is to review the various surgical treatment options for tinnitus, targeting the various disruption sites along the auditory pathway, as well as to indicate novel neuromodulatory techniques as a mode of tinnitus control. METHODS: A comprehensive analysis was conducted on published clinical and basic neuroscience research examining the pathophysiology and treatment options of tinnitus. RESULTS: Stereotactic radiosurgery methods and microvascular decompressions are indicated for tinnitus caused by underlying pathologies such as vestibular schwannomas or neurovascular conflicts of the vestibulocochlear nerve at the level of the brainstem. However, subsequent hearing loss and secondary tinnitus may occur. In patients with subjective tinnitus and concomitant sensorineural hearing loss, cochlear implantation is indicated. Surgical ablation of the cochlea, vestibulocochlear nerve, or dorsal cochlear nucleus, though previously suggested in earlier literature as viable treatment options for tinnitus, has been shown to be ineffective and contraindicated. Recently, emerging research has shown the neuromodulatory capacity of the somatosensory system at the level of the trigeminal nerve on the auditory pathway through its inputs at various nuclei in the central auditory pathway. CONCLUSION: Tinnitus remains to be a difficult disorder to treat despite the many surgical interventions aimed at eliminating the aberrant neuronal activity in the auditory system. A promising novel neuromodulatory approach using the trigeminal system to control such a bothersome and difficult-to-treat disorder deserves further investigation and controlled clinical trials.

The molecular biology and novel treatments of vestibular schwannomas.

Vestibular schwannomas are histopathologically benign tumors arising from the Schwann cell sheath surrounding the vestibular branch of cranial nerve VIII and are related to the NF2 gene and its product merlin. Merlin acts as a tumor suppressor and as a mediator of contact inhibition. Thus, deficiencies in both NF2 genes lead to vestibular schwannoma development. Recently, there have been major advances in our knowledge of the molecular biology of vestibular schwannomas as well as the development of novel therapies for its treatment. In this article the authors comprehensively review the recent advances in the molecular biology and characterization of vestibular schwannomas as well as the development of modern treatments for vestibular schwannoma. For instance, merlin is involved with a number of receptors including the CD44 receptor, EGFR, and signaling pathways, such as the Ras/raf pathway and the canonical Wnt pathway. Recently, merlin was also shown to interact in the nucleus with E3 ubiquitin ligase CRL4(DCAF1). A greater understanding of the molecular mechanisms behind vestibular schwannoma tumorigenesis has begun to yield novel therapies. Some authors have shown that Avastin induces regression of progressive schwannomas by over 40% and improves hearing. An inhibitor of VEGF synthesis, PTC299, is currently in Phase II trials as a potential agent to treat vestibular schwannoma. Furthermore, in vitro studies have shown that trastuzumab (an ERBB2 inhibitor) reduces vestibular schwannoma cell proliferation. With further research it may be possible to significantly reduce morbidity and mortality rates by decreasing tumor burden, tumor volume, hearing loss, and cranial nerve deficits seen in vestibular schwannomas.

Accuracy of frame-based stereotactic magnetic resonance imaging vs frame-based stereotactic head computed tomography fused with recent magnetic resonance imaging for postimplantation deep brain stimulator lead localization.

BACKGROUND: Introduction of the portable intraoperative CT scanner provides for a precise and cost-effective way of fusing head CT images with high-tesla MRI for the exquisite definition of soft tissue needed for stereotactic targeting. OBJECTIVE: To evaluate the accuracy of stereotactic electrode placement in patients undergoing deep brain stimulation (DBS) by comparing frame-based postimplantation intraoperative CT (iCT) images fused to a recent 3T-MRI with frame-based postimplantation intraoperative MRI (iMRI) alone. METHODS: Frame-based DBS surgeries of 46 targets performed from February 8, 2007 to April 28, 2008 in 26 patients with the use of immediate postimplantation iMRI for target localization were compared with frame-based immediate postimplantation iCT fused with a recent 3T brain MRI for DBS localization of 50 targets performed from August 13, 2008 to February 18, 2010 in 26 patients. Pre- and postoperative mid anterior commissure-posterior commissure line coordinates and XYZ coordinates for preoperatively calculated DBS targets (intended target) and for the permanent DBS lead tips were determined. The differences between preoperative DBS target and postoperative permanent DBS lead-tip coordinates based on postimplantation intraoperative MRI for the MRI-alone group and based on postimplantation intraoperative CT fused to recent preoperative MRI in the CT-MRI group were measured. The t test and Yuen test were used for comparison. RESULTS: No statistically significant differences were found between the 2 groups when comparing the pre- and postperative changes in mid anterior commissure-posterior commissure line coordinates and XYZ coordinates. CONCLUSION: Postimplantation DBS lead localization and therefore targeting accuracy was not significantly different between frame-based stereotactic 1.5T-MRI and frame-based stereotactic head CT fused with recent 3T-MRI.

Spontaneous intracranial hypotension and immediate improvement following epidural blood patch placement demonstrated by intracranial pressure monitoring. Case report.

The presentation of spontaneous intracranial hypotension (SIH) can be associated with various clinical and neuroimaging features that may impede a rapid diagnosis of this entity. The authors report the case of a patient who presented with bilateral third cranial nerve palsies and bilateral subdural hematomas. Intracranial pressure monitoring proved to be useful in the diagnosis and management of SIH in this patient.