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Daily bibliographic review of the Neurosurgery Department. La Fe University Hospital. Valencia, Spain

Flatness of the infratentorial space associated with hemifacial spasm

Flatness of the infratentorial space associated with hemifacial spasm

Acta Neurochir (2016) 158:1405–1412

Whether a difference in morphology of the infratentorial space is associated with hemifacial spasm is not well understood. The aim of this study was to analyze the three-dimensional conformation of the infratentorial space and evaluate any possible contribution of morphological characteristics to the development of neurovascular compression leading to hemifacial spasm.

Methods We enrolled 25 patients with hemifacial spasm and matched them by age and sex to controls. The extent of the three-dimensional axes and the volume of the infratentorial space were measured using image analysis software for three-dimensional MRI.We evaluated the correlation between a morphological difference in the infratentorial space and changes in vascular configuration in the brain stem.

Results We found no statistical difference in volumetric analyses. The mean aspect ratio on the coronal plane (the ratio of the Z to X extent) of the infratentorial space in patients with hemifacial spasm was significantly lower (p < 0.01) than that in controls, as was the mean aspect ratio on the sagittal plane (the ratio of Z to Yextent, p <0.01). A smaller sagittal aspect ratio was correlated (p < 0.05) with greater lateral deviation of the basilar artery.

Conclusions Our results suggest that flatness of the superior-inferior dimension of the infratentorial space is an anatomical feature that characterizes patients with hemifacial spasm. We hypothesize that this unique structural variation may exaggerate the lateral deviation of the vertebrobasilar arteries due to arteriosclerosis and exacerbate the space competition among vessels and cranial nerves.

Deep Brain Stimulation in DYT1 Dystonia: A 10-Year Experience

Electrode-Implantation-for-Deep-Brain-Stimulation-small1

Neurosurgery 73:86–93, 2013

Globus Pallidus Interna (GPi) deep brain stimulation (DBS) is an effective treatment for DYT1-associated dystonia, but long-term results are lacking.

OBJECTIVE: To evaluate the long-term effects of GPi DBS in patients with DYT1 dystonia.

METHODS: A retrospective chart review (cohort study) of 47 consecutive DYT11 patients treated by a single surgical team over a 10-year period and followed for up to 96 months (mean, 46 months) was performed. Symptom severity was quantified with the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) motor (M) and disability (D) sub-scores.

RESULTS: As measured with the BFMDRS (M), symptom severity was reduced to less than 20% of baseline after 2 years of DBS therapy (P = .001). The disability scores were reduced to ,30% of baseline (P = .001). Symptomatic improvement was durable throughout available follow-up. Sixty-one percent of patients had discontinued all dystonia-related medications at their last follow-up. Ninety-one percent had discontinued at least 1 class of medication. Infections requiring removal and later reimplantation of hardware occurred in 4 of 47 patients (8.5%). Hardware malfunction including lead fractures occurred in 4 of 47 cases (8.5%). Lead revision to address poor clinical response was performed in 2 of 92 implanted leads (2.2%).

CONCLUSION: GPi DBS is an effective therapy for DYT1-associated torsion dystonia. Statistically significant efficacy is maintained for up to 7 years. Neurologic complications are rare, but long-term hardware-related complications can be significant.

Thalamic and Subthalamic Deep Brain Stimulation for Essential Tremor: Where Is the Optimal Target?

Neurosurgery 70:840–846, 2012 DOI: 10.1227/NEU.0b013e318236a809

The ventrolateral thalamus (ventral intermediate nucleus [Vim]) is the traditional target for neurosurgical treatment of essential tremor. The target, however, has varied substantially among different neurosurgeons.

OBJECTIVE: To evaluate the effect of deep brain stimulation in the thalamus and posterior subthalamic area (PSA) in relation to electrode location.

METHODS: Thirty-six (17 Vim/19 PSA) patients with 44 deep brain stimulation electrodes were included in this retrospective study. The effect of stimulation was evaluated with standardized settings for each contact using items from the Essential Tremor Rating Scale.

RESULTS: When each contact was evaluated in terms of the treated hand with standardized stimulation, the electrode contact providing the best effect in the individual patient was located in the zona incerta or radiation prelemniscalis in 54% and the Vim in 12%. Forty contacts provided a tremor reduction of . 90%. Of these, 43% were located in the PSA and 18% in the Vim according to the Schaltenbrand atlas. Of these 40 contacts, 37 were found in the PSA group.

CONCLUSION: More contacts yielding an optimal effect were found in the PSA group than in the Vim. Many patients operated on in the Vim got the best effect from a contact located in the PSA. This might suggest that the PSA is a more efficient target than the Vim.

An Assessment of Current Brain Targets for Deep Brain Stimulation Surgery With Susceptibility- Weighted Imaging at 7 Tesla

Neurosurgery 67:1745–1756, 2010 DOI: 10.1227/NEU.0b013e3181f74105

Deep brain stimulation (DBS) surgery is used for treating movement disorders, including Parkinson disease, essential tremor, and dystonia. Successful DBS surgery is critically dependent on precise placement of DBS electrodes into target structures. Frequently, DBS surgery relies on normalized atlas-derived diagrams that are superimposed on patient brain magnetic resonance imaging (MRI) scans, followed by microelectrode recording and macrostimulation to refine the ultimate electrode position. Microelectrode recording carries a risk of hemorrhage and requires active patient participation during surgery.

OBJECTIVE: To enhance anatomic imaging for DBS surgery using high-field MRI with the ultimate goal of improving the accuracy of anatomic target selection.

METHODS: Using a 7-T MRI scanner combined with an array of acquisition schemes using multiple image contrasts, we obtained high-resolution images of human deep nuclei in healthy subjects.

RESULTS: Superior image resolution and contrast obtained at 7 T in vivo using susceptibility-weighted imaging dramatically improved anatomic delineation of DBS targets and allowed the identification of internal architecture within these targets. A patient-specific, 3-dimensional model of each target area was generated on the basis of the acquired images.

CONCLUSION: Technical developments in MRI at 7 T have yielded improved anatomic resolution of deep brain structures, thereby holding the promise of improving anatomicbased targeting for DBS surgery. Future study is needed to validate this technique in improving the accuracy of targeting in DBS surgery.

Bilateral Deep Brain Stimulation for Cervical Dystonia: Long-term Outcome in a Series of 10 Patients

Neurosurgery 67:957–963, 2010 DOI: 10.1227/NEU.0b013e3181ec49c7

Bilateral globus pallidus internus (GPi) deep brain stimulation (DBS) was shown to be effective in cervical dystonia refractory to medical treatment in several small short-term and 1 long-term follow-up series. Optimal stimulation parameters and their repercussions on the cost/benefit ratio still need to be established.

OBJECTIVE: To report our long-term outcome with bilateral GPi deep brain stimulation in cervical dystonia.

METHODS: The Toronto Western Spasmodic Torticollis Rating Scale was evaluated in 10 consecutive patients preoperatively and at last follow-up. The relationship of improvement in postural severity and pain was analyzed and stimulation parameters noted and compared with those in a similar series in the literature.

RESULTS: The mean (standard deviation) follow-up was 37.6 (16.9) months. Improvement in the total Toronto Western Spasmodic Torticollis Rating Scale score as evaluated at latest follow-up was 68.1% (95% confidence interval: 51.5-84.6). In 4 patients, there was dissociation between posture severity and pain improvement. Prevalently bipolar stimulation settings and high pulse widths and amplitudes led to excellent results at the expense of battery life.

CONCLUSION: Improvement in all 3 subscale scores of the Toronto Western Spasmodic Torticollis Rating Scale with bilateral GPi deep brain stimulation seems to be the rule. Refinement of stimulation parameters might have a significant impact on the cost/ benefit ratio of the treatment. The dissociation of improvement in posture severity and pain provides tangible evidence of the complex nature of cervical dystonia and offers interesting insight into the complex functional organization of the GPi.

A role of diffusion tensor imaging in movement disorder surgery

Acta Neurochir DOI 10.1007/s00701-010-0742-2

The safe and reversible nature of deep brain stimulation (DBS) has allowed movement disorder neurosurgery to become commonplace throughout the world. Fundamental understanding of individual patient’s anatomy is critical for optimizing the effects and side effects of DBS surgery. Three patients undergoing stereotactic surgery for movement disorders, at the institution’s intraoperative magnetic resonance imaging operating suite, were studied with fiber tractography. Stereotactic targets and fiber tractography were determined on preoperative magnetic resonance imagings using the Schaltenbrand–Wahren atlas for definition in the BrainLab iPlan software (BrainLAB Inc., Feldkirchen, Germany). Subthalamic nucleus, globus pallidus interna, and ventral intermediate nucleus targets were studied. Diffusion tensor imaging parameters used ranged from 2 to 8 mm for volume of interest in the x/y/z planes, fiber length was kept constant at 30 mm, and fractional anisotropy threshold varied from 0.20 to 0.45. Diffusion tensor imaging tractography allowed reliable and reproducible visualization and correlation between frontal eye field, premotor, primary motor, and primary sensory cortices via corticospinal tracts and corticopontocerebellar tracts. There is an apparent increase in the number of cortical regions targeted by the fiber tracts as the region of interest is enlarged. This represents a possible mechanism of the increased effects and side effects observed with higher stimulation voltages. Currently available diffusion tensor imaging techniques allow potential methods to characterize the effects and side effects of DBS. This technology has the potential of being a powerful tool to optimize DBS neurosurgery

Microvascular decompression for treating hemifacial spasm: lessons learned from a prospective study of 1,174 operations

Neurosurg Rev (2010) 33:325–334.DOI 10.1007/s10143-010-0254-9

The authors critically analyzed a large series of patients with hemifacial spasm (HFS) and who underwent microvascular decompression (MVD) under a prospective protocol. We describe several “lessons learned” that are required for achieving successful surgery and proper postoperative management.

The purpose of this study is to report on our experience during the previous 10 years with this procedure and we also discuss various related topics.

From April 1997 to June 2009, over 1,200 consecutive patients underwent MVD for HFS. Among them, 1,174 patients who underwent MVD for HFS with a minimum 1 year follow-up were enrolled in the study. The median follow-up period was 3.5 years (range, 1-9.3 years). Based on the operative and medical records, the intraoperative findings and the postoperative outcomes were obtained and then analyzed. At the 1- year follow-up examination, 1,105 (94.1%) patients of the total 1,174 patients exhibited a “cured” state, and 69 (5.9%) patients had residual spasms. In all the patients, the major postoperative complications included transient hearing loss in 31 (2.6%), permanent hearing loss in 13 (1.1%), transient facial weakness in 86 (7.3%), permanent facial weakness in 9 (0.7%), cerebrospinal fluid leak in three (0.25%) and cerebellar infarction or hemorrhage in two (0.17%). There were no operative deaths.

Microvascular decompression is a very effective, safe modality of treatment for hemifacial spasm. MVD is not sophisticated surgery, but having a basic understanding of the surgical procedures is required to achieve successful surgery

Effect of subthalamic deep brain stimulation on postural abnormality in Parkinson disease

J Neurosurg 112:1283–1288, 2010.DOI: 10.3171/2009.10.JNS09917

Parkinson disease (PD) is often accompanied by various postural abnormalities such as camptocormia (bent spine) or Pisa syndrome (lateral flexion). The authors studied the effect of subthalamic nucleus deep brain stimulation (STN DBS) on postural abnormality in patients with PD.

Methods. The authors retrospectively reviewed the clinical course of 18 patients who suffered from significant postural abnormality and underwent bilateral STN DBS. Patients whose preoperative posture score (Unified Parkinson’s Disease Rating Scale III, item 28) was 2 or more in the “medication-on” state were enrolled in this study. Eight patients were considered to have camptocormia, and 10 patients were considered to have so-called Pisa syndrome. Nine patients showed apparent thoracolumbar spinal deformity on radiography. Most patients had significant motor fluctuations from levodopa.

Results. In 13 patients with moderate postural abnormality (score of 2 on item 28), 9 patients improved soon after surgery, but 1 patient relapsed. Two patients improved gradually over a long period after surgery, whereas 2 patients did not improve at all. In 5 patients with severe postural abnormality (score of 3 or 4 on item 28), 2 patients improved slightly in the long-term follow-up period after surgery, but 3 patients did not improve at all.

Conclusions. Postural abnormality in patients with PD could be ameliorated by STN DBS, and therefore surgery should be considered before irreversible spinal deformity develops

Implantation of Deep Brain Stimulator Electrodes Using Interventional MRI

Philip A. Starr, MD, Alastair J.Martin, PhD, Paul S. Larson, MD

Neurosurgery Clinics of North America

Volume 20, Issue 2, Pages 207-217 (April 2009)

The authors describe a method for placement of deep brain stimulator electrodes using interventional MRI in conjunction with a skull-mounted aiming device (Medtronic Nexframe). This approach adapts the procedure to a standard-configuration 1.5-T diagnostic MRI scanner in a radiology suite. Preoperative imaging, device implantation, and postimplantation MRI are integrated into a single procedure performed under general anesthesia, providing real-time, high-resolution magnetic resonance confirmation of electrode position. The method is conceptually simpler than the current standard technique for deep brain stimulator placement, as it eliminates the stereotactic frame, the subsequent requirement for registration of the brain in stereotactic space, physiologic testing, and the need for patient cooperation. With further technical refinement, the interventional MRI method should improve the accuracy, safety, and speed of deep brain stimulator electrode placement.

Neurosurgery Department. “La Fe” University Hospital. Valencia, Spain

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