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David R. Blatt, William A. Friedman, Frank J. Bova, Daniel P. Theele and J. Parker Mickle

✓ To characterize the temporal course of radiosurgical lesions, 19 cats were irradiated in an animal linear accelerator radiosurgical device. The animals were followed clinically and, at 3.5, 6, 12, 18, 23, 29, and 63 weeks, were studied with gadolinium-enhanced magnetic resonance (MR) imaging. They were then sacrificed after Evans blue dye perfusion, and gross pathological and histopathological studies were performed.

Mild neurological deficits developed between 3.5 and 4.5 weeks, correlating with the onset of mass effect both grossly and radiographically and with the maximum amount of white matter edema on T2-weighted MR imaging and microscopic examination. Clinical improvement occurred within several weeks as these resolved. The lesions were of similar size at all time intervals. Gadolinium-enhanced MR imaging demonstrated lesions with peripheral areas of enhancement and central nonenhancing regions which correlated histologically with areas of vascular proliferation and radiation necrosis, respectively. In the early lesions at 3.5 and 6 weeks, necrosis and edema were predominant. From 12 to 29 weeks, an intermediate stage was observed, with resorption of the necrotic debris as evidenced by progressive cavitation and microglial response and by increased perilesional vascularity. At 63 weeks, resorption was still taking place, but gliosis and diminution of the vascular response were seen.

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Zoe E. Teton, Daniel Blatt, Katherine Holste, Ahmed M. Raslan and Kim J. Burchiel

OBJECTIVE

Hemifacial spasm (HFS), largely caused by neurovascular compression (NVC) of the facial nerve, is a rare condition characterized by paroxysmal, unilateral, involuntary contraction of facial muscles. It has long been suggested that these symptoms are due to compression at the transition zone of the facial nerve. The aim of this study was to examine symptom-free survival and long-term quality of life (QOL) in HFS patients who underwent microvascular decompression (MVD). A secondary aim was to examine the benefit of utilizing fused MRI and MRA post hoc 3D reconstructions to better characterize compression location at the facial nerve root exit zone (fREZ).

METHODS

The authors retrospectively analyzed patients with HFS who underwent MVD at a single institution, combined with a modified HFS-7 telephone questionnaire. Kaplan-Meier analysis was used to determine event-free survival, and the Wilcoxon signed-rank test was used to compare pre- and postoperative HFS-7 scores.

RESULTS

Thirty-five patients underwent MVD for HFS between 2002 and 2018 with subsequent 3D reconstructions of preoperative images. The telephone questionnaire response rate was 71% (25/35). If patients could not be reached by telephone, then the last clinic follow-up date was recorded and any recurrence noted. Twenty-four patients (69%) were symptom free at longest follow-up. The mean length of follow-up was 2.4 years (1 month to 8 years). The mean symptom-free survival time was 44.9 ± 5.8 months, and the average symptom-control survival was 69.1 ± 4.9 months. Four patients (11%) experienced full recurrence. Median HFS-7 scores were reduced by 18 points after surgery (Z = −4.013, p < 0.0001). Three-dimensional reconstructed images demonstrated that NVC most commonly occurred at the attached segment (74%, 26/35) of the facial nerve within the fREZ and least commonly occurred at the traditionally implicated transition zone (6%, 2/35).

CONCLUSIONS

MVD is a safe and effective treatment that significantly improves QOL measures for patients with HFS. The vast majority of patients (31/35, 89%) were symptom free or reported only mild symptoms at longest follow-up. Symptom recurrence, if it occurred, was within the first 2 years of surgery, which has important implications for patient expectations and informed consent. Three-dimensional image reconstruction analysis determined that culprit compression most commonly occurs proximally along the brainstem at the attached segment. The success of this procedure is dependent on recognizing this pattern and decompressing appropriately. Three-dimensional reconstructions were found to provide much clearer characterization of this area than traditional preoperative imaging. Therefore, the authors suggest that use of these reconstructions in the preoperative setting has the potential to help identify appropriate surgical candidates, guide operative planning, and thus improve outcome in patients with HFS.

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Diana Ko, Daniel Blatt, Chafic Karam, Kunal Gupta and Ahmed M. Raslan

Nusinersen (Spinraza) is a US Food and Drug Administration–approved intrathecal medication for the treatment of spinal muscular atrophy (SMA). Adult patients with SMA often undergo thoracolumbar fusion to treat neurogenic scoliosis, preventing thecal access. The authors report a laminotomy technique and the ease of intrathecal access in three SMA patients with prior thoracolumbar fusions.

Patients were positioned in the lateral decubitus position or prone. Lumbar laminotomy was performed below the conus, between the lateral longitudinal rods, to preserve mechanical stability. Fluoroscopy provided real-time identification of instruments. Hardware was contoured with a carbide drill bit to develop the surgical window. Fiducial screws were placed along the perimeter for demarcation. Sublaminar wire removal caused dural defects that were repaired with a layer of dural substitute onlay and sealant. All patients successfully received nusinersen thecal injections via lumbar puncture by an interventional radiologist. Fluoroscopy time ranged from 6 to 36 seconds. No postoperative pseudomeningoceles, cerebrospinal fluid leaks, or wound complications occurred.

For patients with SMA and posterior fusion from prior scoliosis treatment, lumbar laminotomy is an effective method for creating thecal access for the administration of nusinersen.

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Zoe E. Teton, Daniel Blatt, Amr AlBakry, James Obayashi, Gulsah Ozturk, Vural Hamzaoglu, Philippe Magown, Nathan R. Selden, Kim J. Burchiel and Ahmed M. Raslan

OBJECTIVE

Despite rapid development and expansion of neuromodulation technologies, knowledge about device and/or therapy durability remains limited. The aim of this study was to evaluate the long-term rate of hardware and therapeutic failure of implanted devices for several neuromodulation therapies.

METHODS

The authors performed a retrospective analysis of patients’ device and therapy survival data (Kaplan-Meier survival analysis) for deep brain stimulation (DBS), vagus nerve stimulation (VNS), and spinal cord stimulation (SCS) at a single institution (years 1994–2015).

RESULTS

During the study period, 450 patients underwent DBS, 383 VNS, and 128 SCS. For DBS, the 5- and 10-year initial device survival was 87% and 73%, respectively, and therapy survival was 96% and 91%, respectively. For VNS, the 5- and 10-year initial device survival was 90% and 70%, respectively, and therapy survival was 99% and 97%, respectively. For SCS, the 5- and 10-year initial device survival was 50% and 34%, respectively, and therapy survival was 74% and 56%, respectively. The average initial device survival for DBS, VNS, and SCS was 14 years, 14 years, and 8 years while mean therapy survival was 18 years, 18 years, and 12.5 years, respectively.

CONCLUSIONS

The authors report, for the first time, comparative device and therapy survival rates out to 15 years for large cohorts of DBS, VNS, and SCS patients. Their results demonstrate higher device and therapy survival rates for DBS and VNS than for SCS. Hardware failures were more common among SCS patients, which may have played a role in the discontinuation of therapy. Higher therapy survival than device survival across all modalities indicates continued therapeutic benefit beyond initial device failures, which is important to emphasize when counseling patients.