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Purvee Patel, Nitesh V. Patel and Shabbar F. Danish

OBJECTIVE

MR-guided laser-induced thermal therapy (MRgLITT) can be used to treat intracranial tumors, epilepsy, and chronic pain syndromes. Here, the authors report their single-center experience with 102 patients, the largest series to date in which the Visualase thermal therapy system was used.

METHODS

A retrospective analysis of all patients who underwent MRgLITT between 2010 and 2014 was performed. Pathologies included glioma, recurrent metastasis, radiation necrosis, chronic pain, and epilepsy. Laser catheters were placed stereotactically, and ablation was performed in the MRI suite. Demographics, operative parameters, length of hospital stay, and complications were recorded. Thirty-day readmission rates were calculated by using the standard method according to America's Health Insurance Plans Center for Policy and Research guidelines.

RESULTS

A total of 133 lasers were placed in 102 patients who required intervention for intracranial tumors (87 patients), chronic pain syndrome (cingulotomy, 5 patients), or epilepsy (10 patients). The procedure was completed in 98% (100) of these patients. Ninety-two patients (90.2%) had undergone previous treatment for their intracranial tumors. The average (± SD) total procedural time was 170.5 ± 34.4 minutes, and the mean laser-on time was 8.7 ± 6.8 minutes. The average intensive care unit (ICU) and hospital stays were 1.8 and 3.6 days, respectively, and the median length of stay for both the ICU and the hospital was 1 day. By postoperative Day 1, 54% of the patients (n = 55) were neurologically stable for discharge. There were 27 cases of morbidity, including new-onset neurological deficits, and 2 perioperative deaths. Fourteen patients (13.7%) developed new deficits after the MRgLITT procedure, and of those 14 patients, 64.3% (n = 9) had complete resolution of deficits within 1 month, 7.1% (n = 1) had partial resolution of symptoms within 1 month, 14.3% (n = 2) had not had resolution of symptoms at the most recent follow-up, and 14.3% (n = 2) died without resolution of symptoms. The 30-day readmission rate was 5.6%

CONCLUSIONS

MRgLITT, although minimally invasive, must be used with caution. Thermal damage to critical and eloquent structures can occur despite MRI guidance. Once the learning curve is overcome, the overall procedural complication rate is low, and most patients can be discharged within 24 hours, with a relatively low readmission rate. In cases in which they occurred, most neurological deficits were temporary. The therapeutic role of MRgLITT in various intracranial diseases will require larger and more rigorous studies.

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Shabbar F. Danish, Jessica A. Wilden and James Schuster

✓The authors describe 2 cases of intraoperative thoracic vertebral body extension fractures in morbidly obese patients with ankylosing spondylitis (AS), undergoing total hip arthroplasty, with resultant acute traumatic paraplegia. The pathophysiology with regard to the surgical positioning and the associated risks of obesity and AS are reviewed. Additionally, strategies for avoiding these types of injuries are discussed.

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Sean M. Munier, Eric L. Hargreaves, Nitesh V. Patel and Shabbar F. Danish

OBJECTIVE

Intraoperative dynamics of magnetic resonance–guided laser-induced thermal therapy (MRgLITT) have been previously characterized for ablations of naive tissue. However, most treatment sessions require the delivery of multiple doses, and little is known about the ablation dynamics when additional doses are applied to heat-damaged tissue. This study investigated the differences in ablation dynamics between naive versus damaged tissue.

METHODS

The authors examined 168 ablations from 60 patients across various surgical indications. All ablations were performed using the Visualase MRI-guided laser ablation system (Medtronic), which employs a 980-nm diffusing tip diode laser. Cases with multiple topographically overlapping doses with constant power were selected for this study. Single-dose intraoperative thermal damage was used to calculate ablation rate based on the thermal damage estimate (TDE) of the maximum area of ablation achieved (TDEmax) and the total duration of ablation (tmax). We compared ablation rates of naive undamaged tissue and damaged tissue exposed to subsequent thermal doses following an initial ablation.

RESULTS

TDEmax was significantly decreased in subsequent ablations compared to the preceding ablation (initial ablation 227.8 ± 17.7 mm2, second ablation 164.1 ± 21.5 mm2, third ablation 124.3 ± 11.2 mm2; p = < 0.001). The ablation rate of subsequent thermal doses delivered to previously damaged tissue was significantly decreased compared to the ablation rate of naive tissue (initial ablation 2.703 mm2/sec; second ablation 1.559 mm2/sec; third ablation 1.237 mm2/sec; fourth ablation 1.076 mm/sec; p = < 0.001). A negative correlation was found between TDEmax and percentage of overlap in a subsequent ablation with previously damaged tissue (r = −0.164; p < 0.02).

CONCLUSIONS

Ablation of previously ablated tissue results in a reduced ablation rate and reduced TDEmax. Additionally, each successive thermal dose in a series of sequential ablations results in a decreased ablation rate relative to that of the preceding ablation. In the absence of a change in power, operators should anticipate a possible reduction in TDE when ablating partially damaged tissue for a similar amount of time compared to the preceding ablation.

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Shabbar F. Danish, Mark G. Burnett and Sherman C. Stein

Deep venous thrombosis (DVT) remains a source of significant morbidity and mortality in patients who undergo craniotomy procedures. Despite several studies in which the safety and efficacy of various prophylactic strategies were examined, there is still no consensus among clinicians. In this paper the authors review the literature with regard to epidemiological and pathophysiological features, screening methods, and prophylactic measures for DVT.

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Nitesh V. Patel, Pinakin R. Jethwa, Anil Shetty and Shabbar F. Danish

OBJECT

Although control of intracranial ependymomas is highly correlated with degree of resection, it is unknown if the same is true for MRI-guided laser-induced thermal therapy (MRgLITT). The authors report their experience with MRgLITT for ependymoma and examine the utility of the real-time thermal damage estimate (TDE), a recent software advance, with respect to completeness of ablation and impact on tumor control. To the authors' knowledge, this is the largest single-center experience utilizing MRgLITT for recurrent ependymomas.

METHODS

Five tumors in 4 patients were treated with the Visualase Thermal Therapy System. Two tumors were treated similarly on recurrence. Ablation was performed using a 980-nm diode laser with a real-time image acquisition system. Single-plane TDEs were calculated and compared with the original lesion area to compute percentage area ablated (PAA). Volumetric analysis was performed, and percentage volume ablated (PVA) was estimated and correlated with the TDE. Tumor control was correlated with the TDE and volumetric data during treatment.

RESULTS

Nine ablations were performed on 5 tumors, 2 of which had multiple recurrences. The average pretreatment lesion volume was 8.4 ± 6.3 cm3, and the average largest 2D area was 5.3 ± 2.7 cm2. The averaged TDE was 3.9 ± 2.1 cm2, average PAA was 80.1% ± 34.3%, and average PVA was 64.4% ± 23.5%. For subtotal ablations, average recurrence time was 4.4 ± 5.3 months; 1 adult case remains recurrence-free at 40 months. Using TDEs, the correlation between recurrence time and PAA was r = 0.93 (p = 0.01), and for PVA was r = 0.88 (p = 0.02). Furthermore, PVA and PAA were strongly correlated (r = 0.88, p = 0.02).

CONCLUSIONS

Through using the PAA, the real-time TDE correlated with the volume of ablation in this initial investigation. Furthermore, the TDE and volumetric data corresponded to the level of tumor control, with time to recurrence dependent on ablation completeness. MRgLITT may have a role in the management of recurrent ependymomas, especially with recent software advances.

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Arthur Carminucci, Ke Nie, Joseph Weiner, Eric Hargreaves and Shabbar F. Danish

OBJECTIVE

The Leksell Gamma Knife Icon (GK Icon) radiosurgery system can utilize cone-beam computed tomography (CBCT) to evaluate motion error. This study compares the accuracy of frame-based and frameless mask-based fixation using the Icon system.

METHODS

A retrospective cohort study was conducted to evaluate patients who had undergone radiosurgery with the GK Icon system between June and December 2017. Patients were immobilized in either a stereotactic head frame or a noninvasive thermoplastic mask with stereotactic infrared (IR) camera monitoring. Setup error was defined as displacement of the skull in the stereotactic space upon setup as noted on pretreatment CBCT compared to its position in the stereotactic space defined by planning MRI for frame patients and defined as skull displacement on planning CBCT compared to its position on pretreatment CBCT for mask patients. For frame patients, the intrafractionation motion was measured by comparing pretreatment and posttreatment CBCT. For mask patients, the intrafractionation motion was evaluated by comparing pretreatment CBCT and additional CBCT obtained during the treatment. The translational and rotational errors were recorded.

RESULTS

Data were collected from 77 patients undergoing SRS with the GK Icon. Sixty-four patients underwent frame fixation, with pre- and posttreatment CBCT studies obtained. Thirteen patients were treated using mask fixation to deliver a total of 33 treatment fractions. Mean setup and intrafraction translational and rotation errors were small for both fixation systems, within 1 mm and 1° in all axes. Yet mask fixation demonstrated significantly larger intrafraction errors than frame fixation. Also, there was greater variability in both setup and intrafraction errors for mask fixation than for frame fixation in all translational and rotational directions. Whether the GK treatment was for metastasis or nonmetastasis did not influence motion uncertainties between the two fixation types. Additionally, monitoring IR-based intrafraction motion for mask fixation—i.e., the number of treatment stoppages due to reaching the IR displacement threshold—correlated with increasing treatment time.

CONCLUSIONS

Compared to frame-based fixation, mask-based fixation demonstrated larger motion variations. The variability in motion error associated with mask fixation must be taken into account when planning for small lesions or lesions near critical structures.

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Pinakin R. Jethwa, Jason H. Lee, Rachid Assina, Irwin A. Keller and Shabbar F. Danish

Supratentorial primitive neuroectodermal tumors (PNETs) are rare tumors that carry a poorer prognosis than those arising from the infratentorial compartment (such as medulloblastoma). The overall prognosis for these patients depends on several factors including the extent of resection, age at diagnosis, CSF dissemination, and site in the supratentorial space. The authors present the first case of a patient with a newly diagnosed supratentorial PNET in which cytoreduction was achieved with MR-guided laser-induced thermal therapy. A 10-year-old girl presented with left-sided facial weakness and a large right thalamic mass extending into the right midbrain. The diagnosis of supratentorial PNET was made after stereotactic biopsy. Therapeutic options for this lesion were limited because of the risks of postoperative neurological deficits with resection. The patient underwent MR-guided laser-induced thermal ablation of her tumor. Under real-time MR thermometry, thermal energy was delivered to the tumor at a core temperature of 90°C for a total of 960 seconds. The patient underwent follow-up MR imaging at regular intervals to evaluate the tumor response to the thermal ablation procedure. Initial postoperative scans showed an increase in the size of the lesion as well as the amount of the associated edema. Both the size of the lesion and the edema stabilized by 1 week and then decreased below preablation levels at the 3-month postsurgical follow-up. There was a slight increase in the size of the lesion and associated edema at the 6-month follow-up scan, presumably due to concomitant radiation she received as part of her postoperative care. The patient tolerated the procedure well and has had resolution of her symptoms since surgery. Further study is needed to assess the role of laser-induced thermal therapy for the treatment of intracranial tumors. As such, it is a promising tool in the neurosurgical armamentarium. Postoperative imaging has shown no evidence of definitive recurrence at the 6-month follow-up period, but longer-term follow-up is required to assess for late recurrence.

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Shabbar F. Danish, Amer Samdani, Amgad Hanna, Phillip Storm and Leslie Sutton

Object

Posterior fossa decompression with duraplasty is routinely used for the treatment of Chiari malformations. It has been traditionally believed that this procedure requires a watertight seal with primary closure of the dura with either pericranium or allograft. In this study, the authors evaluated two synthetic dural substitutes in this patient population for feasibility of use and identification of perioperative morbidity.

Methods

The authors evaluated 56 patients who underwent duraplasty with a synthetic collagen matrix (Dura-Gen) after suboccipital craniectomy and C-1 laminectomy, and 45 patients in whom the dural closure involved acellular human dermis (AlloDerm). Patients in both groups were assessed for the presence of a pseudomeningocele, wound infection, cerebrospinal fluid (CSF) leak, and the need for repeated operation either for wound revision or the placement of a ventriculoperitoneal shunt. Operative times for which DuraGen duraplasty was used were compared with those for AlloDerm closure.

In the DuraGen group, complications included five pseudomeningoceles (8.9%), two wound infections (3.6%), one CSF leak (1.8%), and four repeated operations (three shunt revisions and one reexploration; 7.1%) in nine patients. In the AlloDerm group, there were five pseudomeningoceles (11.1%), one wound infection (2.2%), one CSF leak (2.2%), and two repeated operations (two shunt revisions; 4.4%) in seven patients. The operative time associated with DuraGen was significantly shorter than that of duraplasty that required closure with sutures (92 minutes compared with 128 minutes, p < 0.01).

Conclusions

The synthetic dural substitutes DuraGen and AlloDerm provide a suitable alternative duraplasty with comparable complication rates. DuraGen requires a significantly shorter operative time than AlloDerm.

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Shabbar F. Danish, Dean Barone, Bradley C. Lega and Sherman C. Stein

Decompressive hemicraniectomy is well accepted for the surgical treatment of intractable intracranial hypertension in cases in which medical management fails. Although it is performed as a life-saving procedure when death is imminent from intracranial hypertension, little is known about the functional outcomes for these patients on long-term follow-up. In this study, the authors performed a systematic review of the literature to examine neurological outcome after hemicraniectomy. A literature search revealed 29 studies that reported outcomes using GOS scores. The GOS scores were transformed to utility values for quality of life using a conversion method based on decision analysis modeling. Based on the literature, 1422 cases were analyzed. The average 6-month-postoperative mortality rate was 28.2%. The mean QOL value among survivors was 0.592, which corresponds roughly to a GOS score of 4. Although more studies are needed for validation of long-term neurological outcome after hemicraniectomy, the assumption that most patients remain in a vegetative state after this intervention is clearly incorrect.