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Leonardo Frighetto, Antonio A. F. De Salles, Eric Behnke, Zachary A. Smith and Dennis Chute

✓ Interactive image-guided neuronavigation was used to obtain biopsy specimens of cavernous sinus (CS) tumors via the foramen ovale. In this study the authors demonstrated a minimally invasive approach in the management of these lesions.

In four patients, whose ages ranged from 29 to 89 years (mean 61.2 years) and who harbored undefined lesions invading the CS, neuronavigation was used to perform frameless stereotactic fine-needle biopsy sampling through the foramen ovale. The biopsy site was confirmed on postoperative computerized tomography scanning.

The frameless technique was accurate in displaying a real-time trajectory of the biopsy needle throughout the procedure. The lesions within the CS were approached precisely and safely. Diagnostic tissue was obtained in all cases and treatment was administered with the aid of stereotactic radiosurgery or fractionated stereotactic radiotherapy. The patients were discharged after an overnight stay with no complications.

Neuronavigation is a precise and useful tool for image-guided biopsy sampling of CS tumors via the foramen ovale.

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Zachary A. Smith, Antonio A. F. De Salles, Leonardo Frighetto, Bryan Goss, Steve P. Lee, Michael Selch, Robert E. Wallace, Cynthia Cabatan-Awang and Timothy Solberg

Object. In this study the authors evaluate the efficacy of and complications associated with dedicated linear accelerator (LINAC) radiosurgery for trigeminal neuralgia (TN).

Methods. Between August 1995 and February 2001, 60 patients whose median age was 66.1 years (range 45–88 years) were treated with dedicated LINAC radiosurgery for TN. Forty-one patients (68.3%) had essential TN, 12 (20%) had secondary facial pain, and seven (11.7%) had atypical features. Twenty-nine patients (48.3%) had undergone previous surgical procedures. Radiation doses varied between 70 and 90 Gy (mean 83.3 Gy) at the isocenter, with the last 35 patients (58.3%) treated with a 90-Gy dose. A 5-mm collimator was used in 45 patients (75%) and a 7.5-mm collimator in 15 patients (25%). Treatment was focused at the nerve root entry zone.

At last follow up (mean follow-up period 23 months, range 2–70 months), 36 (87.8%) of the 41 patients with essential TN had sustained significant pain relief (good plus excellent results). Twenty-three patients (56.1%) were pain free without medication (excellent outcome), 13 (31.7%) had a 50 to 90% reduction in pain with or without medication (good outcome), and five (12.2%) had minor improvement or no relief. Of 12 patients with secondary facial pain, significant relief was sustained in seven patients (58.3%); worse results were found with atypical pain. Fifteen (25%) of the 60 patients experienced new numbness postprocedure; no other significant complications were found. Pain relief was experienced at a mean of 2.7 months (range 0–12 months).

Conclusions. Dedicated LINAC radiosurgery is a precise and effective treatment for TN.

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Alessandra G. Pedroso, Antonio A. F. De Salles, Katayoun Tajik, Raymond Golish, Zachary Smith, Leonardo Frighetto, Timothy Solberg, Cynthia Cabatan-Awang and Michael T. Selch

Object. The authors studied outcomes and complications in patients who harbored arteriovenous malformations (AVMs) and underwent stereotactic radiosurgery involving the Novalis shaped beam unit.

Methods. Between January 1998 and January 2002, 83 patients were treated with radiosurgery at University of California, Los Angeles. The mean patient age was 37.8 years. Forty-four patients completed follow up. There were 24 women. Sixteen patients underwent repeated radiosurgery. Embolization was performed in 13 patients and radiosurgery alone in 31. The mean follow-up period after embolization was 54.4 ± 21.9 months and 37.4 ± 14.6 months for radiosurgery alone. The mean peripheral dose was 15 Gy (range 12–18 Gy). The mean preradiosurgery lesion volume was 9.7 ± 11.9 ml for radiosurgery alone and 16.2 ± 11.3 ml for embolization. The AVMs in 13 patients (29.8%) were Spetzler—Martin Grade II, 12 (27.5%) were Grade III, eight (18.2%) Grade IV, and five (11.3%) were Grade V and VI each. Spetzler—Martin grade, volume, and peripheral dose were analyzed in consideration to outcome.

A positive trend (p = 0.086) was observed between Spetzler—Martin grade and obliteration rate. Volume per se did not predict obliteration (p = 0.48). A peripheral dose of 18 Gy was shown to be the most important predictor for occlusion (p = 0.007). The overall obliteration rate was 52.5%. A transient complication was noticed in one case (2.3%) and but no permanent deficits due to radiosurgery have been detected so far. Three patients (6.8%) bled after radiosurgery.

Conclusions. The range of the prescribed peripheral dose was narrow. An association between the mean peripheral dose of 15 Gy, high conformality, and homogeneous dose distribution permitted no permanent complications. Volume per se did not correlate with outcome. The next step will be to increase the peripheral dose shaping the beam and to achieve higher obliteration rates without increasing complications.

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Zachary A. Smith, Parham Moftakhar, Dennis Malkasian, Zhenggang Xiong, Harry V. Vinters and Jorge A. Lazareff

✓Diffuse villous hyperplasia of the choroid plexus is a rare but potential source of nonobstructive hydrocephalus. In addition to discussing the authors' staged surgical approach and medical management decisions in a patient with this rare and challenging condition, immunohistochemical studies of the choroid plexus epithelium are presented to examine the pathophysiological factors involved in abnormal cerebrospinal fluid (CSF) production in this disease.

The patient, a 15-month-old girl born at 36 weeks' gestation, underwent a bilateral craniotomy with resection of the choroid plexus to treat her villous hyperplasia. Immunohistochemical studies of the resected choroid plexus were conducted for the purpose of examining the carbonic anhydrase II (CAII) enzyme and the aquaporin 1 (AQP1) membrane protein. Results were compared with immunohistochemical studies conducted in a small series of autopsy specimens of normal human choroid plexuses. There was no change in the immunoreactivity of CAII in the patient with villous hyperplasia compared with normal controls, whereas AQP1 immunoreactivity was significantly weaker in the patient compared with normal controls. Postoperatively, the patient's CSF overproduction resolved and her neurological symptoms improved over time.

Shunting techniques and presently available pharmaceutical treatments alone do not provide adequate treatment of high-output CSF conditions. Surgical removal of the affected choroid plexus is a feasible and effective treatment. Results of the immunohistochemical studies reported here support the suggestion that the CAII enzyme is retained in villous hyperplasia of the choroid plexus. However, there appears to be decreased expression and perhaps downregulation of AQP1 in villous hyperplasia compared with normal choroid plexus. Future studies may elucidate the significance of these observations.

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Michael E. Sughrue, Isaac Yang, Seunggu J. Han, Derick Aranda, Ari J. Kane, Misha Amoils, Zachary A. Smith and Andrew T. Parsa

Object

While many studies have been published outlining morbidity following radiosurgical treatment of vestibular schwannomas, significant interpractitioner and institutional variability still exists. For this reason, the authors conducted a systematic review of the literature for non-audiofacial-related morbidity after the treatment of vestibular schwannoma with radiosurgery.

Methods

The authors performed a comprehensive search of the English-language literature to identify studies that published outcome data of patients undergoing radiosurgery treatment for vestibular schwannomas. In total, 254 articles were found that described more than 50,000 patients and were analyzed for satisfying the authors' inclusion criteria. Patients from these studies were then separated into 2 cohorts based on the marginal dose of radiation: ≤ 13 Gy and > 13 Gy. All tumors included in this study were < 25 mm in their largest diameter.

Results

A total of 63 articles met the criteria of the established search protocol, which combined for a total of 5631 patients. Patients receiving > 13 Gy were significantly more likely to develop trigeminal nerve neuropathy than those receiving < 13 Gy (p < 0.001). While we found no relationship between radiation dose and the rate of developing hydrocephalus (0.6% for both cohorts), patients with hydrocephalus who received doses > 13 Gy appeared to have a higher rate of symptomatic hydrocephalus requiring shunt treatment (96% [> 13 Gy] vs 56% [≤ 13 Gy], p < 0.001). The rates of vertigo or balance disturbance (1.1% [> 13 Gy] vs 1.8% [≤ 13 Gy], p = 0.001) and tinnitus (0.1% [> 13 Gy] vs 0.7% [≤ 13 Gy], p = 0.001) were significantly higher in the lower dose cohort than those in the higher dose cohort.

Conclusions

The results of our review of the literature provide a systematic summary of the published rates of nonaudiofacial morbidity following radiosurgery for vestibular schwannoma.

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Editorial

Ectopic bone

Vincent C. Traynelis

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Nan-Fu Chen, Zachary A. Smith, Eric Stiner, Sean Armin, Hormoz Sheikh and Larry T. Khoo

Object

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been approved for use in the lumbar spine in conjunction with the lumbar tapered cage. However, off-label use of this osteoinductive agent is observed with anterior fusion applications as well as with both posterior lumbar interbody fusion and transforaminal lumbar interbody fusion (TLIF). Complications using rhBMP-2 in the cervical spine have been reported. Although radiographic evidence of ectopic bone in the lumbar spine has been described following rhBMP-2 use, this finding was not previously believed to be of clinical relevance.

Methods

This study was a retrospective review of 4 patients who underwent minimally invasive spinal TLIF (MIS-TLIF) in which bone fusion was augmented with rhBMP-2 applied to an absorbable collagen sponge. Case presentations, operative findings, imaging data, and follow-up findings were reviewed.

Results

Four cases with delayed symptomatic neural compression following the off-label use of rhBMP-2 with MIS-TLIF were identified.

Conclusions

Although previously believed to be only a radiographic finding, the development of ectopic bone following rhBMP-2 use in lumbar fusion can be clinically significant. This paper describes 4 cases of delayed neural compression following MIS-TLIF. The reader should be aware of this potential complication following the off-label use of rhBMP-2 in the lumbar spine.

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Larry T. Khoo, Zachary A. Smith, Farbod Asgarzadie, Yorgios Barlas, Sean S. Armin, Vartan Tashjian and Baron Zarate

Object

Open transthoracic approaches, considered the standard in treating thoracic disc herniation (TDH), are associated with significant comorbidities. The authors describe a minimally invasive lateral extracavitary tubular approach for discectomy and fusion (MIECTDF) to treat TDH.

Methods

In 13 patients (5 men, 8 women; mean age 51.8 years) with myelopathy and 15 noncalcified TDHs, the authors achieved a far-lateral trajectory by dilating percutaneously to a 20-mm working portal docked at the transverse process–facet junction, which then provided a corridor for a near-total discectomy, bilateral laminotomies, and interbody arthrodesis requiring minimal cord retraction. A cohort of 11 demographically comparable patients treated via transthoracic approaches was used as control.

Results

Preoperative Frankel grades were B in 1 patient, C in 4, D in 5, and E in 3, whereas at mean of 10 months, 11 had Grade E function and 2 had Grade D function. Mean surgical metrics were operating room time 93.75 minutes, blood loss 33 ml, and hospital stay 3.1 days. Complications included 4 transient paresthesias, 1 CSF leak, 1 abdominal wall weakness, and 3 nonwound infections. One-year follow-up MR imaging revealed full decompression in all cases and no cage migration. Mean visual analog scales scores preoperative, at 6 weeks, 3 months, and 1 year were 5.6, 4.5, 3.2, and 1.2, respectively. No differences existed in preoperative clinical and radiographic profile of the study and control groups. Compared with controls, the MIECTDF group achieved superior scores in all metrics (p < 0.01) except for equivalent 1-year neurological outcomes.

Conclusions

Compared with transthoracic procedures, MIECTDF effectively decompressed the spinal canal, yielding identical 1-year radiographic and clinical outcomes to those seen in controls, while producing superior clinical scores in the interim. Thus, MIECTDF is the authors' treatment of choice for TDH.

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Zachary A. Smith, Colin C. Buchanan, Dan Raphael and Larry T. Khoo

Ossification of the posterior longitudinal ligament (OPLL) is an important cause of cervical myelopathy that results from bony ossification of the cervical or thoracic posterior longitudinal ligament (PLL). It has been estimated that nearly 25% of patients with cervical myelopathy will have features of OPLL. Patients commonly present in their mid-40s or 50s with clinical evidence of myelopathy. On MR and CT imaging, this can be seen as areas of ossification that commonly coalesce behind the cervical vertebral bodies, leading to direct ventral compression of the cord. While MR imaging will commonly demonstrate associated changes in the soft tissue, CT scanning will better define areas of ossification. This can also provide the clinician with evidence of possible dural ossification. The surgical management of OPLL remains a challenge to spine surgeons. Surgical alternatives include anterior, posterior, or circumferential decompression and/or stabilization. Anterior cervical stabilization options include cervical corpectomy or multilevel anterior cervical corpectomy and fusion, while posterior stabilization approaches include instrumented or noninstrumented fusion or laminoplasty. Each of these approaches has distinct advantages and disadvantages. While anterior approaches may provide more direct decompression and best improve myelopathy scores, there is soft-tissue morbidity associated with the anterior approach. Posterior approaches, including laminectomy and fusion and laminoplasty, may be well tolerated in older patients. However, there often is associated axial neck pain and less improvement in myelopathy scores. In this review, the authors discuss the epidemiology, imaging findings, and clinical presentation of OPLL. The authors additionally discuss the merits of the different surgical techniques in the management of this challenging disease.