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Vikram V. Nayar, Ronald J. Benveniste and Frederick F. Lang

Object

The infratentorial supracerebellar approach to the pineal region presents special challenges during patient positioning. The head must be flexed and the body positioned to allow an operative trajectory under the straight sinus. Image guidance is not useful during positioning because registration and navigation take place after the head is fixed in its final position. Therefore, a reliable method of positioning based on external, easily identifiable landmarks to estimate the surgical trajectory along the straight sinus toward the pineal region is needed. Based on observation, the authors hypothesized that a line between 2 palpable external landmarks, the inion and the bregma, often approximates the surgical trajectory along the straight sinus. They tested this hypothesis by quantifying the relationship between the straight sinus and the bregma, and describe a method for estimating the working angle during patient positioning.

Methods

The midsagittal, Gd-enhanced, T1-weighted MR images of 102 patients were analyzed. Demographic data and the presence or absence of tentorial pathological entities was recorded. The slant of the straight sinus was classified as common, high, or low, based on a previously described classification system. A line along the bottom of the straight sinus (that is, the straight-sinus line) was extended superiorly to its intersection with the calvaria, and the distance from this intersection point to the bregma was measured.

Results

The intersection point of the straight-sinus line and the calvaria was on average 2 ± 8.2 mm (these values are expressed as the mean ± SD throughout) anterior to the bregma (range 19.9 mm anterior to 19.1 mm posterior). The distance from the intersection point to the bregma was not statistically significantly different in younger or older patients, or in patients with or without tumors involving the pineal region. In patients with a low slant of the straight sinus, the intersection point was 5.3 ± 6.3 mm anterior to the bregma, whereas in patients with a high slant of the straight sinus, the intersection point was 0.21 ± 9.1 mm posterior to the bregma (p = 0.015).

Conclusions

The straight-sinus line, which defines the working angle for the supracerebellar infratentorial approach, intersects the calvaria very close to the bregma in the majority of patients. Therefore, ideal patient positioning can be achieved by flexing the patient's head to optimize the working angle defined by an imaginary line connecting the torcula (inion) to the bregma.

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Casey M. Chai, Matei A. Banu, William Cobb, Neel Mehta, Linda Heier and John A. Boockvar

The authors report 2 cases of orthostatic headaches associated with spontaneous intracranial hypotension (SIH) secondary to CSF leaks that were successfully treated with an alternative dural repair technique in which a tubular retractor system and a hydrogel dural sealant were used. The 2 patients, a 63-year-old man and a 45-year-old woman, presented with orthostatic headache associated with SIH secondary to suspected lumbar and lower cervical CSF leaks, respectively, as indicated by bony defects or epidural fluid collection. Epidural blood patch repair failed in both cases, but both were successfully treated with the minimally invasive application of a hydrogel dural sealant as a novel adjunct to traditional dural repair techniques. Both patients tolerated the procedure well. Moreover, SIH symptoms and MRI signs were completely resolved at 1-month follow-up in both patients.

The minimally invasive dural repair procedure with hydrogel dural sealant described here offers a viable alternative in patients in whom epidural blood patches have failed, with obscure recalcitrant CSF leaks at the cervical as well as lumbar spinal level. The authors demonstrate that the adjuvant use of sealant is a safe and efficient repair method regardless of dural defect location.

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Aristotelis S. Filippidis, M. Yashar S. Kalani, Peter Nakaji and Harold L. Rekate

Object

Negative-pressure and low-pressure hydrocephalus are rare clinical entities that are frequently misdiagnosed. They are characterized by recurrent episodes of shunt failure because the intracranial pressure is lower than the opening pressure of the valve. In this report the authors discuss iatrogenic CSF leaks as a cause of low- or negative-pressure hydrocephalus after approaches to the cranial base.

Methods

The authors retrospectively reviewed cases of low-pressure or negative-pressure hydrocephalus presenting after cranial approaches complicated with a CSF leak at their institution.

Results

Three patients were identified. Symptoms of high intracranial pressure and ventriculomegaly were present, although the measured pressures were low or negative. A blocked communication between the ventricles and the subarachnoid space was documented in 2 of the cases and presumed in the third. Shunt revisions failed repeatedly. In all cases, temporary clinical and radiographic improvement resulted from external ventricular drainage at subatmospheric pressures. The CSF leaks were sealed and CSF communication was reestablished operatively. In 1 case, neck wrapping was used with temporary success.

Conclusions

Negative-pressure or low-pressure hydrocephalus associated with CSF leaks, especially after cranial base approaches, is difficult to treat. The solution often requires the utilization of subatmospheric external ventricular drains to establish a lower ventricular drainage pressure than the drainage pressure created in the subarachnoid space, where the pressure is artificially lowered by the CSF leak. Treatment involves correction of the CSF leak, neck wrapping to increase brain turgor and allow the pressure in the ventricles to rise to the level of the opening pressure of the valve, and reestablishing the CSF route.

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Michael J. Rauzzino, Christopher I. Shaffrey, James Wagner, Russ Nockels and Mark Abel

The indications for surgical intervention in patients with idiopathic scoliosis have been well defined. The goals of surgery are to achieve fusion and arrest progressive curvature while restoring normal coronal and sagittal balance. As first introduced by Harrington, posterior fusion, the gold standard of treatment, has a proven record of success. More recently, anterior techniques for performing fusion procedures via either a thoracotomy or a retroperitoneal approach have been popularized in attempts to achieve better correction of curvature, preserve motion segments, and avoid some of the complications of posterior fusion such as the development of the flat-back syndrome. Anterior instrumentation alone, although effective, can be kyphogenic and has been shown to be associated with complications such as pseudarthrosis and instrumentation failure. Performing a combined approach in patients with scoliosis and other deformities has become an increasingly popular procedure to achieve superior correction of deformity and to minimize later complications. Indications for a combined approach (usually consisting of anterior release, arthrodesis with or without use of instrumentation, and posterior segmental fusion) include: prevention of crankshaft phenomenon in juvenile or skeletally immature adolescents; correction of large curves (75°) or excessively rigid curves in skeletally mature or immature patients; correction of curves with large sagittal-plane deformities such as thoracic kyphosis (> 90°) or thoracic lordosis (> 20°); and correction of thoracolumbar curves that need to be fused to the sacrum. Surgery may be performed either in a staged proceedure or, more commonly, in a single sitting. The authors discuss techniques for combined surgery and complication avoidance.

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Philipp Juergens, Javier Ratia, Jörg Beinemann, Zdzislaw Krol, Kurt Schicho, Christoph Kunz, Hans-Florian Zeilhofer and Stephan Zimmerer

Craniometaphyseal dysplasia is an extremely rare, genetic bone-remodeling disorder. Comparable to osteopetrosis, fibrous dysplasia, and other infrequent conditions, craniometaphyseal dysplasia is characterized by progressive diffuse hyperostosis of the neuro- and viscerocranium. Affected patients present with a pathognomonic dysmorphia: macrocephalus, hypertelorism, bulky facial skeleton, and a prominent mandible. Progressive thickening and petrification of the craniofacial bones can continue throughout life, often resulting in neurological symptoms due to obstruction of the cranial nerves in the foramina and therefore immediately requiring neurosurgical interventions to avoid persistent symptoms with severe impairment of function. Treatment is largely infeasible given the lack of suitable tools to perform a craniotomy through the gross calvarial bone.

In this paper, the authors present a complete process chain from the CT-based generation of an individual patient's model displaying his pathology to optimized preoperative planning of the skull's shape with a thickness of about 6–7 mm. For concise verification of the surgical plan in an operating room environment, a 3D real-time navigation prototype system was utilized. To guarantee realization of the surgery in a reasonable time frame, the mechanical tools were preoperatively selected for optimizing the ablation rate in porcine and bovine bone, which were comparable to that in the patient. This process chain was developed in a modular way, so that it could be easily adopted completely or partially for other surgical indications.

A 21-year-old man was treated according to this sophisticated concept. Skull bone more than 50 mm thick in some regions was reduced to physiological thickness. The patient was thus in a stage that neurosurgical interventions could be performed with a regular risk within a reasonable time of treatment.

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Toshisuke Sakaki, Tetsuya Morimoto, Kiyoshi Takemura, Seiji Miyamoto, Kikuo Kyoi and Shozaburo Utsumi

A cute obstruction of a cortical vein may cause venous congestion, edema, and even intracerebral hemorrhage in the territory affected. With an interhemispheric or a subtemporal surgical approach, cerebral cortical bridging veins are occasionally sacrificed, causing cerebral damage and neurological deterioration. The present paper describes a microsurgical revascularization procedure bridging the proximal and distal sides of the sacrificed vein with a thin-walled silicone tube. Operative Technique When an interhemispheric or subtemporal approach to a

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Lawrence S. Chin, Keith L. Black and Julian T. Hoff

treatment of thoracic intervertebral disc protrusions. J Neurol Neurosurg Psychiatry 34: 68–77, 1971 7. Haley JC , Perry JH : Protrusions of intervertebral discs. Study of their distribution, characteristics and effects on the nervous system. Am J Surg 80 : 394 – 404 , 1950 Haley JC, Perry JH: Protrusions of intervertebral discs. Study of their distribution, characteristics and effects on the nervous system. Am J Surg 80: 394–404, 1950 8. Hulme A : The surgical approach to thoracic intervertebral disc

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John A. Feldenzer, John E. McGillicuddy and Jonathan W. Hopkins

due to infarction (arrow) . Three days postembolization, the patient underwent a combined posterior transsacral (neurosurgical) and lateral transabdominal (general surgical) approach in the right lateral decubitus position. Cystometric and anal sphincter monitoring was utilized during surgery. The initial approach was posterior and the dura was noted to be disrupted (anteriorly and posteriorly) at the S-1 level and below. Nearly all of the posterior wall of the sacrum was eroded. The left S-2 and S-3 foramina were enlarged and the anterior wall of the

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Michael Schaefer, Claude Lapras, Guenther Thomalske, Holger Grau and Ralf Schober

comparable case from our department. This patient was a young woman with sarcoid granulomas in the right temporal lobe. After operation in that case, there has also been no recurrence of the intracranial tumor nor any other organ manifestation of sarcoidosis. The prognosis of these isolated central nervous system granulomas appears favorable when totally removed. We feel that a direct surgical approach is justified even in cases of difficult access like the pineal region. Acknowledgment We are indebted to Professor W. Krücke for his diagnostic evaluation

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Edgar Nathal, Nobuyuki Yasui, Takeshi Sampei and Akifumi Suzuki

surgical approach selected and the amount of brain retraction utilized for exposure. Furthermore, in some cases the operative field is obscured by the effects of a recent hemorrhage or a large aneurysm, making it difficult to recognize vascular structures and to preserve small perforating branches. The present study was undertaken to analyze the intraoperative anatomical findings of the ACoA complex in a series of patients with and without anatomical variations. These patients were treated for an aneurysm of the ACoA complex using one of three different operative