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Sam Safavi-Abbasi, Noritaka Komune, Jacob B. Archer, Hai Sun, Nicholas Theodore, Jeffrey James, Andrew S. Little, Peter Nakaji, Michael E. Sughrue, Albert L. Rhoton and Robert F. Spetzler

OBJECT

The objective of this study was to describe the surgical anatomy and technical nuances of various vascularized tissue flaps.

METHODS

The surgical anatomy of various tissue flaps and their vascular pedicles was studied in 5 colored silicone-injected anatomical specimens. Medical records were reviewed of 11 consecutive patients who underwent repair of extensive skull base defects with a combination of various vascularized flaps.

RESULTS

The supraorbital, supratrochlear, superficial temporal, greater auricular, and occipital arteries contribute to the vascular supply of the pericranium. The pericranial flap can be designed based on an axial blood supply. Laterally, various flaps are supplied by the deep or superficial temporal arteries. The nasoseptal flap is a vascular pedicled flap based on the nasoseptal artery. Patients with extensive skull base defects can undergo effective repair with dual flaps or triple flaps using these pedicled vascularized flaps.

CONCLUSIONS

Multiple pedicled flaps are available for reconstitution of the skull base. Knowledge of the surgical anatomy of these flaps is crucial for the skull base surgeon. These vascularized tissue flaps can be used effectively as single or combination flaps. Multilayered closure of cranial base defects with vascularized tissue can be used safely and may lead to excellent repair outcomes.

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Sam Safavi-Abbasi, Timothy B. Mapstone, Jacob B. Archer, Christopher Wilson, Nicholas Theodore, Robert F. Spetzler and Mark C. Preul

An understanding of the underlying pathophysiology of tethered cord syndrome (TCS) and modern management strategies have only developed within the past few decades. Current understanding of this entity first began with the understanding and management of spina bifida; this later led to the gradual recognition of spina bifida occulta and the symptoms associated with tethering of the filum terminale. In the 17th century, Dutch anatomists provided the first descriptions and initiated surgical management efforts for spina bifida. In the 19th century, the term “spina bifida occulta” was coined and various presentations of spinal dysraphism were appreciated. The association of urinary, cutaneous, and skeletal abnormalities with spinal dysraphism was recognized in the 20th century. Early in the 20th century, some physicians began to suspect that traction on the conus medullaris caused myelodysplasia-related symptoms and that prophylactic surgical management could prevent the occurrence of clinical manifestations. It was not, however, until later in the 20th century that the term “tethered spinal cord” and the modern management of TCS were introduced. This gradual advancement in understanding at a time before the development of modern imaging modalities illustrates how, over the centuries, anatomists, pathologists, neurologists, and surgeons used clinical examination, a high level of suspicion, and interest in the subtle and overt clinical appearances of spinal dysraphism and TCS to advance understanding of pathophysiology, clinical appearance, and treatment of this entity. With the availability of modern imaging, spinal dysraphism can now be diagnosed and treated as early as the intrauterine stage.

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Nikolay L. Martirosyan, M. Yashar S. Kalani, G. Michael Lemole Jr., Robert F. Spetzler, Mark C. Preul and Nicholas Theodore

OBJECT

The arterial basket of the conus medullaris (ABCM) consists of 1 or 2 arteries arising from the anterior spinal artery (ASA) and circumferentially connecting the ASA and the posterior spinal arteries (PSAs). The arterial basket can be involved in arteriovenous fistulas and arteriovenous malformations of the conus. In this article, the authors describe the microsurgical anatomy of the ABCM with emphasis on its morphometric parameters and important role in the intrinsic blood supply of the conus medullaris.

METHODS

The authors performed microsurgical dissections on 16 formalin-fixed human spinal cords harvested within 24 hours of death. The course, diameter, and branching angles of the arteries comprising the ABCM were then identified and measured. In addition, histological sections were obtained to identify perforating vessels arising from the ABCM.

RESULTS

The ASA tapers as it nears the conus medullaris (mean preconus diameter 0.7 ± 0.12 mm vs mean conus diameter 0.38 ± 0.08 mm). The ASA forms an anastomotic basket with the posterior spinal artery (PSA) via anastomotic branches. In most of the specimens (n= 13, 81.3%), bilateral arteries formed connections between the ASA and PSA. However, in the remaining specimens (n= 3, 18.7%), a unilateral right-sided anastomotic artery was identified. The mean diameter of the right ABCM branch was 0.49 ± 0.13 mm, and the mean diameter of the left branch was 0.53 ± 0.14 mm. The mean branching angles of the arteries forming the anastomotic basket were 95.9° ± 36.6° and 90° ± 34.3° for the right- and left-sided arteries, respectively. In cases of bilateral arterial anastomoses between the ASA and PSA, the mean distance between the origins of the arteries was 4.5 ± 3.3 mm. Histological analysis revealed numerous perforating vessels supplying tissue of the conus medullaris.

CONCLUSIONS

The ABCM is a critical anastomotic connection between the ASA and PSA, which play an important role in the intrinsic blood supply of the conus medullaris. The ABCM provides an important compensatory function in the blood supply of the spinal cord. Its involvement in conus medullaris vascular malformations makes it a critical anatomical structure.

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Nikolay L. Martirosyan, Jeanne S. Feuerstein, Nicholas Theodore, Daniel D. Cavalcanti, Robert F. Spetzler and Mark C. Preul

The authors present a review of spinal cord blood supply, discussing the anatomy of the vascular system and physiological aspects of blood flow regulation in normal and injured spinal cords. Unique anatomical functional properties of vessels and blood supply determine the susceptibility of the spinal cord to damage, especially ischemia. Spinal cord injury (SCI), for example, complicating thoracoabdominal aortic aneurysm repair is associated with ischemic trauma. The rate of this devastating complication has been decreased significantly by instituting physiological methods of protection. Traumatic SCI causes complex changes in spinal cord blood flow, which are closely related to the severity of injury. Manipulating physiological parameters such as mean arterial blood pressure and intrathecal pressure may be beneficial for patients with an SCI. Studying the physiopathological processes of the spinal cord under vascular compromise remains challenging because of its central role in almost all of the body's hemodynamic and neurofunctional processes.

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Daniel D. Cavalcanti, Nikolay L. Martirosyan, Ketan Verma, Sam Safavi-Abbasi, Randall W. Porter, Nicholas Theodore, Volker K. H. Sonntag, Curtis A. Dickman and Robert F. Spetzler

Object

Schwannomas occupying the craniocervical junction (CCJ) are rare and usually originate from the jugular foramen, hypoglossal nerves, and C-1 and C-2 nerves. Although they may have different origins, they may share the same symptoms, surgical approaches, and complications. An extension of these lesions along the posterior fossa cisterns, foramina, and spinal canal—usually involving various cranial nerves (CNs) and the vertebral and cerebellar arteries—poses a surgical challenge. The primary goals of both surgical and radiosurgical management of schwannomas in the CCJ are the preservation and restoration of function of the lower CNs, and of hearing and facial nerve function. The origins of schwannomas in the CCJ and their clinical presentation, surgical management, adjuvant stereotactic radiosurgery, and outcomes in 36 patients treated at Barrow Neurological Institute (BNI) are presented.

Methods

Between 1989 and 2009, 36 patients (mean age 43.6 years, range 17–68 years) with craniocervical schwannomas underwent surgical resection at BNI. The records were reviewed retrospectively regarding clinical presentation, radiographic assessment, surgical approaches, adjuvant therapies, and follow-up outcomes.

Results

Headache or neck pain was present in 72.2% of patients. Cranial nerve impairments, mainly involving the vagus nerve, were present in 14 patients (38.9%). Motor deficits were found in 27.8% of the patients. Sixteen tumors were intra- and extradural, 15 were intradural, and 5 were extradural. Gross-total resection was achieved in 25 patients (69.4%). Adjunctive radiosurgery was used in the management of residual tumor in 8 patients; tumor control was ultimately obtained in all cases.

Conclusions

Surgical removal, which is the treatment of choice, is curative when schwannomas in the CCJ are excised completely. The far-lateral approach and its variations are our preferred approaches for managing these lesions. Most common complications involve deficits of the lower CNs, and their early recognition and rehabilitation are needed. Stereotactic radiosurgery, an important tool for the management of these tumors as adjuvant therapy, can help decrease morbidity rates.

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Nicholas C. Bambakidis, Eric M. Horn, Peter Nakaji, Nicholas Theodore, Elizabeth Bless, Tammy Dellovade, Chiyuan Ma, Xukui Wang, Mark C. Preul, Stephen W. Coons, Robert F. Spetzler and Volker K. H. Sonntag

Object

Sonic hedgehog (Shh) is a glycoprotein molecule that upregulates the transcription factor Gli1. The Shh protein plays a critical role in the proliferation of endogenous neural precursor cells when directly injected into the spinal cord after a spinal cord injury in adult rodents. Small-molecule agonists of the hedgehog (Hh) pathway were used in an attempt to reproduce these findings through intravenous administration.

Methods

The expression of Gli1 was measured in rat spinal cord after the intravenous administration of an Hh agonist. Ten adult rats received a moderate contusion and were treated with either an Hh agonist (10 mg/kg, intravenously) or vehicle (5 rodents per group) 1 hour and 4 days after injury. The rats were killed 5 days postinjury. Tissue samples were immediately placed in fixative. Samples were immunohistochemically stained for neural precursor cells, and these cells were counted.

Results

Systemic dosing with an Hh agonist significantly upregulated Gli1 expression in the spinal cord (p < 0.005). After spinal contusion, animals treated with the Hh agonist had significantly more nestin-positive neural precursor cells around the rim of the lesion cavity than in vehicle-treated controls (means ± SDs, 46.9 ± 12.9 vs 20.9 ± 8.3 cells/hpf, respectively, p < 0.005). There was no significant difference in the area of white matter injury between the groups.

Conclusions

An intravenous Hh agonist at doses that upregulate spinal cord Gli1 transcription also increases the population of neural precursor cells after spinal cord injury in adult rats. These data support previous findings based on injections of Shh protein directly into the spinal cord.

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Eric M. Horn, Nicholas Theodore, Rachid Assina, Robert F. Spetzler, Volker K. H. Sonntag and Mark C. Preul

Object

Venous stasis and intrathecal hypertension are believed to play a significant role in the hypoperfusion present in the spinal cord following injury. Lowering the intrathecal pressure via cerebrospinal fluid (CSF) drainage has been effective in treating spinal cord ischemia during aorta surgery. The purpose of the present study was to determine whether CSF drainage increases spinal cord perfusion and improves outcome after spinal injury in an animal model.

Methods

Anesthetized adult rabbits were subjected to a severe contusion spinal cord injury (SCI). Cerebrospinal fluid was then drained via a catheter to lower the intrathecal pressure by 10 mm Hg. Tissue perfusion was assessed at the site of injury, and values obtained before and after CSF drainage were compared. Two other cohorts of animals were subjected to SCI: 1 group subsequently underwent CSF drainage and the other did not. Results of histological analysis, motor evoked potential and motor function testing were compared between the 2 cohorts at 4 weeks postinjury.

Results

Cerebrospinal fluid drainage led to no significant improvement in spinal cord tissue perfusion. Four weeks after injury, the animals that underwent CSF drainage demonstrated significantly smaller areas of tissue damage at the injury site. There were no differences in motor evoked potentials or motor score outcomes at 4 weeks postinjury.

Conclusions

Cerebrospinal fluid drainage effectively lowers intrathecal pressure and decreases the amount of tissue damage in an animal model of spinal cord injury. Further studies are needed to determine whether different draining regimens can improve motor or electrophysiological outcomes.

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Sam Safavi-Abbasi, Mehmet Senoglu, Nicholas Theodore, Ryan K. Workman, Alireza Gharabaghi, Iman Feiz-Erfan, Robert F. Spetzler and Volker K. H. Sonntag

Object

The authors conducted a study to evaluate the clinical characteristics and surgical outcomes in patients with spinal schwannomas and without neurofibromatosis (NF).

Methods

The data obtained in 128 patients who underwent resection of spinal schwannomas were analyzed. All cases with neurofibromas and those with a known diagnosis of NF Type 1 or 2 were excluded. Karnofsky Performance Scale (KPS) scores were used to compare patient outcomes when examining the anatomical location and spinal level of the tumor. The neurological outcome was further assessed using the Medical Research Council (MRC) muscle testing scale.

Results

Altogether, 131 schwannomas were treated in 128 patients (76 males and 52 females; mean age 47.7 years). The peak prevalence is seen between the 3rd and 6th decades. Pain was the most common presenting symptom. Gross-total resection was achieved in 127 (97.0%) of the 131 lesions. The nerve root had to be sacrificed in 34 cases and resulted in minor sensory deficits in 16 patients (12.5%) and slight motor weakness (MRC Grade 3/5) in 3 (2.3%). The KPS scores and MRC grades were significantly higher at the time of last follow-up in all patient groups (p = 0.001 and p = 0.005, respectively).

Conclusions

Spinal schwannomas may occur at any level of the spinal axis and are most commonly intradural. The most frequent clinical presentation is pain. Most spinal schwannomas in non-NF cases can be resected totally without or with minor postoperative deficits. Preoperative autonomic dysfunction does not improve significantly after surgical management.