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  • Journal of Neurosurgery: Spine x
  • By Author: Cohen-Gadol, Aaron A. x
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Ravi Gandhi, Corinne M. Curtis and Aaron A. Cohen-Gadol

Despite the use of advanced microsurgical techniques, resection of intramedullary tumors may result in significant postoperative deficits because of the vicinity or invasion of important functional tracts. Intraoperative monitoring of somatosensory evoked potentials and transcranial electrical motor evoked potentials has been used previously to limit such complications. Electromyography offers an opportunity for the surgeon to map the eloquent tissue associated with the tumor using intraoperative motor fiber stimulation. Similar to the use of cortical simulation in the resection of supratentorial gliomas, this technique can potentially advance the safety of intramedullary spinal cord tumor resection. The authors describe the use of intraoperative motor fiber tract stimulation to map the corticospinal tracts associated with an intramedullary tumor. This technique led to protection of these tracts during resection of the tumor.

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R. Shane Tubbs, Martin M. Mortazavi, Marios Loukas, Anthony V. D'Antoni, Mohammadali M. Shoja, Joshua J. Chern and Aaron A. Cohen-Gadol

Object

Occipital neuralgia can be a debilitating disease and may occur following operative procedures near the occipital and nuchal regions. One nerve of this region, the third occipital nerve (TON), has received only scant attention, and its potential contribution to occipital neuralgia has not been appreciated. Therefore, in the present study the authors aimed to detail the anatomy of this nerve and its relationships to midline surgical approaches of the occiput and posterior neck.

Methods

Fifteen adult cadavers (30 sides) underwent dissection of the upper cervical and occipital regions. Special attention was given to identifying the course of the TON and its relationship to the soft tissues and other nerves of this region. Once identified superficially, the TON was followed deeply through the nuchal musculature to its origin in the dorsal ramus of C-3. Measurements were made of the length and diameter of the TON. Additionally, the distance from the external occipital protuberance was measured in each specimen. Following dissection of the TON, self-retaining retractors were placed in the midline and opened in standard fashion while observing for excess tension on the TON.

Results

Articular branches were noted arising from the deep surface of the nerve in 63.3% of sides. The authors found that the TON was, on average, 3 mm lateral to the external occipital protuberance, and small branches were found to cross the midline and communicate with the contralateral TON inferior to the external occipital protuberance in 66.7% of sides. The TON trunk became subcutaneous at a mean of 5 cm inferior to the external occipital protuberance. In all specimens, the cutaneous main trunk of the TON was intimately related to the nuchal ligament. Insertion of self-retaining retractors in the midline placed significant tension on the TON in all specimens, both superficially and more deeply at its adjacent facet joint.

Conclusions

Although damage to the TON may often be unavoidable in midline approaches to the craniocervical region, appreciation of its presence and knowledge of its position and relationships may be useful to the neurosurgeon who operates in this region and may assist in decreasing postoperative morbidity.

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R. Shane Tubbs, Jeffrey R. Lancaster, Martin M. Mortazavi, Mohammadali M. Shoja, Joshua J. Chern, Marios Loukas and Aaron A. Cohen-Gadol

Object

Assimilation of the atlas to the occiput may result in symptoms that are often compressive in nature around the outlet of the foramen magnum. The aim of the present study was to elucidate the morphological features of the bone through this foramen.

Methods

Thirteen adult skulls with atlantooccipital fusion underwent morphometrical analysis of the outlet of the foramen magnum.

Results

All specimens but one were found to have a decreased area of the outlet of the foramen magnum. In those 12 specimens, a decrease of 15%–35% was seen. Fusions of the atlas that were based primarily along the anterior rim of the foramen magnum resulted in more obstruction of its outlet. In general, the horizontal diameters of the outlet of these foramina were more decreased from the normal range.

Conclusions

These findings demonstrate that in the majority of cases, assimilation of the atlas to the occiput results in a compromised outlet of the foramen magnum.

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R. Shane Tubbs, Justin D. Hallock, Virginia Radcliff, Robert P. Naftel, Martin Mortazavi, Mohammadali M. Shoja, Marios Loukas and Aaron A. Cohen-Gadol

The specialized ligaments of the craniocervical junction must allow for stability yet functional movement. Because injury to these important structures usually results in death or morbidity, the neurosurgeon should possess a thorough understanding of the anatomy and function of these ligaments. To the authors' knowledge, a comprehensive review of these structures is not available in the medical literature. The aim of the current study was to distill the available literature on each of these structures into one offering.

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R. Shane Tubbs, Mohammadali M. Shoja, Marios Loukas, Jeffrey Lancaster, Martin M. Mortazavi, Eyas M. Hattab and Aaron A. Cohen-Gadol

Object

There is conflicting and often anecdotal evidence regarding the potential motor innervation of the trapezius muscle by cervical nerves, with most authors attributing such fibers to proprioception. As knowledge of such potential motor innervations may prove useful to the neurosurgeon, the present study aimed to elucidate this anatomy further.

Methods

Fifteen adult cadavers (30 sides) underwent dissection of the posterior triangle of the neck and harvesting of cervical nerve fibers found to enter the trapezius muscle. Random fibers were evaluated histologically to determine fiber type (that is, motor vs sensory axons).

Results

In addition to an innervation from the spinal accessory nerve, the authors also identified cervical nerve innervations of all trapezius muscles. For these innervations, 3 sides were found to have fibers derived from C-2 to C-4, 2 sides had fibers derived from C-2 to C-3, and 25 sides had fibers derived from C-3 to C-4. Fibers derived from C-2 to C-4 were classified as a Type I innervation, those from C-2 to C-3 were classified as a Type II innervation, and those from C-3 to C-4 were classified as a Type III innervation. Immunohistochemical analysis of fibers from each of these types confirmed the presence of motor axons.

Conclusions

Based on the authors' study, cervical nerves innervate the trapezius muscle with motor fibers. These findings support surgical and clinical experiences in which partial or complete trapezius function is maintained after injury to the spinal accessory nerve. The degree to which these nerves innervate this muscle, however, necessitates further study. Such information may be useful following nerve transfer procedures, denervation techniques for cervical dystonia, or sacrifice of the spinal accessory nerve due to pathological entities.

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R. Shane Tubbs, Martin M. Mortazavi, Andrew J. Denardo and Aaron A. Cohen-Gadol

The artery of Desproges-Gotteron is rarely mentioned in the literature and is unfamiliar to most neurosurgeons. The authors report a unique case of an arteriovenous malformation (AVM) of the conus in an adult woman, which received blood supply from an artery of Desproges-Gotteron. The patient presented with intermittent pain radiating down the right posterior thigh and foot and transient bladder incontinence. On examination, there was weakness of the right lower limb with hypalgesia of the plantar aspect of the right foot. Magnetic resonance imaging revealed a mass near the anterior aspect of the conus medullaris and angiography confirmed a spinal AVM at the L-1 level and a shunt located at the inferior L-3 level. The patient underwent transarterial embolization, and at 2-year follow-up, repeat angiography demonstrated no evidence of residual or recurrent spinal AVM, intermittent and tolerable pain without treatment interventions, and a normal neurological examination. The artery of Desproges-Gotteron appears to be a rare arterial variation. Moreover, the authors believe this to be the first case of a conal AVM supplied by such an artery. The anatomy and implications of such an arterial variant are discussed.

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Hormuzdiyar H. Dasenbrock, Courtney Pendleton, Aaron A. Cohen-Gadol, Jean-Paul Wolinsky, Ziya L. Gokaslan, Alfredo Quinones-Hinojosa and Ali Bydon

Although Harvey Cushing was a neurosurgical pioneer, his work on the spine remains largely unknown. In fact, other than his own publications, Cushing's patients with pathological lesions of the spine who were treated while he was at the Johns Hopkins Hospital, including those with spinal cord tumors, have never been previously described. The authors report on 7 patients with spinal cord tumors that Cushing treated surgically between 1898 and 1911: 2 extradural, 3 intradural extramedullary, and 2 intramedullary tumors. The authors also describe 10 patients in whom Cushing performed an “exploratory laminectomy” expecting to find a tumor, but in whom no oncological pathological entity was found. Cushing's spine surgeries were limited by challenges in making the correct diagnosis, lack of surgical precedent, and difficulty in achieving adequate intraoperative hemostasis. Other than briefly mentioning 2 of the 4 adult patients in his landmark monograph on meningiomas, these cases—both those involving tumors and those in which he performed exploratory laminectomies—have never been published before. Moreover, these cases illustrate the evolution that Harvey Cushing underwent as a spine surgeon.

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R. Shane Tubbs, Matthew R. Levin, Marios Loukas, Eric A. Potts and Aaron A. Cohen-Gadol

Object

To date, only scant descriptions of the cluneal nerves are available. As these nerves, and especially the superior group, may be encountered and injured during posterior iliac crest harvest for spinal arthrodesis procedures, the present study was performed to better elucidate their anatomy and to provide anatomical landmarks for their localization.

Methods

The superior and middle cluneal nerves were dissected from their origin to termination in 20 cadaveric sides. The distance between the posterior superior iliac spine (PSIS) and superior cluneal nerves at the iliac crest and the distance between this bony prominence and the origin of the middle cluneals were measured. The specific course of each nerve was documented, and the diameter and length of all cluneal nerves were measured.

Results

Superior and middle cluneal nerves were found on all sides. An intermediate superior cluneal nerve and lateral superior cluneal nerve were not identified on 4 and 5 sides, respectively. The superior cluneal nerves always passed through the psoas major and paraspinal muscles and traveled posterior to the quadratus lumborum. The mean diameters of the superior and middle cluneal nerves were 1.1 and 0.8 mm, respectively. From the PSIS, the superior cluneal branches passed at means of 5, 6.5, and 7.3 cm laterally on the iliac crest. At their origin, the middle cluneal nerves had mean distances of 2 cm superior to the PSIS, 0 cm from the PSIS, and 1.5 cm inferior to the PSIS. In their course, the middle cluneal nerves traversed the paraspinal muscles attaching onto the dorsal sacrum.

Conclusions

Knowledge of the cutaneous nerves that cross the posterior aspect of the iliac crest may assist in avoiding their injury during bone harvest. Additionally, an understanding of the anatomical pathway that these nerves take may be useful in decompressive procedures for entrapment syndromes involving the cluneal nerves.

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R. Shane Tubbs, Marios Loukas, James D. Callahan and Aaron A. Cohen-Gadol

Object

Surgical approaches to the upper anterior thoracic spine can be a challenge. Various techniques such as transsternal routes have been employed but access to the midthoracic vertebrae is limited due to the position of the heart and great vessels. In the present study the authors' goal was to evaluate in cadavers a novel approach to the upper anterior thoracic spine.

Methods

In 12 adult cadavers the majority of the left first rib was removed following infraclavicular transection of the attachment of the anterior and middle scalene muscles from this bone. Inferior retraction of the parietal pleura and lung was performed and dissection was carried out inferior to the left subclavian artery and superior and posterior to the aorta, to the anterior aspect of the upper thoracic spine.

Results

The aforementioned approach and surgical corridor allowed a good access to the anterior aspect of the upper thoracic vertebrae and caudally to the inferior aspect of T-4 vertebral body in all cadavers. No obvious neurovascular injury was identified in any specimen.

Conclusions

To the authors' knowledge, the method described herein has not been previously reported. Based on their cadaveric study, they believe such an approach can be used in the patients with pathology in this region of the thoracic spine. Surgical series are now needed to confirm our findings.