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Editorial

Hypertonic saline

Alan Hoffer and Warren R. Selman

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

Object

Knowledge of the variations in the nerves of the posterior cranial fossa may be important during skull base approaches. To the authors' knowledge, intracranial neural interconnections between the glossopharyngeal and vagus nerves have not been previously investigated.

Methods

The senior author (A.C.G.) noted the presence of an intracranial interneural connection between the glossopharyngeal and vagus nerves during microvascular decompression surgery in a patient suffering from hemifacial spasm. To further investigate the approximate incidence and significance of such an interneural connection, the authors studied 40 adult human cadavers (80 sides) and prospectively evaluated 16 additional patients during microvascular procedures of the posterior cranial fossa.

Results

In the cadavers, the incidence of intracranial neural connections between the glossopharyngeal and vagus nerves was 2.5%. The only such connection found in our series of living patients was in the patient in whom the connection was initially identified. These interconnections were more common on the left side. Based on our findings, we classified these neural connections as Types I and II. In the cadavers, the length and width of this connection were approximately 9 mm and 1 mm, respectively. Histological analysis of these connections verified their neural content.

Conclusions

Although these connections are rare and the significance is unknown, knowledge of them may prove useful to surgeons who operate in the posterior fossa region so that they may avoid inadvertent traction or transection of these interconnections. Additionally, such connections might be considered in patients with recalcitrant neuralgia after microvascular decompression and rhizotomy of the glossopharyngeal nerve.

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

Object

Knowledge of the detailed anatomy of the craniocervical junction is important to neurosurgeons. To the authors' knowledge, no study has addressed the detailed anatomy of the intracranial (first) denticulate ligament and its intracranial course and relationships.

Methods

In 10 embalmed and 5 unembalmed adult cadavers, the authors performed posterior dissection of the craniocervical junction to expose the intracranial denticulate ligament. Rotation of the spinomedullary junction was documented before and after transection of unilateral ligaments.

Results

The first denticulate ligament was found on all but one left side and attached to the dura of the marginal sinus superior to the vertebral artery as it pierced the dura mater. The ligament always traveled between the vertebral artery and spinal accessory nerve. On 20% of sides, it also attached to the intracranial vertebral artery and, histologically, blended with its adventitia. In general, this ligament tended to be thicker laterally and was often cribriform in nature medially. The hypoglossal nerve was always superior to the ligament, which always concealed the ventral roots of the C-1 spinal nerve. The posterior spinal artery traveled posterior to this ligament on 93% of sides. On one left side, the ascending branch of the posterior spinal artery traveled anterior to the ligament and the descending branch traveled posterior to it. Following unilateral transection of the intracranial denticulate ligament, rotation of the spinomedullary junction was increased by approximately 25%.

Conclusions

Knowledge of the relationships of the first denticulate ligament may prove useful to the neurosurgeon during procedures at the craniocervical junction.

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

Object

Additional nerve transfer options are important to the peripheral nerve surgeon to maximize patient outcomes following nerve injuries. Potential regional donors may also be injured or involved in the primary disease. Therefore, potential contralateral donor nerves would be desirable. To the authors' knowledge, use of the contralateral spinal accessory nerve (SAN) has not been explored for ipsilateral neurotization procedures. In the current study, therefore, the authors aimed to evaluate the SAN as a potential donor nerve for contralateral nerve injuries by using a novel technique.

Methods

In 10 cadavers, the SAN was harvested using a posterior approach, and tunneled subcutaneously to the contralateral side for neurotization to various branches of the brachial plexus. Measurements were made of the SAN available for transfer and of its diameter.

Results

The authors found an SAN length of approximately 20 cm (from transition of upper and middle fibers of the trapezius muscle to approximately 2–4 cm superior to the insertion of the trapezius muscle onto the spinous process of T-12) available for nerve transposition. The average diameter was 2.5 mm.

Conclusions

Based on these findings, the contralateral SAN may be considered for ipsilateral neurotization to the suprascapular and axillary nerves.

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Joshua J. Chern, Amber J. Gordon, Martin M. Mortazavi, R. Shane Tubbs and W. Jerry Oakes

Object

In 1998 the authors identified 5 patients with syringomyelia and no evidence of Chiari malformation Type I (CM-I). Magnetic resonance imaging of the entire neuraxis ruled out other causes of a syrinx. Ultimately, abnormal CSF flow at the foramen magnum was the suspected cause. The label “Chiari 0” was used to categorize these unique cases with no tonsillar ectopia. All of the patients underwent posterior fossa decompression and duraplasty identical to the technique used to treat patients with CM-I. Significant syrinx and symptom resolution occurred in these patients. Herein, the authors report on a follow-up study of patients with CM-0 who were derived from over 400 operative cases of pediatric CM-I decompression.

Methods

The authors present their 12-year experience with this group of patients.

Results

Fifteen patients (3.7%) were identified. At surgery, many were found to have physical barriers to CSF flow near the foramen magnum. In most of them, the syringomyelia was greatly diminished postoperatively.

Conclusions

The authors stress that this subgroup represents a very small cohort among patients with Chiari malformations. They emphasize that careful patient selection is critical when diagnosing CM-0. Without an obvious CM-I, other etiologies of a spinal syrinx must be conclusively ruled out. Only then can one reasonably expect to ameliorate the clinical course of these patients via posterior fossa decompression.

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Martin M. Mortazavi, R. Shane Tubbs, Maja Andrea Brockerhoff, Marios Loukas and W. Jerry Oakes

Few are familiar with the neurological contributions of the German pathologist Theodor Langhans. Even fewer are aware of his significant and early contributions to the study of what is now known as the Chiari I malformation. In at least 4 cases, Langhans described the association between tonsillar ectopia and syringomyelia. Moreover, this early pioneer speculated that there was a cause and effect with hindbrain herniation resulting in improper flow at the craniocervical junction and consequent development of syringomyelia. These cases were reported prior to Hans Chiari's descriptions, and Langhans' theory of impeded foramen magnum flow as a cause of syringomyelia was novel and preceded the current understanding of this mechanism by almost a century. The authors discuss the life of Langhans and translate excerpts from his 1881 work regarding tonsillar ectopia and syringomyelia.

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Martin M. Mortazavi, R. Shane Tubbs, Daniel Harmon and W. Jerry Oakes

Chronic emesis may result from a variety of causes. To the authors' knowledge, compression of the area postrema by regional vessels resulting in chronic emesis has not been reported.

The authors report on a child who presented with chronic medically intractable emesis and significant weight loss requiring jejunostomy feeding. Surgical exploration of the posterior cranial fossa found unilateral compression of the area postrema by the posterior inferior cerebellar artery. Microvascular decompression resulted in postoperative and long-term resolution of the patient's emesis.

Although apparently very rare, irritation of the area postrema from the posterior inferior cerebellar artery with resultant medically intractable chronic emesis may occur. Therefore, the clinician should be aware of this potential etiology when dealing with such patients.

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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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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, Olivia J. Rompala, Ketan Verma, Martin M. Mortazavi, Brion Benninger, Marios Loukas and M. Rene Chambers

Object

Although the uncovertebral region is neurosurgically relevant, relatively little is reported in the literature, specifically the neurosurgical literature, regarding its anatomy. Therefore, the present study aimed at further elucidation of this region's morphological features.

Methods

Morphometry was performed on the uncinate processes of 40 adult human skeletons. Additionally, range of motion testing was performed, with special attention given to the uncinate processes. Finally, these excrescences were classified based on their encroachment on the adjacent intervertebral foramen.

Results

The height of these processes was on average 4.8 mm, and there was an inverse relationship between height of the uncinate process and the size of the intervertebral foramen. Degeneration of the vertebral body (VB) did not correlate with whether the uncinate process effaced the intervertebral foramen. The taller uncinate processes tended to be located below C-3 vertebral levels, and their average anteroposterior length was 8 mm. The average thickness was found to be 4.9 mm for the base and 1.8 mm for the apex. There were no significant differences found between vertebral level and thickness of the uncinate process. Arthritic changes of the cervical VBs did not necessarily deform the uncinate processes. With axial rotation, the intervertebral discs were noted to be driven into the ipsilateral uncinate process. With lateral flexion, the ipsilateral uncinate processes aided the ipsilateral facet joints in maintaining the integrity of the ipsilateral intervertebral foramen.

Conclusions

A good appreciation for the anatomy of the uncinate processes is important to the neurosurgeon who operates on the spine. It is hoped that the data presented herein will decrease complications during surgical approaches to the cervical spine.