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Tarvinder Singh and Michel Kliot

Recent advancements in the field of imaging, particularly magnetic resonance imaging, have improved the way peripheral nerve tumors are diagnosed, monitored, and treated both medically and surgically. When combined with the all-important clinical evaluation and electrodiagnostic studies, imaging permits a clinician to accomplish the following: identify the size, shape, location, and distribution of mass lesions; infer the risks in resecting a mass lesion by displaying its relationship to nearby nerve fascicles; determine growth rates when serial imaging studies are available; suggest the nature of the pathological entity; and visualize muscle denervation associated with nerve damage. The authors describe some of the commonly used imaging modalities and discuss their use in evaluating and treating peripheral nerve tumors and other mass lesions.

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Robert Goodkin, David R. Haynor and Michel Kliot

✓ The authors describe the use of intraoperative ultrasonography with a small high-frequency (15 mHz) probe for evaluation of the extent of lateral bone removal during anterior cervical vertebrectomy. The relationship of the bone resection margins to the lateral aspect of the spinal cord was visualized. Postoperative computerized tomography scans revealed the extent of bone removal to be similar to that demonstrated by ultrasound. Intraoperative ultrasonography may be useful during anterior cervical surgery to assure adequate decompression of the spinal canal and spinal cord.

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Thomas Anthony Gallagher, Neil G. Simon and Michel Kliot

Successful management of peripheral nerve trauma relies on accurate localization of the injury and grading of the severity of nerve injury to determine whether surgical intervention is required. Existing techniques, such as electrodiagnostic studies and conventional imaging modalities, provide important information, but are limited by being unable to distinguish severe nerve lesions in continuity that will recover from those that will not. Diffusion tensor imaging (DTI) and tractography of peripheral nerves provide a novel technique to localize and grade nerve injury, by assessing the integrity of the nerve fibers across the site of nerve injury. Diffusion tensor imaging and tractography also hold promise as markers of early nerve regeneration, prior to clinical and electrodiagnostic evidence of recovery. In the present review, the techniques of peripheral nerve DTI and tractography are discussed with respect to peripheral nerve trauma, with illustrative cases demonstrating potential roles of these novel approaches.

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Michael Gofeld, Sandee J. Bristow, Sheila Chiu and Michel Kliot

Object

Surgical exposure of a peripheral nerve can be technically challenging, making the operation more extensive and time consuming, particularly in the treatment of small nerves with an anatomically variable position. This study describes the application of ultrasound to facilitate surgical access and localization of targeted peripheral nerves.

Methods

A preclinical feasibility study was performed at the University of Washington's Willed Body Program laboratory. Unembalmed cadavers were placed on the dissection table in positions mimicking those typically required for surgical access to specific nerves that can be challenging to localize. A high-frequency portable ultrasound system was used to identify the nerves. An extraneural injection of methylene blue immediately adjacent to the target nerve was performed under ultrasound guidance as the experimental nerve mapping procedure. Surgical dissections through a small skin incision parallel to skin tension lines were guided by the transducer position and angle. Success was determined by the accuracy and rapidity of surgical identification and exposure of the nerve.

Results

Using ultrasound-guided mapping, all anticipated peripheral nerves were correctly identified via a direct approach from the skin incision. This was confirmed by performing an anatomical dissection to expose and identify the intended nerve and its relation to the injected methylene blue dye. In no case was intraneural injection of the dye observed.

Conclusions

Preoperative ultrasound-guided nerve mapping may be useful in facilitating surgical access to a targeted nerve and thereby minimizing tissue dissection and operating time.

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Kimberly K. Amrami, Michel Kliot, Martijn J. A. Malessy and Robert J. Spinner

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Robert J. Spinner, Kimberly K. Amrami, Michel Kliot, Shawn P. Johnston and Joaquim Casañas

Object

Unlike the more commonly noted paralabral cysts (extraneural ganglia), which are well known to result in suprascapular nerve compression, only four cases of suprascapular intraneural ganglia have been reported. Because of their rarity, the pathogenesis of suprascapular intraneural ganglia has been poorly understood and a pathoanatomical explanation has not been provided. In view of the growing literature demonstrating strong associations between paralabral cysts and labral (capsular) pathology, joint connections, and joint communications, the authors retrospectively reviewed the magnetic resonance (MR) imaging studies and postoperative results in the two featured patients to test a hypothesis that suprascapular intraneural ganglia would have analogous findings.

Methods

Two patients who presented with suprascapular neuropathy were found to have intraneural ganglia. Connections to the glenohumeral joint could be established in both patients through posterior labrocapsular complex tears. In neither patient was the joint connection identified preoperatively or intraoperatively, and cyst decompression was performed by itself without attention to the labral tear. The suprascapular intraneural ganglia extended from the glenohumeral joint as far proximally as the level of the nerves’ origin from the upper trunk in the supraclavicular fossa. Although both patients experienced symptomatic improvement after surgery, neurological recovery was incomplete. In both cases, postoperative MR images revealed cyst persistence. In addition, previously unrecognized superior labral anteroposterior (SLAP) Type II lesions (tears of the superior labrum extending anteroposterior and involving the biceps anchor at the labrum without actual extension into the tendon) were visualized. In one patient with a persistent cyst, an MR arthrogram was obtained and demonstrated a communication between the joint and the cyst.

Conclusions

The findings in these two patients support the synovial theory for intraneural ganglia. Based on their experience with intraneural ganglia at other sites, the authors believe that suprascapular intraneural ganglia arise from the glenohumeral joint, egress through a superior (posterior) labral tear, and dissect within the epineurium along an articular branch into the main nerve, following the path of least resistance. Furthermore, these two cases of intraneural ganglia with SLAP lesions are directly analogous to the many cases of paralabral cysts associated with these types of labral tears. By better understanding the origin of this unusual type of ganglia and drawing analogies to the more common extraneural cysts, surgical strategies can be formulated to address the underlying pathoanatomy, improve operative outcomes, and prevent recurrences.

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Joseph A. Osorio, Jonathan D. Breshears, Omar Arnaout, Neil G. Simon, Ashley M. Hastings-Robinson, Pedram Aleshi and Michel Kliot

OBJECT

The objective of this study was to provide a technique that could be used in the preoperative period to facilitate the surgical exploration of peripheral nerve pathology.

METHODS

The authors describe a technique in which 1) ultrasonography is used in the immediate preoperative period to identify target peripheral nerves, 2) an ultrasound-guided needle electrode is used to stimulate peripheral nerves to confirm their position, and then 3) a methylene blue (MB) injection is performed to mark the peripheral nerve pathology to facilitate surgical exploration.

RESULTS

A cohort of 13 patients with varying indications for peripheral nerve surgery is presented in which ultrasound guidance, stimulation, and MB were used to localize and create a road map for surgeries.

CONCLUSIONS

Preoperative ultrasound-guided MB administration is a promising technique that peripheral nerve surgeons could use to plan and execute surgery.

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Tene A. Cage, Neil G. Simon, Suzanne Bourque, Roger Noss, John W. Engstrom, Jeffrey W. Ralph and Michel Kliot

Traumatic peripheral nerve injury can lead to significant long-term disability for previously healthy persons. Damaged nerve trunks have been traditionally repaired using cable grafts, but nerve transfer or neurotization procedures have become increasingly popular because the axonal regrowth distances are much shorter. These techniques sacrifice the existing nerve pathway, so muscle reinnervation depends entirely on the success of the repair. Providing a supplemental source of axons from an adjacent intact nerve by using side-to-side anastomosis might reinnervate the target muscle without compromising the function of the donor nerve.

The authors report a case of biceps muscle reinnervation after side-to-side anastomosis of an intact median nerve to a damaged musculocutaneous nerve. The patient was a 34-year-old man who had sustained traumatic injury primarily to the right upper and middle trunks of the brachial plexus. At 9 months after the injury, because of persistent weakness, the severely damaged upper trunk of the brachial plexus was repaired with an end-to-end graft. When 8 months later biceps function had not recovered, the patient underwent side-to-side anastomosis of the intact median nerve to the adjacent distal musculocutaneous nerve via epineural windows. By 9 months after the second surgery, biceps muscle function had returned clinically and electrodiagnostically. Postoperative electromyographic and nerve conduction studies confirmed that the biceps muscle was being reinnervated partly by donor axons from the healthy median nerve and partly by the recovering musculocutaneous nerve.

This case demonstrates that side-to-side anastomosis of an intact median to an injured musculocutaneous nerve can provide dual reinnervation of the biceps muscle while minimizing injury to both donor and recipient nerves.

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Neil G. Simon, Tene Cage, Jared Narvid, Roger Noss, Cynthia Chin and Michel Kliot

The goals of the present study were to demonstrate the ability of high-resolution ultrasonography to delineate normal nerve fascicles within or around peripheral nerve sheath tumors (NSTs). A blinded examiner evaluated 2 patients with symptomatic upper limb NSTs with high-resolution ultrasonography performed in the perioperative suite using a portable ultrasonography system. Ultrasonographic examinations located the tumor mass and identified the normal nerve fascicles associated with the mass. The locations of normal nerve tissue were mapped and correlated with results of MR tractography, operative inspection, and intraoperative electrophysiological monitoring. The study demonstrated a close correlation between normal nerve fascicles identified by ultrasonography, MR tractography, and intraoperative electrophysiological mapping. In particular, ultrasonographic examinations accurately identified the surface regions of the tumor without overlying normal nerve tissue. These preliminary data suggest that preoperative ultrasonographic examinations may provide valuable information, supplementary to the information obtained from intraoperative electrophysiological monitoring. Identification of normal nerve tissue prior to surgery may provide additional information regarding the risk of iatrogenic nerve injury during percutaneous tumor biopsy or open resection of the tumor and may also aid in selecting the optimum surgical approach.

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Dilantha B. Ellegala, Stephen J. Monteith, David Haynor, Thomas D. Bird, Robert Goodkin and Michel Kliot

Object. Charcot-Marie-Tooth (CMT) disease is a collection of related genetic disorders affecting peripheral nerves with an incidence of one in every 2500 individuals. A diagnosis of CMT disease has classically relied on a medical history, examination, and measurement of nerve conduction velocities. Advancements in genetic testing and magnetic resonance (MR) imaging techniques may provide clinicians with a more precise diagnostic armamentarium. The authors investigated MR neurography as a possible method to characterize CMT subtypes.

Methods. The authors performed MR neurography to evaluate sciatic nerves in the mid-thigh area of seven patients with genetically defined subtypes of CMT, one patient with chronic inflammatory demylinating polyneuropathy, and one patient without neuropathy. The authors correlate their findings with normal nerve conduction velocities (NCVs) and present their results as a descriptive case series.

Although MR neurography could not be used to distinguish subtypes of CMT disease on nerve area or fascicle number, it appears to characterize phenotypic features and disease progression noninvasively in patients with some subtypes.

Conclusions. In conjunction with NCV measurements, MR neurography may be useful in the diagnosis of CMT neuropathies and in monitoring disease progression.