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Mark A. Mahan

Stretch injuries are among the most devastating forms of peripheral nerve injury; unfortunately, the scientific understanding of nerve biomechanics is widely and impressively conflicting. Experimental models are unique and disparate, victim to different testing conditions, and thus yield gulfs between conclusions. The details of the divergent reports on nerve biomechanics are essential for critical appraisal as we try to understand clinical stretch injuries in light of research evidence. These conflicts preclude broad conclusion, but they highlight a duality in thought on nerve stretch and, within the details, some agreement exists. To synthesize trends in nerve stretch understanding, the author describes the literature since its introduction in the 19th century. Research has paralleled clinical inquiry, so nerve research can be divided into epochs based largely on clinical or scientific technique. The first epoch revolves around therapeutic nerve stretching—a procedure known as neurectasy—in the late 19th century. The second epoch involves studies of nerves repaired under tension in the early 20th century, often the result of war. The third epoch occurs later in the 20th century and is notable for increasing scientific refinement and disagreement. A fourth epoch of research from the 21st century is just dawning. More than 150 years of research has demonstrated a stable and inherent duality: the terribly destructive impact of stretch injuries, as well as the therapeutic benefits from nerve stretching. Yet, despite significant study, the precise border between safe and damaging stretch remains an enigma.

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Hussam Abou-Al-Shaar, Nam Yoon and Mark A. Mahan

Traumatic proximal sciatic nerve rupture poses surgical repair dilemmas. Disruption often causes a large nerve gap after proximal neuroma and distal scar removal. Also, autologous graft material to bridge the segmental defect may be insufficient, given the sciatic nerve diameter. The authors utilized knee flexion to allow single neurorrhaphy repair of a large sciatic nerve defect, bringing healthy proximal stump to healthy distal segment. To avoid aberrant regeneration, the authors split the sciatic nerve into common peroneal and tibial divisions. After 3 months, the patient can fully extend the knee and has evidence of distal regeneration and nerve continuity without substantial injury.

The video can be found here: https://youtu.be/lsezRT5I8MU.

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Mark A. Mahan, Kimberly K. Amrami and Robert J. Spinner

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Hussam Abou-Al-Shaar and Mark A. Mahan

Endoscopic surgery has revolutionized the field of minimally invasive surgery. Nerve injury after laparoscopic surgery is presumably rare, with only scarce reports in the literature; however, the use of these techniques for new purposes presents the opportunity for novel complications. The authors report a case of subcostal nerve injury after an anterior laparoscopic approach to a posterior abdominal wall lipoma.

A 62-year-old woman presented with a left abdominal flank bulge (pseudohernia) that developed after laparoscopic posterior flank wall lipoma resection. Imaging demonstrated frank ballooning of the oblique muscles; denervation atrophy and thinning of the external oblique, internal oblique, and transverse abdominis muscles; and thinning of the rectus abdominis muscle. The patient underwent subcostal nerve repair and removal of a foreign plastic material from the laparoscopic procedure. At 8 months, she has regained substantial improvement in abdominal wall strength.

Although endoscopic procedures have resulted in significant reduction in morbidity, “minimally invasive” approaches should not be confused with “low risk” when approaching novel pathology. The subcostal nerve is at risk of injury in posterior abdominal wall surgery, whether laparoscopic or not. With the pseudohernia and abdominal bulge after this surgery, the cosmetic appeal of laparoscopic incisions was definitively undone. Selecting an approach based on the anatomy of adjacent structures may lead to a better functional result.

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Mark A. Mahan, Jaime Gasco, David B. Mokhtee and Justin M. Brown

OBJECT

Surgical transposition of the ulnar nerve to alleviate entrapment may cause otherwise normal structures to become new sources of nerve compression. Recurrent or persistent neuropathy after anterior transposition is commonly attributable to a new distal compression. The authors sought to clarify the anatomical relationship of the ulnar nerve to the common aponeurosis of the humeral head of the flexor carpi ulnaris (FCU) and flexor digitorum superficialis (FDS) muscles following anterior transposition of the nerve.

METHODS

The intermuscular septa of the proximal forearm were explored in 26 fresh cadaveric specimens. The fibrous septa and common aponeurotic insertions of the flexor-pronator muscle mass were evaluated in relation to the ulnar nerve, with particular attention to the effect of transposition upon the nerve in this region.

RESULTS

An intermuscular aponeurosis associated with the FCU and FDS muscles was present in all specimens. Transposition consistently resulted in angulation of the nerve during elbow flexion when this fascial septum was not released. The proximal site at which the nerve began to traverse this fascial structure was found to be an average of 3.9 cm (SD 0.7 cm) from the medial epicondyle.

CONCLUSIONS

The common aponeurosis encountered between the FDS and FCU muscles represents a potential site of posttransposition entrapment, which may account for a subset of failed anterior transpositions. Exploration of this region with release of this structure is recommended to provide an unconstrained distal course for a transposed ulnar nerve.

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Justin M. Brown, Mark A. Mahan, Ross Mandeville and Bob S. Carter

Neurosurgery is experiencing the emergence of a new subspecialty focused on function restoration. New, evolving, and reappraised surgical procedures have provided an opportunity to restore function to many patients with previously undertreated disorders. Candidates for reconstruction were previously limited to those with peripheral nerve and brachial plexus injuries, but this has been expanded to include stroke, spinal cord injury, and a host of other paralyzing disorders affecting both upper and lower motor neurons. Similar to the recent evolution of the well-established subdisciplines of spinal and vascular neurosurgery, reconstructive neurosurgery requires the adaptation of techniques and skills that were not traditionally a part of neurosurgical training. Neurosurgeons—as the specialists who already manage this patient population and possess the requisite surgical skills to master the required techniques—have a unique opportunity to lead the development of this field. The full development of this subspecialty will lay the foundation for the subsequent addition of emerging treatments, such as neuroprosthetics and stem cell–based interventions. As such, reconstructive neurosurgery represents an important aspect of neurosurgical training that can ameliorate many of the deficits encountered in the traditional practice of neurosurgery.

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Hussam Abou-Al-Shaar, Michael Karsy, Vijay Ravindra, Evan Joyce and Mark A. Mahan

Particularly challenging after complete brachial plexus avulsion is reestablishing effective hand function, due to limited neurological donors to reanimate the arm. Acute repair of avulsion injuries may enable reinnervation strategies for achieving hand function. This patient presented with pan–brachial plexus injury. Given its irreparable nature, the authors recommended multistage reconstruction, including contralateral C-7 transfer for hand function, multiple intercostal nerves for shoulder/triceps function, shoulder fusion, and spinal accessory nerve–to–musculocutaneous nerve transfer for elbow flexion. The video demonstrates distal contraction from electrical stimulation of the avulsed roots. Single neurorrhaphy of the contralateral C-7 transfer was performed along with a retrosternocleidomastoid approach.

The video can be found here: https://youtu.be/GMPfno8sK0U.

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Tomas Marek, Robert J. Spinner, Akshay Syal and Mark A. Mahan

OBJECTIVE

Lipomatosis of nerve (LN) is a massive enlargement of a nerve due to abundant proliferation of adipose and fibrotic tissue within the epineurium—part of the spectrum of adipose lesions of nerves, including intra- and extraneural lipomas. LN has been frequently associated with soft-tissue and/or osseous overgrowth. Unfortunately, much confusion exists since many names have been used for LN (e.g., fibrolipomatous hamartoma, macrodystrophia lipomatosa, and so on). To better understand this condition and to evaluate its association with nerve-territory overgrowth, the authors attempted to compile the world’s literature on published LN cases.

METHODS

PubMed and Google Scholar databases were searched to identify published articles on LN cases, using a variety of terms. Publications in all languages were assessed. All publications with cases determined likely to be LN were read. Cases that provided clear clinicopathological and/or radiological evidence of LN were labeled as “definite” and cases that demonstrated features of LN (e.g., nerve-territory overgrowth) but lacked definite proof of nerve involvement were labeled as “probable.”

RESULTS

Initial screening revealed a total of 2465 papers. After exclusions, 281 publications reported cases with a definite diagnosis of LN and 120 articles reported cases with a probable diagnosis of LN. The authors identified 618 definite and 407 probable cases of LN. Sex distribution was balanced (51% female). Early diagnosis was common, with two-thirds of patients having symptoms in the 1st decade of life. The most commonly affected nerve was the median nerve (n = 391). Nerve-territory overgrowth was common (62% definite LN; 78% combined cases); overgrowth was exclusive to the territory of the affected nerve in all cases but 5.

CONCLUSIONS

The authors present a comprehensive review and analysis of the literature of LN cases. One of the main findings was the nerve-territory overgrowth was associated with LN, especially when present earlier in life. The authors believe that all cases of LN associated with overgrowth can be explained on anatomical grounds, even in the few reported cases in which this is not immediately obvious.

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Michael Karsy, Jian Guan, Walavan Sivakumar, Jayson A. Neil, Meic H. Schmidt and Mark A. Mahan

Genetic alterations in the cells of intradural spinal tumors can have a significant impact on the treatment options, counseling, and prognosis for patients. Although surgery is the primary therapy for most intradural tumors, radiochemothera-peutic modalities and targeted interventions play an ever-evolving role in treating aggressive cancers and in addressing cancer recurrence in long-term survivors. Recent studies have helped delineate specific genetic and molecular differences between intradural spinal tumors and their intracranial counterparts and have also identified significant variation in therapeutic effects on these tumors. This review discusses the genetic and molecular alterations in the most common intradural spinal tumors in both adult and pediatrie patients, including nerve sheath tumors (that is, neurofibroma and schwannoma), meningioma, ependymoma, astrocytoma (that is, low-grade glioma, anaplastic astrocytoma, and glioblastoma), hemangioblastoma, and medulloblastoma. It also examines the genetics of metastatic tumors to the spinal cord, arising either from the CNS or from systemic sources. Importantly, the impact of this knowledge on therapeutic options and its application to clinical practice are discussed.