Combat Injury of the Sciatic Nerve - An Institutional Experience.

INTRODUCTION: Combat injury of the sciatic nerve tends to be severe with variable but often profound consequences, is often associated with widespread soft tissue and bone injuries, significant neurologic impairment, severe neuropathic pain, and a prolonged recovery time. There is little contemporary data that describes the treatment and outcome of this significant military acquired peripheral nerve injury. We describe our institution's experience treating patients with combat-acquired sciatic nerve injury in the recent Iraq and Afghanistan wars. MATERIALS AND METHODS: IRB approval was obtained, and a retrospective review was performed of the records of 5,137 combat-related extremity injuries between June 2007 and June 2015 to identify patients with combat-acquired sciatic nerve injury without traumatic amputation of the injured leg. The most common mechanisms of injury were gunshot wound to the upper thigh or pelvis, followed by blast injury. Thirteen patients were identified that underwent sciatic nerve exploration and repair. Nine patients had nerve repair using long-length acellular cadaveric allografts. Five patients underwent nerve surgery within 30 d of injury and eight had surgery on a delayed basis. The postoperative follow-up period was at least 2 yr. RESULTS: Reduction of neuropathic pain was significant, 7/10 points on the 11-point pain intensity numerical rating scale. Eight patients displayed electrodiagnostic evidence of reinnervation distal to the injury zone; however, functional recovery was poor, as only 3 of 10 patients had detectable motor units distal to the knee, and recovery was only in tibial nerve innervated muscles. There were no serious surgical complications, in particular, wound infection or graft rejection associated with long-length cadaver allograft placement. CONCLUSION: Early surgery to repair sciatic nerve injury possibly promotes significant pain reduction, reduces narcotic usage and facilitates a long rehabilitation process. Allograft nerve placement is not associated with serious complications. A follow-up period longer than 3 yr would be required and is ongoing to assess the efficacy of our treatment of patients with combat-acquired sciatic nerve injury.

Inter-rater reliability determination for two tests of ulnar nerve conduction across the elbow.

INTRODUCTION: The inter-rater variability in determination of ulnar nerve conduction across the elbow compromises test accuracy. The extent of this variability is unknown. The objective of this study was to determine and compare inter-rater reliability of variables derived from 2 different ulnar nerve conduction studies (NCSs) across the elbow. METHODS: Two investigators performed a standard ulnar NCS and a 6-cm conduction time (Six-Centimeter Conduction Time test, SCCT) on 60 extremities of asymptomatic subjects. In the standard test, below-elbow (BE) and above-elbow (AE) stimulation points were ≥ 10 cm apart, measured along a curved path, to calculate across-elbow NCV. In SCCT, BE and AE were precisely 6 cm apart measured linearly to calculate CTE (conduction time elbow). Inter-rater reliability was assessed by means of intraclass correlation coefficients (ICC). RESULTS: ICC for across-elbow NCV and CTE were 0.726 and 0.801, respectively. CONCLUSIONS: Reliability of CTE and across-elbow NCV are similar. Shorter distances, if measured linearly, can be used to determine across-elbow ulnar nerve conduction. Muscle Nerve 55: 664-668, 2017.

High-resolution ultrasound in combat-related peripheral nerve injuries.

INTRODUCTION: Peripheral nerve injuries (PNI) sustained in combat are typically severe and are frequently associated with marked soft tissue damage, anatomic distortion, and retained metallic fragments. These features complicate clinical and electrodiagnostic assessment and may preclude MRI. METHODS: We describe 4 cases of military personnel who sustained high-velocity gunshot wounds or blasts with metal fragment injuries in which high resolution peripheral nerve ultrasound (US) proved beneficial. RESULTS: In these cases, the clinical and electrodiagnostic exams provided inadequate localization and severity data of the nerve injuries, and MRI was either precluded or provided no additional information. In each case, US disclosed focal nerve segment abnormalities, including regions of focal enlargement and nerve discontinuity with end-bulb neuroma, which guided surgical planning for nerve repair. The findings on US were subsequently confirmed intra-operatively. CONCLUSIONS: High resolution peripheral nerve US is a useful modality in assessment of combat-related PNI. Muscle Nerve, 2016 Muscle Nerve 54: 1139-1144, 2016.

Ulnar neuropathy at the elbow: Five new things.

Ulnar neuropathy at the elbow (UNE) is the second most frequent compression neuropathy. While other diagnostic imaging tools are emerging to assist in the diagnosis of UNE, electrodiagnosis remains the gold standard. However, the electrodiagnostic approach to UNE presents unique challenges limiting its diagnostic accuracy. We review advances in 5 areas relevant to the diagnosis of UNE: technologic advancements with modern EMG machines have allowed for reconsideration of the question of experimental error and lesion detection; how temperature effects can lead to misdiagnosis; the effect of body mass index on the electrodiagnosis of UNE; the validation of short segment studies; and the emerging role of high-resolution sonography as a diagnostic tool.

Neuralgic amyotrophy manifested by severe axillary mononeuropathy limited only to the anterior branch.

INTRODUCTION: In this study we describe a case demonstrating clinical, radiographic, electrophysiologic, and surgical evidence of a restricted but severe anterior branch axillary nerve mononeuropathy due to neuralgic amyotrophy (NA). METHODS: On each diagnostic modality there was severe involvement of the anterior and lateral deltoid muscle with sparing of the posterior deltoid and teres minor muscles and cutaneous innervation to the skin overlying the lateral shoulder. RESULTS: No structural etiologies were discovered during surgical exploration. CONCLUSIONS: This case provides another unique manifestation of NA and augments the theory of selective fascicular vulnerability.

Ethical considerations in elective amputation after traumatic peripheral nerve injuries.

Traumatic peripheral nerve injuries often complicate extremity trauma, and may cause substantial functional deficits. We have encountered patients who request amputation of such injured extremities, with the goal of prosthetic replacement as a means to restore function. Data on long-term outcomes of limb salvage vs amputation are limited and somewhat contradictory, leaving how to respond to such requests in the hands of the treating physician. We present example cases, drawn from our experience with wounded soldiers in a peripheral nerve injury clinic, in order to facilitate discussion of the ways in which these patients stress the system of medical decision-making while identifying ethical questions central to responding to these requests.

Effects of pontine lesions on REM sleep.

Over the past several decades, the neural mechanisms underlying REM sleep have become increasingly understood. A more detailed understanding of the respective roles of the pontine nuclei in the generation of REM sleep and its related phenomenon has allowed for the recognition of specific effects that brainstem lesions have on sleep. In humans, however, the effects of such lesions are limited to case reports and small case series. This article offers a comprehensive review of the basic neurobiology of REM sleep. In addition, we discuss specific clinical effects that various pontine lesions have with regard to REM sleep and the spectrum of clinical sleep disorders characterized by abnormalities in REM-related phenomena. We review the existing literature detailing the interactions between clinical sleep manifestations and brainstem pathology.

Sparing of the second lumbrical in a Riche-Cannieu anastomosis: the nearly all-ulnar hand.

The Riche-Cannieu anastomosis (RCA) is an anatomic variant wherein a deep branch of the distal ulnar nerve innervates muscles of the thenar eminence. A few cases in the literature describe an "all-ulnar hand" when the muscles of the thenar eminence get innervation solely from the ulnar nerve without any contribution from the median nerve. Clinically, patients with ulnar mononeuropathies in the setting of an RCA would also have weakness/atrophy of thenar muscles. Conversely, patients with median mononeuropathies would have sparing of these muscles. This case highlights RCA in the setting of carpal tunnel syndrome and documents the persistent innervation of the second lumbrical by the median nerve. No anatomic dissections have disclosed innervation of the second lumbrical by the deep ulnar nerve, negating the concept of the all-ulnar hand.

Genetic polymorphisms associated with exertional rhabdomyolysis.

Exertional rhabdomyolysis (ER) occurs in young, otherwise healthy, individuals principally during strenuous exercise, athletic, and military training. Although many risk factors have been offered, it is unclear why some individuals develop ER when participating in comparable levels of physical exertion under identical environmental conditions and others do not. This study investigated possible genetic polymorphisms that might help explain ER. DNA samples derived from a laboratory-based study of persons who had never experienced an episode of ER (controls) and clinical ER cases referred for testing over the past several years were analyzed for single nucleotide polymorphisms (SNPs) in candidate genes. These included angiotensin I converting enzyme (ACE), α-actinin-3 (ACTN3), creatine kinase muscle isoform (CKMM), heat shock protein A1B (HSPA1B), interleukin 6 (IL6), myosin light chain kinase (MYLK), adenosine monophosphate deaminase 1 (AMPD1), and sickle cell trait (HbS). Population included 134 controls and 47 ER cases. The majority of ER cases were men (n = 42/47, 89.4 %); the five women with ER were Caucasian. Eighteen African Americans (56.3 %) were ER cases. Three SNPs were associated with ER: CKMM Ncol, ACTN3 R577X, and MYLK C37885A. ER cases were 3.1 times more likely to have the GG genotype of CKMM (odds ratio/OR = 3.1, confidence interval/CI 1.33-7.10), 3.0 times for the XX genotype of ACTN3 SNP (OR = 2.97, CI 1.30-3.37), and 5.7 times for an A allele of MYLK (OR = 21.35, CI 2.60-12.30). All persons with HbS were also ER cases. Three distinct polymorphisms were associated with ER. Further work will be required to replicate these findings and determine the mechanism(s) whereby these variants might confer susceptibility.

Clinical features and electrodiagnosis of ulnar neuropathies.

In this review, we delineate clinical, electrodiagnostic, and radiographic features of ulnar mononeuropathies. Ulnar neuropathy at the elbow (UNE) is most commonly due to lesions at the level of the retroepicondylar groove (RTC), with approximately 25% at the humeroulnar arcade (HUA). The term 'cubital tunnel syndrome' should be reserved for the latter. The diagnostic accuracy of nerve conduction studies is limited by biological (e.g. low elbow temperature) and technical factors. Across-elbow distance measurements greater than 10 cm improve diagnostic specificity at the expense of decreased sensitivity. Short-segment incremental studies can differentiate lesions at the HUA from those at the RTC.

Investigation of the relationship between serum creatine kinase and genetic polymorphisms in military recruits.

Genetic polymorphisms may explain why certain individuals will develop exertional rhabdomyolysis (ER) or markedly elevated serum creatine kinase (CK) levels following exertion, while others in the same environment, performing the same exertion, do not. Prospectively, 499 recruits were evaluated during the initial fortnight of Army basic training. Serum CK levels were determined before and during that time. Eleven candidate genetic polymorphisms were studied and compared to CK levels. No subjects developed ER. Baseline CK was significantly greater in interleukin-6 G174C GG and myosin light chain kinase 2 (MLCK 2) AA subjects. Intertraining levels were significantly greater in angiotensin I-converting enzyme D/D and interleukin-6 GG subjects. Among African-Americans, those with MLCK2 AA had greater baseline CK (1,352 +/- 1,102.8 IU/L) than AC and CC genotypes (536.9 +/- 500.6). African-American men have the highest baseline levels and are more likely to have MLCK AA genotype. Whether this finding is associated with an increased incidence of ER requires further study.

Exertional rhabdomyolysis: a clinical review with a focus on genetic influences.

In this review, the clinical and laboratory features of exertional rhabdomyolysis (ER) are discussed in detail, emphasizing the full clinical spectrum from physiological elevations of serum creatine kinase after exertion to life-threatening rhabdomyolysis with acute kidney injury and associated systemic complications. Laboratory markers used to diagnose both ER and rhabdomyolysis are very sensitive, but not very specific, and imperfectly distinguish "subclinical" or asymptomatic from severe, life-threatening illness. However, genetic factors, both recognized and yet to be discovered, likely influence this diverse clinical spectrum of disease and response to exercise. Genetic mutations causative for McArdle disease, carnitine palmitoyl transferase deficiency 2, myoadenylate deaminase deficiency, and malignant hyperthermia have all been associated with ER. Polymorphic variations in the myosin light chain kinase, α-actin 3, creatine kinase-muscle isoform, angiotensin I-converting enzyme, heat shock protein, and interleukin-6 genes have also been associated with either ER or exercise-induced serum creatine kinase elevations typical of ER. The prognosis for ER is significantly better than that for other etiologies of rhabdomyolysis, but the risk of recurrence after an initial episode is unknown. Guidelines for management are provided.

Serum creatine kinase after exercise: drawing the line between physiological response and exertional rhabdomyolysis.

INTRODUCTION: In this investigation we assessed the spectrum of creatine kinase (CK) responses in military recruits undergoing basic training. METHODS: Musculoskeletal examination data, questionnaire findings, and CK levels were obtained from 499 recruits at days 0, 3, 7, and 14 of training. Correlations of CK with ethnicity, age, body mass index, exercise, muscle pain, and climate were obtained. RESULTS: None of the subjects developed clinical exertional rhabdomyolysis (ER). The mean/median serum CK values were 223/157, 734/478, 1226/567, and 667/486 IU/L at days 0, 3, 7, and 14, respectively, with a wide overall range (34-35,056 IU/L). African-American subjects had higher mean CK levels. CONCLUSIONS: CK elevations and muscle pain are common during basic training. Widely accepted laboratory diagnostic values for ER are routinely exceeded in this military recruits, suggesting that CK levels >50 times the upper limit of normal are more specific. The findings support using CK as a marker for ER. Normal laboratory reference ranges for CK should be published by ethnicity.

Conduction time for a 6-cm segment of the ulnar nerve across the elbow: reference values for the 6-cm conduction time test.

Current electrodiagnostic studies for Ulnar nerve mononeuropathy at the elbow have substandard sensitivity and specificity. Reference values for a novel, screening electrodiagnostic test for ulnar nerve mononeuropathy at the elbow were obtained bilaterally from 72 subjects without any upper extremity signs or symptoms. The test used two, 3-cm straight line distances, one proximal, and one distal to the medial epicondyle to avoid a curvilinear measurement. The mean conduction times (CTE) were 1.16 +/- 0.16 milliseconds, 1.23 +/- 0.18 milliseconds, 1.33 +/- 0.24 milliseconds, for subjects 20 to 40, 40 to 60, and >60 years old, respectively. A CTE >1.50 milliseconds, >1.60 milliseconds, and >1.80 milliseconds for each age group would be considered abnormal conferring 98% specificity. The median side-to-side difference of CTE (CTE-diff) was 0.10 milliseconds with a range of 0.00 to 0.55 milliseconds. A CTE-diff >0.45 milliseconds has a specificity of 97%. Potential advantages to this method include straight-line measurement distances to reduce experimental error, and a distance less than 10 cm to improve lesion detection.

Vestibulocochlear nerve.

The vestibulocochlear or eighth cranial nerve (CN VIII) has purely special sensory afferent function. The nerve has two components, the vestibular nerve, that detects head and body motion, and the cochlear nerve that detects sound. The primary receptors that convey information to the vestibular portion of CN VIII are the semicircular canals that detect angular acceleration, and the otolithic organs that detect linear acceleration. The organ of Corti receives auditory signals and conveys its information via the cochlear portion. Processes that affect the receptors or the nerve will cause hearing loss, tinnitus, otalgia, vertigo, oscillopsia, and disequilibrium. In this review, the authors discuss the anatomy of CN VIII, the clinical evaluation of patients with vertigo and hearing loss, and specific disease entities.

Controversial entrapment neuropathies.

There is no significant disagreement about the major common entrapment neuropathies, such as carpal tunnel syndrome (CTS), ulnar neuropathy at the elbow, and peroneal neuropathy at the knee. In contrast, there is a group of entrapment syndromes about which there is major disagreement, including whether or not they even exist. There are other entrapment syndromes about which clinical questions arise on a regular basis, and which are the subject of this discussion. These include thoracic outlet syndrome, radial tunnel syndrome, ulnar nerve entrapment at the arcade of Struthers, piriformis syndrome, and tarsal tunnel syndrome.