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.

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.

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.

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.

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.

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.

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.

The effects of isolated brainstem lesions on human REM sleep.

BACKGROUND: Clinical and electrophysiologic data support the role of multiple brainstem structures responsible for sleep architecture. To determine if patients with isolated brainstem lesions have detectable abnormalities of sleep architecture with polysomnography (PSG). METHOD: The objective of this study is to determine if patients with isolated brainstem lesions defined by magnetic resonance imaging (MRI), and without sleep complaints, underwent PSG. The data was compared to age-matched controls. Eight patients met inclusion criteria. Of the eight locations, one was midbrain, two were pontomesencephalic, four were pontine and one was pontomedullary. RESULTS: Four of the eight patients had a decreased percentage of Rapid Eye Movement (REM) sleep. The abnormal studies occurred in patients with a right paramedian pontine infarct, a left pontomedullary cavernous hemangioma (CH), a left pontine CH, and a right pontomesencephalic CH. REM sleep, as a percentage of total bed time, was 8.7, 12.3, 14.8, and 16.7%, respectively. CONCLUSION: These findings concur with non-human data that depict pontine structures as the major generators of REM sleep.

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.

The difference between fibrillations and positive sharp waves is due to tissue filtering.

Fibrillation potentials and positive sharp waves share many characteristics, and in general have the same clinical importance. Whether they are two species of the same potential or two different waveforms has been a long-standing controversy. The blocking hypothesis and inadvertent intracellular recording are two theories proposed to explain the difference between the two potentials, but neither is entirely satisfactory. In this study, waveforms with fibrillation potential configurations are modified by the standard filter settings on an electromyograph to attain positive sharp wave configurations. Single-fiber muscle action potentials were recorded at a low-frequency filter of 500 Hz and a high-frequency filter of 20 kHz, and had the appearance of a fibrillation potential. Changing the low-frequency filter and high-frequency filter to 0.2 Hz and 100 Hz respectively caused these same potentials to have a positive sharp wave configuration. Similarly, fibrillation potentials recorded from patients at a low-frequency filter and a high-frequency filter of 20 Hz and 10 kHz respectively had the appearance of positive sharp waves when the low-frequency filter and high-frequency filter were changed to 0.2 Hz and 500 Hz respectively. The authors propose that tissue filtering and the spatial relationship of the fibrillating fiber to the recording electrode determine whether the waveform will have a fibrillation potential configuration or a positive sharp wave configuration. The ability to model these waveforms artificially simply by changing the bandpass suggests that the passive electrical properties of the recording environment may suffice to explain much of the difference between fibrillation potentials and positive sharp waves.

EEG characteristics in juvenile Huntington's disease: a case report and review of the literature.

The clinical features of Juvenile Huntington's Disease (J-HD) differ from those of the more common adult-onset form, and include cognitive decline, parkinsonism, myoclonus and seizures. A paucity of literature is available describing the electroencephalographic (EEG) findings. We describe the clinical and EEG characteristics of a patient with genetically confirmed J-HD. A review of previously published cases yielded EEG descriptions in only 23 patients whose disease onset was prior to the age of 32, and only 14 of these were prior to the age of 20. Epileptiform abnormalities were noted in 17 (74%), which was considerably more common than in the adult form. Generalized discharges were noted in nine, with six having polyspike and wave. The remainder had focal or multifocal epileptiform discharges. With genetic testing now available, refinement of the EEG data will be possible.

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.

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.

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.

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.