5. All That glitters is not gold

Neurophysiologic studies and survival in amyotrophic lateral sclerosis

Retrospective review of prospectively collected data. This study aimed to accurately map the lower extremity muscles innervated by the lumbar spinal roots by directly stimulating the spinal roots during surgery. Innervation of the spinal roots in the lower extremities has been estimated by clinical studies, anatomic studies, and animal experiments. However, there have been discrepancies between studies. Moreover, there are no studies that have studied the laterality of lower limb innervation. In 73 patients with lumbar degenerative disease, a total of 147 spinal roots were electrically stimulated and the electromyographic response was recorded at the vastus medialis (VM), gluteus medius (GM), tibialis anterior (TA), biceps femoris (BF), and gastrocnemius (GC). The asymmetry index (AI) was obtained using the following equation to represent the left-right asymmetry in the compound muscle action potential (CMAP) amplitude. Paired t tests were used to compare CMAP amplitudes on the right and left sides. Differences in the AI among the same spinal root groups were determined using one-way analysis of variance. The frequency of CMAP elicitation in VM, GM, TA, BF, and GC were 100%, 75.0%, 50.0%, 83.3%, and 33.3% in L3 spinal root stimulation, 90.4%, 78.8%, 59.6%, 73.1%, and 59.6% in L4 spinal root stimulation, 32.2%, 78.0%, 93.2%, 69.5%, and 83.1% in L5 spinal root stimulation, and 40.0%, 100%, 80.0%, 70.0%, and 80.0% in S1 spinal root stimulation, respectively. The most frequent muscle with maximum amplitude of the CMAP in L3, L4, L5, and S1 spinal root stimulation was the VM, GM, TA, and GM, respectively. Unilateral innervation occurred at high rates in the TA in L4 root stimulation and the VM in L5 root stimulation in 37.5% and 42.3% of patients, respectively. Even in patients with bilateral innervation, a 20% to 38% AI of CMAP amplitude was observed. The spinal roots innervated a much larger range of muscles than what is indicated in general textbooks. Furthermore, a non-negligible number of patients showed asymmetric innervation of lower limb by the lumbar spinal roots.

G.P.292: Nerve ultrasonography and neurophysiological study in amyotrophic lateral sclerosis to assess distal motor dysfunction of median nerve

To describe the incidence and prevalence of peripheral neuropathy in ANCA-associated vasculitis (AAV); to evaluate the correlation of neuropathy with other clinical manifestations; and to review the long-term outcome of treated neuropathy. Presence of neuropathy was determined using items from the BVAS and vasculitis damage index (VDI) during 5 years from enrollment into clinical trials conducted by the European Vasculitis Study Group (EUVAS). Forty (8%) of 506 patients had vasculitic neuropathy at baseline. Incidence of vasculitic motor-involving neuropathy was identical between microscopic polyangiitis (MPA) [16 (7%) out of 237] and granulomatosis with polyangiitis (Wegener's) [19 (7%) out of 269], P = 0.94. Pure sensory neuropathy was reported in 5 (2%) out of 269 patients with granulomatosis with polyangiitis, but not in patients with MPA, P = 0.065. Vasculitic neuropathy at baseline was associated with systemic [odds ratio (OR) = 1.81], cutaneous (OR = 1.29), mucous membranes (OR = 1.21) and ENT (OR = 1.14) manifestations of vasculitis (P < 0.05 for all). There was no association between neuropathy and renal, chest, cardiovascular or abdominal vasculitis or with overall mortality. Of the 40 patients with vasculitic neuropathy at baseline, 35% had complete resolution within 6 months. The cumulative prevalence of chronic neuropathy at any time up to 5 years was 15% (75 of 506). Chronic neuropathy was associated with older age [hazard ratio (HR) = 1.03], higher BVAS (HR = 1.07) and lower baseline creatinine (HR = 0.82) (P < 0.01 for all). Peripheral neuropathy is an occasional accompaniment of AAV that typically remits in concert with non-neuropathic manifestations, usually involves motor nerves, often produces long-lasting symptoms and is not associated with life-threatening organ involvement.

Radiological and electrodiagnostic insights into suprascapular nerve dysfunction: a key predictor of poor functional outcomes in shoulder hemiarthroplasty.

To study the neurophysiological mechanisms of motor deficit in patients with post-traumatic cervical myelopathy. A retrospective clinical and neurophysiological study was conducted for the period 2008-2018. The study included 190 patients with post-traumatic cervical myelopathy (39 women and 159 men, mean age 27 (21,0; 36,0) years, time after spinal cord injury 3 [1,0; 8,0] years). A spinal cord injury was the cause of cervical myelopathy in 92,5% of the patients. The International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) was administered at admission and during rehabilitation. A motor nerve conduction study (NCS) was conducted as well. Compound muscle action potentials (CMAP) amplitude and nerve conduction velocity (NCV) in the distal segment of 160 left and 145 right median nerves, 161 left and 151 right tibial nerves, 90 left and 66 right ulnar nerves were recorded. Re-examination (n=95 patients) was performed 6 (3,0; 10,0) years after injury. The time between examinations was 2,9 (1,0; 4,0) years. The control groups for the median nerve and the tibial nerve consisted of age- and sex-matched 10 patients with traumatic paraplelegia and 12 healthy subjects, respectively. In the main group, the SMAP amplitude for the median nerve was 4,1 [1,6; 6,1] mV, NCV 56 [51,0; 61,0] m/s; in the control group the SMAP was 11 [7,50; 16,40] mV (p=00), NCV 59 [58,0; 6,0] m/s (p=00), in the main group the SMAP amplitude for the tibial nerve was 4,3 [0,65; 7,95] mV, NCV 43 [39,0; 48,0] m/s, in the control group SMAP was 8,4 [6,4; 10,1] mV (p=00), NCV 50 [47,0 ; 51,0] m/s (p=00). About 20% of patients had severe denervation changes. In patients with clinically complete spinal cord injury, axonal neuropathy (a decrease in SMAP) was more pronounced in all nerves than in incomplete patients, and a decrease in NCV was observed in both tibial nerves. In patients with C7-Th1 level, the SMAP amplitude was reduced on the left (2,5 [0,55; 5,65] mV) and right (2,7 [0,80; 6,30] mV) sides compared to those with C4-C6, in which CMAP was 4,6 [2,30; 6,20] mV on the left (p=0.03) and 4,7 [2,80; 6,10] mV on the right sides (p=0.03). The main neurophysiological mechanisms of motor deficit in patients with post-traumatic cervical myelopathy are the combination of the primary neuronal damage at the level of spinal cord injury and the development of secondary axonal neuropathy more caudally at the first three years after spinal cord injury.

Peripheral Nerve Vasculitis: Classification and Disease Associations

The term vasculitis incorporated a large group of clinically heterogeneous conditions that have the following characteristic pathologic features in common: inflammation and structural damage to blood vessel walls that leads to ischemic, hemorrhagic, and thrombotic damage to the tissues supplied by those vessels. Peripheral neuropathy is common in conjunction with most of these vasculitic syndromes, irrespective of whether vasculitis is the primary disease process, as in polyarteritis nodosa or Wegener’s granulomatosis, or is secondary to some other connective tissue disorder, such as rheumatoid arthritis or systemic lupus erythematosus. In patients with secondary vasculitides, it can occasionally be difficult to distinguish vasculitic neuropathy from other types of neuropathy (discussed in Chapter 13). The clinical and pathologic features of vasculitic neuropathy, however, are distinctive enough to merit separate discussion, particularly since neuropathy may be the first, and sometimes only, manifestation of vasculitis. Prompt diagnosis by the neuromuscular clinician is therefore crucial because of the significant potential for improvement with immunosuppressive treatment. In fact, vasculitic neuropathy represents one of the most treatable neuropathies encountered by clinicians.

P627: Is precautionary neurophysiological monitoring useful for beta-thalassemia patients?

It is important to know the effects of prolonged repetitive nerve stimulation (RNS) when it is used in neurophysiological studies. RNS with up to 100 supramaximal stimuli was given to the median, ulnar, and peroneal nerves of normal subjects and the ulnar nerves of subjects with early amyotrophic lateral sclerosis (ALS), recording evoked compound muscle action potentials (CMAPs). In all nerves, there was a decline in the CMAP area and a decrease in CMAP duration. For the peroneal nerve there was a decline in the CMAP amplitude, but a similar decline was not seen in the median or ulnar nerves. Cooling of the muscles resulted in decrement of both the amplitude and area with RNS. In ALS subjects, CMAP amplitude and area both declined after RNS of the ulnar nerve. In this study we describe the changes in CMAP with prolonged RNS among commonly tested normal nerves. Our findings have important implications with regard to RNS.

Detecting acute nerve compression using neurophysiologic studies is an important part of the practice of clinical intra-operative neurophysiology. The goal of this paper was to study the changes in the compound muscle action potential (CMAP) during acute mechanical compression. This is the type of injury most likely to occur during surgery. Thus, understanding the changes in the CMAP during this type of injury will be useful in the detection and prevention using intra-operative neurophysiologic monitoring.The model involved compression of the hamster sciatic nerve over a region of 1.3 mm with pressures up to 2000 mmHg for times on the order of 3 minutes. In this model CMAP amplitude dropped to 50% of its baseline value when a pressure of roughly 1000 mmHg is applied while, at the same time, nerve conduction velocities decline by only 5%. The ability to detect statistically significant changes in the CMAP at low force levels using other descriptors of the CMAP including duration, latency variation, etc alone or in conjunction with amplitude and velocity measures was investigated. However, these other parameters did not allow for earlier detection of significant changes.This study focused on a model in which nerve injury on a short time scale is purely mechanical in origin. It demonstrated that a pure compression injury produced large changes in CMAP amplitude prior to large changes in conduction velocity. On the other hand, ischemic and stretch injuries are associated with larger changes in conduction velocity for a given value of CMAP amplitude reduction.

Finger Extension Weakness and DOwnbeat Nystagmus Motor Neuron Disease (FEWDON-MND) is characterized by motor weakness predominantly affecting finger extension, accompanied by downbeat nystagmus. To date, only 11 patients have been reported. The present study adds a further three and aims to provide a more detailed description of the electrodiagnostic features of these patients. We present the clinical and electrophysiological features of three French patients from specialized motor neuron centers and review the electrophysiological findings of previously reported patients. These three patients presented with pure motor weakness affecting finger extension and downbeat nystagmus. They exhibited a slowly progressive disease course without respiratory involvement. Nerve conduction studies showed decreased compound muscle action potential amplitudes in the extensor indicis muscles. Abnormal spontaneous activity on needle electromyography (EMG) was rare in two patients, absent in one, and otherwise limited to weak muscles. Additionally, chronic motor axon loss features suggestive of motor neuronopathy were seen in our patients. Importantly, they were also detected in distant asymptomatic muscles. The three patients reported here confirm the typical phenotype of FEWDON-MND, characterized by slowly progressive distal motor weakness initially affecting finger extension, associated with downbeat nystagmus. Although chronic motor axon loss features have been found in all reported patients, our three patients show that active denervation can be absent or rare. Thus, finger drop and diffuse chronic neurogenic changes on EMG should lead clinicians to look for downbeat nystagmus and to consider FEWDON-MND.

Mobius syndrome is characterized by congenital facial diplegia, frequent impairment of gaze, variable involvement of other cranial muscles, and various musculoskeletal anomalies. The site of dysfunction remains debatable. We performed detailed electrophysiologic studies in 5 children and 2 adults with Mobius syndrome to better delineate the pathophysiology of this disorder. Sensory and motor conduction studies were normal in the extremities. Facial compound muscle action potential amplitudes were reduced in all patients. The blink reflex R1 responses were unobtainable unilaterally in 2 patients and unobtainable bilaterally in 3 patients. Otherwise, R1 and R2 latencies were variably prolonged. The jaw jerk and masseter silent periods, tested in 2 patients, were normal. Detailed electromyographic studies of facial muscles revealed multifocal, chronic neurogenic changes. The findings indicate a brain stem process predominantly affecting the facial nuclei and their internuclear connections rather than a supranuclear or muscular site of involvement.

Neurophysiological studies were performed in 12 patients with neuromuscular paralysis due to envenomation by the common krait (Bungarus caeruleus). All patients presented with an acute, reversible, oculofaciobulbar paresis. In addition, 7 patients had weakness of the limb muscles and 4 required assisted mechanical ventilation. Neurophysiological abnormalities included: (1) a reduction in the amplitude of the median-elicited compound muscle action potential (CMAP) in 4 patients; and (2) a decremental response (>10%) to 3-Hz repetitive nerve stimulation (RNS) in 4 patients. With 1 exception, these abnormalities were noted only in clinically weak muscles. The administration of edrophonium to 6 patients produced an insignificant increase in CMAP amplitudes as well as partial (not significant) improvement in the decremental response to 3-Hz RNS. Neurophysiological studies were performed in 2 patients before and after the administration of 20 mL of polyvalent antivenom. A decrease in amplitude of the median-elicited CMAP amplitude occurred after the administration of antivenom. In 1 patient, administered 100 mL of antivenom, the median-elicited CMAP amplitude increased and the decrement to 3-Hz RNS decreased. Neurophysiological studies can provide useful information regarding the nature, severity, and therapy of the neuroparalytic syndrome of krait envenomation.

In young, healthy adults, early phase (i.e., 0-50 ms) rate of torque development (RTD) is primarily determined by neural characteristics. However, it is unclear if this remains the case in older adults. PURPOSE: To examine the physiological characteristics of early phase RTD in older men. METHODS: Seventeen older males (age = 73 ± 6 y) completed 2 maximal (MVIC) and 2 rapid (rMVIC) isometric knee extensions. Early phase RTD values were calculated from the first 50 ms (aRTD50) of the rapid contractions and normalized (nRTD50) to maximal torque (%MVIC/s). Muscle activation amplitude (EMG) was calculated during the first 50 ms (nEMG50) of EMG onset and was normalized to the peak-to-peak M-wave amplitude (%MPP) of the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF). Evoked peak twitch torque (PTT) was determined as the maximal torque (Nm) produced from a single electrical stimulus. Motor unit number estimation (MUNE) was calculated as a ratio of the ensemble average of the single MU potential amplitude to the compound muscle action potential amplitude and was corrected for alteration. Muscle quality (MQ) was determined by examining the average muscle cross-sectional area relative to the average muscle echo intensity for each muscle using an ultrasound. Relationships between the predictor variables (nEMG50, MUNE, PTT, MQ) and RTD (aRTD50 and nRTD50) were analyzed via Pearson’s correlation coefficients. Stepwise multiple regression was used to examine the amount of variance in aRTD50 and nRTD50 accounted for by each of the predictor variables. RESULTS: aRTD50 (577.8 ± 241.0 Nm/s-1) was related to MUNE (144.1 ± 47.1, r = .549, p = .023), nEMG (137.5 ± 97.7 %MPP, r = .673, p = .003), and PTT (20.34 ± 12.5 Nm, r = .504, p = .039). nRTD50 (433.2 ± 175.4 %MVIC/s) was related to MUNE (r = .531, p = .028) and nEMG50 (r = .604, p = .010). nEMG50 and PTT were significant determinants (p = .001) that accounted for 45.3% and 15.5% of the variance in aRTD50, respectively. nEMG50 was the only significant predictor (p = .01), explaining 36.4% of the variance in nRTD50. CONCLUSIONS: These pilot data support the notion that early phase RTD is primarily determined by neural factors, even in older adults. These data also suggest that possessing a higher number of viable MUs may influence early phase absolute RTD in older men.