Low specificity of voltage-gated calcium channel antibodies in Lambert-Eaton myasthenic syndrome: a call for caution.

As testing for neuronal antibodies become more readily available, the spectrum of conditions potentially associated with these autoantibodies has been widening. Voltage-gated calcium channel antibodies (VGCC-Ab) are no exception to this trend. The significance of an elevated VGCC-Ab titer beyond its original clinicopathological correlate, Lambert-Eaton myasthenic syndrome (LEMS) remains undetermined. We sought to determine the diagnostic significance of an elevated serum VGCC-Ab titer in a large single-center cohort of 100 patients. The majority of patients (58%) with elevated VGCC-Ab levels lacked an inflammatory or autoimmune etiology of their neurologic diagnosis. Only six cases (6%) of LEMS and two cases (2%) of SCLC (without LEMS) were identified. No significant differences in antibody titers were seen between the autoimmune and non-autoimmune groups. These findings support the notions that: (a) elevated VGCC-Ab titers without clinical correlation must be interpreted with caution, and (b) the clinical and electrodiagnostic criteria for LEMS should remain the mainstay in the diagnosis of LEMS.

Distal Predominance of Electrodiagnostic Abnormalities in Early-Stage Amyotrophic Lateral Sclerosis.

INTRODUCTION: In this study we compared the electrodiagnostic (EDX) yield of limb muscles in revealing lower motor neuron (LMN) dysfunction by electromyography (EMG) in early-stage amyotrophic lateral sclerosis (ALS). METHODS: This investigation was undertaken as a retrospective review at a single center. RESULTS: Our study included 122 consecutive patients with possible ALS, as defined by revised El Escorial criteria. Distal limb muscles showed more frequent EMG abnormalities than proximal muscles. EDX yield was found to be higher in the limb where weakness began and when clinical signs of LMN dysfunction were evident. Adoption of the Awaji criteria significantly increased the yield of EMG-positive segments in the cervical (P < 0.0005) and lumbosacral (P < 0.0001) regions, and upgraded 19 patients into the probable category and 1 patient into the definite category. DISCUSSION: EMG abnormalities are predominant in the distal limb in early-stage ALS. A redefinition of an EDX-positive cervical or lumbosacral segment, with an emphasis on distal limb muscles, may result in an earlier ALS diagnosis. Muscle Nerve 58: 389-395, 2018.

Clinical utility of seropositive voltage-gated potassium channel-complex antibody.

BACKGROUND: Antibodies against voltage-gated potassium channel (VGKC)-complex are implicated in the pathogenesis of acquired neuromyotonia, limbic encephalitis, faciobrachial dystonic seizure, and Morvan syndrome. Outside these entities, the clinical value of VGKC-complex antibodies remains unclear. METHODS: We conducted a single-center review of patients positive for VGKC-complex antibodies over an 8-year period. RESULTS: Among 114 patients positive for VGKC-complex antibody, 11 (9.6%) carrying the diagnosis of limbic encephalitis (n = 9) or neuromyotonia (n = 2) constituted the classic group, and the remaining 103 cases of various neurologic and non-neurologic disorders comprised the nonclassic group. The median titer for the classic group was higher than the nonclassic group (p < 0.0001). A total of 90.9% of the patients in the classic and 21.4% in the nonclassic group possessed high (>0.25 nM) VGKC-complex antibody levels (p < 0.0001). A total of 75.0% of the patients in the high-level group had definite or probable autoimmune basis, while nonautoimmune disorders were seen in 75.6% of patients from the low-level group (p < 0.0001). A total of 26.3% of patients were found with active or remote solid organ or hematologic malignancy, but no antibody titer difference was observed among subgroups of absent, active, or remote malignancy. Compared to age-matched US national census, rates of active cancer in our cohort were higher in patients older than 45 years. CONCLUSIONS: High VGKC-complex antibody titers are more likely found in patients with classically associated syndromes and other autoimmune conditions. Low-level VGKC-complex antibodies can be detected in nonspecific and mostly nonautoimmune disorders. The presence of VGKC-complex antibody, rather than its level, may serve as a marker of malignancy.

Decoding facial blends of emotion: visual field, attentional and hemispheric biases.

Most clinical research assumes that modulation of facial expressions is lateralized predominantly across the right-left hemiface. However, social psychological research suggests that facial expressions are organized predominantly across the upper-lower face. Because humans learn to cognitively control facial expression for social purposes, the lower face may display a false emotion, typically a smile, to enable approach behavior. In contrast, the upper face may leak a person's true feeling state by producing a brief facial blend of emotion, i.e. a different emotion on the upper versus lower face. Previous studies from our laboratory have shown that upper facial emotions are processed preferentially by the right hemisphere under conditions of directed attention if facial blends of emotion are presented tachistoscopically to the mid left and right visual fields. This paper explores how facial blends are processed within the four visual quadrants. The results, combined with our previous research, demonstrate that lower more so than upper facial emotions are perceived best when presented to the viewer's left and right visual fields just above the horizontal axis. Upper facial emotions are perceived best when presented to the viewer's left visual field just above the horizontal axis under conditions of directed attention. Thus, by gazing at a person's left ear, which also avoids the social stigma of eye-to-eye contact, one's ability to decode facial expressions should be enhanced.

Non-enzymatic hydrolysis of creatine ethyl ester.

The rate of the non-enzymatic hydrolysis of creatine ethyl ester (CEE) was studied at 37 degrees C over the pH range of 1.6-7.0 using (1)H NMR. The ester can be present in solution in three forms: the unprotonated form (CEE), the monoprotonated form (HCEE(+)), and the diprotonated form (H(2)CEE(2+)). The values of pK(a1) and pK(a2) of H(2)CEE(2+) were found to be 2.30 and 5.25, respectively. The rate law is found to be Rate=-dCCEE/dt=k++[H2CEE2+][OH-]+k+[HCEE+][OH-]+k0[CEE][OH-] where the rate constants k(++), k(+), and k(0) are (3.9+/-0.2)x10(6)L mol(-1)s(-1), (3.3+/-0.5)x10(4)L mol(-1)s(-1), and (4.9+/-0.3)x10(4)L mol(-1)s(-1), respectively. Calculations performed at the density functional theory level support the hypothesis that the similarity in the values of k(+) and k(0) results from intramolecular hydrogen bonding that plays a crucial role. This study indicates that the half-life of CEE in blood is on the order of one minute, suggesting that CEE may hydrolyze too quickly to reach muscle cells in its ester form.