A novel diagnostic method for myasthenia gravis.

INTRODUCTION/AIMS: Videonystagmography (VNG) which directly records eye movements using infrared video goggles with mini-cameras, is used to measure nystagmus. Our aim is to explore whether VNG can be used to detect a decrement in the extraocular muscle (EOM) activity of patients with myasthenia gravis (MG). METHODS: Thirty-four patients with MG, including 13 with ocular-predominant and 21 with generalized MG, and 23 healthy controls participated. Using VNG we recorded the velocity of the eye movements of the patients as they followed a moving target. We then calculated the gain by dividing the eye movement velocity (degrees/second) by the target velocity (degrees/second). RESULTS: In MG subjects, the mean initial gain (maximum gain) was 1.23 ± 0.31 (range: 0.63-2.15) for the right eye and 1.22 ± 0.37 (range; 0.60-2.28) for the left eye. The mean minimum gain was 0.11 ± 0.12 (0.01-0.58) for the right and 0.14 ± 0.5 (0.02-0.55) for the left. Due to fatigue, the movement gain was reduced by 91.7% in the right eye and 88.2% in the left eye. After reaching minimum velocity, gain remained at a minimum for a mean of 1.08 ± 0.52 (0.3-2.4) s for the right and 1.49 ± 0.85 (0.4-3.6) s for the left, before the velocity increased again. There was no fatigue-induced decrement in healthy subjects. DISCUSSION: Our study documents a decrement in EOM activity recorded by VNG in patients with MG which begins to improve within 1-2 s after reaching minimum velocity, analogous to traditional low-frequency repetitive nerve stimulation testing and its U-shaped pattern. Thus, VNG may be a promising diagnostic test for MG.

Evaluation of median nerve by shear wave elastography and diffusion tensor imaging in carpal tunnel syndrome.

PURPOSE: The aim of the current study is to investigate the diagnostic role of shear-wave elastography and diffusion tensor imaging in patients with carpal tunnel syndrome. MATERIAL AND METHODS: The study included a total of 77 wrists; 18 normal, 35 wrists with mild, 9 wrists with moderate and 15 wrists with severe carpal tunnel syndrome. Elastography of the median nerve was performed by defining the boundaries of a segment of the nerve at sagittal plane at the level of proximal carpal row. Additionally, the cross-sectional area of the median nerve was evaluated. Fractional anisotropy and apparent diffusion coefficient measurements were carried out by placing region-of-interest at three levels: at pisiform bone (carpal tunnel inlet), mid carpal tunnel, and hook of hamate (carpal tunnel outlet). RESULTS: Patients with carpal tunnel syndrome had higher elasticity values of median nerve (53.0 kPa; IQR 40.8-77.0 kPa) compared to control subjects. (36.8 kPa; IQR 31.0-39.9 kPa) Patients with moderate-severe carpal tunnel syndrome had higher elasticity values (82 kPa; IQR 64.0-95.5 kPa) compared to patients with mild carpal tunnel syndrome. (44 kPa; IQR 32.5-59.5 kPa) Patients with carpal tunnel syndrome had lower fractional anisotropy at mid-carpal level (0.382; IQR 0.330-0.495) compared to the control group. (0.494; IQR 0.434-0.537) Patients with moderate-severe carpal tunnel syndrome had lower fractional anisotropy values (0.366; IQR 0.331-0.407) and higher apparent diffusion coefficient values (1.509 mm2/s; IQR 1.374-1.733 mm2/s) compared to patients with mild carpal tunnel syndrome. (0,423; IQR 0.324-0.526 and 1.293 mm2/s; IQR 0.967-1.514 mm2/s) CONCLUSION: Shear-wave elastography and diffusion tensor imaging are helpful imaging modalities in diagnosing carpal tunnel syndrome and assessing its severity.

Circadian changes in cortical excitability in restless legs syndrome.

Various investigations have revealed a widespread and somewhat controversial pattern of cerebral, cerebellar and brainstem involvement in the pathophysiology of restless legs syndrome (RLS). However, several studies which investigated functional or structural aspects indicated cortical involvement in RLS. In this study, we aimed to analyze circadian changes of cortical excitability in idiopathic RLS patients by means of transcranial magnetic stimulation (TMS). Eleven idiopathic RLS patients and eight healthy age and sex matched subjects were investigated using single-pulse TMS and motor nerve conduction studies during early afternoon when there were no symptoms and late at night (22:00-23:00) when the symptoms reappeared. Central motor conduction time, latencies and amplitudes of scalp and cervical motor evoked potentials, resting and active motor thresholds, and cortical silent period were measured. Measured parameters were similar between RLS patients and healthy subjects during the daytime. At night, cortical silent periods tended to shorten, and motor thresholds tended to decrease in the RLS group, whereas in controls they tended to increase. At night, active motor-threshold measurements were significantly lower in the RLS group (28.5 ± 6.2% vs 40.4 ± 8.4%, p=0.006). Therefore, we propose that in patients with RLS, conduction along the motor corticospinal axons is normal, with the possible loss of subcortical inhibition at nighttime.