PURPOSE:Magnetoencephalography (MEG) is traditionally considered impractical if the subject's head moves during measurements. A novel approach to correct the head position and the associated movement-related artifacts does, however, exist: continuous head position monitoring and movement compensation (MC) realized by the signal space separation (SSS) or its temporal extension (tSSS). The latter is especially important for rejection of close-to-sensor artifacts. The goal of the present work was to study how MC-SSS and its temporal extension MC-tSSS would influence MEG results. METHODS:Somatosensory evoked MEG responses to electrical median nerve stimulation were recorded with 204 planar gradiometers and 102 magnetometers. We compared the localization error of the N20m source, the averaged baseline noise, goodness of fit and confidence volume on data processed by MC-SSS vs. MC-tSSS on a subject moving in a controlled manner. RESULTS:We defined two patterns of disturbances with MC-SSS: stimulus artifact increase and random noise increase mainly on the lowermost sensors in very low head positions (5-6 cm shift). Up to 5-cm head shift, MC-SSS decreased mean localization error from 3.91 to 2.13 cm, but at the same time increased noise on gradiometers from 3.4 to 5.3 fT/cm. The noise increment occurred simultaneously with signal enhancement as MC transformed the head position closer to the sensors. Replacement of SSS by tSSS reduced the noise on gradiometers from 5.3 to 2.8 fT/cm and on magnetometers from 1.4 to 0.8 fT, reduced the mean localization error from 2.13 to 0.89 cm and increased the goodness of fit from 61.5% to 76.5%. Thus, tSSS specifically suppressed the random noise and nearby artifacts without suppressing the signal and thereby improved the signal to noise ratio. CONCLUSIONS:Head position recalculation should be combined with a powerful artifact rejection method. We recommend limiting MC use up to 3 cm head shift and using tSSS-based MC.
PURPOSE:This paper describes an improved electrodiagnostic methodology for posterior antebrachial cutaneous nerve (PABC) neuropathy based on retrospective analysis.METHODS:Results of PABC nerve conduction studies in 14 control patients and 3 patients with left PABC neuropathy are included. Stimulation was performed 0.5 to 2.0 cm above the lateral epicondyle, and the recordings were acquired at 12 cm, 15 cm and 20 cm distally. Data was evaluated using the mean A+/- standard deviation, calculated for descriptive analysis of continuous variables whereas frequencies and percentages were determined for categorical variables. Abnormal cutoff values including side-side comparison values were established so that all normal control values would fall within the normal range.RESULTS:PABC conduction studies with 20 cm recording distance demonstrated abnormal electrodiagnostic findings in all 3 patients, while more proximal recordings failed to document the neuropathy.CONCLUSION:The recording of PABC responses at 12 cm, 15 cm and 20 cm distal to the stimulating electrode offers a more comprehensive evaluation and may be a more sensitive test for evaluation of suspected PABC neuropathy, in comparison to traditional 12 cm recording.
PURPOSE:To study the effects of octreotide, a somatostatin analogue, in patients with Idiopathic Intracranial Hypertension (IIH).METHODS:We performed a prospective, open-label study of the effect of Octreotide on 26 patients with symptoms and signs of IIH, investigated by brain MRI and lumbar puncture. Octreotide was administered subcutaneously, at an initial dose of 0.3 mg/day; and was gradually increased until headache was relieved (upper-dose limit: 1 mg/day). Treatment with octreotide at 1 mg/day was administered for a maximum of six to eight months and afterwards the dose was gradually tapered. Patients were followed prospectively every month for three years. CSF opening pressure was measured before the treatment was started and again in the first follow-up examination, on month one. In all follow-up visits the presence of papilledema was evaluated by fundoscopy; visual fields and visual acuity were also examined.RESULTS:Overall 24/26 patients improved significantly (92%). Headache was relieved within days (1-10, median 7 days). Papilledema subsided in all 24 patients, in up to two months (35 to 68, median 45 days). Visual disturbances, initially presenting in 20 of our patients, improved in 18 (90%). The mean reduction in CSF pressure after treatment was 20.72A+/-10.7 cmH2O (range 2 to 48). Patients were followed for three years after cessation of treatment. No recurrence of papilledema, or any other symptoms, has been observed.CONCLUSIONS:Octreotide resulted in a significant and sustained improvement of IIH in our patients. These results suggest that it may be an effective alternative to existing treatments for IIH.
PURPOSE:The true incidence of pregnancy related carpal tunnel syndrome (PRCTS) is unknown. Most of the diagnoses of PRCTS are made based only on clinical symptoms. Here, we report a prospective controlled clinical trial assessing the electrophysiological changes in pregnant women to provide objective measure of the median nerve function.METHODS:Pregnant women in the third trimester (n=69) and age-matched non-pregnant women (n=40) asymptomatic for CTS were included in the study. Nerve conduction studies of the median and ulnar nerves across the carpal tunnel were bilaterally performed with the standard techniques.RESULTS:All the median sensory nerve conduction studies (amplitude, latency and velocity) performed from the ring finger and palmar region to wrist showed significant prolongation of median nerve conduction in the pregnant women compared with the control group (*p</=0.05). Median sensory nerve latencies from palmar branches to wrist were significantly longer in the pregnant group (**p<0.01). Sensory nerve action potential amplitudes recorded in the palmar region were smaller in the pregnant women (45.1AmicroV) than in the control group (56.5AmicroV). Ulnar motor and sensory conduction studies showed no significant difference between the pregnant women and the control group. According to the mean values of median nerve conduction velocity, 8 (11%) pregnant women were electrophysiologically diagnosed as CTS and four of these cases became symptomatic later during pregnancy or after delivery.CONCLUSIONS:Median nerve impairment occurs even in asymptomatic pregnant women. The electrophysiological characteristics of this impairment are defined and the pathophysiology of PRCTS is discussed. Electrophysiological evaluation is a tolerable and feasible technique for the early diagnosis of PRCTS.
Purpose Hand symptoms in uremic patients on dialysis can occur due to peripheral neuropathy, median neuropathy at wrist (carpal tunnel syndrome) or a combination. Routine electrophysiological parameters for diagnosing carpal tunnel syndrome do not differentiate median neuropathy at wrist in cases with concomitant peripheral neuropathy. Measuring 2L-INT latency difference has been described as the most sensitive test in establishing median neuropathy at wrist in cases with severe carpal tunnel syndrome and concomitant peripheral neuropathy. This study tested the significance of 2L-INT latency difference as a predictor of median neuropathy at wrist in uremic patients on dialysis. Methods 80 consecutive cases (158 hands) of end-stage renal failure on either hemodialysis or peritoneal dialysis were subjected to routine electrophysiological studies for carpal tunnel syndrome. 2L-INT latency difference was measured in all cases. Results 132/158 hands (83.5%) had abnormal electrophysiological studies. Routine tests were consistent with neurophysiological carpal tunnel syndrome in 66 (41.8%) hands and 63 of these 66 (95.5%) had prolonged 2L-INT latency difference. Peripheral neuropathy was found in 66 (41.8%) hands but 59 out of these 66 (89.4%) had prolonged 2L-INT latency difference suggesting a concomitant median neuropathy at wrist. Routinely performed tests would have missed median neuropathy at wrist with concomitant peripheral neuropathy in 59 (37.3%) hands. Overall, the incidence of median neuropathy at the wrist in our uremic patients on maintenance dialysis using standard nerve conduction parameters was 41.8%, however the incidences increased substantially to 79.1% if 2L-INT latency difference is included in the criteria for the diagnosis. Conclusions Median neuropathy at wrist is common in patients with end-stage renal failure patients on dialysis. Diagnosis of median neuropathy at wrist is difficult in the presence of peripheral neuropathy when using the routine electrophysiological tests. Second Lumbrical-Interossei latency difference is a sensitive electrophysiological test to predict median neuropathy at wrist in presence of peripheral neuropathy.
PURPOSE Writer's cramp describes a task-specific dystonia, in which the act of writing initiates dystonic posturing of the hands. Previous studies have described the efficacy of injections of botulinum toxin type-A (BTX-A) under electromyographic guidance, in which the injected muscle is either voluntarily, or less often, electrically (electrical motor point stimulation, EMPS) activated to ensure that the needle is in the target muscle. We performed an open label, prospective study to assess the efficacy of BTX-A injections, performed with EMPS under electromyographic guidance. METHODS Eight patients (seven male and one female) of mean age 44 (range 25-66) were recruited. All had idiopathic writer's cramp. Outcome measures, which included timed writing, objective assessment of dystonia (modified Ashworth scale and a visual analog scale rating) and patient assessment of functional disability, were assessed before injections and at six weeks follow-up. RESULTS The total dose of BTX-A injected for writer's cramp ranged from 50 to 130 units, which was less than that reported in previous studies using muscle activation techniques (up to 300 units). Improvements were observed in all outcome measures. Patients reported mild (non-disabling) weakness of injected, but not of uninjected muscles. CONCLUSION Lower dosages of BTX-A, administered using EMPS, offers the advantages of decreased cost and increased accuracy of targeting, while achieving good outcomes.
PURPOSE:Hepatitis C viral [HCV] infection is a chronic multisystem disorder that may have an indolent course initially. Peripheral neuropathy associated with cryoglobulinemia and a systemic vasculitis is a well-described complication of HCV infection. But this neuropathy is not known to have a late-onset acute fulminant phase. This acute fulminant phase is characterized by quadriparesis associated with pulmonary and/or renal insufficiency, and it may occur despite adequate treatment for HCV infection. The purpose of this study is to report that patients treated for chronic HCV infection may manifest a secondary progressive acute fulminant neuropathy associated with respiratory and/or renal insufficiency that is responsive to cyclophosphamide.METHODS:Case series retrospective data analysis.RESULTS:Three patients with biopsy-proven HCV associated vasculitic neuropathy manifested a secondary progressive acute fulminant course resulting in quadriparesis within 5 years of the initial diagnosis. Complete remission was achieved with cyclophosphamide therapy such that all patients became ambulatory.CONCLUSIONS:HCV-associated vasculitic neuropathy may manifest a secondary phase, which is acute, fulminant and progressive that is superimposed on an otherwise slowly progressive disorder. Cyclophosphamide therapy may abort progression and induce remission of this acute fulminant phase.
PURPOSE:To correlate the electrodiagnostic and clinical features of patients with demyelinating abnormalities and neuropathy of otherwise unknown etiology.METHODS:We examined the records of patient with demyelinating abnormalities and no other cause for neuropathy that were evaluated in our electrophysiology laboratory over the course of a year, to correlate the clinical and electrodiagnostic features.RESULTS:Eight percent of all patients had one or more demyelinating abnormalities. Demyelinating features were significantly more numerous in generalized or asymmetric neuropathy than in distal polyneuropathy. The peroneal nerve was the most commonly affected in all phenotypes, and none of the patients with distal neuropathy had F-wave prolongation in the demyelinating range.CONCLUSIONS:The number and type of demyelinating abnormalities in patients with polyneuropathy vary with the clinical phenotype. The clinical presentation should be considered in developing or evaluating electrodiagnostic criteria for demyelinating neuropathies.
PURPOSE:The lateral plantar nerve (LPN) branch of the tibial nerve provides the primary supply to the first dorsal interosseous (FDI) muscle of the foot. A consistent clear response has been observed with recording of the LPN from the FDI muscle. This clarity is not always found with the standard recording site for the LPN. As there are no published normative values for the FDI recording site, the purpose of this study is to describe these values and compare them with standard tibial values.METHODS:Fifty four healthy adult volunteers with 102 limbs were studied to determine the nerve conduction velocity, distal latency, amplitude, and waveform characteristics.RESULTS:The FDI recording demonstrated a significantly greater amplitude than did the standard recording, with the mean values being 7.7 and 3.6 mV respectively. The recording from the FDI also demonstrated much greater waveform clarity than did the standard tibial nerve recordings.CONCLUSIONS:These findings may aid interpretation of data collected from the FDI in tibial nerve testing. LPN recording from the FDI may be particularly valuable in those with global axonal loss or preferential involvement of the LPN as may occur in posterior tarsal tunnel syndrome.
PURPOSE Historically, F-waves have been classified by various linear descriptors like persistence, latency, duration, amplitude, chrono-dispersion and number of repeater waves. But because physiological signals are notoriously nonlinear in nature, the objective of this study was to apply modern nonlinear methodology to F-waves sequences to assess the presence of underlying deterministic structures. Subtle changes in these sensitive markers could give early warnings for neurological problems. METHODS F-waves were elicited in the left abductor pollicis breivs muscle by supra-maximally stimulating the median nerve percutaneously at the wrist. Approximately 200 stimuli were applied (0.5 Hz) to three subjects for at least four trials each. F-wave latencies were measured and assembled into sequences in proper order. Recurrence quantification analysis (RQA) was applied to these F-wave sequences from different dimensional perspectives. Controls were constructed by randomly shuffling the ordered sequences. RQA has a theoretical mathematical foundation and practical performance record on numerous other physiological systems. RESULTS Recurrence analysis showed that sequential F-waves form recurrent patterns with parallel trajectories with deterministic and laminated structures. These features could be destroyed by randomizing the sequential orders of F-waves, upholding the hypothesis that sequences of F-waves are deterministically formed from underlying physiological rules. CONCLUSIONS F-wave time series are fully amenable to recurrence analysis which provides a higher-dimensional perspective on the physiological dynamic. The recurrent patterns are complex, but not random, meaning that physiological rules dominate the sequence of F-waves. Disease processes within the central or peripheral nervous system may alter F-wave patterns. If so, RQA potentially may be a diagnostic tool to help discern subtleties between altered deterministic rules operating in disease.
PURPOSE:We evaluated the use of Vestibular Evoked Myogenic Potentials (VEMPs) in the assessment of neural function, following medullary lesions.METHODS:A 54-year-old male presented with symptoms and signs typical of right lateral medullary (Wallenberg) syndrome. He underwent brain MRI and three successive neurophysiological investigations, which included VEMPs, Brainstem Auditory Evoked Responses (BAERs) and the blink reflex.RESULTS:VEMPs amplitude on the left (unaffected) side was 256.8 microv in the first investigation and remained approximately equal to that value in the following two ones. Their amplitude on the right (affected) side was 37.9 microv, 154.2 microv and 235.2 microv correspondingly. At the same time vertigo, diplopia and nystagmus gradually improved. Right blink reflex comprised a normal R1, but delayed R2 ipsilateral and R2 contralateral responses, which remained unaltered during the follow-up period. Brain MRI disclosed a right dorsolateral medullary infarct.CONCLUSIONS:VEMPs amplitude progressively increased, parallel to the improvement of vestibular symptoms. The blink reflex evolved differently, while BAERs were not affected. As the three evoked responses are mediated by separate neural circuits, they provide information on different aspects of brainstem function. Thus, VEMPs seem to be a useful method that complements existing ones in the assessment of brainstem lesions.
PURPOSE:F-wave studies are valuable tools in clinical neurophysiology. F-wave parameter estimation must be based on multiple F-wave traces due to their inherent variability. Repetitive supramaximal stimulation is uncomfortable for many patients. This study tested the hypothesis that submaximally stimulated nerves yield F-wave parameters equivalent to those obtained with supramaximal stimulation.METHODS:Thirty-five peroneal nerves from 27 subjects were stimulated both supramaximally and submaximally. CMAP and F-wave responses from the extensor digitorum brevis muscle were recorded and analyzed offline. Automated algorithms were used to determine F-wave parameters.RESULTS:Mean, minimum, maximum F-wave latencies, F-wave duration, and chronodispersion showed no statistically significant difference under the two stimulation conditions. F-wave persistence, amplitude, and subject's discomfort level, were lower with statistical significance. The correlation coefficient of submaximal and supramaximal mean F-wave latencies was 0.977 and their intraclass correlation coefficient was 0.976. The bias of the mean latencies was 0.21 ms and the 95% limits of agreement were less than 5% of the mean F-wave latency.CONCLUSIONS:F-waves acquired with submaximal stimulation possess characteristics statistically equivalent to those obtained under supramaximal stimulation, as measured by the latency and duration parameters. Persistence and amplitude were lower. Reduction in discomfort level was also achieved.
PURPOSE:Primary systemic amyloidosis is a rare disorder that has multisystemic manifestations. The most common neuropathy in systemic amyloidosis is a small-fiber axonal polyneuropathy. When the neuropathy is the presenting feature, diagnosis is usually delayed. The diagnosis of systemic amyloidosis may be more difficult when patients present with an atypical polyneuropathy.METHODS:Two cases of primary systemic amyloidosis with a multifocal polyneuropathy with demyelinating features are presented.RESULTS:The patients reported in this series with autopsy proven amyloidosis had evidence of a polyneuropathy with demyelinating features.CONCLUSIONS:Amyloidosis should be considered in the differential when a patients presents with a polyneuropathy that has demyelinating features.
