Aikaterini E. Papagianni

Nomogram for determining lower limit of the sural response

OBJECTIVE Age and height influence on sural sensory nerve action potential (SNAP) have been studied separately. Our aim was to develop an equation for predicting the lower normal limits as a function of both these factors. METHODS One hundred fifty-eight healthy volunteers, 63 male, with mean age 45.8 and mean height 167.3 without symptoms or signs of peripheral neuropathy participated in the study. The sural SNAP was recorded at the level of the ankle joint, just posterior to the lateral malleolus, using surface electrodes. Antidromic supramaximal stimulation was performed 13 cm proximally at the posterior midcalf. RESULTS The mean sural SNAP amplitude was 19.9+/-6.89 microV. Pearson linear correlation showed a negative correlation of the SNAP amplitude with age (R=-0.22, p=0.005) and height (R=-0.19, p=0.03). The multiple linear regression model was applied for both parameters of age and height with SNAP amplitude as the dependent parameter, producing the following equation: SNAP amplitude=62.45-0.1447 x Age-0.2147 x Height. CONCLUSIONS Using our normal data, the computed lower limits of the 95% prediction interval for the sural SNAP amplitude of an individual subject, depending on his age and height, were calculated. SIGNIFICANCE The individualized normal values provided by our equation are essential for the correct interpretation of sural nerve studies.

The two sensory branches of the superficial peroneal nerve: Electrophysiological differences and correlations with gender, age, height and BMI

AIMS OF THE STUDY To detect amplitude differences between the sensory nerve action potentials (SNAP) obtained by simultaneous recording of the two main branches of the superficial peroneal sensory nerve (SPSN), the medial and intermediate dorsal cutaneous sensory nerves (MDCN, IDCN); to investigate whether these differences, if any, are correlated with gender, age, body mass index (BMI), and height of normal subjects; to discuss their clinical significance. POPULATION AND METHODS Seventy-six healthy volunteers (36 males) were included (mean age: 36.5 years, range 20-80). Simultaneous MCND and IDCN recordings were performed via surface electrodes placed at precise positions on the intermalleolus line. Stimulation was performed 14 cm proximally on two different sites over the anterolateral aspect of the right leg. RESULTS Responses were obtained for both nerve branches in all subjects. Median value and lower normal limit for the amplitude of the greater among both MDCN and IDCN responses was 10.95 microV and 4.9 microV, respectively. Statistically significant differences were found between the two branches in median amplitude and frequency of the greater value. These differences were not correlated with gender, age, BMI, or height. CONCLUSION We propose simultaneous recording of the two main branches of the superficial peroneal sensory nerve, placing the recording electrodes and stimulation device on precise positions and measuring the amplitude of the best of both responses. This method is an improvement of an already existent one, and may be clinically useful in detecting abnormal responses of the SPSN.

Objective assessment of C-fiber function by electrically induced axon reflex flare in patients with axonal and demyelinating polyneuropathy.

Introduction: A simple test to evaluate the peripheral C-fiber function is the measurement of axon reflex flare area. In this study, we compared the flare area in healthy subjects and in two groups of patients with predominantly axonal or demyelinating polyneuropathy. Materials and Methods: We examined 42 control subjects and 33 patients. The flare responses were elicited by the application of transcutaneous electrical stimulation and recorded by laser Doppler imaging. Results: There was a significant reduction of electrically induced flare area in both groups of neuropathy patients (P < 0.001; analysis of covariance). Interestingly, patients with an axonal neuropathy had a significantly stronger reduction of flare size as compared to patients with demyelinating neuropathy (P = 0.03). Conclusions: The evaluation of the axon flare response in the arm can be used as a screening test of impaired C-fiber function in polyneuropathy patients with the advantages of simplicity of the procedure and time economy.

A neurophysiological study of facial numbness in multiple sclerosis: Integration with clinical data and imaging findings

OBJECTIVE To integrate neurophysiological findings with clinical and imaging data in a consecutive series of multiple sclerosis (MS) patients developing facial numbness during the course of an MS attack. METHODS Nine consecutive patients with MS and recent-onset facial numbness were studied clinically, imaged with routine MRI, and assessed neurophysiologically with trigeminal somatosensory evoked potential (TSEP), blink reflex (BR), masseter reflex (MR), facial nerve conduction, facial muscle and masseter EMG studies. RESULTS All patients had unilateral facial hypoesthesia on examination and lesions in the ipsilateral pontine tegmentum on MRI. All patients had abnormal TSEPs upon stimulation of the affected side, excepting one that was tested following remission of numbness. BR was the second most sensitive neurophysiological method with 6/9 examinations exhibiting an abnormal R1 component. The MR was abnormal in 3/6 patients, always on the affected side. Facial conduction and EMG studies were normal in all patients but one. CONCLUSIONS Facial numbness was always related to abnormal TSEPs. A concomitant R1 abnormality on BR allowed localization of the responsible pontine lesion, which closely corresponded with MRI findings. We conclude that neurophysiological assessment of MS patients with facial numbness is a sensitive tool, which complements MRI, and can improve lesion localization.

Clinical and neurophysiological study of peroneal nerve mononeuropathy after substantial weight loss in patients suffering from major depressive and schizophrenic disorder: Suggestions on patients' management

Background Peroneal nerve is susceptible to injuries due to its anatomical course. Excessive weight loss, which reduces the fatty cushion protecting the nerve, is considered a common underlying cause of peroneal palsy. Other predisposing factors, such as prolonged postures, traumas of the region or concomitant pathologies (for example diabetes mellitus) contribute to the nerve damage. This study aims to reveal the multiple predisposing factors of peroneal nerve mononeuropathy after substantial weight loss that coexist in psychiatric patients and to make suggestions on their management. Methods Nine psychiatric inpatients, major depressive or schizophrenic, with foot drop underwent a complete clinical neurological and neurophysiological examination. All had excessive weight loss, which was completed in a short period of time and had not resulted from a well-balanced low-calorie diet, but was due to their psychiatric illness. Data regarding predisposing factors to peroneal nerve mononeuropathy were gathered, such as habitual leg crossing, squatting or other prolonged postures. Results The clinical examination and the neurophysiological evaluation in all patients were indicative of a focal lesion of the peroneal nerve at the fibular head. Conclusion Patients with major depressive and schizophrenic disorders gather multiple predisposing factors to peroneal palsy, adequate to classify them at a high risk group. The better focus of the attendant medical and nursing staff on this condition, the early clinical and neurophysiologic evaluation and surgical interventions may enable an improved management and prognosis of these patients.

MUAP values of two facial muscles in normal subjects and comparison of two methods for data analysis

Introduction: This study aimed to obtain normal MUAP values in 2 facial muscles and to compare the results of different analysis methods. Methods: The frontalis muscle of 36 and the mentalis muscle of 28 normal subjects were examined, and mean and outlier values of all MUAP parameters were calculated with the automatic method. Next, manual editing of the recorded raw data provided new sets of values for comparison. Results: The frontalis muscle MUAPs have significantly shorter duration, smaller amplitude and a lower number of turns and phases compared with those of mentalis. Higher MUAP duration values in the frontalis were the only significant difference after the comparison of the different analysis methods. Conclusions: The set of normal values for frontalis and mentalis in this study could be useful in routine practice. Careful manual editing of the frontalis MUAPs is recommended for more accurate determination of their duration. Muscle Nerve 46: 346–350, 2012

Turns-amplitude analysis in normal and myopathic facial muscles.

The purpose of this study was to assess turns/amplitude analysis (TAA) as an objective alternative to conventional qualitative electromyography (EMG) for detection of myopathy in facial muscles. Normal values of TAA parameters were calculated in the frontalis and mentalis muscles of 26 control subjects. We estimated the slope of the regression line of mean amplitude/turn values (MA) plotted against the number of turns/second (NT) and the resulting clouds. The 95% confidence limits of the cloud data were drawn as an ellipse. The sensitivity of TAA was determined from a group of 35 myopathic patients and specificity from a second group of 25 control subjects. Significant differences for every TAA parameter were found between frontalis and mentalis. Cumulative sensitivity and specificity of TAA for frontalis and mentalis were 74.6%, 56.5%, and 73.3%, 70.8%, respectively. With at least two of the aforementioned criteria abnormal, the sensitivity and specificity for frontalis and mentalis were 61.3%, 82.6%, and 56.7%, 100.0%, respectively. Muscle Nerve, 2011

Impaired function of C-nociceptors in chronic inflammatory demyelinating polyradiculopathy indicated by electrically induced axon flare reflex.

INTRODUCTION In chronic inflammatory demyelinating polyradiculopathy (CIDP) the impairment of unmyelinated nerve fibers appears unexpected. The measurement of the electrically induced axon flare reflex is a clinical test to assess the peripheral C-nociceptor function. In this study we compared the flare area in patients suffering from chronic inflammatory demyelinating polyradiculopathy with healthy subjects. MATERIALS AND METHODS We examined 18 patients fulfilling the criteria for CIDP (11 male, mean age 51.8 years, SD 15.1) and 18 age-matched adult healthy volunteers (control group) (11 male, mean age 51.9 years, SD 15.8). The flare responses were elicited by transcutaneous electrical stimulation and recorded by laser Doppler imaging. RESULTS There was a significant reduction of electrically induced maximum flare area in the foot dorsum of CIDP patients (t-value 2.08, p=0.04) which proved to be length-dependent measured by a numerical index comparing the results with the forearm and thigh. The repeated measures ANOVA revealed statistically significant smaller flare areas in all body regions for the CIDP group (p<0.001). CONCLUSION The clinical evaluation of the axon flare response is a non-invasive functional test, that can be used as a screening tool of impaired C-fiber function in CIDP patients with the advantages of simplicity of the procedure, time economy and objectivity.Purpose: In chronic inflammatory demyelinating polyradiculopathy (CIDP), the impairment of unmyelinated nerve fibers appears unexpected. The measurement of the electrically induced axon flare reflex is a clinical test to assess the peripheral C-nociceptor function. In this study, we compared the flare area in patients suffering from CIDP with healthy subjects. Methods: We examined 18 patients fulfilling the criteria for CIDP (11 men, mean age 51.8 years, SD 15.1) and 18 age-matched adult healthy volunteers (control group) (11 men, mean age 51.9 years, SD 15.8). The flare responses were elicited by transcutaneous electrical stimulation and recorded by laser Doppler imaging. Results: There was a significant reduction of electrically induced maximum flare area in the foot dorsum of patients with CIDP (t-value 2.08, P = 0.04) which proved to be length-dependent measured by a numerical index comparing the results with the forearm and thigh. The repeatedmeasures ANOVA revealed statistically significant smaller flare areas in all body regions for the CIDP group (P < 0.001). Conclusions: The axon flare reaction to electrical stimulation was decreased in patients with chronic demyelinating inflammatory polyneuropathy. The evaluation of the axon flare response can be proposed as a noninvasive objective functional test to detect an impaired C-fiber function in CIDP patients with the advantages of simplicity of the procedure, time economy, and objectivity.

P910: Sensory polyneuropathy in ALS

Question: “Sound-induced flash illusion” are a powerful example of crossmodal illusion highlighting the role of modulation and interaction of sensory modalities [1]. When a single flash is accompanied by two auditory beeps, the single flash is perceived as two flashes (“fission” illusion), on the other hand a “fusion” illusion occurs when a single beep causes the fusion of a double flash stimulus. Mechanisms underpinning such illusory perception are yet unknown, but through transcranial direct current stimulation (tDCS), they have been shown to critically depend on excitability of visual and temporal cortices: indeed anodal activating tDCS over occipital cortex and cathodal inhibitory tDCS of temporal cortex can disrupt the illusion[2]. In a previous study we observed that patients with migraine (with and without aura) examined both during attack and interictally show reduced ability to perceive the illusions and we interpreted this as due to visual hyperexcitability. If so, we expect that reducing cortical excitability through cathodal tDCS should normalize illusory perception in migraineurs. Methods: 18 Patients (14 F; mean age 32.11±11.65 years) migraine patients [9 without aura (MWO) and 9 with aura (MWA)] were examined in the interictal phase and compared with 24 neurologically unimpaired, age and sex matched participants. The experimental paradigm for studying the illusion consisted of 1-to-4 or white filled circles presented in the center of a black screen in isolation, or preceded by 1 to 4 beeps in different combinations [2]. It was performed in baseline and after real and sham cathodal tDCS stimulation with the following parameters: site: occipital cortex; intensity: 2 mA; duration: 10 min. Results: MWO and MWA patients showed significantly less illusiosn with respect to healthy controls in baseline; after real cathodal but not sham occipital tDCS, a significant increase of illusory phenomena was observed in MWA but not in MWO patients. Conclusion: MWA and MWO patients perceive less illusions, similarly to what observed by Bolognini et al [2], after increasing visual cortical excitability (through anodal tDCS) in healthy controls. Cross modal illusion can be restored in MWA patient reducing excitability by cathodal tDCS. Taken together these findings suggest a condition of increased ictal and interictal visual cortical excitability in migraine that could be reverted by cathodal tDCS, at least in MWA.

P7-5 Involvement of the pyramidal fibers to Onuf's nucleus in ALS: a transcranial magnetic stimulation study

Therefore, we investigated differences in electrophysiological findings and clinical symptoms of ALS by comparing patients with rapid and slow clinical courses. In 40 ALS patients, 14 patients showed a clinical course lasting less than one year and 13 patients showed a clinical course lasting more than three years. The mean interval from onset to diagnosis of ALS patients with a rapid clinical course was shorter than that of patients with a slow clinical course (4.3 months vs. 20 months P< 0.05). Patients with a rapid clinical course showed FPs in almost all muscles in the examined extremities. The muscle number showing FPs was more than that of patients with a slow clinical course (96.3% vs. 53.1% P< 0.05). However, the rate of muscle with fibs-sw between these groups did not differ significantly. Conclusion: The rate of muscle showing FPs may assist in predicting the clinical prognosis.