Computerized posturography is more sensitive than clinical Romberg Test in detecting postural control impairment in minimally impaired Multiple Sclerosis patients.

Balance impairment, frequent in Multiple Sclerosis patients (MS), is difficult to detect promptly with routine clinical examination. Computerized platforms can measure subtle deficit but, given the complexity of postural system, multiple tests should be adopted. To evaluate whether platform was more sensitive than Romberg Test (RT) in detecting balance abnormalities, we 1) chose a battery of posturographic tests, 2) collected normative data from 58 healthy subjects 3) applied the tests to Clinically Isolated Syndrome (n=42) and minimally impaired MS (n=76). Subjects underwent 3 trials of quiet standing with eyes open and closed (modified Clinical Test of Sensory Interaction on Balance, mCTSIB) and 4 trials of voluntary anterior and lateral maximal leaning on right and left sides (Limits of Stability, LOS), giving 10 postural indexes. For every subject, the best trials were selected for subsequent analysis. Normative values were established in a range from 1st to 99th percentile, defining balance impairment by the presence of at least 2 indexes out of range. Even adopting the above mentioned strict definition of balance impairment, the forceplate resulted more sensitive than RT, detecting abnormalities in 25% of patients, while RT was abnormal in 7% only. In RT-negative patients with 1-year follow-up (n =67) the detection of a single abnormal index was able to predict a subsequent onset of symptomatic balance impairment. The proposed procedure is quick, easy to perform and can improve the assessment of the clinical course of MS, from a pre-clinical stage up to medium degree of disability.

Normative Values for Intertrial Variability of Motor Responses to Nerve Root and Transcranial Stimulation: A Condition for Follow-Up Studies in Individual Subjects.

OBJECTIVE: Intertrial variability (ITV) of motor responses to peripheral (CMAP) and transcranial (MEP) stimulation prevents their use in follow-up studies. Our purpose was to develop strategies to reduce and measure CMAP and MEP ITV to guide long-term monitoring of conduction slowing and conduction failure of peripheral and central motor pathway in the individual patient. METHODS: Maximal compound muscle action potentials to High Voltage Electrical Stimulation (HVES) of lumbo-sacral nerve roots (r-CMAP) and activated, averaged motor evoked potentials (MEPs) to Transcranial Magnetic Stimulation (TMS) using double cone coil were recorded from 10 proximal and distal muscle districts of lower limbs. The procedure was repeated twice, 1-2 days apart, in 30 subjects, including healthy volunteers and clinically stable multiple sclerosis patients, using constant stimulating and recording sites and adopting a standardized procedure of voluntary activation. ITV for latency and area indexes and for the ratio between MEP and r-CMAP areas (a-Ratio) was expressed as Relative Intertrial Variation (RIV, 5th-95th percentile). As an inverse correlation between the size of area and ITV was found, raw ITV values were normalized as a function of area to make them comparable with one another. RESULTS: All RIV values for latencies were significantly below the optimum threshold of ± 10%, with the exception of r-CMAP latencies recorded from Vastus Lateralis muscle. RIVs for a-Ratio, the most important index of central conduction failure, ranged from a maximum of -25.3% to +32.2% (Vastus Medialis) to a minimum of -15.0% to + 17.4% (Flexor Hallucis Brevis). CONCLUSIONS: The described procedure represents an effort to lower as much as possible variability of motor responses in serial recording; the reported ITV normative values are the necessary premise to detect significant changes of motor conduction slowing and failure in the individual patient in follow-up studies.

A new neurophysiological approach to assess central motor conduction damage to proximal and distal muscles of lower limbs.

OBJECTIVE: To develop a neurophysiological method to explore central motor pathways to proximal and distal muscles of lower limbs. METHODS: MEPs to transcranial magnetic stimulation using the double cone coil were bilaterally and simultaneously recorded from vastus medialis, tibialis anterior and flexor hallucis brevis. Voluntary facilitation was controlled using a predefined sequence of movements of constant amplitude. Compound motor action potentials elicited by maximal high voltage electrical stimulation of lumbosacral roots (root-CMAPs) were recorded from the same muscles to obtain the corresponding peripheral conduction times. We studied 28 healthy subjects and 28 multiple sclerosis (MS) patients with no or mild motor impairment. RESULTS: The described facilitation procedure and the averaging of 5 MEPs reduced area variability to about 10%. In MS patients conduction slowing and/or MEP area reduction in at least one muscle was found in 91.7% of cases, with significant correlation with individual motor impairment. CONCLUSIONS: Combined use of stable MEPs and maximal root-CMAPs was able to detect both conduction slowing and conduction failure in central motor pathways to proximal and distal districts of lower limbs in MS patients. SIGNIFICANCE: The proposed method provides an extensive electrophysiological mapping of central motor impairment of lower limbs in clinical application.