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OBJECTIVES: :The purpose of this study was to evaluate the effect of spinal cord stimulation (SCS) on severe spasticity of the lower limbs in patients with traumatic spinal cord injury (SCI) under close scrutiny of the site and parameters of stimulation. MATERIALS AND METHODS: :Eight SCI patients (four women, four men) were included in the study. Levels of spasticity before and during stimulation were compared according to a clinical rating scale and by surface electrode polyelectromyography (pEMG) during passive flexion and extension of the knee, supplemented by a pendulum test with the stimulating device switched either on or off over an appropriate period. RESULTS: :Both the clinical and the experimental parameters clearly demonstrated that SCS, when correctly handled, is a highly effective approach to controlling spasticity in spinal cord injury subjects. The success of this type of treatment hinges on four factors: (1) the epidural electrode must be located over the upper lumbar cord segment (L1, L2, L3); (2) the train frequency of stimulation must be in the range of 50–100 Hz, the amplitude within 2–7 V and the stimulus width of 210 μs; (3) the stimulus parameters must be optimized by clinically assessing the effect of arbitrary combinations of the four contacts of the quadripolar electrode; and (4) amplitudes of stimulation must be adjusted to different body positions. CONCLUSIONS: :Severe muscle hypertonia affecting the lower extremities of patients with chronic spinal cord injuries can be effectively suppressed via stimulation of the upper lumbar cord segment.Spinal Cord (2000) 38, 524–531. [ABSTRACT FROM AUTHOR]

OBJECTIVES: :Analysis of the computed recruitment order of an ensemble of ventral and dorsal root fibers should enlighten the relation between the position of a bipolar electrode and the observed order of muscle twitches. MATERIAL AND METHODS: :Thresholds of selected spinal root fibers are investigated in a two step procedure. First the electric field generated by the electrodes is computed with the Finite Element Method. In the second step the calculated voltage profile along each target neuron is used as input data for a cable model. For every electrode position the electrical excitability is analyzed for 12 large diameter ventral and dorsal root fibers of the second and fourth lumbar and first sacral segment. The predictions of the neural responses of any target fiber are based on the activating function concept and on the more accurate computer simulations of the electrical behavior of all nodes and internodes in the vicinity of the electrode. RESULTS: :For epidural dorsal lumbosacral spinal cord stimulation we found the following rules. (i) The recruitment order of the spinal roots is highly related to the cathode level. (ii) Dorsal root fibers have the lowest threshold values, ventral root fibers are more difficult to excite and dorsal columns are not excitable within the clinical range of 10 V. (iii) For a cathode close to the level of the spinal cord entry of a target fiber thresholds are lowest and spike initiation is expected at the border between cerebrospinal fluid and white matter; excitation of L4 roots is not possible with 210 μs/10 V pulses when cathode is more than 2.2 cm cranial to their entry level (1.5 cm for S1 roots; standard data). (iv) Cathodes positioned (essentially) below the entry level cause spike initiation close to the cathode, in a region where the fibers follow the descending course within the cerebospinal fluid. (v) At rather low stimulation voltage twitches are expected in all investigated lower limb... [ABSTRACT FROM AUTHOR]

OBJECTIVES: :To describe an electrophysiological method for determining the relation between lumbar cord dorsal roots and cathode of epidural electrode for spinal cord stimulation (SCS). MATERIALS AND METHODS: :Data has been collected from 13 subjects who have been under evaluation of effectiveness of SCS for control of spasticity. Induced muscle twitches from both quadriceps (Q), adductors (A), hamstrings (H), tibial anterior muscles (TA) and triceps surae muscles (TS) were simultaneously recorded with surface-electrode polyelectromyography (pEMG) and analyzed for amplitudes, latency times and recruitment order. RESULTS: :Stimulation of dorsal lumbar cord structures evoked characteristic EMG events during muscle twitch responses. Their amplitudes varied with stimulus strength. Latency times were rather invariable regardless of stimulus strength. Two distinct recruitment orders were demonstrated depending on whether the stimulating cathode was placed over the upper (=response from quadriceps and/or adductor muscles) or the lower (=response from tibialis anterior and triceps surae) lumbar cord segments. The chances to stimulate upper lumbar cord segments are best around the 12th thoracic vertebra. CONCLUSIONS: :pEMG recording of muscle twitches enables us to accurately differentiate between upper and lower lumbar cord segments. Furthermore, our findings regarding amplitude, latency and recruitment order strongly suggest that we stimulate posterior roots not posterior columns of the lumbar spinal cord.Spinal Cord (2000) 38, 394–402. [ABSTRACT FROM AUTHOR]

Examines the locomotor capabilities of subjects with incomplete spinal cord injury and the role of the segmental and suprasegmental features of neurocontrol involved in the generation and maintenance of gait of ambulatory SCI subjects. Methodology; Locomotor training; Spinal cord stimulation.

A family is described in which affected members have clinical features consistent with the late onset form of Strümpell's Familial Spastic Paraplegia which is of dominant inheritance. Abnormalities in cortical somatosensory to peroneal nerve stimulation were found in all affected members of the family and in several who were clinically unaffected. In some cases responses were better defined at slow rates of stimulation. Peripheral nerve conduction velocity was normal. These changes are consistent with previous findings of degeneration in the posterior columns at necroscopy and with a dying back process in the first sensory neuron. Clinically unaffected members of the family with abnormalities in the somatosensory response may represent asymptomatic heterozygotes. [ABSTRACT FROM AUTHOR]

ERECTOR SPINAE REFLEX STUDIES IN HEALTHY SUBJECTS REVEALED TWO RESPONSES: a 12·0±1·6 ms latency, oligosynaptic response, and a 30 to 50 ms latency response with polysynaptic reflex characteristics. There was a silent period after the first and second responses. The effect of limb position, trunk, neck, postural changes, Jendrassik manoeuvre and vibration on both responses were also evaluated. [ABSTRACT FROM AUTHOR]

The peripheral and central components in sustained clonus were investigated. The excitability of the motoneurons responding to maintained stretch by clonus was examined by tendon taps, trains of vibratory stimuli and by H-reflex afferent volleys. Every burst of clonic discharge of the motoneurons was shown to be followed by a refractory period, which was followed by a shorter excitatory period. It was concluded that the motoneurons responding clonically to a continuous stretch cannot respond until their excitability has been regained after the refractory period. Attempts to change the rate of clonus in various ways failed to do so. Whether motoneurons of clonic muscles tend to respond maximally to other Ia volleys at the rate of clonus was examined by applying repeated taps to the tendon at rates from 1 to 15 Hz. There was a maximal response at the rate of clonus. Inputs other than those induced by stretch cause clonus; examples of cutaneous inputs causing it are given. [ABSTRACT FROM AUTHOR]