Improved methodology for lumbosacral nerve root stimulation.

The site of S1-S2 root activation following percutaneous high-voltage electrical (ES) and magnetic stimulation were located by analyzing the variations of the time interval from M to H soleus responses elicited by moving the stimulus point from lumbar to low thoracic levels. ES was effective in activating S1-S2 roots at their origin. However supramaximal motor root stimulation required a dorsoventral montage, the anode being a large, circular surface electrode placed ventrally, midline between the apex of the xiphoid process and the umbilicus. Responses to magnetic stimuli always resulted from the activation of a fraction of the fiber pool, sometimes limited to the low-thresholds afferent component, near its exit from the intervertebral foramina, or even more distally. Normal values for conduction velocity in motor and 1a afferent fibers in the proximal nerve tract are provided.

Associated polyneuropathy and demyelinating disease. Case report.

We report a case in which an acute Guillain-Barré-like syndrome was quickly followed by a central demyelinating disease, documented by the clinical findings as well as by magnetic resonance imaging (MRI), electrophysiological and cerebrospinal fluid examinations. The close follow-on of the clinical signs seems to exclude a simple coincidence of two separate diseases and it may constitute further evidence for a possible etiological link between central and peripheral myelin damage. We discuss the possibility of a common pathogenic factor underlying central and peripheral demyelination.

Stretch reflex of quadriceps femoris in normal man: methodological considerations and normative data.

Short- and long-latency responses to stretching have been evoked in various muscles in the healthy subject. The quadriceps femoris, however, has never been investigated in this connection, despite its functional importance. We studied its stretch reflex in 17 healthy subjects with a torque motor to determine its morphological features in relation to the level of background EMG activity, the stretching velocity and duration and the instructions given to the subject. Two bursts of EMG activity were constantly evoked when the muscle was voluntarily activated. Response magnitude was proportional to the background activity and displacement velocity. Short stretching evoked only one EMG burst. These findings are similar to those from other muscles. Intra-individual variability was evaluated repeating the experiment in the same session without changing position of the electrodes, and then after two months. The long-latency response showed a good intra-individual reproducibility.

The effect of temperature on conduction velocity in human muscle fibers.

The effects of variation of intramuscular temperature (T) on conduction velocity (CV) of the action potential along single human muscle fibers of the biceps brachii was studied in situ in 15 normal volunteers (mean age 39 years, range 21-62 years). Cooling was obtained by direct application of ice over a rectangular skin region including the stimulating and recording area. The intramuscular T was monitored by a needle thermocouple (copperconstantane). In all the 24 muscle fibers studied, a linear relationship was observed between CV and T. The slopes of the regression lines, ranging between 0.190 and 0.079 m/s, were positively correlated with the starting CV at 36°C ranging between 2.2 and 5.2 m/s. If conduction changes are expressed as a percentage of the basal CV at 36°C, the CV T coefficient is the same for all the fibers and independent of the individual CV: 3.4% of CV/°C.

Transcranial magnetic stimulation in epileptic patients: usefulness and safety.

We studied 58 patients with partial or generalized epilepsy who had transcranial magnetic stimulation (TMS) of the brain motor regions. Short-term monitoring disclosed that the stimulation did not provoke seizures or EEG changes in any patient. Long-term follow-up disclosed that the epileptic condition was not made worse by TMS. TMS, as currently used for monitoring conduction in central motor pathways, does not induce seizures in drug-treated epileptic patients.

Neuropathy secondary to vitamin E deficiency in acquired intestinal malabsorption.

A patient with acquired intestinal malabsorption developed a motor-sensory polyneuropathy with a recurrent remittent course, normal CSF and reduced motor and sensory conduction velocities. Nerve biopsy showed axonal changes. Serum DL-alpha-tocopherol was abnormally low. Six months supplementation with vitamin E was followed by normalization of DL-alpha-tocopherol serum levels and clinical and electrophysiological improvement.

Early sarcolemmal dysfunction in skeletal muscle amyloidosis.

Weakness and stiffness appeared in a 65-year-old man affected by multiple myeloma. Muscle fibre conduction velocity was recorded in situ in the biceps brachii and found to be significantly decreased. Muscle biopsy, performed in the same muscle, showed amyloid deposition and moderate atrophy of muscle fibres, which was not sufficient to explain the reduction in muscle fibre conduction velocity. The results of the study suggest that amyloid interferes with conduction along the sarcolemma and that this plays a pathogenetic role mainly in the early stages of the disease.

Urinary excretion of 2,5-hexanedione and peripheral polyneuropathies workers exposed to hexane.

Forty shoe factory workers who were exposed to hexane were investigated to see if there was a correlation between electroneuromyographic changes indicative of neuropathy and urinary excretion of 2,5-hexanedione. Urinary samples were analyzed for the presence of the metabolic products of n-hexane and its isomers. Electrodiagnostic examination was carried out following the urinary sampling. A rating scale was used to obtain a cumulative numeric index of electrodiagnostic findings. 2,5-Hexanedione and gamma-valerolactone were discovered in all cases, while 2-hexanol was found in 11 cases. 2,5-Hexanedione was the main metabolite in most cases (39 of 40). Only in 1 case was a low level of 2-methyl-2-pentanol detected; 3-methyl-2-pentanol was never detected. Metabolic products of cyclohexane were present in about one-fifth of the cases, while trichloroethanol, a metabolic product of trichoroethylene, was nearly always present, all at very low concentrations. Electromyographic abnormalities significant for early detection of toxic polyneuropathy were found in 14 cases. A statistically significant correlation of the electroneuromyographic scoring on the urinary concentrations of measured metabolites was observed only with 2,5-hexanedione and gamma-valerolactone, both derived from n-hexane. Since gamma-valerolactone is probably not a true metabolite of n-hexane, our results support the hypothesis that polyneuropathies in shoemakers are due to 2,5-hexanedione. For practical purposes the urinary concentration of 2,5-hexanedione can serve as a predictive measurement for early detection of neurotoxic lesions at preclinical states.

Familial progressive external ophthalmoplegia with multisystem abnormalities: "new" features raising nosological problems.

A 32-year-old female presented with progressive external ophthalmoplegia (PEO) and multisystem abnormalities, strikingly associated with myotonia and muscle hypertrophy. These two features were not found in her brother, who had a complex neuromuscular disorder complicating chronic PEO. In both subjects muscle biopsy revealed "ragged-red" fibres and myofibres containing glycogen granules, which were never bound by membranes. A severe demyelinating neuropathy was revealed by electrophysiological and morphological studies. Cranial CT scan showed extensive demyelination of the cerebral white matter. Genetic studies demonstrated that this familial syndrome is transmitted as an autosomal recessive trait.

Peripheral nerve function and metabolic control in diabetes mellitus.

Measurement of conduction velocity along the H reflex arc was used to study sensorimotor peripheral nerve function in diabetic patients during short- and long-term improvement of hyperglycemia. In ten type I diabetics a slight (p less than 0.05) conduction increase occurred after 6 hours of normal glycemia induced by an artificial endocrine pancreas. Similar but more prominent improvement occurred in twelve type I diabetics treated with continuous subcutaneous insulin injection for 6 months. The results suggest that nerve conduction slowing in diabetic patients stems partly from reversible, nonstructural abnormalities and partly from more slowly reversible morphological or chemical changes in peripheral nerve.

Conduction velocity along human muscle fibers in situ.

When muscle fibers are stimulated in the distal portion of the human biceps brachii, far enough from the end-plate region, a discrete single fiber activity can be picked up proximally by means of a selective recording electrode. The distally evoked potentials show a linear relationship between latency and distance and can be recorded also in curarized patients. The risk of stimulating the intramuscular nerve endings is remote and, when it occasionally happens, the indirectly evoked muscle activity can be distinguished from the direct one. As direct muscle stimulation is feasible and safe, propagation velocity along single fibers can be determined in situ over a long distance. The results obtained in 50 normal subjects are presented.

Interictal conduction slowing in muscle fibers in hypokalemic periodic paralysis.

Conduction velocity in muscle fibers of the short head of biceps brachii was reduced between attacks in all the affected members of a family suffering from hypokalemic periodic paralysis. This finding represents a further evidence of a primary alteration of sarcolemmal function in this disease. Interictal conduction slowing in muscle fibers is consistent with the prevailing pathophysiologic hypothesis, which considers an increased membrane permeability to sodium ions as the fundamental defect underlying all forms of familial periodic paralysis.

[Hypokalemic myopathy caused by fluoroprednisolone in a nasal spray. Observations 2 cases]. / Miopatia ipokaliemica da fluoroprednisolone in spray nasale. Osservazioni su due casi.

Reference is made to the picture observed in two patients with flaccid tetraparesis, severe hypopotassaemia, and myoglobinuric muscle necrosis (hypokalaemic myopathy). Recent onset of hypertension was a feature of both cases. Initially, however, no reason could be assigned for this, nor for the massive loss of potassium. Numerous investigations in the first case (and relatively quick verification in the second) incriminated a steroid, 9-alpha-fluoroprednisolone acetate, in a nasal spray. This has often been reported as the cause of an iatrogenic syndrome due to excess of mineral corticoids, with hypertension, hypokalaemia and alkalosis, suppression of plasma renin activity, and reduction of blood and urinary aldosterone, all of which were observed in these two patients. Withdrawal of the drug and treatment with potassium chloride led to relatively rapid normalisation of the serum electrolytes. Recovery of muscle strength took place after about 20 days, almost at the same time as the normalisation of muscle enzymes. Hypertension, on the other hand, regressed slowly. The nexus between chronic use of the spray and the occurrence of hypokalaemic muscle necrosis is examined in detail. Stress is laid on the importance of specific investigation of the prior use of intranasal steroids in the differentiation of muscle disturbances due to potassium depletion.

The use of the H reflex in serial evaluation of nerve conduction velocity.

Conduction velocity (CV) in the H pathway, expressed by a mixed (sensorimotor) index (HCV), showed a very reduced intra-individual variability when compared to conventional conduction parameters in normal subjects. HCV, tested serially over increasing intervals of time, was about 4 times more stable than motor CV in deep peroneal nerve and about 6 times more stable than the sensory CV in sural nerve. The HCV was so accurate in showing marginal conduction changes that it clearly revealed, in normal persons, a circadian rhythm of conduction velocity, well correlated with circadian variations of body temperature, which totally escaped conventional conduction parameters. owing to its reduced variability, this conduction parameter represents, within the limits in which it can be reliably used in clinical application, a first choice tool for longitudinal conduction studies.

Analysis of conduction velocity in the H pathway. Part 1. Methodology and results in normal subjects.

An electrophysiological method is described for evaluating the conduction velocity in the different partial segments of the monosynaptic reflex pathway of the lower limbs in man. Using the latencies of M and H responses recorded from the soleus muscle elicited by stimulating the posterior tibial nerve at the popliteal fossa (pf) and the sciatic nerve at the upper thigh, the conduction velocities in the entire course (pf-to-spinal cord), in the proximal segment (upper thigh-to-spinal cord), and in the distal segment (pf-to-upper thigh) of the H circuit, were evaluated and expressed by mixed (sensory-motor) conduction indexes. The conduction distances were measured by using the Th11 spinal process as a reference point on the vertebral column. The conduction velocity of the 1a spindle afferent fibres and of the motor fibres was selectively determined in the pf-to-buttock segment. The results obtained in 50 healthy subjects are presented and the methodological problems related to the proposed technique are discussed.

Analysis of conduction velocity in the H pathway. Part 2. An electrophysiological study in diabetic polyneuropathy.

The conduction velocity in the different partial segments of the monosynaptic pathway of the lower limbs has been assessed in 50 unselected diabetic patients in order to evaluate the distribution of conduction slowing in the entire course of peripheral nerves in the most common form of polyneuropathy. According to the method previously described (Troni 1981), the conduction velocity in the entire course (popliteal fossa-to-spinal cord), in the proximal segment (buttock-to-spinal cord) and in the distal segment (pf-to-buttock) of the H pathway, has been determined and expressed by mixed (sensory-motor) conduction indexes. Moreover, the conduction velocity of the 1a afferent and of the motor fibres, has been selectively evaluated in the pf-to-buttock segment. The comparison between the impairment of each partial conduction parameters proves the existence of a clear-cut proximo-distal gradient of conduction slowing in the H pathway in diabetic polyneuropathy. Marked slowing in the larger-diameter 1a afferent fibres can also be demonstrated in the pf-to-buttock segment.