Descending and ascending spinal cord evoked potentials from oesophago-vertebral electrical stimulation in normal awake man

Electrical stimulation of the spinal cord at C7D1 evoked triphasic descending spinal cord evoked potentials (DSCEP) from an oesophago-vertebral recording at D8D8 or D1OD1O. Ascending SCEPs (ASCEP) larger and similar in shape were also observed when the orientation of the stimulating and recording dipoles was reversed. Both SCEPs are in part generated by descending and ascending synchronous excitation of neuronal volume-conducted spinal cord dipoles.

Muscle compound motor action potentials from esophago-vertebral electrical stimulation of the spinal cord in the normal awake man

In 15 normal alert subjects, electrical stimulation of the spinal cord at various levels by a nasopharyngeal probe (cathode) and a vertebral surface electrode (anode) was performed with different orientation of the stimulating dipole. Maximum spinal cord compound motor action potentials (SCCMAPmax) simultaneously recorded from homologous muscles of the upper arm of both sides were not significantly different in amplitude and latency. By stimulating the spinal cord at the cervico-dorsal level it was possible to obtain simultaneous recordings of SCCMAP from muscles of the upper and lower limbs and trunk at a stimulus intensity of 50-70 mA. Stimulating the spinal cord and the peripheral nerve at Erb's point it was also possible to calculate motor propagation velocity of the peripheral nerve of limb-girdle muscles. Central latency of the F wave exceeded by 0.5 to 0.7 ms that of the SCCMAP, suggesting that esophago-vertebral stimulation is able to directly excite the motor neurons. By threshold current intensity, it is possible to obtain a threshold SCCMAP (SCCMAPth) of the same latency as SCCMAPmax and different in shape, duration and amplitude from the CMAP obtained by cortical stimulation with threshold magnetic stimuli. SCCMAPth was different in shape from the motor unit action potential activated at weak voluntary effort, SCCMAPth latency and amplitude were unchanged after voluntary homo- and contralateral activation.

Prevalence of subclinical neuropathy in diabetic patients: assessment by study of conduction velocity distribution within motor and sensory nerve fibres

Nerve conduction velocity distribution (CVD) study is a newly-developed electrodiagnostic method for detecting alterations in the composition of nerve fibres according to their conduction velocity. The presence of subclinical neuropathy was evaluated in 138 diabetic patients by CVD study of four motor nerves (external popliteal and ulnar nerves bilaterally) and two sensory nerves (median nerve bilaterally), and the data obtained were compared with standard electrophysiological parameters in the same nerve segments. CVD studies revealed an altered distribution pattern in 106 of 129 evaluable patients for motor nerves (82%) and in 67 of 115 evaluable patients for sensory nerves (58%), while standard examination gave abnormal findings in 92 of 137 patients (67%) and in 33 of 118 patients (11%), respectively. Of the patients adequately evaluated by both techniques, 21 of 129 patients (16%) revealed altered CVD data unaccompanied by slowing of maximum nerve conduction velocity, and 37 patients of 101 (37%) showed similar findings for sensory nerves. Subclinical alterations of motor and sensory nerve CVD were not significantly related to age or to metabolic control expressed as glycated haemoglobin levels; a significantly longer duration of disease was found in patients with motor and mixed subclinical neuropathy with respect to non-neuropathic patients. The CVD study allowed us to detect subclinical abnormalities of motor and sensory nerve fibres; often this is a more sensitive method than the standard electrodiagnostic study. This method can be very useful as a diagnostic tool and in research in the study of the progression of diabetic neuropathy.

Short and long latency cortical potentials evoked by electrical stimulation of the oesophageal mucosa in normal alert humans

Cerebral responses from the oesophagus were investigated in 16 normal male and female volunteers ranging in age from 20 to 54 years. The stimulus was applied by a naso-oesophageal probe equipped with bipolar ring electrodes. Short and long latency EP (SLEP and LLEP) were observed in all the subjects examined. SLEP consisted in a low threshold potential of 30 to 70 microV amplitude, biphasic or triphasic in shape and of approximately 5 to 10 ms duration; mean latency at the largest peak was 4.5 +/- 1.7 at 25 cm from the nostrils. Early components at about 2.5-3.5 ms and of small amplitude are also present. Recording from the neck at C7 with a common non-cephalic reference, SLEP components occurred from 2 to 6 ms earlier than that from the scalp, suggesting an oligo-synaptic transmission of the excitement via ganglion and lemniscal pathways to the cortex. SLEP was always followed by a complex potential formed of a succession of negative and positive waves with latencies ranging from 20 to 300 ms: the LLEP. This LLEP was usually not very stable and reproducible during the course of successive recordings and in the same subject because it tended to adjust. Preliminary observations concerning the topographical cortical distribution of oesophageal evoked potentials show a circumscribed localization of the SLEP in the parieto-temporal region of the hemisphere whereas LLEP was more widespread. It is the authors' opinion that oesophageal evoked potentials are generated both by the excitation of myelinic fibres with a wide range of conduction speed and of amyelinic fibres from the oesophageal mucosa and the paraoesophageal peripheral nerves of vagal origin.

Electrophysiology of the palmomental reflex in normal and parkinsonian subjects

The palmomental reflex (PMR), obtained by mechanical stimulation of the skin of the thenar and hypothenar eminences of the hand and recording the surface EMG response from the chin muscles homolateral and contralateral to the side of stimulation, was studied in normal subjects and in a group of akinetic parkinsonians, both de novo and treated. PMR was present in most subjects of both groups. No differences regarding the incidence of the PMR homolateral to stimulation of the thenar eminence was found between controls and patients, and it was non-habituating in both groups. When the hypothenar eminence was stimulated, the PMR was present in about half of the subjects of both groups. PMR was present contralaterally in both normal and patients, whereas bilateral PMR prevailed in parkinsonians. Latency and duration of the reflex were significantly shorter in parkinsonians than in controls. The data are discussed in the light of the pathophysiology of the PMR putative pathways in normal subjects and in Parkinson's disease.

Myotonia induced by potassium repletion in a diabetic patient with secondary hypokalemic paralysis

In a woman suffering from insulin-dependent diabetes mellitus, hypokalemic paralysis developed acutely following an episode of diabetes decompensation. During the treatment of this episode, as soon as serum potassium levels were restored to normal values, a marked increase in muscular excitability with an electromyographic picture of myotonia was observed. The patient showed signs of chronic muscle denervation that accounted for an increased sensitivity to potassium-induced depolarization and contraction and that might have been responsible for the appearance of myotonia during potassium repletion.

Peripheral autonomic involvement in the carpal tunnel syndrome

The sympathetic skin response (SSR), evoked from the middle finger of both hands by electrical stimuli to the median nerve (MN) at the wrist, was studied in 21 patients with bilateral carpal tunnel syndrome (CTS) and in 16 patients with monolateral CTS (14 at the right and 2 at the left side) without clinical signs of autonomic involvement. In monolateral and bilateral CTS there was a decrease in the SSR areas of both sides. In monolateral CTS the decrease was greater contralaterally to the lesion. A decrease in the SSR in CTS generally indicates a local blockade of sympathetic nerve excitability due to MN entrapment. Contralateral reduction of the sympathetic response suggests an involvement of the efferent pathway of the autonomic reflex far from the lesion at the wrist. However, dispersion of the excitement over a long distance and throughout numerous synaptic connections may affect contralateral more than homolateral SSR excitability. Finally, sympathetic damage in CTS is in accord with the anatomo-functional correlation (in the peripheral nerve and ganglia) between somatic sensory, which were most markedly involved in our patients, and sympathetic afferent nerve fibers.

An electrophysiological method to assess the distribution of the sensory propagation velocity of the digital nerve in normal and diabetic subjects

We report a new computer-assisted collision method to evaluate sensory conduction velocity (SCV) distribution in the digital nerve of the middle finger in normal subjects and in insulin-dependent diabetic subjects without any neurological impairment. Distribution curves were monomodally shaped in controls, indicating a greater proportion of fibers with relatively slow conduction velocity and a lesser proportion of fibers with faster velocity. In most diabetic nerves, a monomodal trend of the SCV distribution indicated a definite reduction in high and intermediate SCV. In a small proportion of nerves, the SCV distribution tended to be bimodal, with an absolute maximum corresponding to lower velocities and a relative maximum to intermediate-fast velocities. Slowing of the intermediate velocity, or loss of fibers of intermediate velocity, can be hypothesized to represent the early electrical evidence of a subclinical polyneuropathy in insulin-dependent diabetic subjects.

Nerve conduction velocity distribution in normal subjects and in diabetic patients without clinical signs of neuropathy. II. Sensory nerve

A new computer-assisted method to evaluate sensory conduction velocity distribution and dispersion of the digital nerve of the middle finger in normal subjects and in type I and type II diabetic subjects without any neurological impairment is reported. Distribution curves were exponentially shaped in normal and in diabetic subjects. In insulin-dependent diabetics, only slower conduction velocity fibers were involved, whereas no significant difference was observed between the non-insulin-dependent diabetic group and the control group.

Nerve conduction velocity distribution in normal subjects and in diabetic patients without clinical neuropathy. I. Motor nerve

A computer-assisted collision method to evaluate motor conduction velocity distribution of the ulnar and external peroneal nerves in normal subjects and in insulin-dependent and non-insulin-dependent diabetics without clinical signs of neuropathy is described. Distribution curves were sigmoidally (bimodally) shaped in normal and in insulin- and non-insulin-dependent subjects. In insulin-dependent patients, motor conduction velocity of the peroneal nerves was globally impaired, whereas of the ulnar nerves it was normal. In non-insulin-dependent patients, slower conduction velocity was involved in both nerves.

The palmomental reflex from mechanical stimulation in normal man: normative data

The authors report normative data on the electrical response (EMG response) recorded from the mentoneal muscles by repetitive mechanical stimulation of the palmar and dorsal surface of the hand in 23 normal adults: the palmomental reflex (PMR). An early and late response was observed in 11 cases. The PMR potentials showed great variability in latency, amplitude and duration and were present in about 70% of the subjects in whom the PMR was undetectable by visual inspection. In 3 cases the reflex was also observed contralaterally to the side of stimulation. The afferent branch of the normal PMR is constituted of impulses originating mainly from the median nerve skin and muscle receptors. Such impulses could reach facial motor nuclei either through short-(paucisynaptic) or long-loop (thalamocortical) circuits.

Electrophysiological observations on the palmomental reflex in normal neonates

The authors report normative data on the electrical response (EMG response) recorded from the mentoneal muscles by repetitive mechanical stimulation of the thenar eminence surface of the hand in 18 neonates, 1 to 6 days old: the so-called palmomental reflex (PMR) or palm-chin reflex. PMR potentials showed in most cases great variability in amplitude and duration but not in latency, and they were present in all but one of the cases. The PMR was monolateral in one case only. Evoked potentials from the scalp were also recorded after electrical stimulation of the thenar eminence. The afferent branch of the PMR is constituted of impulses originating mainly from median nerve, skin and muscle receptors. Such impulses may reach facial motor nuclei following corticofugal pathways throughout a long-loop circuit.

Propranolol, clonidine, urapidil and trazodone infusion in essential tremor: a double-blind crossover trial

Accelerometric tremorgrams were recorded from 25 subjects affected by essential tremor and analysed by a Berg-Fourier frequency analyser before and during venous infusion of the following drugs: propranolol (beta-blocker), clonidine (alpha-presynaptic adrenergic agonist), urapidil (alpha-postsynaptic blocker), trazodone (adrenolytic agent) and placebo. The washout interval between infusions was 3 days. Recordings and data analyses were performed in a double-blind crossover trial. Tremor was classified as: at rest; postural (arms hyperextended); and intention (finger-nose test). Analysis of the results showed that propranolol and clonidine reduced significantly (P = 0.01 and P = 0.009, respectively) the power spectrum of postural tremor, but left at rest and intention tremors unchanged. No significant effects on the tremor power spectrum were observed after placebo, urapidil or trazodone administration. None of the drugs had any effect on tremor frequency.

Seventh cranial nerve paralysis with myokymia during acute co-infection with hepatitis B and delta viruses

A patient with peripheral cranial nerve paresis and bilateral myokymia is described during the course of acute co-infection with hepatitis B and delta viruses. Specific circulating hepatitis B immune complexes were found by electron microscopy concomitantly with the neurological symptoms.

Clonidine in essential tremor: preliminary observations from an open trial

The authors present ten cases of essential tremor, studied before and after administration of clonidine with clinical tests and electrophysiological recordings. Improvement due to the desynchronizing effect of clonidine on tremor was observed in all cases. Possible mechanisms acting on the central and peripheral nervous system are discussed.

[Etiopathogenetic considerations in 2 cases of dysmetabolic hypokalemic paralysis with signs of increased neuromuscular excitability during potassium repletion]

Increased neuromuscular excitability with varying clinical and EMG features were also observed during KCl administration in both cases. The findings are discussed on the light of the membrane ionic gradients current theory.

[Potentials of individual muscle fibers evoked by stimulation of prejunctional nerve endings in healthy subjects (preliminary observations)]

Electrical responses of the single muscle fibre (SFER) by stimulation of the motor terminal nerve-endings have been investigated in normal subjects at various ages in vivo. Shape, latency, rise-time and interspike distance seem to be SFER's most interesting parameters of the functional organisation of the motor subunits and their terminal fractions. "Time" parameters of SFER are in agreement with the anatomo-functional characteristics of the excited tissues during ageing.

Treatment of denervated muscle by gangliosides

Short-duration cooling of the nerve to the extensor digitorum longus muscle of the rat in vivo induced partially reversible denervation of the muscle and atrophy in the type 2 muscle fibers. Increases in cyclic adenosine monophosphate, cyclic guanosine monophosphate phosphodiesterase, adenylate cyclase, and guanylate cyclase were observed in the denervated muscle. Treatment with gangliosides of the bovine brain cortex seemed to improve the excitability of the surviving motor units and to encourage recovery of neuromuscular trophic control, but it did not affect the nerve conduction velocity or the contractile properties of the denervated muscle.

Morphology and physiology of skeletal muscle in aging rodents

Aging in the rodent is accompanied by a progressive loss of skeletal muscle fibers. The muscle twitch also becomes slower, probably as a result of fiber-type conversion from "fast-twitch" to "slow-twitch." The loss of muscle fibers precedes signs of obvious weakness and appears to involve the loss of entire functioning motor units. In the mouse, this loss of motor units correlated with a loss of axons from the innervating nerve trunks.

A histological and histochemical study of changes of fiber types in experimental myotonia

In both fast and slow muscles of rats treated with 20--25 diazacholesterol there were qualitative alterations, such as changes of fiber outlines, numerous moth-eaten fibers and rare ring fibers. In addition there were generally larger groups of Type I and intermediate fibers than in normal controls ("type-grouping" tendency) in the preparations for oxidative enzymes in the extensor digitorum longus (EDL) of myotonic animals. Quantitative evaluations of EDL and soleus of myotonic rats revealed moderate hypothrophy of Type I and Type II fibers with an increase in the numbers of Type I and of Type III fibers in the EDL and a significant decrease of the nondominant fibers in the soleus muscle. The data are discussed in the light of a neurally mediated and/or direct action of the drug on the muscle fiber.

Effects of hemodialytic treatment on uremic polyneuropathy. A clinical and electrophysiological follow-up study

The involvement of peripheral motor and sensory nerve, at least on a subclinical level, is nearly constant event with chronic renal failure. The study of the motor and sensory propagation velocity indicates that a widespread functional lesion of the axon with a peripheral point of attack and secondary demyelination, may be the basic pathogenetic event of uremic polyneuropathy. Prolonged hemodialytic treatment is substantially unable to influence the evolution of uremic polyneuropathy. The electrophysiological follow-up study of the peripheral nerve does not seem to be an index of adequate dialysis.

Vincristine polyneuropathy in man. A clinical and electrophysiological study

A clinical and electrophysiological follow up study of 14 cases of hemopathic patients patients undergoing VCR therapy showed evidence that the drug has a direct action on the motor and sensory axon but not on the propagation velocity. Sensory nerves seem to be affected earlier and more than motor ones. Correlation was good between clinical and electrophysiological findings for both functions. The findings in man correspond with the animal data and therefore lead to the conclusion that VCR polyneuropathy is due to an involvement of the nerve axon.

Spinal evoked responses recorded from the epidural space in normal and diseased humans

In 22 subjects, including normal subjects and patients with radicular or spinal cord lesions, the authors studied the spinal evoked responses recorded extradurally after stimulating mixed limb nerves. The responses obtained are discussed with particular reference to the clinical value of the changes in amplitude and latency of the spinal evoked potential with particular lesions.

Axonal excitability and motor propagation velocity of peripheral nerves in patients with acute vascular lesions of the brain

From measurements of maximum and minimum motor nerve propagation velocity and neuronal excitability we conclude that there is a functional loss of motor units and distal nerve "dying back" in persons affected with unilateral acute cerebral vascular lesions. The study also suggests that transynaptic degeneration affects the lower motor neurone function on both sides.

Effects of threshold, low frequency, long lasting stimulation on single motor unit electrical responses from the extensor digitorum brevis muscle in normal and myasthenic subjects

The authors studied the recruitment of motor units of EDB muscle by long lasting threshold intensity stimulation at 1 c/sec of external popliteal nerve at the ankle in healthy subjects and in myasthenic patients. In the healthy volunteers, at steady intensity of threshold stimuli, maximum number of motor units never exceeded 5--6 electrical increments with a final incremental response of constant amplitude during 60 min of stimulation. In myasthenic patients, both an early exhaustion of threshold motor units and a marked facilitation phenomenon occurred with massive recruitment of incremental responses, while in a small number of cases no changes were observed. These data are discussed in the light of various morphofunctional hypotheses regarding the localization of the myasthenic impairment.

[Signs of soleus muscle denervation in dystrophic mice (extra and intracellular study)]

Extra and intracellular recording in vivo and in vitro and gold-chloride staining of the dystrophic mouse (Bar Harbour Strain) and of the normal controls soleus nerve-muscle preparation, has shown functional and anatomical denervation findings in the dystrophic muscles.

Nerve supply and experimental myotonia in rats

20, 25-Diazacholesterol does not induce myotonia in denervated mammalian skeletal muscle, and cordotomy also renders the muscles resistant to the induction of myotonia. Denervation of muscle already rendered myotonic, has no effect on the intensity of the phenomenon. Finally, tenotomy and posterior rhizotomy leave the myotonic activity in the "deafferentated" muscles unchanged. These findings are discussed in relation to "trophic" influences of the motor pathways on the postsynaptic structures of skeletal muscle.

Physiological estimates of the sizes and the numbers of motor units in soleus muscles of dystrophic mice

Evidence is presented to support the neurogenic hypothesis for murine dystrophy. Axonal atrophy, decrease in twitch tensions of individual motor units and loss of motor units suggest that "sick" motor units are present in dystrophic mice and that the "sick" motor units were once functional, but had gradually degenerated, possibly due to a neurotrophic deficiency.

Electrophysiological evidence for a neurohormonal dependence in the changes of the late glabellar response in man

In 19 normal adults reserpine administration induced significant changes in the parameters of the second glabellar response (R2): shortening of the latency and duration; decrease of the excitability threshold and complete blockade of the physiological habituation of R2 to the electrical and mechanical stimulation. No changes in the first response (R1) were observed. All the R2 changes disappeared within about 3 days of drug administration. The Parkinson-like effect of reserpine on the glabellar reflex is discussed in the light of a neurohormonal hypothesis in the control of the polysynaptic pathways biasing R2.

Clonazepam in facial neuralgia and cluster headache. Clinical and electrophysiological study

Clonazepam seems to be an effective drug in idiopathic trigeminal neuralgia. Electrophysiological investigations support the idea that this neuralgia is due to a loss of central inhibition. During the first 1-2 weeks of treatment marked drowsiness is observed in the majority of cases. In one case, presence of a synergism between Clonazepam and L-dopa+ inhibitor was also observed.

Cutaneous reflexes in small muscles of the hand

A study has been made of the responses of motoneurones innervating small muscles of the hand to electrical and mechanical stimulation of the skin. Both excitatory and inhibitory effects could be observed in the same muscle after a single stimulus to a given area of skin. The earliest excitatory and inhibitory responses are probably mediated by group III and the smaller group II afferent nerve fibres. A later inhibition results from activity in the larger group II fibres which are connected to cutaneous mechanoreceptors, especially those in the tips of the fingers and thumb. This late inhibitory reflex may operate through the fusimotor system. The possible roles of these reflexes are discussed in relation to previous investigations in man and the cat.