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 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.

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.

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.

Sympathetic skin response versus maximum motor and sensory conduction velocity to detect subclinical neuropathy in non-insulin-dependent diabetics.

Conventional motor (MCV) and sensory conduction velocity (SCV) of the ulnar (UN), peroneal (PN) and median nerves (MN) and the areas of sympathetic sudomotor response (SSR) recorded from the middle finger were measured on both sides in 20 normal and 20 non-insulin-dependent diabetic (NIDD) subjects. Conventional statistical tests (t test, linear correlation coefficient r) and discrimination analysis were applied to the above electrophysiological parameters. To evaluate the capability of the tests to separate NIDD diseased from normal nerves, the results were represented as generalized distances, i.e., difference between mean discriminant normalized combinations adjusted for intra-group variability. The r values were 0.92 (P less than 0.01) for the UN, 0.40 (P greater than 0.05) for the PN, and 0.86 (P less than 0.01) for the MN sensory action potential (SAP) amplitudes. No significant differences were found for normalized latencies. The r values of the SSR areas were 0.62 (P less than 0.01) at the right and 0.77 (P less than 0.01) at the left, homolaterally to the side of stimulation. SR and MCV generalized distances were 1.35 and 1.39, respectively. The discriminating power of SSR, MCV and SCV considered together was higher (2.40) than that of MCV and SCV (1.70). Since motor, sensory and autonomic alterations often did not coexist in NIDD, it was possible to find at least one type of involvement in most of the diabetic subjects.

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]. / Considerazioni eziopatogenetiche su due casi di paralisi ipokaliemica dismetabolica con manifestazioni di aumentata eccitabilità neuromuscolare durante replezione potassica.

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)]. / Potenziali di singola fibra muscolare da stimolazione delle terminazioni nervose pregiunzionali nell'uomo normale (osservazioni preliminari).

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.