Stimulus induced repetitive muscle potentials in the gracile axonal dystrophy (GAD) mouse.

Gracile axonal dystrophy (GAD) is an inherited neurodegenerative disease in the mouse with progressive sensory ataxia and motor paresis. Electromyographic examination was conducted in 25 unanaesthetized GAD mice and 24 controls of the same strain during 6, 9 and 12 wk of postnatal life. Among 9 and 12 wk old mice, about 75% showed resting spontaneous activities--either fibrillation or fasciculation or both. On stimulation of the tibial nerve at ankle, with single pulse, the EMG showed repetitive muscle potentials of large amplitude, following "M" response. The frequency and duration of the train of these stimulus--induced repetitive muscle potentials (SIRMP) were almost constant in a given animal. The SIRMP failed to reappear in response to the second stimulus within 5 s when twin pulses were applied or within 5 min when tetanic stimuli were applied, indicating their fatigability. It is concluded that the SIRMP originate from immature, supplementary motor endplates that develop at ultraterminal nerve sproutings induced by denervation and reinnervation and possibly are due to hyperexcitable trigger points in the peripheral nerve endings. The EMG abnormalities in the GAD mouse are very much similar to those observed in human syndromes with hyperexcitable peripheral nerves that result in sustained muscle activity like neurotonia and hence the GAD mouse is a good model of such motor abnormalities in man.

Clinical, hematological and electrophysiologic study of megaloblastic anemias.

Thirty one cases of megaloblastic anaemia were studied clinically and electrophysiologically. Eight patients had clinical evidence of peripheral neuropathy. MNCV, distal sensory latency, la fibre conduction velocity, proximal conduction velocity and H-reflex amplitude and latency were compared with fourteen age and sex matched healthy controls. MNCV, proximal conduction velocity and H-reflex amplitude were significantly decreased in anaemic subjects while distal sensory latency was increased. No change was seen in la fibre conduction velocity and H-reflex latency. There was no correlation between severity of anaemia and the electrophysiologic abnormalities. MNCV and la fibre conduction velocity improved after correction of anemia.

Spinal somatosensory evoked potentials in mice and their developmental changes.

Spinal somatosensory evoked potentials (SEP) were recorded in 58 normal mice (C3H strain) divided into 4 groups according to age (3-, 6-, 9- and 12 weeks). Monopolar recordings of spinal SEP were made by subdermal needle electrodes from 3 vertebral levels, "low-lumbar", "high-lumbar" and "mid-thoracic", by stimulating the tibial nerve bilaterally at the ankle. Three negative peaks, NI, NII and NIII, presumably due to conduction through muscle afferents, cutaneous afferents (in the dorsal root or dorsal white column) and spinocerebellar tract, respectively, were recorded at the high-lumbar level in the 12-week-old mouse. Besides the NI and NII peaks, a small ventral root potential was also occasionally recorded at the low-lumbar level. At the mid-thoracic level, only NI and NIII were recordable. At both the high-lumbar and mid-thoracic levels, the negative peaks were superimposed over long duration "summation potentials" of opposite polarities. Well-defined standing potentials were also recorded at these two levels. The standing potentials could be the "entry potential" due to the entry of S1 root into the spinal cord at the T13 vertebral level. The summation potential presumably is due to a fixed generator located between the T7 and T12 vertebral levels resulting from intense synaptic activity at this level. In 3- and 6-week-old mice, the entry point potential was recorded in the low-lumbar SEP also, possibly due to less axial growth of the vertebral column at this stage of development.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in motoneuron excitability during postnatal life in the mouse.

H-reflex recovery, H-amplitude and H/M ratio were recorded in 54 mice aged 3-12 weeks to study the motoneuron excitability and changes in it during various stages of development. The H-reflex recovery curve at 12 wk showed 3 phases: an early, relative facilitation (before 10 ms), an almost total inhibition at 10 ms and a rapid recovery thereafter. At 3 wk, however, there was only slow recovery after 10 ms and the H-reflex recovery was significantly low during the 40-100 ms period as compared to those in the other age groups, indicating that between 3 and 6 wk, there was a significant increase in the motoneuron excitability. The H-reflex amplitude also showed a significant increase during the 3-6 wk period. However, the H/M ratio did not show any significant increase either during the 3-6 wk period or thereafter. It is concluded that the H-reflex recovery at 3 wk suggests hypoexcitability of the motoneurons, possibly due to immaturity. Since there was a significant increase in the H-reflex recovery during the 3-6 wk period without any parallel increase in the H/M ratio, it is concluded that presynaptic and polysynaptic mechanisms acting on the motoneurons develop during this period. The increase in the H-reflex amplitude is possibly due to the increase in the muscle mass. The H-reflex recovery pattern at 12 wk, without the phase of late inhibition observed in man, is suggestive of less supra-spinal control mechanisms acting upon the motoneurons.

H-reflex latency and sensory conduction in the assessment of neuropathy in patients of chronic obstructive lung disease.

H-reflex latency, proximal conduction velocity and distal proprioceptive conduction velocity were studied along with distal motor and sensory conduction in 38 patients of chronic obstructive lung disease grouped according to age and duration of the disease, as well as in 35 age-matched smoker controls and 14 non-smoker controls. The mean values of all the parameters studied in all the patient groups were significantly different from those of the non-smoker control group. Smoker controls also showed significant abnormality in all the parameters except motor conduction velocity. Among the patients, significant abnormality (mean +/- greater than 2 SD) was seen in 44.7% in motor conduction, 86.8% in sural nerve distal latency, 97% in Ia conduction velocity, 78.9% in H-reflex latency and 60.5% in proximal conduction velocity, as compared to the non-smoker control values. Among the old patients with more than 10 years of the disease, 62.5% had all the parameters significantly abnormal. More than one parameter was affected in 97.4% of the patients. The intra-group and inter-group differences in all the parameters studied, except motor conduction velocity, were statistically significant indicating that age, chronicity of the disease and smoking can produce nerve conduction defects independently and collectively. It is suggested that though all parameters studied are highly sensitive to neuropathies, proximal H-latency studies are best suited for grading conduction defects in patients of chronic obstructive lung disease, since in many patients sural nerve action potential (52.63%) and distal H-reflex response for Ia conduction studies (81.52%) could not be elicited.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of ganglionic stimulating and blocking agents on the fast components of colonic myoelectrical activity in the rat.

The presence of two types of fast myoelectrical activities, medium fast activity and fast activity, has been demonstrated previously in the electromyogram of colon in normal children and in the rat by the authors. An absence of medium fast activity in Hirschsprung's disease and in experimental aganglionosis of colon in the rat has also been described. In the present study the fast components of colonic myoelectrical activity were analysed during the procedures affecting ganglionic transmission. It was observed that ganglionic stimulants, such as balloon inflation, and intra-arterial injections of acetylcholine and small amounts of nicotine, increased the spike activity and the frequency of medium fast activity without affecting fast activity. The intra-arterial injections of ganglionic blocking agents, such as nicotine in large amounts and pentolinium tartrate, completely abolished the medium fast activity. These observations suggest that the ganglionic activity is responsible for the genesis of medium fast activity and that the absence of cholinergic ganglionic transmission is the most important single factor for the reported altered electromyogram pattern in aganglionosis.

Long latency cutaneous reflex effect on H-reflex recovery in hemiplegics and paraplegics: a longitudinal study for the assessment of motor function.

H-reflex recovery by twin pulses was recorded serially in 10 paraplegics for 5 months and in 23 hemiplegics for 2 months after the lesion. Fifty-one normal subjects acted as controls. The effect of cutaneous tactile stimulation was also studied simultaneously by applying electrical stimuli synchronized with twin pulses to the skin over the lateral border of small toe. In paraplegics, the H-reflex recovery curves recorded serially showed a highly depressed pattern during the first two weeks, an almost normal pattern during the second and third months and a significantly elevated pattern during the fourth and fifth months. Whereas cutaneous stimulation in control subjects produced a highly significant late inhibition of H-reflex recovery between 600 ms and 600 ms, in paraplegics it failed to produce any significant effect, except in two, who besides having a normal H-reflex recovery curve even during the first week, showed a substantial amount of cutaneous inhibition of H-reflex recovery, 4 months after the lesion. A highly depressed pattern of H-reflex recovery was observed on the affected side of the majority of hemiplegics during the first week after the lesion, many of them showing similar pattern on the "unaffected side" also. The serial study showed very good improvement in all hemiplegics both in terms of H-reflex recovery pattern and the amount of cutaneous inhibition. The observations in present study suggest preservation and/or restoration of supraspinal influences in many hemiplegics and in at least two paraplegics. The study also shows that a serial recording of H-reflex recovery curve and the amount of cutaneous reflex effect on it, is a very sensitive method of assessing the supraspinal influences on the spinal motoneurones and so can be of immense help in the diagnosis and prognosis in hemiplegics and paraplegics.

Long latency inhibition of H-reflex recovery by cutaneous tactile stimulation in man: a cutaneous transcortical reflex.

The effect of cutaneous tactile stimulation on motoneuron excitability was studied in 20 normal subjects and in patients of hemiplegia (n = 14) and paraplegia (n = 15) by plotting H-reflex recovery curves during application of twin pulses alone ("basal" H-reflex recovery curve), and twin pulses synchronized with electrical stimuli evoking tactile sensation in skin over the lateral border of the small toe. The "basal" H-reflex recovery curves from normal subjects showed a significant lateral asymmetry of motoneuron excitability, with an even distribution of subjects showing greater excitability on the left and right sides. However, there was no relation between handedness and the side with greater excitability. The cutaneous stimulation produced a highly significant inhibition of the H-reflex recovery between 600 and 6000 ms, with the maximum inhibition recorded at 1000 and 2000 ms, at which time even a complete inhibition of the test H-reflex was observed in some instances. The effect of cutaneous stimulation before 600 ms was statistically insignificant. The amount of cutaneous inhibition of H-reflex recovery showed a lateral asymmetry. The side with greater motoneuron excitability showed more cutaneous inhibition of the H-reflex recovery. A comparison of the H-reflex recovery at higher frequencies of cutaneous stimulation with that at basal frequency showed a slight but statistically insignificant difference in the amount of cutaneous inhibition of the H-reflex recovery. In hemiplegics, the "basal" H-reflex recovery curves showed greater motoneuron excitability on the affected side as compared to those of the unaffected side or controls, with the late inhibitory phase being completely obliterated. A similar pattern was also observed in paraplegics. Significantly, the lateral asymmetry of motoneuron excitability observed in the control group was absent in paraplegics. The cutaneous stimulation failed to produce any significant effect on the H-reflex recovery curves either in the affected side of hemiplegics or in both sides of paraplegics. The significant long latency inhibition of the H-reflex recovery curve produced by cutaneous tactile stimulation is a new finding.(ABSTRACT TRUNCATED AT 400 WORDS)

Role of H-reflex latency studies in the diagnosis of subclinical diabetic neuropathy.

Motor conduction velocity (MCV) in the median, ulnar and peroneal nerves and H-reflex studies have been conducted in 50 diabetics aged 20-65 years and 25 controls. MCV in the upper limb was below the normal range in 16% of diabetics. 28% diabetics showed abnormal MCV in the peroneal nerve. H-reflex abnormality consisting of either prolonged latency or its complete absence could be observed in 54% of diabetics. The results indicate the greater sensitivity of H-reflex in the detection of sub-clinical diabetic neuropathy. Greater prevalence of neuropathy in the early onset diabetes than in the late onset type is also suggested.

Myoelectrical activity in experimental aganglionosis of the colon in the rat.

Experimental aganglionosis of the colon was produced in rats by an experimental "aganglionosis producing" procedure. Radiological examination of the aganglionic colon showed a narrow segment distal to a dilated megacolon. Histologically, a transverse section of the aganglionic segment showed 3-4 ganglia in contrast to 32-40 ganglia per section in the normal colon. The myoelectrical activity of the normal colon presented two fast activities, a fast activity with a frequency of 25-40 cycles per sec superimposed over a medium-fast activity of 4-7 cycles per sec. However the aganglionic colon showed only the fast activity with complete absence of the medium-fast activity. Thus the experimental aganglionosis produced a characteristic alteration in the myoelectrical activity of colon. This confirms our earlier findings in children with Hirschsprung's disease. It also suggests that the causative mechanism for the production of a narrow segment in Hirschsprung's disease may not be the hyperactivity or the absence of any specific neuronal mechanisms as proposed earlier.