The short latency muscle reflex in the diagnosis of disc disease affecting roots L4 and L5.

A segmental monosynaptic reflex that can be evoked by using voluntary muscle contraction to facilitate it is of use in diagnosis. In a group of 15 healthy volunteers the reflex response from tibialis anterior proved to be 31.08 +/- 2.48 msec with a side difference of 0.41 +/- 0.36 msec and from peroneus longus 29.90 +/- 2.20 msec with a side difference of 0.38 +/- 0.25 msec. Of 21 patients with radiologically proven disc herniation (of root L4 in 5 and of root L5 in 16) 16 showed a delay of more than 2.5 SD of the side difference or no response at all. It is hope that this simple and speedy method will be routinely adopted as complement to standard electromyography.

'Excitability changes of muscular responses to magnetic brain stimulation in patients with central motor disorders.

The 'excitability' and 'conductivity' of motor pathways during transcranial stimulation (TCS) have been investigated in 49 patients affected by multiple sclerosis (34), amyotrophic lateral sclerosis (7), spino-cerebellar ataxia (3), primary lateral sclerosis (4) and brain metastasis (1). Hyper-reflexia, spasticity and weakness were correlated with the central motor conduction time (CCT) and with the threshold intensity of TCS required to produce a motor evoked potential (MEP). MEPs to magnetic TCS were recorded from hand and foot muscles during relaxation, contraction and after tendon vibration. Thresholds and CCTs of the patients were compared with those of 30 healthy controls. Increased threshold was found in 37 out of 49 patients (75.5%). Prolongation of the CCT was found in 38 out of 63 clinically affected upper limbs (60.3%) and in 56 out of 77 clinically affected lower limbs (72.7%). Absent motor responses to maximal TCS were found in 20 out of 98 lower limbs (20.4%). Excluding ALS patients (in whom there was a lower threshold for MEP elicitation), a significant linear correlation was found between prolonged CCT and increased threshold. While MEPs with prolonged CCTs have elevated TCS threshold, it is important to note that an elevated threshold was found in 14 out of 49 patients (28.5%) despite unchanged CCT. Spasticity and/or hyper-reflexia were more frequently associated with increased threshold than with prolonged CCT, while weakness was correlated equally well with both these parameters. In this respect magnetic TCS proves to represent a new tool for the detection of abnormal 'excitability' of the central motor tracts.

Non-invasive evaluation of central motor tract excitability changes following peripheral nerve stimulation in healthy humans.

The interval between muscle stretch and the onset of the long latency electromyographic responses (LLRs) has been theoretically fragmented into an afferent time (AT), taken at the peak of wave N20 of somatosensory evoked potentials and an efferent time (ET), calculated by means of magnetic transcranial stimulation (TCS), the two being separated by a cortical interval (CI). If this were the case, the afferent input should progressively 'energize' the sensorimotor cortex during the CI and change the excitability of cortico-spinal tracts. To investigate this, motor evoked potentials (MEPs) from thumb flexor muscles were recorded, whilst a conditioning stimulation of median or ulnar nerve randomly preceded (10-48 msec intervals) magnetic brain TCS. Nerve stimulation was adjusted to motor threshold and amplitudes of conditioned and test MEPs at different nerve-TCS interstimulus intervals were evaluated. Conditioned MEPs were significantly attenuated with nerve-TCS intervals between 16 and 20 msec for elbow and 20 and 22 msec for wrist stimulation. This was followed by MEP potentiation with nerve-TCS intervals corresponding to the sum of AT + CI (mean 23.2 msec, range 21.7-24.8). The onset latency of facilitated conditioned MEPs was about 1 msec briefer than that of test MEPs, but invariably longer than the latency of MEPs facilitated by a voluntary contraction. This protocol did not demonstrate amplitude facilitation of the segmental H reflex, corroborating the idea that the facilitated part of the conditioning nerve-TCS curve receives a transcortical loop contribution.

Bit-mapped somatosensory evoked potentials and muscular reflex responses in man: comparative analysis in different experimental protocols.

Bit-colour maps of somatosensory evoked potentials (SEPs) and muscular responses from forearm and hand muscles were simultaneously recorded after median nerve stimulation. Subjects were asked either to relax totally (A), or to contract the examined muscle continuously and isometrically at 10-20% (B) and 80-100% (C) of the maximal strength. Isotonic contractions ipsilateral (D) and contralateral to the stimulus (E) were also examined. Both SEPs and EMG responses were elicited by individual near-motor threshold pulses delivered at 0.2/sec to the median nerve at the elbow. SEPs were maximal in amplitude during complete relaxation, whilst all the components following the parietal N20 were depressed by muscle contraction. Such decrements affected predominantly the parietal and frontal peaks of positive polarity during condition B, whilst the frontal negative component (wave N30) dropped remarkably in conditions C and D. Early EMG responses (V1 = spinal circuitry) were usually absent in condition A; they were present together with later components (= V2 possibly long-loop, transcortical circuitry) in C and D, whilst they were alone recordable in B and E. The amplitudes of the frontal wave N30 in SEPs and of V2 in LLRs were inversely correlated. This observation is consistent with the hypothesis that a change in the reactivity of the sensorimotor brain areas to afferent impulses is coupled to LLR elicitation in forearm and hand muscles.

On a case of early-onset post-traumatic facial hemispasm.

In a 49 year old woman an injury to the right frontotemporal region was quickly followed first by paresis and then by spasm of the right side of the face. The early onset of the spasm prompts a critical review of current views on the pathogenesis of facial spasm.

Single fibre motor evoked potentials to brain, spinal roots and nerve stimulation. Comparisons of the 'central' and 'peripheral' response jitter to magnetic and electric stimuli.

Single fibre motor evoked potentials to magnetic and electric non-invasive stimulation of brain, spinal cord and peripheral nerve were recorded in 8 healthy volunteers. The 'central motor jitter' and the 'peripheral motor jitter' were respectively calculated and a comparison between the magnetic and electric modalities was made. The highest degree of latency variability was observed for both magnetic and electric central motor jitter, whilst the peripheral motor jitter to nerve stimulation was as low as the neuromuscular one (range 16-60 microsecond). The magnetic 'central motor jitter' (range 94-1024 microsecond) was much larger than the electric one (range 55-280 microsecond), which was in the order of jitter calculated on H-reflex studies; moreover, the former was organized in a bi- or trimodal distribution. On the contrary, no significant differences were observed between the two modalities when the jitter to nerve stimulation was taken into account. Possible contributions of corticocortical circuitries containing several synaptic interruptions during magnetic as opposed to electric transcranial stimulation, is discussed.

[2 cases of mitochondrial encephalomyopathy]. / Su due casi di encefalomiopatia mitocondriale.

Two cases of mitochondrial myopathy are described. An electrophysiological study was also accomplished to investigate the concomitant involvement of the central nervous system (CNS), by means of evoked potentials (EP). The EPs in fact can reveal minimal signs of CNS lesions also when muscular damage is the only clinical evidence.

A case of facial hemiatrophy associated with linear scleroderma and homolateral masseter spasm.

The rare combination of progressive facial hemiatrophy, linear scleroderma and spasm of the homolateral masseter muscle was observed in a 39 year old woman. The possible pathogenetic meaning of the association is discussed on the electrophysiological evidence and in the light of published cases.

[3 cases of essential blepharospasm: pathogenetic problems correlated]. / Tre casi di blefarospasmo essenziale: problemi patogenetici correlati.

Three clinical cases of essential blepharospasm are discussed. On the basis of both therapeutical results and a review of the literature, pathogenetic hypothesis concerning such pathology are reexamined.

[Bell's palsy. Longitudinal study of 120 cases]. / Paralisi di Bell. Studio longitudinale su 120 casi.

The Authors have studied 120 cases of Bell's palsy, who underwent regular controls along 360 days from the beginning of the disease. The study has been carried out by means of two different parameters of evaluation, a clinical and electrophysiological one, which allowed us to obtain very interesting results, especially as regards the prognostic aspect.