Saccadic latency measurements in dementia.

We measured saccadic latencies in patients with Alzheimer's dementia (AD) and other types of dementia. The saccadic latencies for both groups were considerably longer than those for age-matched controls. The prolongation was as extensive in patients with other types of dementia as it was in those with AD. There was no correlation between latency and the severity of the dementia.

Successful treatment of acquired pendular elliptical nystagmus in multiple sclerosis with isoniazid and base-out prisms.

We treated 3 multiple sclerosis patients who had pendular nystagmus with isoniazid (800 to 1,000 mg/d). Isoniazid abolished the nystagmus and relieved oscillopsia in 2 patients but was ineffective in the 3rd in whom the nystagmus was damped with convergence and vision improved with converging (base-out) prisms.

Unilateral occipital lesion causing hemianopia affects the acoustic saccadic programming.

Infrared oculographic recordings of saccades evoked by auditory or visual targets in four patients with hemianopia due to an occipital lesion showed that these patients employed a different strategy to find visual and auditory targets in each hemifield. In the seeing hemifield, the patients acquired auditory targets with both monosaccadic and multiple saccadic refixations. The first saccade, the largest, brought the eyes toward the target; the following smaller saccades completed the search as in normal subjects. Saccades to visual targets consisted of one orthometric saccade or two saccades. By contrast, in the blind hemifield the patients acquired auditory targets by a staircase strategy consisting of stepwise saccadic search movements similar to those used for visual targets in the same hemifield. The similarity of strategy to auditory and visual targets suggests a common motor program controlled by the visual input. The latency, accuracy, and velocities of visual and acoustic responses were equal in both hemifields.

Evoked potentials in patients with non-neurological Wilson's disease.

In Wilson's disease neurological manifestations result from the damage in the basal ganglia, even if a widespread degeneration of the brain occurs. The few studies performed using evoked potentials with the aim of identifying subclinical dysfunction in the three major sensory pathways have never shown abnormalities in patients without neurological manifestations. To verify this observation we studied 12 patients suffering from Wilson's disease in a pre-neurological stage by using pattern visual evoked potentials (VEPs), somatosensory evoked potentials (SEPs) to median nerve stimulation and brainstem auditory evoked potentials (BAEPs). Four of these patients had not yet been treated with penicillamine or trientine (triethylenetetramine dihydrochloride), while the remaining 8 patients were on treatment for at least 1 year. In 3 patients of this second group and in 1 patient of the first group we observed a significant (3 SD over the mean) increase in P100 wave latency, while SEPs and BAEPs were found to be abnormal in only 1 patient, respectively.

Upbeat nystagmus as an early sign of cerebellar astrocytoma.

A boy with a left-hemispheric cerebellar astrocytoma had upbeat nystagmus exhibiting increasing-velocity slow phases. The nystagmus improved after excision of the tumour.

Modulation of flexor carpi radialis H reflex by lateral tilts in man.

Static vestibular influences on upper limb flexor tone were studied in man by analyzing the changes in flexor carpi radialis H reflex area with lateral tilting of the longitudinal body axis. Ten healthy volunteers and 2 labyrinthine defective patients were tested in an experimental situation designed to minimize all afferent inputs except vestibular ones. Each subject was seated on a chair which could be tilted laterally to the left or the right from the vertical. Head and trunk were fixed upright, upper and lower limbs in half-flexed position and forearm in an intermediate position between supination and pronation. Lateral tilting was applied at random from the vertical (0 degrees control position) to left and right (4 degrees, 8 degrees, 12 degrees, 16 degrees, 20 degrees test positions). Each test position was followed by a return to 0 degrees and in each control and test position 20 consecutive H reflexes were recorded. The data observed in the normal subjects showed flexor tone inhibition in the arm which was tilted downwards and facilitation in the contralateral arm. These findings suggest that in man, like in animals, labyrinth reflexes act asymmetrically and in the opposite direction to neck reflexes.

Audio-ocular response: saccadic programming.

The eye movements elicited by auditory stimuli--the audio-ocular response (AOR)--differ from those made in response to a visual target. The movements consist of both monosaccadic and multiple saccadic refixations (MSR). In visual refixation, monosaccadic refixations are always accurate; in AOR, they rarely are. In MSR, many strategies were used in the attempt to find the target but they were not always successful. However, final amplitudes of the total refixation were quite accurate in both MSR and monosaccadic refixations. Velocity profiles of the AOR showed such anomalies as discrete decelerations and multiple, closely-spaced saccades. These data suggest that, without visual feedback, the location of acoustic targets is difficult. In the absence of visual afference, when vigilance may be decreased by the lack of arousal, the velocity profiles also became abnormal, even at small amplitudes. Thus, for cockpit warning devices, a combination of auditory and visual indicators should be used.

Diagnostic value of extensor digitorum brevis F-wave in L5 root compression.

The sensibility of F-wave in detecting lumbosacral radicular compression has been found to range from 65% to 18%. The present study was performed on 24 patients suffering from unilateral L5 compressive radiculopathy. The aim was to verify the reliability of extensor digitorum brevis (EDB) F-wave in the diagnosis of L5 root impairment, by using different parameters such as minimal, mean, maximal latency and the difference of these parameters between the affected and unaffected sides. In all patients conventional needle EMG was also performed bilaterally. While the needle EMG showed abnormalities in L5 innervated muscles of all patients, at least one of the different EDB F-wave parameters was found to be abnormal in only 7 patients (29.2%). Moreover no significant relation was observed between the severity of EMG and F-wave abnormalities. We conclude that conventional needle EMG appears to be the most useful electrophysiological technique in the diagnosis of L5 compressive radiculopathy, while EDB F-wave does not provide additional information.

Eating seizures and distraction-arousal functions. A case study.

Reports of epileptic seizures evoked by eating are very scarce in the literature. A review of the reported cases suggests that various mechanisms may act as triggering factors in this form of reflex epilepsy. We studied a 17-year-old boy in whom the seizures precipitated by eating had been prevented by giving him some alerting stimuli during the meal. The attention-arousal coupling sustained by the meal seems to play a role in triggering the attacks.

Tonic neck reflexes on upper limb flexor tone in man.

The asymmetric tonic neck reflexes on upper limbs in man have been studied by analyzing the changes in flexor carpi radialis H-reflex amplitude following body rotation around the longitudinal axis with a stationary head. In eight normal subjects 15 consecutive H-reflexes were recorded from the right flexor carpi radialis muscle at each test position. The tested body rotation angles were 4, 8, 12, 16, and 20 degrees both to the right side and to the left side. Before and after each test position 15 H-reflexes were recorded at 0 degrees. The linear correlation coefficient r, computed by plotting the H-reflex amplitudes against the relevant body rotation angles, was significant in all the subjects. The FCR H-reflex amplitude increased with contralateral body rotation (i.e., ipsilateral head rotation) and decreased with ipsilateral body rotation (i.e., contralateral head rotation). It has been suggested that these findings, which are opposite to those observed in animal experiments, are the consequence of the acquired antigravity function of upper limb flexor muscles in man.

Influences of neck receptors on soleus motoneuron excitability in man.

We studied the influence of the asymmetric tonic neck reflexes on the excitability of the human soleus motoneuronal pool by mapping the H amplitude as a function of rotation of the body relative to the fixed head. Eight normal adult volunteers were tested. On each subject 15 consecutive H reflexes were recorded from the right soleus muscle, for each of the following test position, 4 degrees, 8 degrees, 12 degrees, 16 degrees, as well as at the control position (0 degrees), both before and after each change in body position. Our results showed that the H reflex amplitude was progressively facilitated for contralateral rotation in respect to the recording side and conversely inhibited for ipsilateral rotation. The results indicate that neck receptors of one side enhance the excitability of the contralateral soleus motoneurons and depress the ipsilateral ones.

Diabetic polyneuropathy and insulin secretion in type II diabetic patients.

Electrophysiological examination was performed on 50 type II diabetic patients to verify whether insulin secretory reserve is a factor influencing the susceptibility to develop polyneuropathy. The results showed that less significant metabolic derangement related to high insulin secretory reserve, and not the high insulin secretory reserve by itself, may prevent the development of neuropathic disorders. These data are consistent with the current opinion that diabetic polyneuropathy is the consequence of the metabolic derangement caused by chronic hyperglycemia.

Carbamazepine versus diphenylhydantoin in the treatment of myotonia.

A double-blind controlled trial was performed on 6 patients affected with Steinert's disease in order to evaluate the efficacy of two different dosages of diphenylhydantoin (PHT, 200 and 300 mg/day) and carbamazepine (CBZ, 600 and 800 mg/day) on the myotonic afterdischarge. Both dosages of PHT and CBZ induced a significant improvement of myotonia. For PHT a trend towards decreased efficacy is pointed out at toxic or at high dosages.

Long-term therapy with carbamazepine: effects on nerve conduction velocity.

Peripheral nerve function was evaluated in 30 epileptic patients on chronic therapy with carbamazepine (CBZ) and 20 healthy controls. The electrophysiological data indicated a mild progressive reduction of both motor and sensory conduction velocity in the patients on long-term treatment with the drug. The impairment of nerve function paralleled the duration of therapy (i.e. 1 through 3 years). CBZ plasma levels were constantly within the therapeutic range. Folic acid levels were below normal in about 50% of the subjects. In the absence of other evidence, the hypothesis cannot be excluded that folate deficiency may have played some role in the development of the peripheral nerve dysfunction.

Downbeat nystagmus with a pseudocycloid waveform: improvement with base-out prisms.

Downbeat nystagmus in primary position and oscillopsia resulted from nutritional deficiency during prolonged intravenous therapy of a patient with hyperemesis gravidarum. Wide bandwidth infrared oculography demonstrated a pseudocycloid nystagmus waveform with an increasing-velocity exponential slow phase. Because the oscillopsia decreased and the nystagmus was damped with convergence, visual acuity improved with the addition of base-out prisms to each spectacle lens.

Brain uptake of carbamazepine in the cat.

Carbamazepine (CBZ) was determined by EMIT assay in plasma, cerebrospinal fluid (CSF), and brain samples of cats after administration of the drug (40 mg/kg, i.p.). Plasma and CSF levels increase in a parallel manner from time 0 to 90 min after completion of injection, indicating a passive transport from one body fluid to the other. Brain levels reach a steady state at 15 min, with no significant difference being found between the concentrations at 15, 30, 60, and 90 min postinjection; this indicates that substantial early binding occurs in the brain. Since peak CSF concentrations occur at 90 min, concomitant with those for plasma, while brain levels are already high at 15 min, it is likely that CBZ enters the two compartments by independent mechanisms.

Variable waveforms in downbeat nystagmus imply short-term gain changes.

A patient with downbeat nystagmus subsequent to ankylosing spondylitis was studied. His nystagmus was found to exhibit both increasing- and decreasing-velocity exponential slow phases as well as the linear form more often reported. Alternation between waveforms sometimes occurred on a beat-to-beat or even intrabeat basis. Possible explanations for all three waveforms are presented in terms of short-term gain changes in cerebellar compensation for leaky brainstem neural integrators. A computer model was developed and its results are discussed.

Old and new genetics help ordering loci at the telomere of the human X-chromosome long arm.

A Sardinian pedigree described in 1964 for having been found to segregate at the X-linked loci for the Xga antigen, G6PD deficiency, Protan and Deutan color blindness, with an instance of recombination between the last two loci, was re-examined with respect to four common X-linked DNA polymorphisms detected by molecular probes homologous to critical subregions of the human X chromosome. Two branches of this pedigree--including the one with the Protan-Deutan recombinant--were found to segregate also for the common BamHI polymorphism identified with the cDNA probe pHPT-2 or the HPRT gene (Xq26). The analysis of the chromosome haplotypes in the male offspring of the phase known penta-heterozygous mother suggests that the probable order of the relevant loci is HPRT, Deutan, G6PD, Protan, Xq telomere. Though we are fully aware of the risks of generalizing the significance of observations made on a single exceptional pedigree, we believe that this report outlines the potential of families of the type described as research tools to resolve the linear order of tightly X-linked loci and to investigate the biology of genetic recombination in humans.