Predicting the Readmission and Mortality in Older Patients Hospitalized with Pneumonia with Preadmission Frailty

BACKGROUND

In older people, frailty has been recognized as an important prognostic factor. However, only a few studies have focused on multidimensional frailty as a predictor of mortality and readmission among inpatients with pneumonia.

OBJECTIVE

The present study aimed to assess the association between preadmission frailty and clinical outcomes after the hospitalization of older patients with pneumonia.

DESIGN

Single-center, retrospective case-control study.

SETTING

Acute phase hospital at Kobe, Japan.

PARTICIPANTS

The present study included 654 consecutive older inpatients with pneumonia.

MEASUREMENTS

Frailty status before admission was assessed using total Kihon Checklist (KCL) score, which has been used as a self-administered questionnaire to assess comprehensive frailty, including physical, social, and cognitive status. The primary outcome was a composited 6-month mortality and readmission after discharge.

RESULTS

In total, 330 patients were analyzed (median age: 79 years, male: 70.4%, median total KCL score: 10 points), of which 68 were readmitted and 10 died within 6 months. After multivariate analysis, total KCL score was associated with a composited 6-month mortality and readmission (adjusted hazard ratio, 1.07; 95% confidence interval, 1.02-1.12; p = 0.006). The cutoff value for total KCL score determined by receiver operating characteristic curve analysis was 15 points (area under the curve = 0.610). The group with a total KCL score ≥ 15 points had significantly higher readmission or mortality rates than the groups with a total KCL score < 15 points (p < 0.001).

CONCLUSIONS

Preadmission frailty status in older patients with pneumonia was an independent risk factor for readmission and survival after hospitalization.

Neuroleptic malignant syndrome with prolonged catatonia in a dopa-responsive dystonia patient

The authors describe a patient with dopa-responsive dystonia who developed neuroleptic malignant syndrome with prolonged catatonia following treatment with neuroleptic agents. Use of these agents probably expanded the patient's neuronal dysfunction beyond the nigrostriatal system to involve multiple dopaminergic systems. Electroconvulsive treatment alleviated the prolonged catatonia.

Heterogeneity of presenile dementia with bone cysts (Nasu-Hakola disease): three genetic forms

Nasu-Hakola disease (NHD) is an autosomal recessive disorder characterized by presenile dementia and bone cysts. Finnish patients revealed a large deletion in DAP12 gene encoding a key element for transducing activation signal. The authors examined six Japanese cases for DAP12 alleles. Five of the six had loss-of-function mutation, either a single-base deletion or a novel point mutation. The single patient without mutation normally expressed DAP12 protein. Japanese NHD has at least three genetic forms regarding DAP12.

Attenuated familial adenomatous polyposis associated with advanced rectal cancer in a 16-year-old boy: report of a case

We herein present a case of attenuated familial adenomatous polyposis (AFAP) with advanced rectal cancer in a 16-year-old boy. His mother and younger brother both had subcutaneous soft tissue tumors in the back and sparse-type colorectal polyposis. His mother also had dental anomalies and gastric fundic gland polyposis. The patient was admitted to our hospital for investigation of bloody stools. Barium enema and colonofiberscopy revealed advanced rectal cancer and sparse (<50) colorectal polyps. He also had dental anomalies, a subcutaneous soft tissue tumor in the back, and gastric fundic gland polyposis as extracolonic manifestations. A total proctocolectomy and ileoanal anastomosis were performed, and histological examination of the resected specimens confirmed moderately differentiated adenocarcinomas of the rectum with metastases to the regional lymph nodes. The other colorectal polyps were tubular adenomas with no evidence of malignancy. Germline mutations in the APC gene were observed in codons 486, 545, 1493, and 1556. This case serves to demonstrate that a total proctocolectomy with ileoanal anastomosis should be the procedure of choice for young patients found to have advanced rectal cancer associated with FAP.

Abnormal axonal inward rectifier in streptozocin-induced experimental diabetic neuropathy

In order to explore the pathophysiology of diabetic neuropathy, we studied serial changes of axonal excitability in 20 adult Wistar rats with streptozocin-induced diabetes using the technique of threshold electrotonus (TE). After persistent hyperglycaemia had developed, rats were divided into two groups: nine were fed a diet containing aldose reductase inhibitor (Epalrestat 30 mg/kg/day) (ARI(+) group) and 11 were fed a diet without the inhibitor (ARI(-) group). Eight normal control rats of similar age (NC group) were also studied. We monitored membrane properties of motor axons in the tail for 3 months using TE to measure the changes in excitability induced by subthreshold polarizing currents while recording compound muscle action potentials (CMAPs) in the tail muscle. The ARI(-) group showed a significant increase in CMAP latency 1 month after streptozocin injection, and by 3 months there was significantly lower excitability after hyperpolarization for 100 ms compared with the NC group. A similar change in TE was reproduced by injection of caesium chloride, an inhibitor of inward rectification. By contrast, the ARI(+) group exhibited no significant change in TE or latency at 3 months, although they showed significant body weight loss and hyperglycaemia. These findings indicate that inward rectification is reduced in an experimental model, as in human diabetes, and that blocking the polyol pathway with an ARI prevents this reduction. Reduced inward rectification potentiates conduction block caused by activity-dependent hyperpolarization and may underlie the decreased vibratory sensation seen in the early stage of diabetic neuropathy.

Abnormal premovement gating of somatosensory input in writer's cramp

One characteristic of focal dystonia is the sensory trick, by which sensory input to a certain area of the body can reduce abnormal contractions in muscles nearby. This suggests that adjusting the link between sensory input and movement allows motor commands to be issued more effectively from the brain. To explore this sensorimotor link, we studied the attenuation (gating) of somatosensory evoked potentials (SEPs) before and during hand movements in patients with writer's cramp. For premovement gating, 10 patients and 11 age-matched normal subjects were given a warning sound followed 1s later by an electric stimulus to the right median nerve at the wrist. The latter served both as a reaction signal to start a finger extension task and as the input to evoke SEPs over the scalp. Because reaction times always exceeded 70 ms, short-latency SEPs thus obtained were unaffected by the afferents activated by the movement. The amplitudes of frontal N30 components were significantly decreased over the frontal leads compared with SEPs elicited at rest (P: < 0.002) in the normal group, whereas significant gating was found not for N30 but for frontal P22 (P: = 0. 002) in the patient group. For midmovement gating studies, SEPs to the right median nerve stimulation were recorded in 16 patients and 12 age-matched normal subjects at rest, and during active and passive finger extension-flexion movements. In contrast to the premovement SEPs, the frontal N30 was equally gated during active and passive movements both in the patient (P: < or = 0.002) and the normal group (P: < or = 0.003). These findings indicate that in writer's cramp the sensitivity of sensory input channels from the hand is wrongly set by the central command to move. Perhaps the sensory trick, by supplying additional input not usually present during unobstructed movement, is a manoeuvre to correct this imbalance. Dystonia may result not only from abnormalities in the central motor command but also from disturbed central processing of sensory input.

High-frequency SEP components generated in the somatosensory cortex of the monkey

To investigate the origin of high-frequency somatosensory evoked potential (SEP) components, we recorded median nerve SEPs from the scalp and the depth in six monkeys. Laminar field potentials were analyzed in area 3b (N10; corresponding to human N20) and area 1 (P12; corresponding to human P25). After digital filtering (300-900 Hz), 4-6 components were identified, and the 1st to 4th peaks in area 3b (7-11 ms in latency) and the 3rd to 5th in area 1 (9-13 ms) showed clear polarity reversals between the surface and the depth of the cortex. These results provide direct evidence for intracortical origin of early high-frequency components in area 3b and of late ones in area 1.

Activity-dependent conduction block in multifocal motor neuropathy

Patients with multifocal motor neuropathy may complain of muscle fatigue, even though the degree of conduction block assessed at rest has improved with treatment. To explore the mechanism involved, we examined changes in muscle force during maximum voluntary contraction (MVC) and monitored conduction block before and after MVC in five patients with multifocal motor neuropathy. The results were compared with those for the contralateral unaffected homonymous muscles. For one patient, who had bilateral involvement, a normal subject of a similar age and stature served as the control. Results of conduction studies were also compared with those from six patients with amyotrophic lateral sclerosis (ALS) with similar compound muscle action potential (CMAP) amplitudes after proximal stimulation. During MVC for 60 s, the affected muscles developed prominent fatigue; the force at the end of contraction compared with the initial force was significantly lower for the affected muscles [42 +/- 19% (mean +/- standard deviation) of the initial force] than for the control muscles (94 +/- 9%; P = 0.01). After MVC, the amplitude ratio of CMAPs after proximal versus distal nerve stimulation transiently decreased to 19 +/- 14% of that before MVC in the affected muscles, but not in the control muscles (94 +/- 3.8% of that before MVC) and in patients with ALS (95 +/- 6.7%). In one patient with a focal lesion in the forearm, nerve excitability was monitored at the lesion site before and after MVC for 120 s. There were significant increases in axonal threshold (approximately 48%) and supernormality (approximately 135%) immediately after MVC, suggesting that the axonal membrane had undergone hyperpolarization and, by extrapolation, that this had precipitated the conduction block. This study is the first to show that activity-dependent conduction block plays a role in human disease by causing muscle fatigue.

Role of primary sensorimotor cortices in generating inhibitory motor response in humans

To clarify the mechanism by which inhibitory motor responses such as cortical negative myoclonus are generated in humans, three patients with medically intractable partial epilepsy (two with frontal lobe epilepsy and one with parietal lobe epilepsy) were studied by means of direct cortical stimulation with a single electric pulse through subdural electrodes. All underwent chronic long-term video/EEG monitoring, cortical mapping by 50 Hz electric cortical stimulation and recording of cortical somatosensory evoked potentials with chronically implanted subdural grid electrodes (3 mm in diameter and centre-to-centre distance of 1 cm) to map both epileptogenic and functional zones. After these clinical evaluations, cortical stimulation by single electric pulse (0.3 ms duration, 1 Hz) was carried out through pairs of subdural electrodes located at the primary sensorimotor area (MI-SI), pre-supplementary motor area (pre-SMA) and lateral negative motor area (lateral NMA), while surface EMG was recorded from the muscles of the contralateral hand. The results showed that (i) in all subjects, single pulse stimulation of MI-SI elicited a motor evoked potential (MEP) followed by a silent period (SP) in the contralateral distal hand muscles, the latter lasting 300 ms after the stimulus. The duration of SP was proportional to the size of the preceding MEP. In one subject, SP without any preceding MEP was elicited, and, in another subject, there was a short SP immediately before MEP in the contralateral thenar muscle. (ii) Following the stimulation of either pre-SMA or lateral NMA, no SP was observed. It is concluded that the inhibitory mechanism within the MI-SI, but probably not in the non-primary motor areas, either closely linked to or completely independent of excitation, most likely plays an important role in eliciting brief negative motor phenomena such as cortical negative myoclonus or SP.

F-wave latency serves as the most reproducible measure in nerve conduction studies of diabetic polyneuropathy: multicentre analysis in healthy subjects and patients with diabetic polyneuropathy

AIMS/HYPOTHESIS

For use in future drug development for diabetic polyneuropathy, we conducted multicentre trials to assess the reproducibility of nerve conduction studies.

METHODS

All measurements were repeated twice at a time interval of 1-4 weeks in 132 healthy subjects (63 men) and 172 patients (99 men) with diabetic polyneuropathy. Using a standardised method, 32 centres participated in the study of control subjects and 65, in patients with diabetic polyneuropathy. Motor nerve conduction studies consisted of stimulating the left median and tibial nerves and recording the compound action potential from abductor policis and adductor hallucis for measuring amplitude, terminal latency and minimal F-wave latency. For sensory conduction studies, sensory nerve action potentials were recorded antidromically from the second digit and the posterior aspect of the lateral malleous after distal stimulation of the left median and sural nerves. We also calculated motor conduction velocity, F-wave conduction velocity and sensory conduction velocity. The relative intertrial variation and intraclass correlation coefficient were used as an index of reproducibility.

RESULTS

Of all the measurements, F-wave latency yielded the highest intraclass correlation coefficient with the smallest relative intertrial variation for both median and tibial nerves in both groups.

CONCLUSION/INTERPRETATION

Median and tibial F-wave latency provide the most reproducible measures for a nerve conduction study, serving as one of the best measures in multicentre drug trials for diabetic polyneuropathies.

Membranous lipodystrophy presenting with palilalia: a PET study of cerebral glucose metabolism

A case of membranous lipodystrophy (Nasu-Hakola disease; NHD) associated with palilalia was reported. A 38-year-old Japanese woman developed walking difficulty in her twenties. At age 35 she manifested neuropsychiatric symptoms characterized by euphoria, palilalia and dementia. A bone marrow biopsy showed periodic acid Schiff-positive membranous cystic lesions in the adipose tissue. Positron emission tomography with (18F)-2-fluoro-2-deoxy-D-glucose disclosed that regional cerebral glucose metabolism was decreased in the bilateral frontal white matter with mild hypometabolism in the thalamus and basal ganglia; all predominantly on the right. Taken together with the previous postmortem findings, it is postulated that frontal lobe hypofunction, predominantly in the right hemisphere, produced the unique neuropsychiatric symptoms in this patient.

Cortical potentials associated with voluntary mandibular movements

Movement-related cortical potentials (MRCPs) are negative potentials over the scalp, which gradually increase prior to voluntary movements, and might be applied to elucidate the cortical efferent function of the mandibular movements. We compared the MRCPs accompanying various mandibular movements to study the motor control mechanism underlying these movements. Electroencephalograms (EEGs) were recorded from 11 electrodes placed over the scalp (F3, Fz, F4, T3, C3, Cz, C4, T4, P3, Pz, and P4), according to the International 10-20 System, and electromyograms (EMGs) were obtained from surface electrodes over the masseter muscle and the anterior belly of the digastric muscle. Ten healthy subjects were requested to make brisk and self-paced mandibular movements in 4 different directions (mouth-opening and -closing, and left and right lateral movements). We obtained MRCPs by averaging the EEG, using the visually determined EMG onset as a trigger signal. In all the movements, a slowly increasing, bilaterally widespread negativity starting 1.5 to 2.0 sec before the EMG onset (Bereitschaftspotential, or BP proper) was observed, with the maximum over the vertex region. The negative slope (NS') occurred about 300 to 700 msec before the EMG onset. The cortical maps of BP/NS' (BP and NS' combined), immediately prior to the mouth-opening and closing, showed a symmetrical distribution, whereas that for the lateral movements showed a tendency of predominance over the hemisphere ipsilateral to the direction of the movement. BP/NS' amplitudes at the onset of movement differed significantly or tended to do so between open, close, and lateral movements, suggesting that MRCP recordings may thus provide a means to explore the role of the cerebral cortex in the control of mandibular movements.

Chronic motor axonal neuropathy associated with antibodies monospecific for N-acetylgalactosaminyl GD1a

We report on three patients with chronic motor neuropathy who had elevated titers of immunoglobulin (Ig)G antibodies against N-acetylgalactosaminyl GD1a (GalNAc-GD1a) and normal titers of antibodies against other gangliosides. Presenting with progressive muscular atrophy, fasciculations, and no sensory deficits, the patients had been diagnosed to have motor neuron disease. Electrodiagnostic features were predominantly axonal. Two patients clinically improved after intravenous Ig infusion and cyclophosphamide therapy. Increased titers of IgM antibodies to GalNAc-GD1a were also found in two of 15 patients with multifocal motor neuropathy with conduction block but were associated with concomitant rise of anti-GM1 antibodies. These three cases represent a chronic motor axonal neuropathy in which antibody testing for a minor ganglioside was helpful for instituting therapy.

Effect of maturation on nerve excitability in an experimental model of threshold electrotonus

Threshold electrotonus (TE) is a new tool for investigating axonal function noninvasively in vivo. To increase its potential clinical value, we developed a rat model of TE, and examined the effects of maturation and pharmacological intervention. We recorded TE in 92 male rats (body weight 90-650 g) by stimulating the motor nerve in the tail, and applying 100-ms conditioning currents. Motor conduction velocities increased up to a body weight of 330 g, and remained constant thereafter. TE in mature rats was similar to that in humans, and two parameters were analyzed: TEd(10-20) or the mean threshold reduction 10-20 ms after the onset of the depolarizing conditioning current at 40% of threshold intensity; and TEh(10-20) or the corresponding threshold decrease on hyperpolarization. Like latency, the absolute value of TEh(10-20) decreased up to 330 g, and then stabilized thereafter, probably reflecting the progressive increase in the axonal diameter and relative reduction in internodal impedance. In contrast, TEd(10-20) gradually decreased up to 330 g, and then jumped to a higher level, which was maintained for animals of >400 g. 4-Aminopyridine, a blocker of fast potassium channels, selectively increased TEd(10-20) only in the immature or young (<330 g) rats. This suggests that, in the mature animals, fast potassium channels become sequestrated from the nodal membrane and not activated in response to nodal depolarization. These findings indicate that mature rats (>400 g) may provide a useful experimental model for interpreting abnormal TE responses in humans, and provide evidence for nonlinear maturation of potassium channel function in myelinated axons.

Pre-movement gating of short-latency somatosensory evoked potentials

Somatosensory evoked potentials (SEPs) are reduced in amplitude during movement (gating). The mechanism involves central gating of afferent input and competition from other afferents activated by the movement. We distinguished these two by giving 11 normal subjects a warning sound followed 1 s later by an electric stimulus to the right median nerve at the wrist. The latter served both as a cue to start a finger movement and as stimulation to evoke SEPs. Gating effects were widespread in frontal (N30) and central (N60) areas, but were also seen, albeit to a lesser extent, in the recordings at P3 (P30). Since finger movement began after the stimulus, such gating must have been purely central in origin, presumably reflecting motor preparation.

An electrophysiological study of the corticospinal projections in amyotrophic lateral sclerosis

OBJECTIVE

To elucidate the pattern of corticospinal tract involvement in patients with amyotrophic lateral sclerosis (ALS), we analyzed motor evoked potential (MEP) waveforms and their relationship to the behaviour of single motor units using the peristimulus time histogram (PSTH) technique.

METHODS

Abnormality of the corticospinal pathways was studied in 35 ALS patients using MEPs. PSTHs were also constructed to assess the effect of magnetic cortical stimulation on the discharge pattern of a voluntarily activated motor unit.

RESULTS

MEPs showed a complex waveform in 10 out of 18 (56%) ALS patients with upper motor neuron signs (UMN). PSTHs revealed double primary peaks (PPs), PP1 and PP2, in 6 out of 16 motor units (38%) in ALS with UMN, as compared to only 2 out of 16 (13%) motor units in multiple sclerosis or cerebrovascular disease with UMN. None of the patients with lower motor neuron diseases or ALS without UMN had these abnormalities. The late component of complex MEPs showed a good correlation to PP2 (P < 0.0001), both probably being mediated by relatively preserved slower conducting corticospinal volleys.

CONCLUSIONS

These findings suggest preferential involvement of the fast conducting direct corticospinal tracts, sparing the slower or polysynaptic projections in ALS.

[Myasthenia gravis with electrophysiological features of Lambert-Eaton myasthenic syndrome: usefulness of serum autoantibodies assay and neuromuscular junction biopsy]

A 60-year-old man with a 40-year history of seronegative ocular myasthenia gravis (MG) developed generalized weakness cumulating crisis over 2 years. On admission, ophthalmoplegia, severe ptosis and marked generalized weakness were observed without autonomic symptoms and signs. The deep tendon reflexes were decreased, but were normalized after repeated muscle contractions. EMG of the abductor digiti minimi muscle showed low amplitude in compound muscle action potentials (0.6 mV), waxing phenomenon (292%) with 20 Hz repetitive nerve stimulation (RNS), waning phenomenon (34%) in 3 Hz RNS, and posttetanic facilitation (393%). Stimulated single fiber EMG showed reduced jitter with higher stimulation rates. Serum anti-P/Q-type voltage-gated calcium channel antibodies were negative with no evidence of malignancy. Sensitive assay of acetylcholine receptor antibody in serum revealed a positive titer, while conventional assay was negative. A muscle biopsy was performed and immune complex deposition was demonstrated at the endplate. A nearly complete clinical remission and normalization of electrophysiological features followed immunoadsorption and prednisolone therapy. A sensitive immunoassay of acetylcholine receptor antibodies and immunolocalization of complement at the endplate are useful diagnostic tools in cases presenting with features of myasthenia gravis and Lambert-Eaton myasthenic syndrome.

Cortical distribution of Bereitschaftspotential and negative slope potential preceding mouth-opening movements in humans

Cortical potentials associated with the voluntary movement of various body parts are known as movement-related cortical potentials, which allow evaluation of the cortical efferent function and other higher functions controlling voluntary movement. The cortical potentials have three main components: the Bereitschaftspotential (or 'readiness potential'), the negative slope and the motor potential. Here, the cortical potentials preceding mouth-opening movements were recorded to investigate which of these components could be observed. Electroencephalograms (EEGs) were recorded from 11 electrodes placed over the scalp (F3, Fz, F4, T3, C3, Cz, C4, T4, P3, Pz and P4) according to the international 10-20 system. Electromyograms (EMGs) were recorded from the anterior belly of the digastric and the masseter. The 10 healthy participants were requested to make brisk and self-paced mouth-opening movements. All data were digitized with a sampling frequency of 200 Hz and stored for off-line analysis. Movement-related cortical potentials were obtained by averaging the EEG, using the digastric EMG onset as a trigger signal. The Bereitschaftspotential was recorded as a gradually increasing, bilaterally widespread negativity starting 1.7 s (mean) +/-0.23 s (S.D.) before the onset of the opening movement. The amplitude, which was measured at movement onset, was maximum at Cz (3.8 +/- 1.3 microV). The negative slope was observed 500-600 ms before the movement onset, and the motor potential was not clearly identified, because of postmotion artefacts. The cortical maps of the Bereitschaftspotential and negative slope combined together before to the mouth opening showed a symmetrical distribution with a maximum at the vertex region. The study reveals that the Bereitschaftspotential and the negative slope, two components of the movement-related cortical potentials, can be observed preceding mouth-opening movements and are similar to those associated with other voluntary movements. Findings such as distribution, amplitude and onset of the potentials could provide important information for studying the cortical control of mandibular movements.

[Abnormal hyperexcitability in ALS]

The defect of neuromuscular transmission is one of the important signs in ALS. The amplitude of a single motor unit potential from patients with ALS often decrease during tonic voluntary contraction. This phenomenon is closely correlated with fatigue seen in the patient. Overfunctioning of Ach release in the nerve terminal might cause the failure of neuromuscular transmission in ALS. Fasciculations is an another characteristic sign and considered mainly to be peripheral axons in origin. It is postulated that the dysfunction of potassium channel in ALS axons makes the hyperexcitability of the axon membrane, causing fasciculations. Magnetic cortical stimulation sometimes evokes the same potentials as fasciculations, implying the hyperexcitability might be present also in spinal motoneurons or even in pyramidal neurons in ALS. All of these findings lead to the hypothesis that hyperexcitability or overactivity of central and peripheral motoneurons is an essential feature in ALS.

Effect of ultrahigh-dose methylcobalamin on compound muscle action potentials in amyotrophic lateral sclerosis: a double-blind controlled study

To develop a symptomatic treatment for amyotrophic lateral sclerosis, we compared the effects of ultrahigh-dose and low-dose (25 and 0.5 mg/day, intramuscularly, for 14 days) methylcobalamin on averaged compound muscle action potential amplitudes (CMAPs) in a double-blind trial. No significant changes in CMAP amplitude were found in 12 patients who had the low-dose treatment at either 2 or 4 weeks after start of treatment. By contrast, 12 patients assigned to the ultrahigh-dose group demonstrated a significant increase at 4 weeks. This method may provide a clinically useful measure to improve or retard muscle wasting, if a larger extended trial fulfills its promise.

Muscle afferent block for the treatment of oromandibular dystonia

Oromandibular dystonia is a focal dystonia involving the masticatory and tongue muscles, causing difficulties in speech or mastication. We treated 13 patients with this condition by injecting diluted lidocaine and alcohol intramuscularly. This method is aimed at reducing muscle spindle afferent activity. The symptoms had been resistant to other therapies such as pharmacotherapy or dental treatment. All patients showed clinical improvement after this therapy with reduced EMG activities in the affected muscles, whereas control injection of normal saline gave no changes in EMG activities. The overall subjective improvement was 57.7 +/- 25.1% (mean +/- standard deviation) in a self-rating scale. The mean response of the jaw elevator muscles (70 +/- 13.1%) was significantly higher (p < 0.02, t test) than that of the depressor muscles (38 +/- 28.4%). Despite the precise mechanism being unknown, this difference might be related to the smaller number of muscle spindles in the depressor than the elevator muscles. This therapy is useful for the treatment of drug-resistant oromandibular dystonia.

Electrophysiological studies of early stage corticobasal degeneration

We conducted electrophysiological studies in two Asian patients with probable corticobasal degeneration (CBD). The duration of illness from onset was 16 and 20 months, respectively. The clinical manifestations were markedly asymmetric and characterized by cortical sensory loss, apraxia, action myoclonus, action tremor, and akinetic-rigid parkinsonism. Neither patient responded to levodopa therapy. Simple photon-emission computed tomography (SPECT) study showed significantly decreased regional cerebral blood flow in the frontoparietal areas and thalamus opposite to the predominantly affected limb. A series of electrophysiological studies failed to identify giant somatosensory evoked potentials (SEPs), enhanced long latency electromyography (EMG) reflex, and cortical spikes preceding myoclonic jerk. However, the earliest cortical component of the median nerve SEP was exclusively enlarged in one patient and preserved with depression of the subsequent components in the other patient. Significantly shorter postmotor-evoked potential (MEP) silent period was found after the transcranial magnetic stimulation of the motor cortex in both patients. CBD is a unique clinical entity characterized by action myoclonus probably the result of the pathologic hyperexcitability of the motor cortex, based on a loss of inhibitory input from the sensory cortex.

The physiological effect of anti-GM1 antibodies on saltatory conduction and transmembrane currents in single motor axons

Anti-ganglioside (anti-GM1) antibodies have been implicated in the pathogenesis of Guillain-Barré syndrome, multifocal motor neuropathy and motor neuron diseases. It has been held that they may interfere with saltatory conduction by blocking sodium channels. We tested this hypothesis by analysing action potentials from 140 single nerve fibres in 22 rat ventral roots using external longitudinal current measurement. High-titre anti-GM1 sera from Guillain-Barré syndrome or multifocal motor neuropathy patients, or anti-GM1 rabbit sera were applied to the rat ventral root, where saltatory conduction in single motor fibres was serially observed for 4-12 h (mean 8.2 h). For control experiments, we also tested anti-galactocerebroside (anti-GalC) sera, which causes acute demyelinative conduction block, and tetrodotoxin (TTX), a sodium channel blocker. Conduction block was found in 82% of the fibres treated with anti-GalC sera and 100% treated with TTX, but only in 2% (one out of 44) treated with the patients' sera and 5% (two out of 38) treated with rabbit anti-GM1 sera. All the nodes blocked by anti-GM1 sera revealed intense passive outward membrane current, in the internode just beyond the last active node. This pattern of current flow was similar to that in fibres blocked by demyelination with anti-GalC sera, and quite different from that seen in fibres blocked by reducing sodium currents with TTX. Our findings suggest that anti-GM1 sera neither mediate conduction block nor block sodium channels on their own. We conclude that physiological action of the antibody alone is insufficient to explain clinically observed conduction block in human diseases.