SUMMARY1. In ten normal volunteers, a transcranial magnetic or electric stimulus that was subthreshold for evoking an EMG response in relaxed muscles was used to condition responses evoked by a later, suprathreshold magnetic or electric test shock. In most experiments the test stimulus was given to the lateral part of the motor strip in order to evoke EMG responses in the first dorsal interosseous muscle (FDI).2. A magnetic conditioning stimulus over the hand area of cortex could suppress responses produced in the relaxed FDI by a suprathreshold magnetic test stimulus at interstimulus intervals of 1-6 ms. At interstimulus intervals of 10 and 15 ms, the test response was facilitated.3. Using a focal magnetic stimulus we explored the effects of moving the conditioning stimulus to different scalp locations while maintaining the magnetic test coil at one site. If the conditioning coil was moved anterior or posterior to the motor strip there was less suppression of test responses in the FDI. In contrast, stimulation at the vertex could suppress FDI responses by an amount comparable to that seen with stimulation over the hand area. With the positions of the two coils reversed, conditioning stimuli over the hand area suppressed responses evoked in leg muscles by vertex test shocks.4. The intensity of both conditioning and test shocks influenced the amount of suppression. Small test responses were more readily suppressed than large responses. The best suppression was seen with small conditioning stimuli (0 7-0 9 times motor threshold in relaxed muscle); increasing the intensity to motor threshold or above resulted in less suppression or even facilitation.5. Two experiments suggested that the suppression was produced by an action * Present address: Third Department of Internal Medicine, Division of Neurology, Yamagata University, School of Medicine, 2-2-2 Iida-Nishi, Yamagata City 990-23, Yamagata, Japan.

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The presence of autoantibodies to voltage-gated potassium channels and glutamic acid decarboxylase suggests that the immune system may contribute to certain forms of epilepsy or seizure-associated disorders. Further studies are needed to determine whether the antibodies are pathogenic.

The largest kindred with inherited prion disease P102L, historically Gerstmann-Sträussler-Scheinker syndrome, originates from central England, with émigrés now resident in various parts of the English-speaking world. We have collected data from 84 patients in the large UK kindred and numerous small unrelated pedigrees to investigate phenotypic heterogeneity and modifying factors. This collection represents by far the largest series of P102L patients so far reported. Microsatellite and genealogical analyses of eight separate European kindreds support multiple distinct mutational events at a cytosine-phosphate diester-guanidine dinucleotide mutation hot spot. All of the smaller P102L kindreds were linked to polymorphic human prion protein gene codon 129M and were not connected by genealogy or microsatellite haplotype background to the large kindred or each other. While many present with classical Gerstmann-Sträussler-Scheinker syndrome, a slowly progressive cerebellar ataxia with later onset cognitive impairment, there is remarkable heterogeneity. A subset of patients present with prominent cognitive and psychiatric features and some have met diagnostic criteria for sporadic Creutzfeldt-Jakob disease. We show that polymorphic human prion protein gene codon 129 modifies age at onset: the earliest eight clinical onsets were all MM homozygotes and overall age at onset was 7 years earlier for MM compared with MV heterozygotes (P = 0.02). Unexpectedly, apolipoprotein E4 carriers have a delayed age of onset by 10 years (P = 0.02). We found a preponderance of female patients compared with males (54 females versus 30 males, P = 0.01), which probably relates to ascertainment bias. However, these modifiers had no impact on a semi-quantitative pathological phenotype in 10 autopsied patients. These data allow an appreciation of the range of clinical phenotype, modern imaging and molecular investigation and should inform genetic counselling of at-risk individuals, with the identification of two genetic modifiers.

SummaryBackgroundThe propagation of prions, the causative agents of Creutzfeldt-Jakob disease and other human prion diseases, requires post-translational conversion of normal cellular prion protein to disease-associated forms. The antimalarial drug quinacrine (mepacrine) prevents this conversion in vitro, and was given to patients with various prion diseases to assess its safety and efficacy in changing the course of these invariably fatal and untreatable diseases.MethodsPatients with prion disease were recruited via the UK national referral system and were offered a choice between quinacrine (300 mg daily), no quinacrine, or randomisation to immediate quinacrine or deferred quinacrine in an open-label, patient-preference trial. The primary endpoints were death and serious adverse events possibly or probably related to the study drug. This study is registered, ISRCTN 06722585.Findings107 patients with prion disease (45 sporadic, two iatrogenic, 18 variant, and 42 inherited) were enrolled, 23 in a pilot study and 84 in the main study. Only two patients chose randomisation; 40 took quinacrine during follow-up (37 who chose it at enrolment). Choice of treatment was associated with disease severity, with those least and most severely affected more likely to choose not to receive quinacrine. 78 (73%) patients died: one randomly assigned to deferred treatment, 26 of 38 who chose immediate quinacrine, and 51 of 68 who chose no quinacrine. Although adjusted mortality was lower in those who chose to take quinacrine than in those who did not, this was due to confounding with disease severity, and there was no difference in mortality between groups after adjustment. Four of 40 patients who took quinacrine had a transient response on neurological rating scales. Only two of 14 reported serious adverse events were judged quinacrine-related.InterpretationQuinacrine at a dose of 300 mg per day was reasonably tolerated but did not significantly affect the clinical course of prion diseases in this observational study.FundingDepartment of Health (England); UK Medical Research Council.

Chorea-acanthocytosis (ChAc) is a severe, neurodegenerative disorder that shares clinical features with Huntington's disease and McLeod syndrome. It is caused by mutations in VPS13A, which encodes a large protein called chorein. Using antichorein antisera, we found expression of chorein in all human cells analyzed. However, chorein expression was absent or noticeably reduced in ChAc patient cells, but not McLeod syndrome and Huntington's disease cells. This suggests that loss of chorein expression is a diagnostic feature of ChAc.

Abstractexamined data from a community based stroke register Objective-To determine whether diurnal varia-in which the type of stroke was determined in 90% of tion occurs in the onset of stroke.cases.Design-Community based study over four years. Setting-Oxfordshire, United Kingdom. Subjects-105 000 people, of whom 675 had a first Patients and methods ever stroke. 545 had a cerebral infarction, 66 hadThe Oxfordshire community stroke project is a primary intracerebral haemorrhage, 33 had sub-prospective, community based study of first ever arachnoid haemorrhage, and in 31 the type of stroke stroke in a defined population of about 105 000 people was not known.in Oxfordshire. Definitions of type of stroke and Main outcome measures-Time of stroke and details of the methods used in the project are given degree of activity at onset.elsewhere.910 Six hundred and seventy five cases of Results-In the 578 patients for whom it was clinically definite first ever stroke were registered over known whether onset occurred while asleep or four years. Complete case ascertainment was obtained awake, the proportion with onset during sleep was through the collaboration of general practitioners and 25% (135/545) for cerebral infarction, 17% (11/66) for examination of hospital admission registers, the primary intracerebral haemorrhage, and 0% (0/33) Oxford record linkage system, and death certificates. for subarachnoid haemorrhage. This difference per-Most patients (614) were seen by a neurologist in the sisted if patients in whom it was not known whether study at a median time of four days after the onset of they were asleep or awake at onset were classed as symptoms, and a witness was interviewed when no asleep. For all stroke types together there was a history was available from the patient.In all, 574 had computed tomography or a postwith a morning peak between 0800 and 1000, which mortem examination. In the remaining patients the persisted even after allowing for strokes first noted type of stroke was determined with the Guy's Hospital on waking by redistributing the hour of onset through diagnostic score."I Stroke type was classified as cerebral the preceding eight hours (x2=47, p<0001). infarction, primary intracerebral haemorrahge, or sub-A significant diurnal variation was also found in arachnoid haemorrahge (all cases of subarachnoid the onset of cerebral infarction (peak 0800-1000, haemorrhage were included in the study).'°Cerebral x2=208-4, p