RNA Foci in Two bi-Allelic RFC1 Expansion Carriers

Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) is a late-onset, autosomal recessive neurodegenerative disorder caused by biallelic AAGGG/ACAGG repeat expansion (AAGGG-exp/ACAGG-exp) in RFC1. The recent identification of patients with CANVAS exhibiting compound heterozygosity for AAGGG-exp and truncating variants supports the loss-of-function of RFC1 in CANVAS patients. We investigated the pathological changes in 2 autopsied patients with CANVAS harboring biallelic ACAGG-exp and AAGGG-exp. RNA fluorescence in situ hybridization of the 2 patients revealed CCTGT- and CCCTT-containing RNA foci, respectively, in neuronal nuclei of tissues with neuronal loss. Our findings suggest that RNA toxicity may be involved in the pathogenesis of CANVAS. ANN NEUROL 2024;95:607-613.

Lateral olfactory tract usher substance (LOTUS), an endogenous Nogo receptor antagonist, ameliorates disease progression in amyotrophic lateral sclerosis model mice

Nogo-Nogo receptor 1 (NgR1) signaling is significantly implicated in neurodegeneration in amyotrophic lateral sclerosis (ALS). We previously showed that lateral olfactory tract usher substance (LOTUS) is an endogenous antagonist of NgR1 that prevents all myelin-associated inhibitors (MAIs), including Nogo, from binding to NgR1. Here we investigated the role of LOTUS in ALS pathogenesis by analyzing G93A-mutated human superoxide dismutase 1 (SOD1) transgenic (Tg) mice, as an ALS model, as well as newly generated LOTUS-overexpressing SOD1 Tg mice. We examined expression profiles of LOTUS and MAIs and compared motor functions and survival periods in these mice. We also investigated motor neuron survival, glial proliferation in the lumbar spinal cord, and neuromuscular junction (NMJ) morphology. We analyzed downstream molecules of NgR1 signaling such as ROCK2, LIMK1, cofilin, and ataxin-2, and also neurotrophins. In addition, we investigated LOTUS protein levels in the ventral horn of ALS patients. We found significantly decreased LOTUS expression in both SOD1 Tg mice and ALS patients. LOTUS overexpression in SOD1 Tg mice increased lifespan and improved motor function, in association with prevention of motor neuron loss, reduced gliosis, increased NMJ innervation, maintenance of cofilin phosphorylation dynamics, decreased levels of ataxin-2, and increased levels of brain-derived neurotrophic factor (BDNF). Reduced LOTUS expression may enhance neurodegeneration in SOD1 Tg mice and ALS patients by activating NgR1 signaling, and in this study LOTUS overexpression significantly ameliorated ALS pathogenesis. LOTUS might serve as a promising therapeutic target for ALS.

Long-read sequencing revealing intragenic deletions in exome-negative spastic paraplegias

Hereditary spastic paraplegias (HSPs) are a heterogeneous group of neurodegenerative disorders characterized by progressive spasticity and weakness in the lower extremities. To date, a total of 88 types of SPG are known. To diagnose HSP, multiple technologies, including microarray, direct sequencing, multiplex ligation-dependent probe amplification, and short-read next-generation sequencing, are often chosen based on the frequency of HSP subtypes. Exome sequencing (ES) is commonly used. We used ES to analyze ten cases of HSP from eight families. We identified pathogenic variants in three cases (from three different families); however, we were unable to determine the cause of the other seven cases using ES. We therefore applied long-read sequencing to the seven undetermined HSP cases (from five families). We detected intragenic deletions within the SPAST gene in four families, and a deletion within PSEN1 in the remaining family. The size of the deletion ranged from 4.7 to 12.5 kb and involved 1-7 exons. All deletions were entirely included in one long read. We retrospectively performed an ES-based copy number variation analysis focusing on pathogenic deletions, but were not able to accurately detect these deletions. This study demonstrated the efficiency of long-read sequencing in detecting intragenic pathogenic deletions in ES-negative HSP patients.

Phosphorylated CRMP1, axon guidance protein, is a component of spheroids and is involved in axonal pathology in amyotrophic lateral sclerosis

In amyotrophic lateral sclerosis (ALS), neurodegeneration is characterized by distal axonopathy that begins at the distal axons, including the neuromuscular junctions, and progresses proximally in a “dying back” manner prior to the degeneration of cell bodies. However, the molecular mechanism for distal axonopathy in ALS has not been fully addressed. Semaphorin 3A (Sema3A), a repulsive axon guidance molecule that phosphorylates collapsin response mediator proteins (CRMPs), is known to be highly expressed in Schwann cells near distal axons in a mouse model of ALS. To clarify the involvement of Sema3A–CRMP signaling in the axonal pathogenesis of ALS, we investigated the expression of phosphorylated CRMP1 (pCRMP1) in the spinal cords of 35 patients with sporadic ALS and seven disease controls. In ALS patients, we found that pCRMP1 accumulated in the proximal axons and co-localized with phosphorylated neurofilaments (pNFs), which are a major protein constituent of spheroids. Interestingly, the pCRMP1:pNF ratio of the fluorescence signal in spheroid immunostaining was inversely correlated with disease duration in 18 evaluable ALS patients, indicating that the accumulation of pCRMP1 may precede that of pNFs in spheroids or promote ALS progression. In addition, overexpression of a phospho-mimicking CRMP1 mutant inhibited axonal outgrowth in Neuro2A cells. Taken together, these results indicate that pCRMP1 may be involved in the pathogenesis of axonopathy in ALS, leading to spheroid formation through the proximal progression of axonopathy.

Inhibition of Crmp1 Phosphorylation at Ser522 Ameliorates Motor Function and Neuronal Pathology in Amyotrophic Lateral Sclerosis Model Mice

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive and fatal neurodegenerative disorder that affects upper and lower motor neurons; however, its pathomechanism has not been fully elucidated. Using a comprehensive phosphoproteomic approach, we have identified elevated phosphorylation of Collapsin response mediator protein 1 (Crmp1) at serine 522 in the lumbar spinal cord of ALS model mice overexpressing a human superoxide dismutase mutant (SOD1G93A). We investigated the effects of Crmp1 phosphorylation and depletion in SOD1G93A mice using Crmp1S522A (Ser522→Ala) knock-in (Crmp1ki/ki ) mice in which the S522 phosphorylation site was abolished and Crmp1 knock-out (Crmp1-/-) mice, respectively. Crmp1ki/ki /SOD1G93A mice showed longer latency to fall in a rotarod test while Crmp1-/-/SOD1G93A mice showed shorter latency compared with SOD1G93A mice. Survival was prolonged in Crmp1ki/ki /SOD1G93A mice but not in Crmp1-/-/SOD1G93A mice. In agreement with these phenotypic findings, residual motor neurons and innervated neuromuscular junctions (NMJs) were comparatively well-preserved in Crmp1ki/ki /SOD1G93A mice without affecting microglial and astroglial pathology. Pathway analysis of proteome alterations showed that the sirtuin signaling pathway had opposite effects in Crmp1ki/ki /SOD1G93A and Crmp1-/-/SOD1G93A mice. Our study indicates that modifying CRMP1 phosphorylation is a potential therapeutic strategy for ALS.

Case Report: Severe Osteoporosis and Preventive Therapy in RNA Polymerase III-Related Leukodystrophy

RNA polymerase III (POLR3)-related leukodystrophy is an autosomal recessive form of leukodystrophy caused by homozygous or compound heterozygous mutations of the RNA polymerase III subunit genes, including subunit A (POLR3A). With respect to the manifestation triad, hypomyelination, hypodontia, and hypogonadotropic hypogonadism, it is also known as 4H leukodystrophy. Here, we report a 41-year-old woman of POLR3-related leukodystrophy by carrying compound heterozygous pathogenic variants of c.2554A>G (p.M852V) and c.2668G>T (p.V890F) in the POLR3A gene. She was amenorrheic and became a wheelchair user from the age of 15 years and suffered from multiple episodes of pathologic fractures, starting with a subtrochanteric fracture of the right femur after a tonic seizure at age 30 years. Head magnetic resonance imaging demonstrated hypomyelination and atrophies of the cerebellum, brainstem, and corpus callosum. Laboratory examination revealed a marked decrease of gonadotropins and estrogen, low bone density, and high bone resorption markers. Administration of anti-receptor activator of nuclear factor kappa-B ligand monoclonal antibody restored bone resorption markers to a normal level and prevented further pathological bone fractures. Our case emphasizes that osteoporosis should be recognized as a potential but serious complication in POLR3-related leukodystrophy. It may be feasible to prevent pathologic fractures by intensive osteoporosis therapy after endocrinological examinations and evaluation of bone metabolism.

Exploratory investigation on antibodies to GluN1 and cognitive dysfunction in patients with chronic autoimmune psychosis

INTRODUCTION

Mild cognitive dysfunction has been implicated in a number of psychiatric diseases and affects social functioning. Although clinical criteria were recently proposed for autoimmune psychosis (AP), biomarkers have not yet been established for the severity and prognosis of cognitive dysfunction. We herein investigated the relationships between 3 types of serum antibodies and cognitive dysfunction in chronic psychiatric patients suspected of AP.

METHODS

We included 31 patients suspected of AP and obtained information on their clinical characteristics. Three types of autoantibodies (the anti-N-methyl-_D-aspartate receptor (anti-NMDAR Ab), anti-N-terminal of GluN1 (anti-GluN1-NT Ab), and anti-thyroid antibodies) were evaluated in serum. Cognitive function was assessed using Wechsler Adult Intelligence Scale-III. We examined the relationships between serum autoantibodies and cognitive dysfunction in patients using multiple regression models.

RESULTS

Serum titers of anti-GluN1-NT Ab significantly contributed to the estimated score of working memory (B= -55.85, β= -0.46, p= 0.01), while no correlation was observed between the other 2 types of antibodies and cognitive function.

CONCLUSIONS

The present results indicate the potential of serum anti-GluN1-NT Ab as a biomarker for the severity and prognosis of cognitive dysfunction underlying various psychiatric symptoms in patients with AP. The pathological significance of anti-GluN1-NT Ab needs to be verified in future studies.

Hepatitis B Virus-related Vasculitic Neuropathy in an Inactive Virus Carrier Treated with Intravenous Immunoglobulin

We herein report a 33-year-old woman who was an asymptomatic hepatitis B virus (HBV) carrier and presented with distal muscle weakness in the legs and asymmetrical paresthesia in the distal extremities. A nerve biopsy specimen revealed fibrinoid necrosis associated with inflammatory infiltration in the perineural space, and deposition of hepatitis B core antigen and C4d complement was detected in the vascular endothelial cells as well as around the vessels. She was diagnosed with HBV-related vasculitic neuropathy and treated with intravenous immunoglobulin (IVIG). Her symptoms completely subsided after eight weeks. Vasculitic neuropathy rarely develops in the chronic inactive stages of HBV infection. This is the first report of an HBV-inactive carrier with vasculitic neuropathy successfully treated with IVIG.

Tonsillectomy Improved Therapeutic Response in Anti-SRP Myopathy With Chronic Tonsillitis

Chronic tonsillitis has been attracted attention as a source of abnormal immune responses and a possible trigger of autoimmune diseases such as IgA nephritis, IgA vasculitis, palmoplantar pustulosis, psoriasis, rheumatoid arthritis, Behçet’s disease, and myositis. Here we present the first report of anti–signal recognition particle antibody–associated necrotizing myopathy (anti-SRP myopathy) with IgA nephropathy and chronic tonsillitis in which the therapeutic response to intravenous immunoglobulin (IVIG) treatment was dramatically improved after tonsillectomy and accompanied by a rapid increase in ΔIgG, defined as the change in serum IgG levels 2 weeks after the start of IVIG treatment relative to pre-treatment levels. Moreover, serum anti-SRP antibody titers became undetectable after tonsillectomy even though the resected tonsils did not produce anti-SRP antibodies. Tonsillectomy should be considered when chronic tonsillitis is observed in patients with autoimmune diseases showing poor response to treatment, including anti-SRP myopathy.

[A case of subacute hypertrophic pachymeningitis caused by Pseudomonas aeruginosa infection presenting with subdural hygroma]

A 78-year-old woman with bilateral fungal sinusitis, which resulted in right orbital apex syndrome, underwent endoscopic sinus surgery and optic nerve decompression. Two months after the operation, she complained of anxiety and insomnia. Head CT showed subdural hematoma-like effusion and burr hole drainage was conducted. The collected fluid was not hematoma, but bloody, xanthochromic effusion with no pathogenic bacteria. Ten days later, she underwent drainage and dural biopsy after craniotomy because of relapse of subdural hygroma and progression of hypertrophic pachymeningitis associated with aggravation of psychiatric symptoms. A sample of the dura mater showed dense fibrosis with thickening, and Pseudomonas aeruginosa (P. aeruginosa) was detected by culture. Although otitis or sinusitis secondary to P. aeruginosa infection has been reported as a leading cause of infectious pachymeningitis, psychiatric symptoms alone and concomitant refractory subdural hygroma are atypical and unreported manifestations. In patients with pachymeningitis and a history of transnasal endoscopic surgery, P. aeruginosa infection should be considered, irrespective of an atypical clinical course and negative blood or fluid culture. Additionally, dural biopsy might help in detection of pathogenic bacteria.

Long-read sequencing identifies the pathogenic nucleotide repeat expansion in RFC1 in a Japanese case of CANVAS

Recently, a recessively inherited intronic repeat expansion in replication factor C1 (RFC1) was identified in cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome (CANVAS). Here, we describe a Japanese case of genetically confirmed CANVAS with autonomic failure and auditory hallucination. The case showed impaired uptake of iodine-123-metaiodobenzylguanidine and ¹²³I-ioflupane in the cardiac sympathetic nerve and dopaminergic neurons, respectively, by single-photon emission computed tomography. Long-read sequencing identified biallelic pathogenic (AAGGG)n nucleotide repeat expansion in RFC1 and heterozygous benign (TAAAA)n and (TAGAA)n expansions in brain expressed, associated with NEDD4 (BEAN1). Enrichment of the repeat regions in RFC1 and BEAN1 using a Cas9-mediated system clearly distinguished between pathogenic and benign repeat expansions. The haplotype around RFC1 indicated that the (AAGGG)n expansion in our case was on the same ancestral allele as that of European cases. Thus, long-read sequencing facilitates precise genetic diagnosis of diseases with complex repeat structures and various expansions.

Proteomic analysis of exosome-enriched fractions derived from cerebrospinal fluid of amyotrophic lateral sclerosis patients

Exosomes contain many proteins associated with neurodegenerative diseases. To identify new candidate biomarkers and proteins associated with amyotrophic lateral sclerosis (ALS), we performed liquid chromatography-tandem mass spectrometry proteomic analysis of exosome-enriched fractions isolated from cerebrospinal fluid (CSF) of sporadic ALS patients using gel filtration chromatography. Proteomic data revealed that three proteins were increased and 11 proteins were decreased in ALS patients. The protein with the greatest increase in exosome-enriched fractions of CSF derived from ALS was novel INHAT repressor (NIR), which is closely associated with nucleolar function. By immunohistochemical analysis, we found that NIR was reduced in the nucleus of motor neurons in ALS patients. Our results demonstrate the potential utility of our methodology for proteomic analysis of CSF exosomes and suggest that nucleolar stress might play a role in sporadic ALS pathogenesis through the dysfunction of NIR.

GGC Repeat Expansion of NOTCH2NLC in Adult Patients with Leukoencephalopathy

Leukoencephalopathies comprise a broad spectrum of disorders, but the genetic background of adult leukoencephalopathies has rarely been assessed. In this study, we analyzed 101 Japanese patients with genetically unresolved adult leukoencephalopathy using whole-exome sequencing and repeat-primed polymerase chain reaction for detecting GGC expansion in NOTCH2NLC. NOTCH2NLC was recently identified as the cause of neuronal intranuclear inclusion disease. We found 12 patients with GGC expansion in NOTCH2NLC as the most frequent cause of adult leukoencephalopathy followed by NOTCH3 variants in our cohort. Furthermore, we found 1 case with de novo GGC expansion, which might explain the underlying pathogenesis of sporadic cases. ANN NEUROL 2019;86:962-968.

Novel VRK1 Mutations in a Patient with Childhood-onset Motor Neuron Disease

A 24-year-old Japanese man exhibited slowly progressive gait disturbance from childhood to young adulthood. Physical and physiological examinations showed the involvement of both upper and lower motor neurons, fulfilling the diagnostic criteria for amyotrophic lateral sclerosis (ALS). Mild cognitive impairment and subclinical sensory involvement were also observed. A genetic analysis revealed novel compound heterozygous mutations, c.767C>T (p.Thr256Ile) and c.800A>G (p.Asp267Gly), in the vaccinia-related kinase 1 gene (VRK1). This is the first report of a Japanese patient with a motor neuron disease phenotype caused by VRK1 mutations. This diagnosis should be considered in atypical cases of juvenile-onset and slowly progressive types of motor neuron disease.

Ataxic phenotype with altered CaV3.1 channel property in a mouse model for spinocerebellar ataxia 42

Spinocerebellar ataxia 42 (SCA42) is a neurodegenerative disorder recently shown to be caused by c.5144G > A (p.Arg1715His) mutation in CACNA1G, which encodes the T-type voltage-gated calcium channel Ca_V3.1. Here, we describe a large Japanese family with SCA42. Postmortem pathological examination revealed severe cerebellar degeneration with prominent Purkinje cell loss without ubiquitin accumulation in an SCA42 patient. To determine whether this mutation causes ataxic symptoms and neurodegeneration, we generated knock-in mice harboring c.5168G > A (p.Arg1723His) mutation in Cacna1g, corresponding to the mutation identified in the SCA42 family. Both heterozygous and homozygous mutants developed an ataxic phenotype from the age of 11-20 weeks and showed Purkinje cell loss at 50 weeks old. Degenerative change of Purkinje cells and atrophic thinning of the molecular layer were conspicuous in homozygous knock-in mice. Electrophysiological analysis of Purkinje cells using acute cerebellar slices from young mice showed that the point mutation altered the voltage dependence of Ca_V3.1 channel activation and reduced the rebound action potentials after hyperpolarization, although it did not significantly affect the basic properties of synaptic transmission onto Purkinje cells. Finally, we revealed that the resonance of membrane potential of neurons in the inferior olivary nucleus was decreased in knock-in mice, which indicates that p.Arg1723His Ca_V3.1 mutation affects climbing fiber signaling to Purkinje cells. Altogether, our study shows not only that a point mutation in CACNA1G causes an ataxic phenotype and Purkinje cell degeneration in a mouse model, but also that the electrophysiological abnormalities at an early stage of SCA42 precede Purkinje cell loss.

Cerebrospinal fluid level of Nogo receptor 1 antagonist lateral olfactory tract usher substance (LOTUS) correlates inversely with the extent of neuroinflammation

Background

Although inflammation in the central nervous system is responsible for multiple neurological diseases, the lack of appropriate biomarkers makes it difficult to evaluate inflammatory activities in these diseases. Therefore, a new biomarker reflecting neuroinflammation is required for accurate diagnosis, appropriate therapy, and comprehension of pathogenesis of these neurological disorders. We previously reported that the cerebrospinal fluid (CSF) concentration of lateral olfactory tract usher substance (LOTUS), which promotes axonal growth as a Nogo receptor 1 antagonist, negatively correlates with disease activity in multiple sclerosis, suggesting that variation in LOTUS reflects the inflammatory activities and is a useful biomarker to evaluate the disease activity. To extend this observation, we analyzed the variation of LOTUS in the CSF of patients with bacterial and viral meningitis, which are the most common neuroinflammatory diseases.

Methods

CSF samples were retrospectively obtained from patients with meningitis (n = 40), who were followed up by CSF study at least twice, and from healthy controls (n = 27). Patients were divided into bacterial (n = 14) and viral meningitis (n = 18) after exclusion of eight patients according to the criteria of this study. LOTUS concentrations, total protein levels, and CSF cell counts in the acute and recovery phases were analyzed chronologically. We also used lipopolysaccharide-injected mice as a model of neuroinflammation to evaluate LOTUS mRNA and protein expression in the brain.

Results

Regardless of whether meningitis was viral or bacterial, LOTUS concentrations in the CSF of patients in acute phase were lower than those of healthy controls. As the patients recovered from meningitis, LOTUS levels in the CSF returned to the normal range. Lipopolysaccharide-injected mice also exhibited reduced LOTUS mRNA and protein expression in the brain.

Conclusions

CSF levels of LOTUS correlated inversely with disease activity in both bacterial and viral meningitis, as well as in multiple sclerosis, because neuroinflammation downregulated LOTUS expression. Our data strongly suggest that variation of CSF LOTUS is associated with neuroinflammation and is useful as a biomarker for a broader range of neuroinflammatory diseases.

Autosomal recessive spinocerebellar ataxias in Japan

Recent new sequencing techniques allow the identification of novel responsible genes for autosomal recessive spinocerebellar ataxias (ARCAs). However, the same phenotypes are sometimes attributed to the different responsible genes in ARCAs. On the contrary, the same responsible genes may cause heterogeneous phenotypes with respect to the age at onset, symptoms, and the severity of the disease progression. In addition, it is an important issue to clarify whether the gene mutations identified in Caucasian patients with infantile-onset ARCAs are also observed in Japanese patients with adult-onset ARCAs. In this article we review the characteristics of several ARCAs, the existence of which has been recently identified or confirmed in Japan.

Social isolation perturbs experience-driven synaptic glutamate receptor subunit 4 delivery in the developing rat barrel cortex

In neonates, the stress of social isolation can alter developing neural circuits and cause mental illness. However, the molecular and cellular bases for these effects are poorly understood. Experience-driven synaptic AMPA receptor delivery is crucial for circuit organisation during development. In the rat, whisker experience drives the delivery of glutamate receptor subunit 4 (GluA4) but not glutamate receptor subunit 1 (GluA1) to layer 4-2/3 pyramidal synapses in the barrel cortex during postnatal day (P)8-10, whereas GluA1 but not GluA4 is delivered to these synapses during P12-14. We recently reported that early social isolation disrupts experience-driven GluA1 delivery to layer 4-2/3 pyramidal synapses during P12-14. Here, we report that neonatal isolation affects even earlier stages of development by preventing experience-dependent synaptic GluA4 delivery. Thus, social isolation severely affects synaptic maturation throughout early postnatal development.

Developmental AMPA receptor subunit specificity during experience-driven synaptic plasticity in the rat barrel cortex

During early postnatal brain development, experience-driven delivery of AMPA receptors to synapses participates in the initial organization of cortical function. By combining virus-mediated in vivo gene delivery with in vitro whole cell recordings, we identified a subunit-specific developmental program of experience-driven AMPA receptor delivery to synapses in rat barrel cortex. We expressed green fluorescent protein (GFP)-tagged AMPA receptors (GFP-GluR1, or GFP-GluR4) into layer 2/3 pyramidal neurons at two distinct developmental periods, postnatal day (P)8-P10 and P12-P14. Two days after viral infection, acute brain slices were prepared, and synaptic transmission from layer 4 to layer 2/3 was analyzed by whole cell recordings. We found that whisker experience drives GluR4 but not GluR1 into these synapses early in postnatal development (P8-P10). However, at P12-14, GluR1 but not GluR4 is delivered into synapses by whisker experience. This precise developmental plan suggests unique plasticity properties endowed in different AMPA receptor subunits which shape the initial experience-driven organization of cortical function.

The value of long-term clinical follow-up for cases of spontaneous carotid cavernous fistula

To clarify the value of clinical long-term follow-up with radiological examination, ranging from 12 to 63 months (average: 35 months), 18 consecutive patients suffering from spontaneous carotid cavernous fistula (CCF), were studied prospectively. Five aged patients without aggressive symptoms were treated conservatively, and the other 13 underwent transarterial embolization. The radiological follow-up was primarily by magnetic resonance angiography (MRA), performed from 2 to 6 times (average: 4.1 times) during the follow-up period. In three cases, CCFs persisted, but the other fifteen (83%) demonstrated complete cure as defined by long-term follow-up MRA. The three patients with persistent CCFs were comparatively young, less than 60 years old, had no atherosclerotic factors and demonstrated multiple venous drainage routes with cortical venous drainage on angiography. In two of them, the symptoms completely disappeared, and the other had only mild chemosis. However, surprisingly, in two, MRA revealed residual CCF with drainage into only cortical veins through the sphenoparietal sinus, this radiological finding being well known to signify danger. During the follow-up period, central retinal vein thrombosis occurred in two cases. The common point in these cases was that the superior ophthalmic vein was the only venous drainage route. This is also a point requiring care. We therefore emphasize the importance of careful long-term radiological follow-up for spontaneous CCF patients even when their symptoms improve or disappear. MRA is particularly suitable for this purpose and applicable in the out-patient clinic because of its non-invasive nature.

Endovascular Approach to a Ligated External Carotid Artery

A 37-year-old female with left sided multiple congenital haemangiomata presented with repeated haemorrhage. The haemorrhagic origin was from the angiomatous lesion with arteriovenous (AV) shunting in the tongue and pharynx. The patient had already undergone ligation of the external carotid artery. Vascularization was mainly from the portion of the external carotid artery distal to the occlusion. Our first approach via the collateral channels to the haemangioma failed. Through direct puncture of the distal end of the external carotid artery with the use of two dimensional road mapping, we succeeded in catheterizing the distal end of the external carotid artery at the first attempt without placing any pressure on the neck, and carried out selective embolisation without mishap.

Venous ischemia caused by dural arteriovenous malformation. Case report

A case is presented of tentorial dural arteriovenous malformation (AVM) associated with visual hallucinations and quadrant hemianopsia. Computerized tomography (CT) and magnetic resonance imaging showed an ischemic region, mainly affecting the white matter of the right occipital lobe, that was defined as an area of increased blood volume on dynamic CT scans and as a decrease in cerebral blood flow on N-isopropyl-p-123I-iodoamphetamine single-photon emission CT scans. Angiography demonstrated venous congestion, probably because the retrograde arterial inflow from the dural AVM into the corticomedullary vein was direct and not via the sinuses. The symptoms and radiological findings improved immediately after endovascular treatment. The origin of these symptoms was fully evaluated and confirmed to be a reversible ischemic change caused by disturbance of the volume of venous return over an extensive area.

Narrow energy distribution of output electrons from a modified single channel electron multiplier

New methods which reduce the unfavorable energy spread of output electrons from a single channel electron multiplier are presented. A modified output electrode produces a pronounced narrowing effect on the energy distribution without much affect on the gain. A simplified analysis of the field inside the channel shows that the fixed channel wall potential near the output end is responsible for the narrow energy distributions obtainable.