Investigating genotype-phenotype relationship of extreme neuropathic pain disorders in a UK national cohort

The aims of our study were to use whole genome sequencing in a cross-sectional cohort of patients to identify new variants in genes implicated in neuropathic pain, to determine the prevalence of known pathogenic variants and to understand the relationship between pathogenic variants and clinical presentation. Patients with extreme neuropathic pain phenotypes (both sensory loss and gain) were recruited from secondary care clinics in the UK and underwent whole genome sequencing as part of the National Institute for Health and Care Research Bioresource Rare Diseases project. A multidisciplinary team assessed the pathogenicity of rare variants in genes previously known to cause neuropathic pain disorders and exploratory analysis of research candidate genes was completed. Association testing for genes carrying rare variants was completed using the gene-wise approach of the combined burden and variance-component test SKAT-O. Patch clamp analysis was performed on transfected HEK293T cells for research candidate variants of genes encoding ion channels. The results include the following: (i) Medically actionable variants were found in 12% of study participants (205 recruited), including known pathogenic variants: SCN9A(ENST00000409672.1): c.2544T>C, p.Ile848Thr that causes inherited erythromelalgia, and SPTLC1(ENST00000262554.2):c.340T>G, p.Cys133Tr variant that causes hereditary sensory neuropathy type-1. (ii) Clinically relevant variants were most common in voltage-gated sodium channels (Nav). (iii) SCN9A(ENST00000409672.1):c.554G>A, pArg185His variant was more common in non-freezing cold injury participants than controls and causes a gain of function of NaV1.7 after cooling (the environmental trigger for non-freezing cold injury). (iv) Rare variant association testing showed a significant difference in distribution for genes NGF, KIF1A, SCN8A, TRPM8, KIF1A, TRPA1 and the regulatory regions of genes SCN11A, FLVCR1, KIF1A and SCN9A between European participants with neuropathic pain and controls. (v) The TRPA1(ENST00000262209.4):c.515C>T, p.Ala172Val variant identified in participants with episodic somatic pain disorder demonstrated gain-of-channel function to agonist stimulation. Whole genome sequencing identified clinically relevant variants in over 10% of participants with extreme neuropathic pain phenotypes. The majority of these variants were found in ion channels. Combining genetic analysis with functional validation can lead to a better understanding as to how rare variants in ion channels lead to sensory neuron hyper-excitability, and how cold, as an environmental trigger, interacts with the gain-of-function NaV1.7 p.Arg185His variant. Our findings highlight the role of ion channel variants in the pathogenesis of extreme neuropathic pain disorders, likely mediated through changes in sensory neuron excitability and interaction with environmental triggers.

Acute and chronic neuropathies

Peripheral nerve disorders are common and often treatable. The 'default' presentation of a polyneuropathy is a chronic, length-dependent, sensorimotor axonopathy. Recognizing deviations from this default, informed by the clinical features and investigations, can help identify the cause of a neuropathy in most cases. For inflammatory causes, such as Guillain-Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy, there are effective immunomodulatory treatments. For other neuropathies, management consists of supportive care and treatment of the underlying cause, to prevent or limit progression.

Vasculitis and the peripheral nervous system

Peripheral neuropathy is a common feature of systemic vasculitis and can also occur when vessel wall inflammation is confined to the vasa nervorum, as a tissue-specific condition—non-systemic vasculitic neuropathy (NSVN). Typically, the clinical picture in both systemic and non-systemic cases is of a lower limb predominant, distal, asymmetric or multifocal neuropathy, which is painful and subacute in onset. For NSVN, nerve biopsy is required to make the diagnosis, and nerve biopsy also has a role when vasculitic neuropathy is suspected and a systemic process has not yet declared itself. Early recognition of the disorder is important, because it is treatable, and without treatment potentially disabling, or even lethal if part of an undiagnosed systemic process. Treatment is generally with combination therapy (glucocorticoid plus other immunosuppressant), after which motor and sensory recovery are likely to occur, albeit slowly, but the patient may be left with chronic neuropathic pain.

POEMS syndrome: clinical update

POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M-protein, skin changes) is a rare paraneoplastic syndrome, caused by a plasma cell proliferative disorder, which is most commonly lambda restricted. The neurological hallmark, which forms one of the mandatory criteria for diagnosis, is a subacute onset demyelinating neuropathy, which can be rapidly disabling and painful. A number of multi-system features are also characteristic of this disorder, and certainly not restricted to those included in its acronym, which though limited, remains a useful and memorable name, helping distinguish POEMS syndrome from other paraproteinaemic neuropathies. The discovery of vascular endothelial growth factor (VEGF) in association with POEMS syndrome has been extremely useful in aiding clinical diagnosis, and monitoring response to treatment, as well as helping understand the underlying mechanism of disease. Interestingly, however, treatment targeting VEGF has been disappointing, suggesting other disease mechanisms or inflammatory processes are also important. Current understanding of the pathogenesis of POEMS syndrome is outlined in detail in the accompanying article by Cerri et al. Here, we review the clinical features of POEMS syndrome, differential diagnosis and available treatment options, based on current literature.

Cryopyrin-Associated Periodic Fever Syndrome and the Nervous System

PURPOSE OF REVIEW

The purpose of this review is to highlight the molecular and clinical characteristics of the cryopyrin-associated periodic fever syndrome (CAPS) and its management. CAPS is an autosomal dominantly inherited autoinflammatory disorder associated with mutations in the NLRP3 gene, which ultimately lead to excessive production of interleukin-1β (IL-1β) and systemic inflammation. Typical systemic features include fever, urticarial rash and arthralgia, and ultimately amyloidosis. There are also multiple neurological manifestations including, but not restricted to, headache, sensorineural hearing loss, aseptic meningitis, myalgia and optic nerve involvement.

RECENT FINDINGS

Since the recognition of CAPS as a single disease entity and discovery of the underlying causative gene, there has been a major breakthrough in terms of its treatment by pharmacological IL-1β inhibition. Highly targeted therapies against IL-1 have been shown to be remarkably effective in the treatment of CAPS and make early diagnosis of this condition crucial. It is hoped that starting pharmacological intervention in a timely manner will prove neuroprotective. There are three drugs licensed for treatment of CAPS; canakinumab, anakinra and rilonacept. The former two are widely used: canakinumab is a fully humanised anti-IL-1β monoclonal antibody administered as a subcutaneous injection once every 8 weeks starting at a dose of 150 mg in patients weighing more than 40 kg. Anakinra is a recombinant form of the IL-1 receptor antagonist and the adult daily dose is 100 mg subcutaneously. CAPS is a highly debilitating disorder characterised by unregulated IL-1β production driven by autosomal dominantly inherited mutations in the NLRP3 gene. Effective therapies targeted against IL-1 are now available and are vital to prevent long-term complications.

Arthroscopic management of suprascapular neuropathy of the shoulder improves pain and functional outcomes with minimal complication rates

PURPOSE

The purpose of this study was to systematically assess the arthroscopic management of suprascapular neuropathy, including the aetiology, surgical decision-making, clinical outcomes, and complications associated with the procedure.

METHODS

Three databases [PubMed, Ovid (Medline), and Embase] were searched. Systematic literature screening and data abstraction was performed in duplicate to present a review of studies reporting on arthroscopic management of suprascapular neuropathy. The quality of the included studies was assessed using level of evidence and the MINORS (Methodological Index for Nonrandomized Studies) checklist.

RESULTS

In total, 40 studies (17 case reports, 20 case series, 2 retrospective comparative studies, and 1 prospective comparative study) were identified, including 259 patients (261 shoulders) treated arthroscopically for suprascapular neuropathy. The most common aetiology of suprascapular neuropathy was suprascapular nerve compression by a cyst at the spinoglenoid notch (42%), and the decision to pursue arthroscopic surgery was most commonly based on the results of clinical findings and investigations (47%). Overall, 97% of patients reported significant improvement in or complete resolution of their pre-operative symptoms (including pain, strength, and subjective function of the shoulder) over a mean follow-up period of 23.7 months. Further, there was a low overall complication rate (4%) associated with the arthroscopic procedures.

CONCLUSION

While most studies evaluating arthroscopic management of suprascapular neuropathy are uncontrolled studies with lower levels of evidence, results indicate that such management provides patients with significant improvements in pain, strength, and subjective function of the shoulder, and has a low incidence of complications. Patients managed arthroscopically for suprascapular neuropathy may expect significant improvements in pain, strength, and subjective function of the shoulder.

LEVEL OF EVIDENCE

Level IV, systematic review of level II to IV studies.

Myelopathy: chameleons and mimics

The diagnosis of spinal cord disease may be delayed or missed if the presentation does not conform to the expected pattern of a symmetrical spastic paraparesis with sphincter dysfunction and a sensory level. This may occur when a myelopathy has yet to evolve fully, or is highly asymmetrical, as in Brown-Séquard syndrome. Other potential distractions include fluctuating symptoms, as may accompany spinal cord demyelination, and pseudoneuropathic features, as seen acutely in spinal shock and in the chronic setting with some high cervical cord lesions. A second pathology, such as a polyneuropathy or polyradiculopathy, can mask the presence of a myelopathy. The converse situation, of non-myelopathic disease mimicking a cord lesion, arises typically when symptoms and/or signs approximate bilateral symmetry. This may happen with certain diseases of the brain, or of the peripheral nerves, with functional disorders and even occasionally with non-neurological disease. These sources of diagnostic difficulty assume clinical importance when they delay the recognition of conditions that require urgent treatment.

Neurology of the cryopyrin-associated periodic fever syndrome

BACKGROUND AND PURPOSE

The cryopyrin-associated periodic fever syndrome (CAPS) is an autosomal dominant autoinflammatory disorder caused by mutations in the NLRP3 gene and is typified by recurrent episodes of systemic inflammation resulting in fever, urticarial rash and arthralgia. In addition to these systemic aspects, CAPS has multiple neurological manifestations. The largest case series to date is presented focusing on the neurological features of this disorder.

METHODS

The case histories of a cohort of 38 UK patients with genetically proven CAPS who were treated with interleukin 1β (IL-1β) inhibition as part of a national treatment programme and underwent detailed neurological assessment were reviewed.

RESULTS

Across the entire disease course neurological manifestations were present in 95% of patients; 84% had some form of headache; 66% sensorineural hearing loss; 60% myalgia; 34% papilloedema and 26% optic atrophy. Patients with the T348M mutation tended to have a more severe neurological phenotype with an earlier age of onset. Four patients had cerebrospinal fluid examination, three of whom had evidence of aseptic meningitis. There was a marked response to IL-1β inhibition, which has revolutionized management of these patients (29/32 patients with headache responding).

CONCLUSION

Neurological symptoms are extremely common in CAPS and these results highlight the importance of increasing awareness amongst neurologists, particularly as highly effective therapies are available.

TRPA1 insensitivity of human sural nerve axons after exposure to lidocaine

TRPA1 is an ion channel of the TRP family that is expressed in some sensory neurons. TRPA1 activity provokes sensory symptoms of peripheral neuropathy, such as pain and paraesthesia. We have used a grease gap method to record axonal membrane potential and evoked compound action potentials (ECAPs) in vitro from human sural nerves and studied the effects of mustard oil (MO), a selective activator of TRPA1. Surprisingly, we failed to demonstrate any depolarizing response to MO (50, 250 μM) in any human sural nerves. There was no effect of MO on the A wave of the ECAP, but the C wave was reduced at 250 μM. In rat saphenous nerve fibres MO (50, 250 μM) depolarized axons and reduced the C wave of the ECAP but had no effect on the A wave. By contrast, both human and rat nerves were depolarized by capsaicin (0.5 to 5 μM) or nicotine (50 to 200 μM). Capsaicin caused a profound reduction in C fibre conduction in both species but had no effect on the amplitude of the A component. Lidocaine (30 mM) depolarized rat saphenous nerves acutely, and when rat nerves were pretreated with 30 mM lidocaine to mimic the exposure of human nerves to local anaesthetic during surgery, the effects of MO were abolished whilst the effects of capsaicin were unchanged. This study demonstrates that the local anaesthetic lidocaine desensitizes TRPA1 ion channels and indicates that it may have additional mechanisms for treating neuropathic pain that endure beyond simple sodium channel blockade.

The nerve biopsy: indications, technical aspects, and contribution

This chapter discusses the indications for biopsying a peripheral nerve and the factors involved in justifying this decision and then deciding which nerve to take. There is a table summarizing some of the causes of neuropathy and attempting to relate these to the probability that nerve biopsy would be helpful in diagnosis. The surgical procedure for the nerve biopsy is described including aftercare and possible complications. The techniques involved in processing and staining the nerve are discussed. This section includes the possibilities of creating artefactual damage by mishandling or poor technique, and how to avoid these. Modification to the standard resin processing schedule to allow the teasing out of individual nerve fibers is briefly described, as are methods for measuring fiber density, fiber size and myelin thickness. There is also a brief discussion of the applications of immunohistochemistry. This is followed by a section on interpretation by light and electron microscopy in which some of the more important diagnostic features are described and illustrated, as are nonspecific morphological findings. Interpretation of teased fiber preparations is discussed. Finally, some common causes of incorrect interpretation are mentioned.

Fabry International Prognostic Index: a predictive severity score for Anderson-Fabry disease

BACKGROUND

Anderson-Fabry disease (AFD) is a disorder of glycosphingolipid metabolism resulting from deficiency of α-galactosidase A and accumulation of globotriaosylceramide. Presentation is heterogeneous and, despite guidelines for initiation of therapy, there is no basis for defining subgroups that will progress more rapidly, whether treated or not. The authors of this study used clinical and pathological data recorded on 1483 patients in the Fabry Outcome Survey, a large international registry, to develop a prognostic severity score.

METHODS

Parameters relevant to disease progression or outcome were initially selected, using variables that are readily available in clinical practice. Individual end points for renal, cardiac, neurological disease, and death were selected, and a composite end point developed. Potential prognostic variables were correlated with each end point, before multivariate analysis. Variables retaining significance were then used to construct organ specific and composite prognostic scores. Kaplan-Meier (KM) analysis, according to score, was performed for each end point.

RESULTS

Analysis demonstrated that it is possible to differentiate groups of patients with different outcome probabilities. Cardiac, renal and neurological end points could each be categorised into three separate groups. The 80% event-free survival for these groups differed by approximately 10 years. The overall composite score, the Fabry International Prognostic Index (FIPI), distinguished two distinct groups where the 50% event-free survival differed by 10 years.

CONCLUSIONS

A prognostic scoring system for AFD has been developed and retrospective validation performed. The FIPI should prove to be a valuable tool in the counselling and management of AFD patients, and in comparative analyses of outcome using different therapies.

Phase I study of pemetrexed in recurrent/metastatic head and neck squamous cell cancer (HNSCC) and to assess the need for steroid premedication

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Background: Pemetrexed is a novel antimetabolite that inhibits both purine and pyrimidine biosynthesis. Because its mechanism of action is similar to that of both methotrexate and 5-FU, it may also have activity in recurrent/metastatic HNSCC, a disease with limited treatment options and very poor median survival. Pemetrexed is traditionally prescribed with steroids due to skin toxicities observed in early studies; however vitamin supplementation (B12 and folic acid) was not standard at the time of those studies. No study to date has evaluated the optimal use of steroids with pemetrexed in the era of vitamin supplementation. Methods: All patients had metastatic or recurrent HNSCC, were treated with at least one prior chemotherapy regimen, and had ECOG PS of 0–2. The first cohort of patients received pemetrexed 500 mg/m2 every 3 weeks and the next receiving 600 mg/m2 based on a predefined standard dose escalation design. Within each dose level, patients were randomized to one of 3 premedication regimens: no dexamethasone, 20 mg IV on day 1, or standard 4 mg orally bid for 3 days. All patients received vitamin supplementation. The primary endpoint of the study was to determine the maximum tolerated dose of pemetrexed based on steroid premedication. Results: From October 2005 to March 2008, 36 patients were enrolled and 31 were available for evaluation. Median age was 57 years (range 42–82). 51.5% of patients had more than one prior chemotherapy regimens, 81.8% of patients had prior radiation therapy, and 48.5% of patients had prior surgery. Incidence of rash and combined skin toxicities were: 1/11 (9%) and 3/11 (27%) of patients without steroids, 1/11 (9%) and 3/11 (27%) with single IV dose, and 4/9 (44%) and 5/9 (55%) with oral steroids. No treatment-related grade 3 toxicities were observed. One patient initially received no steroid and required dose reduction and addition of steroid due to grade 2 rash. A partial response was observed in one patient (3.2%), and stable disease in 8 patients (25.8%) for a disease control rate of 29%. Conclusions: This is the first study to report the role of steroids as a premedication for pemetrexed. Our data suggests that no steroid premedication is needed with pemetrexed and vitamin supplementation.

[Table: see text]

Phase II study of dasatinib in the treatment of head and neck squamous cell carcinoma (HNSCC)

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Background: Dasatinib is a potent inhibitor of src-family kinases, ephA2, PDGFR, Abl, and c-kit. A single-center, open-label, phase II trial was conducted to evaluate the safety, tolerability, pharmacokinetics (PK), and efficacy of dasatinib in recurrent or metastatic HNSCC. Methods: Pts with measurable disease by RECIST, who received 0 or 1 prior regimen for recurrent or metastatic HNSCC with an ECOG performance status 0–1 and tumor tissue appropriate for IHC and FISH were eligible. Dasatinib 100 mg bid was given for 28-day cycles. Primary endpoints were 12-wk progression-free survival (PFS) and objective response rate (ORR). Pts who took at least 1 dose of dasatinib and who died or left study before 12 wks were counted as progressive disease (PD). A 2 stage design, closure after accrual of 15 pts was required if PFS was 45% or less and ORR was 0. Otherwise, planned accrual was 35. Response was assessed at 4 and 12 wks. PK was studied in pts receiving dasatinib per PEG. Biomarkers relevant to Src pathway were planned in tissue and blood. Results: Fifteen pts were accrued. To date, 13 pts are evaluable for response, and 15 pts for toxicity. No grade 3/4 hematologic toxicities were noted. Grade 2–4 nonhematologic toxicities(n): pleural effusion(2), nausea/vomiting(2), dehydration(1), diarrhea(1), dyspnea(1). Toxicity led to hospitalization of 4 pts and drug discontinuation in 5 pts. ORR was 0. One pt was stable at 12 wks (PFS: 7.6%). This pt stopped drug at 15 wks due to toxicity, but also had PD. One pt died on study and cause was deemed unlikely related. Conclusions: Dosed at 100mg bid, dasatinib led to a characteristic toxicity profile in this pt population. Rates of hospitalization and discontinuation for toxicity were fairly high. Final efficacy parameters are pending evaluation of 2 pts. Evaluation of PK and tissue/blood biomarkers is ongoing.

No significant financial relationships to disclose.

Characterization of a novel TYMP splice site mutation associated with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE)

Mitochondrial neurogastrointestinal encephalomyopathy is an autosomal recessive disorder caused by loss-of-function mutations in the thymidine phosphorylase gene (TYMP). We report here a patient compound heterozygous for two TYMP mutations: a novel g.4009G>A transition affecting the consensus splice donor site of intron 9, and a previously reported g.675G>C splice site mutation. The novel mutation causes exon 9 skipping but leaves the reading frame intact; however, TYMP protein was not detected by immunoblot analysis, suggesting that neither mutant allele is expressed as protein. The patient's fibroblasts showed gradual loss of the mitochondrial DNA-encoded subunit I of cytochrome-c oxidase, suggesting a progressive mitochondrial DNA defect in culture.

The use of nerve and muscle biopsy in the diagnosis of vasculitis: a 5 year retrospective study

INTRODUCTION

Peripheral nerve vasculitis is an important condition which can be diagnostically challenging and is one of the principal current indications for nerve and muscle biopsy. Previous studies have suggested that combined nerve and muscle biopsy (usually of the superficial peroneal nerve and peroneus brevis muscle) produces a higher diagnostic yield than nerve biopsy alone in the investigation of vasculitis.

OBJECTIVE

To determine whether in our two centres combined nerve (usually the sural) and muscle (usually the vastus lateralis) biopsy improved diagnostic yield compared with nerve biopsy alone.

METHODS

We interrogated our database of all nerve biopsies (usually of the sural nerve) performed at our institutions over 5 years and identified 53 cases of biopsy proven peripheral nerve vasculitis. Clinicopathological and neurophysiological data in these patients were reviewed.

RESULTS

The most common clinical presentation was with a painful asymmetric axonal polyneuropathy or mononeuritis multiplex (66% of cases). Nerve biopsy demonstrated definite vasculitis in 36%, probable vasculitis in 62% and no vasculitis in 2% of cases. In 24 patients a muscle biopsy (usually the vastus lateralis) was also performed and vasculitis was demonstrated in 46% of these (in 13% showing definite and 33% probable vasculitis). There was only one patient in whom vasculitis was demonstrated in muscle but not in peripheral nerve.

CONCLUSION

Combined nerve (usually sural) and vastus lateralis muscle biopsy did not significantly increase the diagnostic yield compared with nerve biopsy alone. A sensible approach to the diagnosis of peripheral nerve vasculitis is to choose a nerve to biopsy which is clinically affected and amenable to biopsy. If the sural nerve is chosen, the data suggest that it is not routinely worth doing a vastus lateralis biopsy at the same time, whereas if the superficial peroneal nerve is chosen, it seems appropriate to do a combined superficial peroneal nerve and peroneus brevis biopsy. It is still not known if both the sural and superficial peroneal nerves are involved clinically which one gives the higher yield if biopsied.

Effective treatment of an elderly patient with Gaucher's disease and Parkinsonism: A case report of 24 months’ oral substrate reduction therapy with miglustat

We report here the results of 24 months' treatment with oral miglustat of a patient with mild-to-moderate Gaucher's disease (GD) and Parkinsonism. The patient's progressive Parkinsonian tremor, in addition to restricted vascular access, necessitated switching treatment for GD from intravenously infused enzyme replacement therapy (ERT) that had been administered for the previous 7 years. With control of haematological parameters and markers of GD activity improved or maintained and no notable adverse effects, miglustat treatment proved an effective and well-tolerated therapeutic alternative to ERT. Oral miglustat should be considered for the treatment of patients with type I GD and concurrent movement disorders who are unsuitable for ERT.

CNS manifestations of Fabry's disease

BACKGROUND

Fabry's disease is a rare hereditary lysosomal storage disease with multiorgan involvement. Deficiency of alpha-galactosidase A activity leads to accumulation of neutral glycosphingolipids, especially in vascular endothelial and smooth-muscle cells. Along with progressive renal and cardiac dysfunction, stroke is a major and often life-threatening burden of the disease. Cerebral vasculopathy, confirmed by neuropathological, neuroradiological, and functional studies, occurs commonly and leads to ischaemic cerebrovascular events at an early age.

RECENT DEVELOPMENTS

Fabry's disease is an X-linked disease and women have been regarded as only mildly affected carriers. However, research has shown a high prevalence of ischaemic stroke and transient ischaemic attacks, along with imaging evidence of CNS involvement, in female patients with the disease, which suggests that at least in a subgroup of clinically affected women the severity of CNS disease is comparable to that in men. Another study has shown a high prevalence of the disease in young patients of both sexes with cryptogenic stroke, emphasising the need for more clinical attention to be paid to this under-diagnosed disease. WHERE NEXT?: These new findings should be replicated in larger samples. Brain structural changes and CNS involvement in the disease need to be monitored carefully in follow-up studies to broaden our knowledge of the course of neurobiological changes and to identify potential effects of enzyme-replacement therapy, which is already showing some benefit in cardiac and renal dysfunction in the disease. Finally, a diagnosis of Fabry's disease should always be considered in young patients who have had a stroke.

Magnetic resonance imaging changes in Fabry disease

Recognized magnetic resonance imaging (MRI) abnormalities in the brains of patients with Fabry disease include the consequences of infarction and haemorrhage, non-specific white and grey matter lesions, vascular anomalies, in particular dolicho-ectasia, and a characteristic appearance of the posterior thalamus. A preliminary analysis of MRI findings in patients registered in FOS, the Fabry Outcome Survey, indicates that most patients had abnormal scans (25/47). The commonest abnormality, in males and females, was the presence of cerebral white matter lesions, the number of which increased with patient age.

CONCLUSION

MRI is a valuable resource for assessing the CNS complications of Fabry disease, and their response to time and treatment.

Brachial plexus hypertrophy in chronic inflammatory demyelinating polyradiculoneuropathy

We present the clinical, imaging and neuropathological findings in three patients with predominant brachial plexus neuropathy. MR scanning was key to determining the brachial plexus involvement. Biopsy of the brachial plexus was performed in one patient. The appearances of the brachial plexus on MRI, in conjunction with the clinical presentations of these patients, suggest that they are unusual variants within the spectrum of chronic inflammatory demyelinating polyradiculoneuropathy.

Natural history of the cerebrovascular complications of Fabry disease

Fabry disease is a rare, X-linked lysosomal storage disease caused by an inborn deficiency of alpha-galactosidase A, which results in progressive accumulation of globotriaosylceramide in a range of cells and tissues. Neurological symptoms of Fabry disease, including peripheral neuropathy and cerebrovascular events, are among the most significant clinical aspects. In this paper we present the natural history and mechanisms involved in the cerebrovascular complications of Fabry disease using data reported in FOS-- the Fabry Outcome Survey--and other registries and clinical studies. We discuss ways in which these manifestations can be modified by intervention, including both general measures for cerebrovascular disease and enzyme replacement therapy.

CONCLUSION

Data from FOS have provided important insights into the natural history of the cerebrovascular complications of Fabry disease. Furthermore, the database has demonstrated that significant renal or cardiac disease often co-exists with cerebrovascular disease, and may predispose patients with Fabry disease to neurological disability and stroke.

A novel RAB7 mutation associated with ulcero-mutilating neuropathy

There are two known autosomal dominant genes for the hereditary ulcero-mutilating neuropathies: SPTLC1 (hereditary sensory neuropathy type 1) and RAB7 (Charcot-Marie-Tooth disease type 2B). We report a family with autosomal dominant ulcero-mutilating neuropathy, developing in the teens and characterized by ulcers, amputations, sensory involvement in the feet but no motor features. Sequencing the RAB7 gene showed a novel heterozygous A to C mutation, changing asparagine to threonine at codon 161. The mutation is situated adjacent to a previously identified valine to methionine mutation at codon 162, implying a hotspot for mutations in the highly conserved C terminus of RAB7.

Exophytic ependymomas of the spinal cord

Intramedullary ependymomas of the spinal cord with exophytic components are rare outside the filum or conus region. Two cases of combined intradural intramedullary and extramedullary ependymomas of the spinal cord are presented. At operation, the tumours proved to be primarily intramedullary but had a contiguous exophytic component that extruded either through a defect in the ventral pia to encase the anterior spinal artery in one patient, or through the dorsal root entry zone in the second patient. When removing intramedullary spinal tumours with an exophytic component, separate removal of the intramedullary and extramedullary components is recommended, rather than en bloc resection, to prevent possible injury to the vascular supply of the spinal cord.

A clinical, genetic and biochemical study of SPG7 mutations in hereditary spastic paraplegia

Mutations in the SPG7 gene, encoding the mitochondrial protein paraplegin, were the first to be identified in autosomal recessive hereditary spastic paraplegia (ARHSP). Four different SPG7 mutations have been described so far in association with both pure and complicated HSP phenotypes. Muscle biopsies from the most severely affected patients have shown histological evidence of an oxidative phosphorylation defect. We identified six ARHSP kindreds, in whom linkage to SPG7 could not be excluded, and 29 sporadic spastic paraplegia patients. The 17 exons and flanking regions of the SPG7 gene were screened for mutations using a combination of single-stranded conformation polymorphism (SSCP) analysis and sequencing. Three patients were found to carry compound heterozygous SPG7 mutations, comprising five novel and one previously described mutation. Muscle biopsies from two SPG7 mutation patients did not show any histological evidence of an oxidative phosphorylation defect. However, biochemical analysis revealed a reduction in citrate synthase-corrected complex I and complex II/III activities in muscle and complex I activity in mitochondrial-enriched fractions from cultured myoblasts, suggesting that either a primary or a secondary defect of respiratory chain function may play an important role in the pathogenesis of the disease.

Coexistent hereditary and inflammatory neuropathy

Classically, the course of Charcot-Marie-Tooth (CMT) disease is gradually progressive. We describe eight atypical patients who developed acute or subacute deterioration. Seven of these had genetically proven CMT disease type 1A (CMT1A) due to chromosome 17p11.2-12 duplication, and one had X-linked disease (CMTX) due to a mutation in the GJB1 gene. In this group there was sufficient clinical, electrophysiological and neuropathological information to indicate a diagnosis of a superimposed inflammatory polyneuropathy. The age range of the patients was 18-69 years, with a mean of 39 years. A family history of a similar neuropathic condition was present in only four patients. All eight had an acute or subacute deterioration following a long asymptomatic or stable period. Seven had neuropathic pain or prominent positive sensory symptoms. Nerve biopsy demonstrated excess lymphocytic infiltration in all eight patients. Five patients were treated with steroids and/or intravenous immunoglobulin, with variable positive response; three patients received no immunomodulatory treatment. Inflammatory neuropathy has previously been recognized in patients with hereditary neuropathy, with uncharacterized genetic defects and with CMT1B. We present detailed assessments of patients with CMT1A and CMTX, including nerve biopsy, and conclude that coexistent inflammatory neuropathy is not genotype-specific in hereditary motor and sensory neuropathy. Although this was not a formal epidemiological study, estimates of the prevalence of CMT disease and chronic inflammatory demyelinating polyneuropathy indicate that the association is more frequent than would be expected by chance. This has implications for understanding the pathogenesis of inflammatory neuropathies and raises important considerations in the management of patients with hereditary neuropathies. If a patient with CMT disease experiences an acute or subacute deterioration in clinical condition, treatment of a coexistent inflammatory neuropathy with steroids or immunoglobulin should be considered.

Pathological findings in a patient with ventilatory failure and chronic inflammatory demyelinating polyneuropathy

Chronic inflammatory demyelinating polyneuropathy (CIDP) may cause significant disability, but severe respiratory complications are uncommon. We describe the case of a 49-year-old man with clinical features of CIDP for 5 years who died of respiratory failure. Post-mortem findings of denervation in diaphragm muscle and axonal loss in phrenic nerve are presented. Severe ventilatory failure may occur in CIDP when neuropathy affects the respiratory muscles. Attention to early clinical features of respiratory insufficiency may facilitate the prevention of more severe features of respiratory failure.

Peripheral nerve granuloma in a patient with tuberculosis

The cause of peripheral neuropathy associated with tuberculosis is controversial. Possibilities include an immune mediated neuropathy, direct invasion of nerves, vasculitic neuropathy, compressive neuropathy, a meningitic reaction, and the toxic effects of antituberculous chemotherapy. This report describes the unusual finding of granulomas in the peripheral nerve of a patient with tuberculosis. The pathological findings were of a delayed hypersensitivity reaction, but with no more specific indications of the mechanism of the neuropathy.