The histopathological spectrum of malignant hyperthermia and rhabdomyolysis due to RYR1 mutations.

OBJECTIVE: The histopathological features of malignant hyperthermia (MH) and non-anaesthetic (mostly exertional) rhabdomyolysis (RM) due to RYR1 mutations have only been reported in a few cases. METHODS: We performed a retrospective multi-centre cohort study focussing on the histopathological features of patients with MH or RM due to RYR1 mutations (1987-2017). All muscle biopsies were reviewed by a neuromuscular pathologist. Additional morphometric and electron microscopic analysis were performed where possible. RESULTS: Through the six participating centres we identified 50 patients from 46 families, including patients with MH (n = 31) and RM (n = 19). Overall, the biopsy of 90% of patients showed one or more myopathic features including: increased fibre size variability (n = 44), increase in the number of fibres with internal nuclei (n = 30), and type I fibre predominance (n = 13). Abnormalities on oxidative staining, generally considered to be more specifically associated with RYR1-related congenital myopathies, were observed in 52%, and included unevenness (n = 24), central cores (n = 7) and multi-minicores (n = 3). Apart from oxidative staining abnormalities more frequently observed in MH patients, the histopathological spectrum was similar between the two groups. There was no correlation between the presence of cores and the occurrence of clinically detectable weakness or presence of (likely) pathogenic variants. CONCLUSIONS: Patients with RYR1-related MH and RM exhibit a similar histopathological spectrum, ranging from mild myopathic changes to cores and other features typical of RYR1-related congenital myopathies. Suggestive histopathological features may support RYR1 involvement, also in cases where the in vitro contracture test is not informative.

Outcome of children with acetylcholine receptor (AChR) antibody positive juvenile myasthenia gravis following thymectomy.

Most evidence supporting the benefit of thymectomy in juvenile myasthenia gravis (JMG) is extrapolated from adult studies, with only little data concerning paediatric populations. Here we evaluate the outcome of children with generalized JMG who underwent thymectomy between 1996 and 2010 at 2 tertiary paediatric neurology referral centres in the United Kingdom. Twenty patients (15 female, 5 male), aged 13months to 15.5years (median 10.4years) at disease onset, were identified. Prior to thymectomy, disease severity was graded as IIb in 3, III in 11, and IV in 6 patients according to the Osserman classification. All demonstrated positive anti-acetylcholine receptor (AChR) antibody titres. All patients received pyridostigmine and 14 received additional steroid therapy. Transternal thymectomy was performed at the age of 2.7-16.6years (median 11.1years). At the last follow-up (10months to 10.9years, median 2.7years, after thymectomy), the majority of children demonstrated substantial improvement, although some had required additional immune-modulatory therapies. About one third achieved complete remission. The postoperative morbidity was low. No benefit was observed in one patient with thymoma. We conclude that thymectomy should be considered as a treatment option early in the course of generalised AChR antibody-positive JMG.

Homozygous variegate porphyria presenting with developmental and language delay in childhood.

Variegate porphyria is an autosomal dominant disorder that usually presents with photosensitivity and acute neurological crises in adulthood. It is caused by heterozygous mutations in the protoporphyrinogen oxidase gene (PPOX). A rarer variant, homozygous variegate porphyria (HVP), presents in childhood with recurrent skin blisters and scarring. More variable features of HVP are short stature, brachydactyly, nystagmus, epilepsy, developmental delay and mental retardation. We describe a child who presented with nystagmus, developmental delay and ataxia, combined with a photosensitive eruption. Analysis of porphyrins in plasma, urine and stool supported a clinical diagnosis of HVP. DNA from the patient showed that he is compound heterozygous for two novel missense mutations in the PPOX coding region: c.169G>C (p.Gly57Arg) and c.1259C>G (Pro420Arg). Interestingly, cranial magnetic resonance imaging showed an absence of myelin, a feature not previously reported in HVP, which expands the differential diagnosis of childhood hypomyelinating leucoencephalopathies.

Mutations in RYR1 are a common cause of exertional myalgia and rhabdomyolysis.

Mutations in the skeletal muscle ryanodine receptor (RYR1) gene are a common cause of neuromuscular disease, ranging from various congenital myopathies to the malignant hyperthermia (MH) susceptibility trait without associated weakness. We sequenced RYR1 in 39 unrelated families with rhabdomyolysis and/or exertional myalgia, frequent presentations in the neuromuscular clinic that often remain unexplained despite extensive investigations. We identified 9 heterozygous RYR1 mutations/variants in 14 families, 5 of them (p.Lys1393Arg; p.Gly2434Arg; p.Thr4288_Ala4290dup; p.Ala4295Val; and p.Arg4737Gln) previously associated with MH. Index cases presented from 3 to 45 years with rhabdomyolysis, with or without exertional myalgia (n=12), or isolated exertional myalgia (n=2). Rhabdomyolysis was commonly triggered by exercise and heat and, less frequently, viral infections, alcohol and drugs. Most cases were normally strong and had no personal MH history. Inconsistent additional features included heat intolerance, and cold-induced muscle stiffness. Muscle biopsies showed mainly subtle changes. Familial RYR1 mutations were confirmed in relatives with similar or no symptoms. These findings suggest that RYR1 mutations may account for a substantial proportion of patients presenting with unexplained rhabdomyolysis and/or exertional myalgia. Associated clinico-pathological features may be subtle and require a high degree of suspicion. Additional family studies are paramount in order to identify potentially MH susceptible relatives.

Charcot-Marie-Tooth (CMT) disease 1A with superimposed inflammatory polyneuropathy in children.

Charcot-Marie-Tooth (CMT) disease is genetically heterogeneous and subdivided into demyelinating (CMT 1) and axonal (CMT 2) types based on neurophysiology findings. CMT1A, the commonest form associated with duplication of the PMP22 segment on chromosome 17p, often arises in childhood but is generally a slowly progressive disease. We report 2 children presenting with clinical features of an acute inflammatory demyelinating polyneuropathy (AIDP) who were subsequently diagnosed with underlying CMT1A. Both children had neurophysiology and histopathology features consistent with CMT1. Immunoglobulin treatment was initiated considering the evidence of superimposed inflammation and appeared to modify disease progression. Our findings indicate that CMT1A predisposes to a superimposed inflammatory neuropathy. Recognition of this association is difficult, particularly in children without clear family history, but of great importance as immunomodulatory treatment may improve outcome. In addition, we postulate that an underlying genetic polyneuropathy should be suspected if the recovery from AIDP is slower than expected, or incomplete.

Interfamilial phenotypic heterogeneity in SMARD1.

Spinal muscular atrophy with respiratory distress (SMARD1: mu-binding protein 2 gene mutation) is characterised by low birth weight, progressive distal limb weakness, diaphragmatic paralysis and subsequent respiratory failure manifesting before 13 months of age. Our case report illustrates marked phenotype variability in two siblings with an identical genetic mutation of SMARD1, one of whom died of fulminant respiratory failure aged 6 months, whereas the other shows limb weakness but, only mild sleep hypoventilation aged 12 years. This suggests other compensatory mechanisms may play a role in modifying SMARD1; broadening our perception of phenotype. Therefore, SMARD1 phenotype should be considered in cases of atypical spinal muscular atrophy even in the absence of overt diaphragmatic weakness.

Surgery for scoliosis in Duchenne muscular dystrophy.

BACKGROUND: Scoliosis in people with Duchenne muscular dystrophy is usually progressive and treated with surgery. However, it is unclear whether the existing evidence is sufficiently scientifically rigorous to support a recommendation for spinal surgery for most people with Duchenne muscular dystrophy and scoliosis. OBJECTIVES: The objectives of this systematic review were to determine the effectiveness and safety of spinal surgery in Duchenne muscular dystrophy patients with scoliosis. We intended to test whether spinal surgery is effective in increasing life expectancy, improving respiratory function, improving quality of life and overall functioning; and whether spinal surgery is associated with severe adverse effects. SEARCH STRATEGY: We searched the specialized registers of the Cochrane Neuromuscular Disease Group and Cochrane Back Group, the Cochrane Central Register of Controlled Trials (January 2006), MEDLINE (January 1966 to January 2006), EMBASE (January 1980 to January 2006), Dissertation Abstracts International (1861 to Jan 2006), CINAHL (January 1982 to January 2006), and the National Institute of Health Clinical Trials Database (January 2006). No language restrictions were imposed. SELECTION CRITERIA: Controlled clinical trials using random or quasi-random allocation of treatment evaluating all forms of spinal surgery for scoliosis in patients with Duchenne muscular dystrophy were to be included in the review. The control interventions would have been no treatment, non-operative treatment, or a different form of spinal surgery. DATA COLLECTION AND ANALYSIS: Two authors examined the search results and evaluated the study characteristics against inclusion criteria to decide which ones would be included in the review. MAIN RESULTS: A total of 402 studies were identified from electronic searching. Thirty-six studies were relevant but none met the inclusion criteria for the review, because they were not clinical trials but prospective or retrospective reviews of case series. AUTHORS' CONCLUSIONS: Since there were no randomized controlled clinical trials available to evaluate the effectiveness of scoliosis surgery in people with Duchenne muscular dystrophy, no evidence-based recommendation can be made for clinical practice. Patients should be informed about the uncertainty of benefits and potential risks of surgery for scoliosis. Randomized controlled trials are needed to investigate the effectiveness of scoliosis surgery, in terms of patients' quality of life, functional status, respiratory function and life expectancy.

A proposed classification for subtypes of arterial ischaemic stroke in children.

The aim of this study was to propose a classification system for childhood arterial ischaemic stroke (AIS). Subtypes from the Trial of Org 10172 in Acute Stroke Therapy (TOAST) classification, previously shown to be applicable to children, were retained in the proposed Paediatric Stroke Classification (PSC). Additional important paediatric AIS aetiologies were identified from a literature review. Preliminary validation was performed by three raters who categorized clinical vignettes from 135 patients (66 male; median age 6.3 y, range 0.1 to 16 y). Eight aetiological subtypes were identified and defined, as follows: (1) sickle cell disease; (2) cardioembolic; (3) moyamoya syndrome; (4) cervical arterial dissection; (5) steno-occlusive cerebral arteriopathy; (6) other determined aetiology; (7) multiple probable/possible aetiologies; and (8) undetermined aetiology. There was very good agreement between the raters about categorization of the vignettes. Causes of disagreement were identified and final categories and definitions were modified accordingly. We conclude that the PSC enables the categorization of children with AIS into aetiological subtypes relevant to this age group. This will be useful in multicentre studies of natural history and treatment but will require further independent validation.

Arterial dissection complicating tonsillectomy.

Tonsillectomy is a frequently performed surgical procedure. Surgical complications can be serious. We report the case of a 7-year-old female who experienced an arterial ischaemic cerebral infarction following elective adenotonsillectomy.

Ischaemic stroke subtypes in children and adults.

Ischaemic stroke subtypes in children and adults were compared to determine the similarity in aetiologies. Thirty-six children (22 females, 14 males; median age 5 years 7 months, range 6 weeks to 15 years 10 months) and 50 adults (35 males, 15 females; median age 44 years, range 17 years 2 months to 49 years 11 months) who had presented with ischaemic stroke between 1995 and 2000, were categorized using a modified version of the Trial of Org 10172 in Acute Stroke Therapy (TOAST) classification. Proportions of patients in the subtypes of the TOAST classification system were significantly different in the two groups (chi2 test, p<0.01). The first three subtypes (large artery atherosclerosis, cardioembolic, and small vessel disease) accounted for the majority of adult strokes (27 of 50). In contrast, only three of 36 children were accounted for within these three subtypes. The majority of children (29 of 36) were classified within the 'other determined aetiology' subtype. Aetiology was undetermined in 12 of 50 adults compared with three of 36 children. Causes of ischaemic stroke in children and adults are distinct. A classification system for ischaemic stroke in children would be useful for collaborative studies.

Fat oxidation defect presenting with overwhelming ketonuria.

Ketonuria accompanying hypoglycaemia is conventionally thought to exclude fat oxidation defects. We describe a 2 year old girl with hypoglycaemic encephalopathy in whom a diagnosis of very long chain acyl CoA dehydrogenase deficiency was suggested on the basis of acylcarnitine analysis despite massive ketonuria.

Idiopathic intracranial hypertension: is papilloedema inevitable?

Headaches and papilloedema are key features of idiopathic (benign) intracranial hypertension (IIH). We describe three children in whom IIH was diagnosed in the absence of papilloedema. Recognition of atypical cases of IIH is important because pressure lowering treatment may be effective.

Investigation of daytime wetting: when is spinal cord imaging indicated?

BACKGROUND: Most children with daytime wetting have detrusor instability. A minority have neuropathic vesicourethral dysfunction. The commonest cause is spina bifida, which may be closed. Clinical features suggestive of closed spina bifida include cutaneous, neuro-orthopaedic or lumbosacral spine x ray abnormalities, impaired bladder sensation, and incomplete bladder emptying. MRI is the ideal method for detecting spinal cord abnormality. It has been suggested that MRI spine is an unnecessary investigation in children with daytime wetting in the absence of cutaneous, neuro-orthopaedic, or lumbosacral spine x ray abnormalities. AIM: To clarify indications for magnetic resonance imaging (MRI) of the spine in children with voiding dysfunction. METHODS: Retrospective study of children with voiding dysfunction referred from the Guy's Hospital neurourology clinic for MRI spine between April 1998 and April 2000. Clinical notes and results of investigations, including urodynamic studies and MRI spine were reviewed. RESULTS: There were 48 children (median age 9.1 years). Closed spina bifida was detected in five, of whom four had neuropathic vesicourethral dysfunction confirmed by urodynamic studies. Impaired bladder sensation and incomplete bladder emptying were more frequent in these children than in those with normal MRI spine. One child with spinal cord abnormality had no cutaneous, neuro-orthopaedic, or lumbosacral spine x ray abnormalities. CONCLUSION: Spinal cord imaging should be considered in children with daytime wetting when this is associated with impaired bladder sensation or poor bladder emptying, even in the absence of neuro-orthopaedic, cutaneous, or lumbosacral spine x ray abnormalities.

Hydrocarbon humps in the marine environment: synthesis, toxicity, and aqueous solubility of monoaromatic compounds.

A recent study has shown that some monoaromatic hydrocarbon constituents of the so-called unresolved complex mixtures (UCMs) or gas chromatographic humps, which are widespread in the marine environment, are toxic to the mussel Mytilus edulis. Here we describe the synthesis and toxicological assessment of 6-cyclohexyltetralin, 7-cyclohexyl-1-methyltetralin, and 7-cyclohexyl-1-n-propyltetralin, which contain structural features consistent with some monoaromatic UCM hydrocarbons. The compounds were all toxic to M. edulis when measured in the assay used previously to determine the toxicity of a monoaromatic UCM. The aqueous solubilities of the hydrocarbons in fresh and seawater at different temperatures were determined and found to range from about 10 to 110 microg/L (10-60 microg/L in seawater at 15 degrees C). Further studies of the aromatic UCM composition of a wide range of oils and oil residues are required to determine whether such alkylated compounds as 7-cyclohexyl-1-methyltetralin and 7-cyclohexyl-1-n-propyltetralin or their analogues are widespread in oils. If these aromatic compounds prove to be important in UCMs, toxicity experiments should be conducted with other biological end points and monitoring studies of pollutant hydrocarbons should probably include measurement of aromatic UCM hydrocarbons.

Aromatic hydrocarbon "humps" in the marine environment: unrecognized toxins?

Gas chromatographic analysis of the hydrocarbons of environmental samples often reveals that unresolved complex mixtures (UCMs) or gas chromatographic "humps" of aliphatic and aromatic hydrocarbons are most abundant--yet little consideration seems to have been given to the possible toxicological impacts of hydrocarbon "humps". Here we show, using a well-accepted bioassay, that monoaromatic components of a UCM of hydrocarbons from a crude oil elicit a sublethal toxic response in a typical marine pollution indicator organism (the mussel, Mytilus edulis). Furthermore, coastal U.K. mussels shown previously to have unexplained impaired health contained high concentrations of UCMs, including monoaromatic UCMs. These findings may have important implications for our understanding of the toxicological sublethal effects of oil residues in the environment. Given the relatively resistant nature of UCM hydrocarbons, the effects of both acute oil spills and more chronic discharges may need further consideration.

Effects of temperature on polyunsaturation in cytostatic lipids of Haslea ostrearia.

Unusual chemicals produced by the-'blue oyster' diatom, Haslea ostrearia, include the water-soluble blue pigment marennine and numerous polyunsaturated sesterterpene oils or haslenes. Aqueous extracts of the alga exhibit in vitro and in vivo activities against human lung cancer cells and anti-HIV effects. Here we report that three haslenes also demonstrate in vitro cytostatic action against a human lung cancer cell line. The most active haslene is the most unsaturated and unsaturation in the haslenes increases with increasing algal growth temperature.