David O. Hutchinson

Cerebral amyloid angiopathy related inflammation: three case reports and a review

Cerebral amyloid angiopathy related inflammation (CAA-I), previously described under various names, is a treatable encephalopathy usually occurring in older adults. Here, three patients are described with histopathologically confirmed CAA-I, and summarised data from the published literature are presented. CAA-I has a characteristic combination of clinical and radiological features. Definite diagnosis requires brain and leptomeningeal biopsy. A favourable response to immunosuppressive therapy is common and treatment without brain biopsy may be considered in selected patients. Diagnostic criteria for CAA-I are proposed.

Autosomal dominant nemaline myopathy with intranuclear rods due to mutation of the skeletal muscle ACTA1 gene: clinical and pathological variability within a kindred.

Nemaline Myopathy with Intranuclear Rods is a rare variant of nemaline myopathy, due in almost all instances to mutation of ACTA1, the gene encoding skeletal muscle alpha-actin. We describe the novel autosomal dominant occurrence in a three-generation kindred, and review previously reported cases. Onset of myopathic symptoms in our kindred was in infancy or early childhood. Beyond infancy, limb muscle weakness was non-disabling and minimally progressive. A tall thin face and facial myopathy were prominent features in the affected adults. By light microscopy, muscle biopsies ranged from almost normal, to chronic myopathy with sarcoplasmic and intranuclear rods. A heterozygous GTG-ATG mutation (Val163Met) was found in exon 4 of ACTA1 in affected individuals. Actin is normally present within the nucleus in only trace amounts. Mutation at postion 163 may result in intranuclear rods by virtue of its close proximity to a nuclear export signal within the actin molecule.

Intranuclear Rod Myopathy : Molecular Pathogenesis and Mechanisms of Weakness

Mutations in the α‐skeletal actin gene (ACTA1) result in a variety of inherited muscle disorders characterized by different pathologies and variable clinical phenotypes. Mutations at Val163 in ACTA1 result in pure intranuclear rod myopathy; however, the molecular mechanisms by which mutations at Val163 lead to intranuclear rod formation and muscle weakness are unknown.

Neuromuscular disease and respiratory failure

Neurologists should be able to anticipate and recognise the onset of respiratory failure in patients with neuromuscular disorders. Symptoms will differ depending on the speed of onset of the respiratory muscle weakness. Careful monitoring of respiratory function is particularly important in acute disorders such as Guillain-Barré syndrome. Patients with an unrecognised neuromuscular disorder may occasionally present with respiratory failure. Important investigations include vital capacity, mouth pressures, arterial blood gases, chest x ray and sometimes overnight respiratory monitoring. Patients with Guillain-Barré and other acute conditions may require short-term ventilatory support in the intensive care unit. Patients with some chronic disorders, such as motor neuron disease and Duchenne dystrophy, can be successfully treated with non-invasive ventilation, usually in collaboration with a respiratory physician. New-onset weakness of limb and respiratory muscles in the intensive care unit is usually due to critical illness myopathy or critical illness polyneuropathy, and treatment is supportive.

Presentation of intravascular lymphomatosis as lumbosacral polyradiculopathy

A 53‐year‐old man developed progressive sensory disturbance and weakness in the legs, sphincter disturbance, back pain, systemic symptoms, and pancytopenia. Electrophysiological tests indicated a widespread lumbosacral polyradiculopathy. Spinal magnetic resonance imaging and routine cerebrospinal fluid analysis showed minor nonspecific abnormalities. Bone marrow and liver biopsies showed hemophagocytosis; and polymerase chain reaction of cerebrospinal fluid, bone marrow, and serum suggested active infection with human herpesvirus‐6. Autopsy revealed that his neurological symptoms resulted from intravascular lymphomatosis (angiotropic large cell lymphoma), a rare variant of lymphoma with predilection for the nervous system.

HnRNP L and hnRNP LL antagonistically modulate PTB-mediated splicing suppression of CHRNA1 pre-mRNA

CHRNA1 gene, encoding the muscle nicotinic acetylcholine receptor alpha subunit, harbors an inframe exon P3A. Inclusion of exon P3A disables assembly of the acetylcholine receptor subunits. A single nucleotide mutation in exon P3A identified in congenital myasthenic syndrome causes exclusive inclusion of exon P3A. The mutation gains a de novo binding affinity for a splicing enhancing RNA-binding protein, hnRNP LL, and displaces binding of a splicing suppressing RNA-binding protein, hnRNP L. The hnRNP L binds to another splicing repressor PTB through the proline-rich region and promotes PTB binding to the polypyrimidine tract upstream of exon P3A, whereas hnRNP LL lacking the proline-rich region cannot bind to PTB. Interaction of hnRNP L with PTB inhibits association of U2AF65 and U1 snRNP with the upstream and downstream of P3A, respectively, which causes a defect in exon P3A definition. HnRNP L and hnRNP LL thus antagonistically modulate PTB-mediated splicing suppression of exon P3A.

Autonomic dysfunction is a major feature of cerebellar ataxia, neuropathy, vestibular areflexia ‘CANVAS’ syndrome

Cerebellar ataxia, neuropathy and vestibular areflexia syndrome (CANVAS) is a recently recognized neurodegenerative ganglionopathy. Prompted by the presence of symptomatic postural hypotension in two patients with CANVAS, we hypothesized that autonomic dysfunction may be an associated feature of the syndrome. We assessed symptoms of autonomic dysfunction and performed autonomic nervous system testing among 26 patients from New Zealand. After excluding three patients with diabetes mellitus, 83% had evidence of autonomic dysfunction; all patients had at least one autonomic symptom and 91% had more than two symptoms. We also found a higher rate of downbeat nystagmus (65%) than previously described in CANVAS. We confirmed that sensory findings on nerve conduction tests were consistent with a sensory ganglionopathy and describe two patients with loss of trigeminal sensation consistent with previous pathological descriptions of trigeminal sensory ganglionopathy. Our results suggest that autonomic dysfunction is a major feature of CANVAS. This has implications for the management of patients with CANVAS as the autonomic symptoms may be amenable to treatment. The findings also provide an important differential diagnosis from multiple system atrophy for patients who present with ataxia and autonomic failure.

Resolution of alcoholic neuropathy following liver transplantation

Between 10 and 20% of adult liver transplants are performed for end‐stage alcoholic liver disease. Severe extrahepatic end‐organ damage from alcoholism (cardiomyopathy, pancreatitis, central nervous system injury, and neuropathy) is widely regarded as an absolute contraindication to liver transplantation, despite a lack of data on the effect of transplantation on these complications. We describe such a patient who presented with decompensated alcoholic liver disease and moderately severe peripheral neuropathy. Both his liver failure and neuropathy progressed despite 9 months abstinence and intensive nutritional support. By 12 months post‐transplant, however, this patient had regained almost normal muscle strength, with associated recovery in sensory and motor conduction velocities. Direct alcohol toxicity, nutritional and vitamin deficiencies, and liver failure were all likely etiologic factors in this patients neuropathy. In conclusion, this case suggests that peripheral neuropathy in a patient with alcoholic cirrhosis may resolve following liver transplantation and should not constitute a contraindication to transplantation, even when it is disabling. (Liver Transpl 2004;10:1545–1548.)

Functional Characterization of C-terminal Ryanodine Receptor 1 Variants Associated with Central Core Disease or Malignant Hyperthermia

BACKGROUND Central core disease and malignant hyperthermia are human disorders of skeletal muscle resulting from aberrant Ca2+ handling. Most malignant hyperthermia and central core disease cases are associated with amino acid changes in the type 1 ryanodine receptor (RyR1), the skeletal muscle Ca2+-release channel. Malignant hyperthermia exhibits a gain-of-function phenotype, and central core disease results from loss of channel function. For a variant to be classified as pathogenic, functional studies must demonstrate a correlation with the pathophysiology of malignant hyperthermia or central core disease. OBJECTIVE We assessed the pathogenicity of four C-terminal variants of the ryanodine receptor using functional analysis. The variants were identified in families affected by either malignant hyperthermia or central core disease. METHODS Four variants were introduced separately into human cDNA encoding the skeletal muscle ryanodine receptor. Following transient expression in HEK-293T cells, functional studies were carried out using calcium release assays in response to an agonist. Two previously characterized variants and wild-type skeletal muscle ryanodine receptor were used as controls. RESULTS The p.Met4640Ile variant associated with central core disease showed no difference in calcium release compared to wild-type. The p.Val4849Ile variant associated with malignant hyperthermia was more sensitive to agonist than wild-type but did not reach statistical significance and two variants (p.Phe4857Ser and p.Asp4918Asn) associated with central core disease were completely inactive. CONCLUSIONS The p.Val4849Ile variant should be considered a risk factor for malignant hyperthermia, while the p.Phe4857Ser and p.Asp4918Asn variants should be classified as pathogenic for central core disease.

Congestive myeloradiculopathy in a patient with Cowden syndrome.

We present a patient with newly diagnosed Cowden syndrome and congestive myeloradiculopathy secondary to spinal dural arteriovenous fistula (SDAVF). This patient illustrates the difficulties that can be encountered in diagnosing SDAVF and emphasises the need to pursue the diagnosis in the appropriate clinical setting, as treatment can lead to significant neurological improvement. To our knowledge this is also the first reported case of an association between Cowden syndrome and SDAVF.