Manu Jokela

Late onset spinal motor neuronopathy is caused by mutation in CHCHD10.

A study was undertaken to identify the responsible gene defect underlying late onset spinal motor neuronopathy (LOSMoN/SMAJ; Online Mendelian Inheritance in Man #615048), an autosomal dominant disease mapped to chromosome 22q11.2.

Late-onset lower motor neuronopathy: a new autosomal dominant disorder.

Objective: Characterization of a new type of late-onset autosomal dominant lower motor neuron disease. Methods: Patients from 2 families underwent detailed neurologic, electrophysiologic, muscle biopsy, and laboratory investigations. MRI of lower limbs was performed in selected patients. DNA samples from leukocytes were used for molecular genetic linkage studies. Results: First symptoms were muscle cramps and fasciculations after age 25–30, followed by a slowly progressive proximal and distal weakness without overt atrophy during the first decades of symptoms. Nerve conduction velocities were within normal range and EMG showed widespread neurogenic alterations. Muscle biopsy revealed characteristic neurogenic findings: fiber type grouping and group atrophy. MRI showed diffuse fatty-degenerative changes, marked in medial gastrocnemius. Conclusion: Exactly the same clinical phenotype has not previously been described, and linkage studies showed exclusion of known chromosomal loci for hereditary motor neuropathies, suggesting the disease we report may represent a new disorder.

Autosomal dominant late-onset spinal motor neuronopathy is linked to a new locus on chromosome 22q11.2-q13.2

Spinal muscular atrophies (SMAs) are hereditary disorders characterized by degeneration of lower motor neurons. Different SMA types are clinically and genetically heterogeneous and many of them show significant phenotypic overlap. We recently described the clinical phenotype of a new disease in two Finnish families with a unique autosomal dominant late-onset lower motor neuronopathy. The studied families did not show linkage to any known locus of hereditary motor neuron disease and thus seemed to represent a new disease entity. For this study, we recruited two more family members and performed a more thorough genome-wide scan. We obtained significant linkage on chromosome 22q, maximum LOD score being 3.43 at marker D22S315. The linked area is defined by flanking markers D22S686 and D22S276, comprising 18.9 Mb. The region harbours 402 genes, none of which is previously known to be associated with SMAs. This study confirms that the disease in these two families is a genetically distinct entity and also provides evidence for a founder mutation segregating in both pedigrees.

Late-onset spinal motor neuronopathy - a common form of dominant SMA.

We previously described two Finnish families with a new autosomal dominant late-onset spinal motor neuronopathy that was mapped to chromosome 22q11.2-q13.2. In the current screening study of 43 lower motor neuron disease patients from Finland and Sweden, we identified 26 new late-onset spinal motor neuronopathy patients sharing the founder haplotype. In addition to the main symptoms and signs: painful cramps, fasciculations, areflexia and slowly evolving muscle weakness, new features such as mild bulbar findings, were identified. The disease is relatively benign in terms of life expectancy and rate of disability progression, and it is therefore noteworthy that three patients were initially misdiagnosed with ALS. Significant recombinants in this new patient cohort restricted the disease locus by 90% to 1.8Mb. Late-onset spinal motor neuronopathy seems not to be very rare, at least not in Finland, with 38 patients identified in a preliminary ascertainment.

Towards a European Registry and Biorepository for Patients with Spinal and Bulbar Muscular Atrophy

Pathomechanisms of spinal and bulbar muscular atrophy (SBMA) have been extensively investigated and are partially understood, but no effective treatment is currently available for this disabling disorder. Its rarity, the slow disease progression, and lack of sensitive-to-change outcome measures render design and conduction of clinical trials a challenging task. Therefore, it is fundamental to strengthen the network of clinical centers interested in SBMA for clinical trial readiness. We propose to create and maintain an International SBMA Registry where as many well-characterized patients as possible can be included, with the following aims: facilitate planning of clinical trials and recruitment of patients, define natural history of the disease, characterize epidemiology, develop standards of care, and inform the community of patients about research progresses and ongoing trials. We also aim at developing harmonized and coordinated biorepositories. The experience obtained during the last years in the field of other neuromuscular disorders and of Huntington disease offers valuable precedents.

Diagnostic Clinical, Electrodiagnostic and Muscle Pathology Features of Spinal and Bulbar Muscular Atrophy.

Kennedy’s disease or spinal and bulbar muscular atrophy (SBMA) is a multi-system disorder affecting adult males, which is characterized by weakness of limbs and faciobulbar muscles primarily due to loss of lower motor neurons. Besides the obvious motor neuronopathy, additional findings in a substantial proportion of SBMA patients include sensory neuropathy and signs of androgen deficiency, such as poor sexual functioning and reduced fertility with gynaecomastia. The presence of elevated glucose, liver pathology or dyslipidaemia is less consistent features. We review the striking clinical, electrodiagnostic and muscle pathology features characteristic of Kennedy’s disease, which has some peculiar and diagnostically useful features not observed in many other neuromuscular disorders.

Botulinum toxin alleviates dysphagia of patients with inclusion body myositis

OBJECTIVES Oropharyngeal dysphagia is a disabling and undertreated symptom that often occurs in patients with sporadic inclusion body myositis (s-IBM). In this study, we examined the effect of botulinum neurotoxin A (BoNT-A) injections to the cricopharyngeus muscle (CPM) of patients with s-IBM and dysphagia. PATIENTS, MATERIALS AND METHODS A single-center retrospective study involving 40 biopsy-proven s-IBM-patients treated in the District of Southwest Finland from 2000 to 2013. The incidence of dysphagia, rate of aspirations, rate of aspiration pneumonias and treatment results of dysphagia were analyzed. Patients treated for dysphagia were evaluated before and after surgery by video-fluoroscopy and/or using a questionnaire. RESULTS Twenty-five of the 40 s-IBM patients (62.5%) experienced dysphagia. BoNT-A was injected a median of 2 times (range 1-7) in 12 patients with dysphagia. Before the injections 7 patients reported aspiration, none afterwards. The corresponding figures for aspiration pneumonia were 3 and 0. All of these patients had normal swallowing function 12months (median, range 2-60) after the last injection. CONCLUSION BoNT-A injections to the CPM alleviate the dysphagia of s-IBM patients reversibly and appear to reduce the rate of aspiration effectively.

CHCHD10 mutations and motor neuron disease: the distribution in Finnish patients

Motor neuron disorders (MNDs) are a heterogeneous group of diseases that result from degeneration of motor neurons. If both upper and lower motor neurons (UMNs and LMNs) are affected, the disease is classified as amyotrophic lateral sclerosis (ALS). Primary lateral sclerosis (PLS) and progressive muscular atrophy (PMA) selectively affect the UMNs or LMNs, respectively, but are sometimes considered to be incomplete ALS variants because their phenotype may evolve into typical ALS over time. Bulbar affection in a UMN disease would favour a diagnosis of PLS over hereditary spastic paraplegia (HSP), whereas rapid progression may separate PMA from adult-onset spinal muscular atrophy (SMA). Some SMA-like or even ALS-like phenotypes have been incorporated into the large category of sensorimotor axonal neuropathies (Charcot-Marie-Tooth disease type 2, CMT2),1 although sensory abnormalities may be subtle in some forms.2 On the other hand, spinal and bulbar muscular atrophy (Kennedy disease) is classified as a form of adult-onset SMA despite prominent sensory abnormalities. It has recently been argued that the current classification system of MNDs is unsatisfactory and should be revised to include genetically and prognostically important categories.3 We have recently identified a new form of motor neuron disease in 55 patients from 17 Finnish families, where distinctive phenotype did not match any pre-existing neuromuscular disease category.4–6 Spinal muscular atrophy Jokela type (SMAJ, OMIM #615048) is characterised by painful cramps, fasciculations, decreased or absent tendon reflexes, elevated creatine kinase and hand tremor. The first symptoms appear commonly after age 30–40. Electromyography (EMG) and muscle biopsy display widespread neurogenic findings and a proportion of patients show sensory abnormalities. Muscle weakness and atrophy appear much later in the disease course, and patients have remained ambulant for several decades and their life expectancy is within normal range.4 ,5 SMAJ is caused by a dominant …

Spontaneous activity in electromyography may differentiate certain benign lower motor neuron disease forms from amyotrophic lateral sclerosis

There is limited data on electromyography (EMG) findings in other motor neuron disorders than amyotrophic lateral sclerosis (ALS). We assessed whether the distribution of active denervation detected by EMG, i.e. fibrillations and fasciculations, differs between ALS and slowly progressive motor neuron disorders. We compared the initial EMG findings of 43 clinically confirmed, consecutive ALS patients with those of 41 genetically confirmed Late-onset Spinal Motor Neuronopathy and 14 Spinal and Bulbar Muscular Atrophy patients. Spontaneous activity was more frequently detected in the first dorsal interosseus and deltoid muscles of ALS patients than in patients with the slowly progressive motor neuron diseases. The most important observation was that absent fibrillations in the first dorsal interosseus muscle identified the benign forms with sensitivities of 66%-77% and a specificity of 93%. The distribution of active denervation may help to separate ALS from mimicking disorders at an early stage.

Double trouble: spinal muscular atrophy type II and seropositive myasthenia gravis in the same patient.

Autosomal recessive proximal spinal muscular atrophy is caused by deletions in the survival of motor neuron (SMN1) gene, while autoimmune myasthenia gravis is an acquired disorder. An association between these two diseases has not been reported. Our patient with intermediate spinal muscular atrophy (SMA type II) did not need alimentary or respiratory aid until age 51 when he suddenly developed bulbar weakness and respiratory insufficiency. Seropositive myasthenia gravis was confirmed and the corresponding symptoms resolved on treatment.