Facial onset sensory and motor neuronopathy: a motor neuron disease with an oligogenic origin?

TARDBP Mutations in Facial-Onset Sensory and Motor Neuronopathy

Objectives

Facial-onset sensory and motor neuronopathy (FOSMN) is a rare neuromuscular disorder characterized by progressive facial sensory impairment followed by motor dysfunction in a rostro-caudal distribution. FOSMN is clinically and pathologically associated with amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD). In contrast to ALS/FTD, the genetic profile of patients with FOSMN and the role of genetic testing are poorly defined.

Methods

A 66-year-old woman was evaluated in our neuromuscular clinic for progressive facial pain, dysphagia, and dysarthria. Her diagnostic evaluation included brain and cervical MRI, nerve conduction studies and EMG, and an ALS/FTD next-generation sequencing panel.

Results

The patient was diagnosed with FOSMN, and we identified a N390D variant in transactive response DNA-binding protein (TDP-43/TARDBP). This variant has never been reported in FOSMN but was previously reported in 2 cases of ALS, and a N390S variant was also previously reported in FOSMN. A review of the literature revealed that TARDBP mutations are overrepresented in patients with FOSMN compared with patients with ALS/FTD. By contrast, other common familial forms of ALS, including C9ORF72 or SOD1, are respectively absent or rare in FOSMN.

Discussion

FOSMN is pathologically and genetically associated with TDP-43. Therefore, ALS genetic testing that includes specifically TARDBP should be considered in patients with FOSMN.

Diagnosis and differential diagnosis of MND/ALS: IFCN handbook chapter

•Accurate and rapid diagnosis of amyotrophic lateral sclerosis (ALS) is important to prevent erroneous interventions. •The recent Gold Coast criteria are easily applicable and have high sensitivity and specificity. •Future developments will help to distinguish ALS as a specific clinical-pathologic entity.

Accurate and rapid diagnosis of amyotrophic lateral sclerosis (ALS) is essential in order to provide accurate information for patient and family, to avoid time-consuming investigations and to permit an appropriate management plan. ALS is variable regarding presentation, disease progression, genetic profile and patient reaction to the diagnosis. It is obviously important to exclude treatable conditions but, in most patients, for experienced neurologists the diagnosis is clear-cut, depending on the presence of progressive upper and lower motor neuron signs. Patients with signs of restricted lower motor neuron (LMN) or upper motor neuron (UMN) dysfunction may present diagnostic difficulty, but electromyography (EMG) is often a determinant diagnostic test since it may exclude other disorders. Transcranial magnetic stimulation may aid detection of UMN dysfunction, and brain and spinal cord MRI, ultrasound and blood neurofilament measurements, have begun to have clinical impact, although none are themselves diagnostic tests. Several sets of diagnostic criteria have been proposed in the past; all rely on clinical LMN and UMN signs in different anatomic territories, EMG changes, exclusion of other disorders, and disease progression, in particular evidence of spreading to other anatomic territories. Fasciculations are a characteristic clinical feature and increased importance is now attached to fasciculation potentials detected by EMG, when associated with classical signs of denervation and reinnervation. The Gold Coast diagnostic criteria rely on the presence of UMN and LMN signs in one (or more) anatomic territory, or LMN signs in two (or more) anatomic territories, recognizing the fundamental clinical requirements of disease progression and exclusion of other diseases. Recent studies confirm a high sensitivity without loss of specificity using these Gold Coast criteria. In considering the diagnosis of ALS a critical question for future understanding is whether ALS should be considered a syndrome or a specific clinico-pathologic entity; this can only be addressed in the light of more complete knowledge.

Presence of Rare Variants is Associated with Poorer Survival in Chinese Patients with Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder with phenotypic and genetic heterogeneity. Recent studies have suggested an oligogenic basis of ALS, in which the co-occurrence of two or more genetic variants has additive or synergistic deleterious effects. To assess the contribution of possible oligogenic inheritance, we profiled a panel of 43 relevant genes in 57 sporadic ALS (sALS) patients and eight familial ALS (fALS) patients from five pedigrees in east China. We filtered rare variants using the combination of the Exome Aggregation Consortium, the 1000 Genomes and the HuaBiao Project. We analyzed patients with multiple rare variants in 43 known ALS causative genes and the genotype-phenotype correlation. Overall, we detected 30 rare variants in 16 different genes and found that 16 of the sALS patients and all the fALS patients examined harbored at least one variant in the investigated genes, among which two sALS and four fALS patients harbored two or more variants. Of note, the sALS patients with one or more variants in ALS genes had worse survival than the patients with no variants. Typically, in one fALS pedigree with three variants, the family member with three variants (Superoxide dismutase 1 (SOD1) p.V48A,  Optineurin (OPTN) p.A433V and TANK binding kinase 1 (TBK1) p.R573H) exhibited much more severe disease phenotype than the member carrying one variant (TBK1 p.R573H). Our findings suggest that rare variants could exert a negative prognostic effect, thereby supporting the oligogenic inheritance of ALS.

Facial onset sensory and motor neuronopathy (FOSMN syndrome): Cases series and systematic review

OBJECTIVE

To provide new and comprehensive evidence for diagnosis and management of FOSMN syndrome.

METHODS

We reviewed our database to identify patients with FOSMN syndrome. Online database including PubMed, EMBASE, and OVID were also searched for relevant cases.

RESULTS

We identified a total of 71 cases, including 4 cases from our database and 67 ones from online searching. A predominance of male was observed [44 (62.0%)] with median onset age of 53 (range: 7-75) years old. The median (range) disease duration was 60 (3-552) months at the time of the visit. The initial symptoms could be sensory deficits in face (80.3%) or oral cavity (4.2%), bulbar paralysis (7.0%), dysosmia (1.4%), dysgeusia (4.2%), weakness or numbness of upper limbs (5.6%), or lower limbs (1.4%). Abnormal blink reflex was presented in 64 (90.1%) patients. CSF tests showed elevated protein level in 5 (7.0%) patients. Six (8.5%) patients had MND-related gene mutation. Five (7.0%) patients showed transient responsiveness to immunosuppressive therapy, then deteriorated relentlessly. Fourteen (19.7%) patients died, with an average survival time of around 4 years. Among them, five patients died of respiratory insufficiency.

CONCLUSION

The age of onset, progress of disease course, and prognosis of FOSMN syndrome could be varied significantly. The prerequisites of diagnosis were progressive and asymmetric lower motor neuron dysfunction, with sensory dysfunction which usually showed in face at the onset. Immunosuppressive therapy could be tried in some patients with suspected inflammatory clues. In general, FOSMN syndrome tended to be motor neuron disease with sensory involvement.

Facial Onset Sensory and Motor Neuronopathy-Like Syndrome: A Case Report

OBJECTIVES

Facial onset sensory and motor neuronopathy syndrome (FOSMN) is a rare motor neuron disorder characterized by facial sensory and motor aberrations that progress to the upper limbs. We present a case of FOSMN-like syndrome that has characteristics of FOSMN but is confined to the craniofacial region.

METHODS

Retrospective chart review and review of the literature.

RESULTS

A 70-year-old woman presented with a 1-month history of progressive bilateral facial sensory loss and weakness affecting the trigeminal and hypoglossal nerves. Within 12 months, she developed debilitating weakness affecting her lower and midface bilaterally. After an extensive workup, a diagnosis of FOSMN-like syndrome was made, as symptoms failed to progress to the upper extremities.

CONCLUSIONS

This case demonstrates a unique presentation of FOSMN that we classify as FOSMN-like syndrome. Clinicians must maintain a high index of suspicion when a patient presents with clinical features characteristic of FOSMN syndrome without progression of symptoms distal to the craniofacial region because it may represent a FOSMN-like syndrome.

Small fiber neuropathy for assessment of disease severity in amyotrophic lateral sclerosis: corneal confocal microscopy findings

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder with progressive motor system impairment, and recent evidence has identified the extra-motor involvement. Small fiber neuropathy reflecting by sensory and autonomic disturbances in ALS has been reported to accompany the motor damage. However, non-invasive assessment of this impairment and its application in disease evaluation of ALS is scarce. We aim to evaluate the use of corneal confocal microscopy (CCM) to non-invasively quantify the corneal small fiber neuropathy in ALS and explore its clinical value in assessing disease severity of ALS.

METHODS

Sixty-six patients with ALS and 64 healthy controls were included in this cross-sectional study. Participants underwent detailed clinical assessments and corneal imaging with in vivo CCM. Using ImageJ, the following parameters were quantified: corneal nerve length (IWL) and dendritic cell density (IWDC) in the inferior whorl region and corneal nerve fiber length (CNFL), nerve fiber density (CNFD), nerve branch density (CNBD), and dendritic cell density (CDC) in the peripheral region. Disease severity was evaluated using recognized scales.

RESULTS

Corneal nerve lengths (IWL and CNFL) were lower while dendritic cell densities (IWDC and CDC) were higher in patients with ALS than controls in peripheral and inferior whorl regions (p < 0.05). Additionally, corneal nerve complexity in the peripheral region was greater in patients than controls with higher CNBD (p = 0.040) and lower CNFD (p = 0.011). IWL was significantly associated with disease severity (p < 0.001) and progression (p = 0.002) in patients with ALS. Patients with bulbar involvement showed significantly lower IWL (p = 0.014) and higher IWDC (p = 0.043) than patients without bulbar involvement.

CONCLUSIONS

CCM quantified significant corneal neuropathy in ALS, and alterations in the inferior whorl region were closely associated with disease severity. CCM could serve as a noninvasive, objective imaging tool to detect corneal small fiber neuropathy for clinical evaluation in ALS.

Facial Onset Sensory and Motor Neuronopathy: New Cases, Cognitive Changes, and Pathophysiology

Purpose of Review

To improve our clinical understanding of facial onset sensory and motor neuronopathy (FOSMN).

Recent Findings

We identified 29 new cases and 71 literature cases, resulting in a cohort of 100 patients with FOSMN. During follow-up, cognitive and behavioral changes became apparent in 8 patients, suggesting that changes within the spectrum of frontotemporal dementia (FTD) are a part of the natural history of FOSMN. Another new finding was chorea, seen in 6 cases. Despite reports of autoantibodies, there is no consistent evidence to suggest an autoimmune pathogenesis. Four of 6 autopsies had TAR DNA-binding protein (TDP) 43 pathology. Seven cases had genetic mutations associated with neurodegenerative diseases.

Summary

FOSMN is a rare disease with a highly characteristic onset and pattern of disease progression involving initial sensory disturbances, followed by bulbar weakness with a cranial to caudal spread of pathology. Although not conclusive, the balance of evidence suggests that FOSMN is most likely to be a TDP-43 proteinopathy within the amyotrophic lateral sclerosis–FTD spectrum.