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

Update on recent advances in amyotrophic lateral sclerosis

In the last few years, our understanding of disease molecular mechanisms underpinning ALS has advanced greatly, allowing the first steps in translating into clinical practice novel research findings, including gene therapy approaches. Similarly, the recent advent of assistive technologies has greatly improved the possibility of a more personalized approach to supportive and symptomatic care, in the context of an increasingly complex multidisciplinary line of actions, which remains the cornerstone of ALS management. Against this rapidly growing background, here we provide an comprehensive update on the most recent studies that have contributed towards our understanding of ALS pathogenesis, the latest results from clinical trials as well as the future directions for improving the clinical management of ALS patients.

Amyotrophic lateral sclerosis; clinical features, differential diagnosis and pathology

Amyotrophic lateral sclerosis (ALS) is a late-onset syndrome characterized by the progressive degeneration of both upper motor neurons (UMN) and lower motor neurons (LMN). ALS forms a clinical continuum with frontotemporal dementia (FTD), in which there are progressive language deficits or behavioral changes. The genetics and pathology underlying both ALS and FTD overlap as well, with cytoplasmatic misvocalization of TDP-43 as the hallmark. ALS is diagnosed by exclusion. Over the years several diagnostic criteria have been proposed, which in essence all require a history of slowly progressive motor symptoms, with UMN and LMN signs on neurological examination, clear spread of symptoms through the body, the exclusion of other disorder that cause similar symptoms and an EMG that it is compatible with LMN loss. ALS is heterogeneous disorder that may present in multitude ways, which makes the diagnosis challenging. Therefore, a systematic approach in the diagnostic process is required in line with the most common presentations. Subsequently, assessing whether there are cognitive and/or behavioral changes within the spectrum of FTD and lastly determining the cause is genetic. This chapter, an outline on how to navigate this 3 step process.

A nationwide survey of facial onset sensory and motor neuronopathy in Japan

The epidemiology and etiology of facial onset sensory and motor neuronopathy (FOSMN), a rare syndrome that initiates with facial sensory disturbances followed by bulbar symptoms, remain unknown. To estimate the prevalence of FOSMN in Japan and establish the characteristics of this disease, we conducted a nationwide epidemiological survey. In the primary survey, we received answers from 604 facilities (49.8%), leading to an estimated number of 35.8 (95% confidential interval: 21.5-50.2) FOSMN cases in Japan. The secondary survey collected detailed clinical and laboratory data from 21 cases. Decreased or absent corneal and pharyngeal reflexes were present in over 85% of the cases. Electrophysiological analyses detected blink reflex test abnormalities in 94.1% of the examined cases. Immunotherapy was administered in 81% of cases and all patients received intravenous immunoglobulin. Among them, 35.3% were judged to have temporary beneficial effects evaluated by the physicians in charge. Immunotherapy tended to be effective in the early stage of disease. The spreading pattern of motor and sensory symptoms differed between cases and the characteristics of the motor-dominant and sensory-dominant cases were distinct. Cases with motor-dominant progression appeared to mimic amyotrophic lateral sclerosis. This is the first nationwide epidemiological survey of FOSMN in Japan. The clinical course of FOSMN is highly variable and motor-dominant cases developed a more severe condition than other types of cases. Because clinical interventions tend to be effective in the early phase of the disease, an early diagnosis is desirable.

Sensory neuropathy in amyotrophic lateral sclerosis: a systematic review

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the degeneration of both upper and lower motoneurons, leading to motor and non-motor symptoms. Recent evidence suggests that ALS is indeed a multisystem disorder, associated with cognitive impairment, dysautonomia, pain and fatigue, excess of secretions, and sensory symptoms. To evaluate whether sensory neuropathy could broaden its spectrum, we systematically reviewed its presence and characteristics in ALS, extracting data on epidemiological, clinical, neurophysiological, neuropathological, and genetic features. Sensory neuropathy can be found in up to 20% of ALS patients, affecting both large and small fibers, although there is a great heterogeneity related to different techniques used for its detection (electromyography vs skin biopsy vs nerve biopsy). Moreover, the association between CIDP-like neuropathy and ALS needs to be better explored, although it could be interpreted as part of the neuroinflammatory process in the latter disease. Sensory neuropathy in ALS may be associated with a spinal onset and might be more frequent in SOD1 patients. Moreover, it seems mutually exclusive with cognitive impairment. No associations with sex and other genetic mutation were observed. All these data in the literature reveal the importance of actively looking for sensory neuropathy in ALS patients, and suggest including sensory neuropathy among ALS non-motor features, as it may explain sensory symptoms frequently reported throughout the course of the disease. Its early identification could help avoid diagnostic delays and improve patients' treatment and quality of life.

Facial-onset sensory and motor neuronopathy with myasthenia gravis: A case report

RATIONALE

Facial-onset sensory and motor neuronopathy (FOSMN) is a greatly rare disease, so far, autopsy evidence that is associated with neurodegenerative. Myasthenia gravis (MG) is an antibody-mediated and complement-involved acquired autoimmune disorder of the post-synaptic neuromuscular junction. There have been few reports about if there is related between the 2. In this study, we present the case of a man who was diagnosed as FOSMN with MG in continuity.

PATIENT CONCERNS

The patient chief complaints were right-side facial numbness and right-eyelid incomplete closure, followed by slurred speech and dysphagia, and the symptoms gradually progressed. The patient serum was positive for anti-AchR and anti-Titin antibodies.

DIAGNOSES

The patient was diagnosed FOSMN with MG.

INTERVENTIONS

The patient symptoms were relieved after pyridostigmine bromide and prednisolone treatment.

OUTCOMES

Symptoms have improved.

LESSONS

Facial-onset sensory and motor neuronopathy and MG have disparate clinical features. Therefore, we reported a rare case in which the 2 conditions concurrently existed. Immune dysfunction might be the pathogenesis of this association, while there is no definite evidence to support it, further studies are needed.

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.

Atypical motor neuron disease variant: facial-onset sensory and motor neuronopathy syndrome (FOSMN)

Background

Facial-onset sensory and motor neuronopathy (FOSMN) is a rare disease whose cardinal features are initial asymmetrical facial sensory deficits slowly evolving and followed by bulbar symptoms and spreading of sensory and motor deficits from face to scalp, neck, and extremities.

Case presentation

We described a 70-year-old man who presented with 6-month history of facial numbness on the left side, and gradual worsening of symptoms. Over several months, facial muscle weakness, dysarthria, and fasciculation had progressed. NCS, needle EMG and blink reflex responses suggested the diagnosis of FOSMN. The ganglioside panel (anti-GM1 and Gd1b) was positive. Considering the FOSMN autoimmune pathology hypothesis, IVIG treatment was given.

Conclusion

In this case, we aimed to highlight the key clinical aspects of FOSMN and how to differentiate it from motor neuron disease and bring FOSMN to the attention of neurologists as a recently recognized and distinctive disorder.

Molecular Dissection of TDP-43 as a Leading Cause of ALS/FTLD

TAR DNA binding protein 43 (TDP-43) is a DNA/RNA binding protein involved in pivotal cellular functions, especially in RNA metabolism. Hyperphosphorylated and ubiquitinated TDP-43-positive neuronal cytoplasmic inclusions are identified in the brain and spinal cord in most cases of amyotrophic lateral sclerosis (ALS) and a substantial proportion of frontotemporal lobar degeneration (FTLD) cases. TDP-43 dysfunctions and cytoplasmic aggregation seem to be the central pathogenicity in ALS and FTLD. Therefore, unraveling both the physiological and pathological mechanisms of TDP-43 may enable the exploration of novel therapeutic strategies. This review highlights the current understanding of TDP-43 biology and pathology, describing the cellular processes involved in the pathogeneses of ALS and FTLD, such as post-translational modifications, RNA metabolism, liquid–liquid phase separation, proteolysis, and the potential prion-like propagation propensity of the TDP-43 inclusions.

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 neuropathy in a pain clinic outpatient: a case report

Background

Facial onset sensory and motor neuropathy is a very rare sensorimotor disorder characterized by facial onset and gradual progression, with approximately 100 cases reported worldwide in 2020. We report on our experience with a facial onset sensory and motor neuropathy case in our outpatient pain clinic.

Case presentation

A 71-year-old Japanese man with a previous diagnosis of trigeminal nerve palsy complained of facial paresthesia, cervical pain, and arm numbness. Cervical facet arthropathy was diagnosed initially, but neither pharmacotherapy nor nerve blocking alleviated his symptoms. We suspected bulbar palsy based on the presence of tongue fasciculation, which prompted referral to a neurologist. Based on a series of neurological examinations, facial onset sensory and motor neuropathy was ultimately diagnosed.

Conclusions

Pain clinicians must be mindful of rare diseases such as facial onset sensory and motor neuropathy; if they are unable to make a diagnosis, they should consult with other competent specialists.

TDP-43 proteinopathies: a new wave of neurodegenerative diseases

Inclusions of pathogenic deposits containing TAR DNA-binding protein 43 (TDP-43) are evident in the brain and spinal cord of patients that present across a spectrum of neurodegenerative diseases. For instance, the majority of patients with sporadic amyotrophic lateral sclerosis (up to 97%) and a substantial proportion of patients with frontotemporal lobar degeneration (~45%) exhibit TDP-43 positive neuronal inclusions, suggesting a role for this protein in disease pathogenesis. In addition, TDP-43 inclusions are evident in familial ALS phenotypes linked to multiple gene mutations including the TDP-43 gene coding (TARDBP) and unrelated genes (eg, C9orf72). While TDP-43 is an essential RNA/DNA binding protein critical for RNA-related metabolism, determining the pathophysiological mechanisms through which TDP-43 mediates neurodegeneration appears complex, and unravelling these molecular processes seems critical for the development of effective therapies. This review highlights the key physiological functions of the TDP-43 protein, while considering an expanding spectrum of neurodegenerative diseases associated with pathogenic TDP-43 deposition, and dissecting key molecular pathways through which TDP-43 may mediate neurodegeneration.