Tongue atrophy and fasciculations in transthyretin familial amyloid neuropathy: An ALS mimicker

Lingual Fasciculation as a Point of Call for the Diagnosis of Amyotrophic Lateral Sclerosis: A Literature Review

BACKGROUND AND AIM

Dental surgeons often play a pivotal role in the initial detection of lingual fasciculations (LFs). These involuntary micro-movements of the tongue can serve as early clinical indicators of neurodegenerative diseases, with amyotrophic lateral sclerosis (ALS) being the most concerning. Therefore, it is imperative to educate dental surgeons on identifying LF and understanding the potential underlying pathologies.

OBJECTIVES

This study aimed to pinpoint the pathologies in which LFs could emerge as an early clinical marker. Our review focused on articles delineating patient populations exhibiting LF within broader pathological contexts, encompassing neurological and other conditions, with the aim of elucidating their etiologies.

METHODS

We conducted a comprehensive literature review across four databases (PubMed, Embase, Web of Science, and Scopus). Two authors independently extracted data, with consultation from a third author when necessary. Eligible articles included those describing patients with LFs, detailing the methods of detection, diagnosis, and associated pathologies.

RESULTS

Our review identified 22 articles encompassing 153 patients with LF, with an average age of 45.8 years and a female prevalence of 43%. Electromyography and ultrasound emerged as the predominant detection methods. ALS constituted the primary diagnosis in the majority of cases (91%). Additionally, other conditions diagnosed included Machado-Joseph disease (0.046%), familial transthyretin amyloid neuropathy (0.013%), Brown-Vialetto-Van-Laere syndrome (0.006%), chronic inflammatory demyelinating polyneuropathy (0.006%), bulbospinal amyotrophy or Kennedy's disease (0.006%), and osmotic demyelination syndrome (0.006%). LF secondary to organophosphate poisoning was also documented. Symptoms associated with LF encompassed taste alterations, dysphagia, difficulty swallowing, and slurred speech.

CONCLUSION

While primarily indicative of ALS, LFs may also signal diverse underlying pathologies. Healthcare practitioners should be vigilant in their detection and expedite patient referrals to facilitate early integration into care protocols.

Nerve conduction study on the split-hand plus index in Amyotrophic lateral sclerosis: correlations with lower motor neuron impairment

INTRODUCTION

In the arms of patients with Amyotrophic lateral sclerosis (ALS) two peculiar patterns of dissociated muscular atrophy have been described: the split-hand sign (with predominant atrophy of the lateral aspect of the hand, compared to hypothenar eminence) and the split-hand-plus sign (SHPS), a predominant abductor pollicis brevis (ABP) atrophy with sparing of flexor pollicis longus (FPL).

AIMS

In this case-control study, we evaluated the diagnostic utility of a neurophysiological indicator of SHPS and assessed its association with clinical features.

METHODS

We prospectively studied 59 incident ALS patients, 61 patients with ALS-mimic disorders (OND) and 61 non-neurological controls (NNCs). ABP and FPL compound muscle action potentials (CMAP) amplitudes were obtained by supramaximal stimulation of median nerve at elbow. Split-hand plus index (SHPI) was calculated according to the formula: APB-CMAP/FPL-CMAP.

RESULTS

SHPI was significantly lower in ALS compared to OND patients and NNCs (p < 0.0001). SHPI value < 1 was observed in 2% of NNCs and 9% of OND patients and demonstrated an accuracy of 71% in differentiating ALS from OND and an accuracy of 74% in differentiating ALS from NNC. SHPI was associated with higher LMN score, and higher disease severity as quantified by the ALSFRS-r.

CONCLUSION

Our results indicate that SHPI is a reliable indicator to distinguish ALS patients from ONDs and NNCs. SHPI was significantly associated to the degree of lower motor neuron impairment but showed no association with upper motoneuron impairment.

Lingual fasciculation: A point of call for the diagnosis of amyotrophic lateral sclerosis

A 60-year-old female patient, with no notable medical history, was referred by the internal medicine department for a dry mouth workup. The clinical examination revealed an absence of dryness, and the presence of lingual fasciculations, associated with difficulties in mastication and phonation. These symptoms appeared spontaneously 9 months before the consultation, after leaving confinement. Given the presence of lingual fasciculations, the diagnostic hypothesis of a neurological pathology, in particular amyotrophic lateral sclerosis (ALS), was suspected. After performing an electromyogram (EMG), the diagnosis of ALS was retained. Riluzole treatment was then started, and physical therapy sessions were scheduled. Riluzole allows an average gain of 4 to 6 months of life expectancy. Speech therapy and physical therapy allow to maintain the functions as long as possible and to improve the end-of-life conditions. The interest of early detection of ALS allows delaying the progression of the disease.

Novel approaches to diagnosis and management of hereditary transthyretin amyloidosis

Hereditary transthyretin amyloidosis (ATTRv) is a severe, adult-onset autosomal dominant inherited systemic disease predominantly affecting the peripheral and autonomic nervous system, heart, kidney and the eyes. ATTRv is caused by mutations of the transthyretin (TTR) gene, leading to extracellular deposition of amyloid fibrils in multiple organs including the peripheral nervous system. Typically, the neuropathy associated with ATTRv is characterised by a rapidly progressive and disabling sensorimotor axonal neuropathy with early small-fibre involvement. Carpal tunnel syndrome and cardiac dysfunction frequently coexist as part of the ATTRv phenotype. Although awareness of ATTRv polyneuropathy among neurologists has increased, the rate of misdiagnosis remains high, resulting in significant diagnostic delays and accrued disability. A timely and definitive diagnosis is important, given the emergence of effective therapies which have revolutionised the management of transthyretin amyloidosis. TTR protein stabilisers diflunisal and tafamidis can delay the progression of the disease, if treated early in the course. Additionally, TTR gene silencing medications, patisiran and inotersen, have resulted in up to 80% reduction in TTR production, leading to stabilisation or slight improvement of peripheral neuropathy and cardiac dysfunction, as well as improvement in quality of life and functional outcomes. The considerable therapeutic advances have raised additional challenges, including optimisation of diagnostic techniques and management approaches in ATTRv neuropathy. This review highlights the key advances in the diagnostic techniques, current and emerging management strategies, and biomarker development for disease progression in ATTRv.

Amyotrophic lateral sclerosis mimics

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset motor neuron disorder characterized by progressive degeneration of cortical, bulbar, and spinal motor neurons. When a patient presents with a progressive upper and/or lower motor syndrome, clinicians must pay particular attention to any atypical features in the history and/or clinical examination suggesting an alternate diagnosis, as up to 10% percent of patients initially diagnosed with ALS have a mimic of ALS. ALS is a clinical diagnosis and requires the exclusion of other disorders that may have similar presentations but a more favorable prognosis or an effective therapy. Because there is currently no specific diagnostic biomarker that is sensitive or specific for ALS, understanding the spectrum of clinical presentations of ALS and its mimics is paramount. While true mimics of ALS are rare, the clinician must correctly identify these disorders to avoid the misdiagnosis of ALS and to initiate effective treatment where available.

Thr124Met myelin protein zero mutation mimicking motor neuron disease

Mutations in myelin protein zero (MPZ) are associated with heterogeneous manifestations. In this study, we report clinical, electrophysiological, pathological, and muscle MRI findings from two relatives with MPZ Thr124Met variants, disclosing different phenotypes. The proband was a 73-year-old female with a 12-year-story of atrophy, weakness, and fasciculations in her proximal and distal lower limbs. EMG examination showed neurogenic signs with active denervation together with reduced sensory action potentials, without sensory symptoms. The initial diagnosis was of a slowly progressive lower motor neuron disease (MND) with subclinical sensory axonal neuropathy. Two years later, the observation of her 60-year-old nephew, who had a distal sensory-motor neuropathy, prompted the analysis of inherited neuropathies-related genes and revealed a MPZ Thr124Met mutation in both cases. Our findings expand the clinical spectrum of MPZ-related neuropathy and highlight that Thr124Met mutation may cause a syndrome mimicking MND. The challenging issue to detect sensory features in the diagnostic MND work up is discussed.

Motor neuron disease in three asymptomatic pVal50Met TTR gene carriers

We describe three unrelated patients with sporadic motor neuron disease (MND) and hereditary amyloid transthyretin (ATTRv) amyloidosis family history, who were asymptomatic carriers of the pVal50Met mutation of transthyretin (TTR) gene. Patients 1 and 2 were a 43-year-old man with a spinal-onset of ALS and a 37-year-old woman with a bulbar-onset of ALS, who died due to respiratory complications five and two years after disease onset, respectively. Patient 3 is a 52-year-old woman, with a two-year history of a probable primary lateral sclerosis, and a frontotemporal dysfunction. Imaging, cerebrospinal fluid (CSF) and nerve conduction and small fiber tests were normal in all. Genetic testing for ALS was negative in the two patients tested. Previous studies in MND patients have identified reduced TTR levels in CSF and neuronal gene overexpression, suggesting a neuroprotective role of TTR. The association of MND in patients with TTR gene mutations has not yet been described.

Tongue atrophy as a neurological finding in hereditary polyneuropathy in Alaskan malamutes

Background

Tongue atrophy with wrinkling as a clinical sign of inherited polyneuropathies has not been reported in dogs.

Objectives

Clinically describe tongue atrophy as well as morphology of the tongue and hypoglossal nerve in Alaskan malamute polyneuropathy (AMPN).

Animals

Six client‐owned Alaskan malamute dogs diagnosed with AMPN, all homozygous for the causative mutation in the N‐myc downstream‐regulated gene 1 (NDRG1) and 1 neurologically normal control Alaskan malamute.

Methods

Prospective case study. Clinical and neurological examinations were performed on affected dogs. Necropsy samples from the tongue muscle and hypoglossal nerve were examined by light and electron microscopy.

Results

All affected dogs had abnormal wrinkles and grooves on the dorsal surface of the tongue, a clinical sign not described previously in dogs with AMPN. Electromyography of the tongue performed in 2 dogs showed spontaneous activity. Five affected dogs underwent necropsy studies. Histopathology of the tongue showed groups of angular atrophic myofibers and changes in the hypoglossal nerve included thinly myelinated fibers, small onion bulbs, folded myelin, and axonal degeneration.

Conclusion and Clinical Importance

Histopathologic changes in the tongue and hypoglossal nerve were consistent with previously reported changes in skeletal muscle and other nerves from dogs with AMPN. Therefore, we conclude that macroscopic tongue atrophy is part of the disease phenotype of AMPN and should be considered a potential clinical sign in dogs with polyneuropathies.

What Is in the Literature

What is in the Literature focuses on peripheral neuropathies with new and practical information related to the diagnosis, treatment, and management. Diagnostic and treatment guidelines are available for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) but not all clinicians follow them resulting in erroneous diagnoses and prolonged treatment. Secondary axonal loss in CIDP causes increased connective tissue in muscle. Antibodies to proteins at the node of Ranvier are found in a small percentage of patients with CIDP. The differential diagnosis for CIDP-like neuropathies includes amyloid neuropathy and POEMS (polyneuropathy, organomegaly, endocrinopathy, M-protein, skin changes) and amyloidosis. Upper limits for cerebral spinal fluid protein are 0.45 g/L and cell count <10/µL, but both may be too low. Hyperactive reflexes may occur in Guillain-Barré syndrome and should not exclude the diagnosis. In severely affected Guillain-Barré syndrome patients, a second dose of intravenous immune globulin within 4 weeks of onset is not likely to be effective.

Expert consensus recommendations to improve diagnosis of ATTR amyloidosis with polyneuropathy

Amyloid transthyretin (ATTR) amyloidosis with polyneuropathy (PN) is a progressive, debilitating, systemic disease wherein transthyretin protein misfolds to form amyloid, which is deposited in the endoneurium. ATTR amyloidosis with PN is the most serious hereditary polyneuropathy of adult onset. It arises from a hereditary mutation in the TTR gene and may involve the heart as well as other organs. It is critical to identify and diagnose the disease earlier because treatments are available to help slow the progression of neuropathy. Early diagnosis is complicated, however, because presentation may vary and family history is not always known. Symptoms may be mistakenly attributed to other diseases such as chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), idiopathic axonal polyneuropathy, lumbar spinal stenosis, and, more rarely, diabetic neuropathy and AL amyloidosis. In endemic countries (e.g., Portugal, Japan, Sweden, Brazil), ATTR amyloidosis with PN should be suspected in any patient who has length-dependent small-fiber PN with autonomic dysfunction and a family history of ATTR amyloidosis, unexplained weight loss, heart rhythm disorders, vitreous opacities, or renal abnormalities. In nonendemic countries, the disease may present as idiopathic rapidly progressive sensory motor axonal neuropathy or atypical CIDP with any of the above symptoms or with bilateral carpal tunnel syndrome, gait disorders, or cardiac hypertrophy. Diagnosis should include DNA testing, biopsy, and amyloid typing. Patients should be followed up every 6–12 months, depending on the severity of the disease and response to therapy. This review outlines detailed recommendations to improve the diagnosis of ATTR amyloidosis with PN.

Hereditary transthyretin amyloidosis: a model of medical progress for a fatal disease

Hereditary amyloidogenic transthyretin (ATTRv) amyloidosis with polyneuropathy (also known as familial amyloid polyneuropathy) is a condition with adult onset caused by mutation of transthyretin (TTR) and characterized by extracellular deposition of amyloid and destruction of the somatic and autonomic PNS, leading to loss of autonomy and death. This disease represents a model of the scientific and medical progress of the past 30 years. ATTRv amyloidosis is a worldwide disease with broad genetic and phenotypic heterogeneity that presents a diagnostic challenge for neurologists. The pathophysiology of the neuropathy is increasingly understood and includes instability and proteolysis of mutant TTR leading to deposition of amyloid with variable lengths of fibrils, microangiopathy and involvement of Schwann cells. Wild-type TTR is amyloidogenic in older individuals. The main symptoms are neuropathic, but the disease is systemic; neurologists should be aware of cardiac, eye and kidney involvement that justify a multidisciplinary approach to management. Infiltrative cardiomyopathy is usually latent but present in half of patients. Disease-modifying therapeutics that have been developed include liver transplantation and TTR stabilizers, both of which can slow progression of the disease and increase survival in the early stages. Most recently, gene-silencing drugs have been used to control disease in the more advanced stages and produce some degree of improvement.

Hereditary transthyretin-related amyloidosis

Hereditary transthyretin(TTR)-related amyloidosis (ATTRm amyloidosis) is an endemic/non-endemic, autosomal-dominant, early- and late-onset, rare, progressive disorder, predominantly manifesting as length-dependent, small fiber dominant, axonal polyneuropathy and frequently associated with cardiac disorders and other multisystem diseases. ATTRm amyloidosis is due to variants in the TTR gene, with the substitution Val30Met as the most frequent mutation. TTR mutations lead to destabilization and dissociation of TTR tetramers into variant TTR monomers, and formation of amyloid fibrils, which are consecutively deposited extracellularly in various tissues, such as nerves, heart, brain, eyes, intestines, kidneys, or the skin. Neuropathy may not only include large nerve fibers but also small fibers, and not only sensory and motor fibers but also autonomic fibers. Types of TTR variants, age at onset, penetrance, and clinical presentation vary between geographical areas. Suggestive of a ATTRm amyloidosis are a sensorimotor polyneuropathy, positive family history, autonomic dysfunction, cardiomyopathy, carpal tunnel syndrome, unexplained weight loss, and resistance to immunotherapy. If only sensory A-delta or C fibers are affected, small fiber neuropathy ensues. Diagnostic tests for small fiber neuropathy include determination of intraepidermal nerve fiber density, laser-evoked potentials, heat- and cold-detection thresholds, and measurement of the electrochemical skin conductance. Therapy currently relies on liver transplantation and TTR-stabilizers (tafamidis, diflunisal).

Autosomal-dominant transthyretin (TTR)-related amyloidosis is not a frequent CMT2 neuropathy "in disguise"

Transthyretin (TTR)-related familial amyloid polyneuropathy (TTR-FAP) is a life-threatening autosomal dominant, systemic disease. First symptoms usually occur from the second to over sixth decade of life with a length-dependent axonal neuropathy with prominent involvement of the small fibers and multi-organ systemic failure.

Early diagnosis is pivotal for effective therapeutic options, but it is hampered by the heterogeneity of the clinical spectrum which can lead to misdiagnosis with other neurological condition/disorder such as axonal sensory-motor neuropathy (CMT2) as described in literature.

The aim of our study was to search for TTR mutations in a large cohort of selected undiagnosed axonal sensory-motor neuropathy patients to establish if misdiagnosis is frequent or rare in the Italian population.

No TTR pathogenic variants were found in our cohort. In conclusion, our study shows that TTR testing not should be straightforward recommended in CMT2 patients but only when “red flags” TTR’s features are present.

Mass spectrometry analysis of plasma from amyotrophic lateral sclerosis and control subjects

Mass spectrometry was used to study blood samples from patients with amyotrophic lateral sclerosis (ALS) and healthy controls. Addenbrooke's cognitive examination-III (ACE-III) was used to test for cognitive impairment (CI). Nano liquid chromatography and time of flight mass spectrometry (MS) were performed on samples from 42 ALS patients and 18 healthy controls. SWATH™ proteomic analysis was utilized to look for differences between groups. Western blot analysis was used to study levels of 4 proteins, selected as being of possible interest in ALS, in the MS discovery cohort and a second validation group of 10 ALS patients and 10 healthy controls. INGENUITY PATHWAY ANALYSIS (IPA) was applied to the final proteomic data. Between ALS patients and controls, there were significant differences in the expression of 30 proteins. Between controls and ALS patients without CI, there were significant differences in 15 proteins. Between controls and ALS patients with CI, there were significant differences in 32 proteins. Changes in levels of gelsolin, clusterin, and CD5L were validated by using western blot analysis in the discovery cohort. Changes in the expression of gelsolin, clusterin, and ficolin 3 were replicated in a validation group. In ALS, the LXR/RXR and coagulation pathways were downregulated whereas the complement pathway was upregulated. The proteomic data were used to produce two new networks, centered on IL1 and on NFkB, which showed altered levels in ALS. This study highlights the usefulness of MS of blood samples as a tool to study ALS.

Causally treatable, hereditary neuropathies in Fabry's disease, transthyretin-related familial amyloidosis, and Pompe's disease

OBJECTIVES

Most acquired neuropathies are treatable, whereas genetic neuropathies respond to treatment in Fabry's disease (FD), transthyretin-related familial amyloidosis (TTR-FA), and Pompe's disease (PD). This review summarizes and discusses recent findings and future perspectives concerning etiology, pathophysiology, clinical presentation, diagnosis, treatment, and outcome of neuropathy in FD, TTR-FA, and PD.

METHODS

Literature review.

RESULTS

Neuropathy in FD concerns particularly small, unmyelinated, or myelinated sensory fibers (small fiber neuropathy [SFN]) and autonomic fibers, manifesting as acroparesthesias, Fabry's crises, or autonomous disturbances. FD neuropathy benefits from agalsidase alpha (0.2 mg/kg every second week intravenously) or from beta (1.0 mg/kg every second week intravenously). Neuropathy in TTR-FA is axonal and affects large and small sensory, motor, and autonomous fibers. Neuropathy in TTR-FA profits from liver transplantation and the TTR kinetic stabilizer tafamidis (20 mg/d). Neuropathy in PD particularly occurs in late-onset PD and manifests as mononeuropathy, polyneuropathy, or SFN. PD neuropathy presumably responds to alglucosidase-alpha (20 mg/kg every second week intravenously).

CONCLUSIONS

Neuropathy in FD, TTR-FA, and PD is predominantly a SFN and can be the dominant feature in FD and TTR-FA. SFN in FD, TTR-FA, and PD needs to be recognized and benefits from enzyme replacement treatment or TT-kinetic stabilizers.

Exome sequencing establishes a gelsolin mutation as the cause of inherited bulbar-onset neuropathy

INTRODUCTION

Progressive bulbar motor neuropathy is primarily caused by bulbar-onset ALS. Hereditary amyloidosis type IV also presents with a bulbar neuropathy that mimics motor neuron disease. The disease is prevalent in Finland only and is not commonly included in the differential diagnosis of ALS.

METHODS

We studied 18 members of a family in which some had bulbar motor neuropathy, and we performed exome sequencing.

RESULTS

Five affected family members were found to have a D187Y substitution in the GSN gene known to cause hereditary amyloidosis type IV.

CONCLUSIONS

This American family presented with progressive bulbar neuropathy due to a gelsolin mutation not found in Finland. Hereditary amyloidosis type IV presents with bulbar motor neuropathy and not with peripheral neuropathy as occurs with common forms of amyloidosis. This report demonstrates the power of exome sequencing to determine the cause of rare hereditary diseases with incomplete or atypical phenotypes. Muscle Nerve 56: 1001-1005, 2017.