Neurophysiological features of primary lateral sclerosis

Upper motor neuron signs in primary lateral sclerosis and hereditary spastic paraplegia

INTRODUCTION/AIMS

The frequency and distribution of upper motor neuron (UMN) signs in primary lateral sclerosis (PLS) are unknown. We aimed to study the spectrum of UMN signs in PLS and compare it with hereditary spastic paraplegia (HSP).

METHODS

We retrospectively analyzed the frequency of different UMN signs, including hyperreflexia (limbs and jaw), limb and tongue spasticity, Babinski, and Hoffman signs, in PLS patients at first observation and compared this respect to onset region and symptom duration. We also compared PLS versus HSP patients.

RESULTS

We included 34 PLS and 20 HSP patients, with a median symptom duration at first visit of 3.0 (interquartile range, IQR = 4.0) and 19.0 (IQR = 22.0) years, respectively. In PLS patients, hyperreflexia of upper (UL) (88.2%) and lower (LL) (91.2%) limbs, and LL spasticity (79.4%) were the most common findings. Spasticity of LL was significantly (p = .012) more frequent in LL-spinal onset subgroup, tongue spasticity in bulbar-onset subgroup (p = .021), and Hoffman sign in UL-spinal onset subgroup (p = .024). The PLS subgroup with shorter disease duration had a higher frequency of abnormal jaw jerk reflex (p = .037). Compared with HSP, PLS patients had a higher frequency of UL hyperreflexia (88.2% vs. 42.1%, p < .001) and UL spasticity (44.1% vs. 0.0%, p < .001). Asymmetric distribution of UMN signs was present in PLS and not in HSP.

DISCUSSION

In PLS, UL UMN signs are nearly always present and UMN sign distribution appears to be associated with onset region. At first observation, bulbar involvement, asymmetrical distribution of UMN signs and UL spasticity may indicate PLS versus HSP.

Novel approaches to motoneuron disease/ALS treatment using non-invasive brain and spinal stimulation: IFCN handbook chapter

Non-invasive brain stimulation techniques have been exploited in motor neuron disease (MND) with multifold objectives: to support the diagnosis, to get insights in the pathophysiology of these disorders and, more recently, to slow down disease progression. In this review, we consider how neuromodulation can now be employed to treat MND, with specific attention to amyotrophic lateral sclerosis (ALS), the most common form with upper motoneuron (UMN) involvement, taking into account electrophysiological abnormalities revealed by human and animal studies that can be targeted by neuromodulation techniques. This review article encompasses repetitive transcranial magnetic stimulation methods (including low-frequency, high-frequency, and pattern stimulation paradigms), transcranial direct current stimulation as well as experimental findings with the newer approach of trans-spinal direct current stimulation. We also survey and discuss the trials that have been performed, and future perspectives.

Current challenges in primary lateral sclerosis diagnosis

INTRODUCTION

Primary lateral sclerosis (PLS) is a rare, adult-onset and slowly progressive motor neuron disorder whose clinical core is characterized by upper motor neuron (UMN) dysfunction. Its formal diagnosis is clinically based and disease duration-dependent. Differentiating PLS from other disorders involving UMN can be challenging, particularly in the early stages.

AREAS COVERED

Our review covers and discusses different aspects of the PLS field, including the diagnostic criteria and its limitations, its differential diagnosis and their major pitfalls, and the actual role of neurophysiology, neuroimaging, genetics, and molecular biomarkers. Symptomatic treatment of the different manifestations is also addressed. The authors searched MEDLINE and Scopus. They also searched the reference lists of articles identified by our search strategy and reviewed and selected those deemed relevant. They selected papers and studies based on the quality of the report, significance of the findings, and on the author's critical appraise and expertise.

EXPERT OPINION

It is important to investigate novel molecular biomarkers and plan multicenter clinical trials for PLS. However, this will require a large international project to recruit enough patients, particularly given the diagnostic uncertainty of the current clinical criteria. A better understanding of PLS pathophysiology is crucial for designing disease-targeted therapies.

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.

Clinical Features and Biomarkers to Differentiate Primary and Amyotrophic Lateral Sclerosis in Patients With an Upper Motor Neuron Syndrome

OBJECTIVES

Differentiation between primary (PLS) and amyotrophic lateral sclerosis (ALS) entails relevant consequences for prognosis and management but is mostly unreliable at early stages. The objectives of the study are (1) to determine the features at onset that could help to differentiate between PLS and ALS, (2) to evaluate the diagnostic performance of an integrated serum biomarker panel, and (3) to identify the prognostic factors for patients presenting with upper motor neuron (UMN) syndrome.

METHODS

We selected and retrospectively analyzed the clinical data of patients presenting with UMN syndrome. At the first evaluation, when available, serum biomarkers were measured using ultrasensitive single molecule array.

RESULTS

The study population included 55 patients with PLS and 50 patients with ALS. Patients with PLS presented a longer time to first neurologic evaluation (PLS: 35.0 months, interquartile range [IQR] 17.0-38.0 months; ALS: 12.5 months, IQR 7.0-21.3 months; p < 0.01) and lower levels of neurofilament light chain (NfL) (PLS: 81.8 pg/mL, IQR 38.4-111.1 pg/mL; ALS: 155.9 pg/mL, IQR 85.1-366.4 pg/mL; p = 0.01). Two patients with PLS and 3 patients with ALS carried the C9orf72 expansion. NfL resulted an independent predictor of final diagnosis (odds ratio 1.01, 95% CI 1.00-1.02; p = 0.04) and an independent prognostic factor (hazard ratio 1.01, 95% CI 1.00-1.01; p < 0.01).

DISCUSSION

NfL might help to differentiate patients with PLS from patients with ALS and to predict prognosis in patients with UMN syndrome.

Does limited EMG denervation in early primary lateral sclerosis predict amyotrophic lateral sclerosis?

Objective: We assessed whether a cohort of patients with primary lateral sclerosis (PLS) and limited electromyography (EMG) motor unit denervation changes evolve into amyotrophic lateral sclerosis (ALS) with prolonged follow-up. Methods: We initially ascertained all PLS patients diagnosed at Mayo Clinic-Rochester (1990-2016). Of 64 total cases, 43 had normal EMGs ("pure" PLS) during the first 4 years after symptom onset and were the focus of a prior publication, documenting absence of evolution to ALS. The remaining 21 patients had limited motor unit changes on EMG needle examination (denervation and most with fibrillation or fasciculation potentials) but insufficient to raise a strong suspicion of ALS; these 21 patients were followed to determine whether they evolved into ALS. Results: Of these 21 patients, the median follow-up was 7 years' disease duration (range: 4-27 years; IQR 5-8.5). They included 11 females (52%) with median onset-age of 57 years (range: 42-72 years). Two patients (10%) subsequently met revised El Escorial criteria for ALS after 7 and 13 years, respectively. The remainder had stable EMG changes with a persistent PLS phenotype. Among these remaining 19 patients, the PLS course was somewhat more aggressive than our previously reported series of 43 patients devoid of EMG denervation. The paraparetic variant was more common than the hemiparetic and bulbar variants, similar to "pure" PLS. Conclusions: Among PLS patients with definite but limited EMG denervation, 2/21 (10%) later developed ALS. The patients in this series had a more progressive clinical course compared to our previously reported pure PLS cases.

Electromyographic findings in primary lateral sclerosis during disease progression

OBJECTIVE

To characterize electromyographic (EMG) findings in patients with primary lateral sclerosis (PLS) during the disease course.

METHODS

In PLS patients we scored spontaneous activity and motor unit action potential (MUP) pattern on EMG. We compared patients according to lower (group A) and higher (group B) EMG scores. EMG studies were repeated at intervals longer than 11 months; two or three repeat studies were required for inclusion in the analysis.

RESULTS

We studied 22 patients. Fasciculation potentials were found in 13 and fibrillations/positive sharp waves (fibs/sw) in 3 patients. Both were stable over time. Most patients had MUP abnormalities (n = 17), with worsening in the lower limbs in patients with three evaluations (p = 0.010). Compared to group A (n = 12), patients of group B (n = 10) had a significant shorter disease duration (median 10.9 vs 15.2 years, p < 0.001), lower functional score at both first (39 vs 45, p = 0.034) and last (29 vs 38, p = 0.003) evaluations, and had a faster functional decline (0.19 vs 0.08, p = 0.004).

CONCLUSIONS

Most PLS patients showed minor and stable EMG abnormalities, without progression to ALS. Patients with more EMG abnormalities have a faster progression.

SIGNIFICANCE

EMG abnormalities in most PLS patients are minor and stable.

Familial clustering of primary lateral sclerosis and amyotrophic lateral sclerosis: Supplementary evidence for a continuum

BACKGROUND AND PURPOSE

Primary lateral sclerosis (PLS) is a motor neuron disorder characterized by a pure upper motor neuron degeneration in the bulbar and spinal regions. The key difference with amyotrophic lateral sclerosis (ALS) is the lower motor neuron system integrity. Despite important literature on this disease, the pathophysiology of PLS remains unknown, and the link with ALS still balances between a continuum and a separate entity from ALS.

METHODS

We report nine families in which both PLS and ALS cases occurred, in general among first-degree relatives.

RESULTS

The patients with PLS and ALS had a typical disease presentation. Genetic studies revealed mutations in SQSMT1, TBK1, and TREM2 genes in two PLS patients and one ALS patient.

CONCLUSIONS

These results strongly support a phenotypic continuum between PLS and ALS.

Better understanding the neurobiology of primary lateral sclerosis

Primary lateral sclerosis (PLS) is a rare neurodegenerative disease characterized by progressive degeneration of upper motor neurons (UMNs). Recent studies shed new light onto the cellular events that are particularly important for UMN maintenance including intracellular trafficking, mitochondrial energy homeostasis and lipid metabolism. This review summarizes these advances including the role of Alsin as a gene linked to atypical forms of juvenile PLS, and discusses wider aspects of cellular pathology that have been observed in adult forms of PLS. The review further discusses the prospects of new transgenic upper motor neuron reporter mice, human stem cell-derived UMN cultures, cerebral organoids and non-human primates as future model systems to better understand and ultimately treat PLS.