Supranuclear ophthalmoparesis and vacuolar degeneration of the cerebral white matter in amyotrophic lateral sclerosis: a clinicopathological study

Association of Clinically Evident Eye Movement Abnormalities With Motor and Cognitive Features in Patients With Motor Neuron Disorders

BACKGROUND AND OBJECTIVES

Although oculomotor abnormalities (OMAs) are not usually considered prominent features of amyotrophic lateral sclerosis (ALS), they may represent potential clinical markers of neurodegeneration, especially when investigated together with cognitive and behavioral alterations. The aim of our study was to identify patterns of clinically evident OMAs in patients with ALS and to correlate such findings with cognitive-behavioral data.

METHODS

Three consecutive inpatient cohorts of Italian patients with ALS and controls were retrospectively evaluated to assess the frequency of OMAs and cognitive-behavioral alterations. The ALS population was divided into a discovery cohort and a replication cohort. Controls included a cohort of cognitively impaired individuals and patients with Alzheimer disease (AD). Participants underwent bedside eye movement evaluation to determine the presence and pattern of OMAs. Cognitive assessment was performed with a standard neuropsychological battery (discovery ALS cohort and AD cohort) and the Italian Edinburgh Cognitive and Behavioural ALS Screen (ECAS) (replication ALS cohort).

RESULTS

We recruited 864 individuals with ALS (635 discovery, 229 replication), 798 who were cognitively unimpaired and 171 with AD. OMAs were detected in 10.5% of our ALS cohort vs 1.6% of cognitively unimpaired controls (p = 1.2 × 10^-14) and 11.4% of patients with AD (p = NS). The most frequent deficits were smooth pursuit and saccadic abnormalities. OMA frequency was higher in patients with bulbar onset, prominent upper motor neuron signs, and advanced disease stages. Cognitive dysfunction was significantly more frequent in patients with OMAs in both ALS cohorts (p = 1.1 × 10^-25). Furthermore, OMAs significantly correlated with the severity of cognitive impairment and with pathologic scores at the ECAS ALS-specific domains. Last, OMAs could be observed in 35.0% of cognitively impaired patients with ALS vs 11.4% of patients with AD (p = 6.4 × 10^-7), suggesting a possible involvement of frontal oculomotor areas in ALS.

CONCLUSION

Patients with ALS showed a range of clinically evident OMAs, and these alterations were significantly correlated with cognitive, but not behavioral, changes. OMAs may be a marker of neurodegeneration, and bedside assessment represents a rapid, highly specific tool for detecting cognitive impairment in ALS.

Coexistence of neuronal intranuclear inclusion disease and amyotrophic lateral sclerosis: an autopsy case

Background

Neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disease. Pathologically, it is characterized by eosinophilic hyaline intranuclear inclusions in the cells of the visceral organs as well as central, peripheral, and autonomic nervous system cells. Recently, a GGC repeat expansion in the NOTCH2NLC gene has been identified as the etiopathological agent of NIID. Interestingly, this GGC repeat expansion was also reported in some patients with a clinical diagnosis of amyotrophic lateral sclerosis (ALS). However, there are no autopsy-confirmed cases of concurrent NIID and ALS.

Case presentation

A 60-year-old Taiwanese woman reported a four-month history of progressive weakness beginning in the right foot that spread to all four extremities. She was diagnosed with ALS because she met the revised El Escorial diagnostic criteria for definite ALS with upper and lower motor neuron involvement in the cervical, thoracic, and lumbosacral regions. She died of respiratory failure at 22 months from ALS onset, at the age of 62 years. Brain magnetic resonance imaging (MRI) revealed lesions in the medial part of the cerebellar hemisphere, right beside the vermis (paravermal lesions). The subclinical neuropathy, indicated by a nerve conduction study (NCS), prompted a potential diagnosis of NIID. Antemortem skin biopsy and autopsy confirmed the coexistence of pathology consistent with both ALS and NIID. We observed neither eccentric distribution of p62-positive intranuclear inclusions in the areas with abundant large motor neurons nor cytopathological coexistence of ALS and NIID pathology in motor neurons. This finding suggested that ALS and NIID developed independently in this patient.

Conclusions

We describe a case of concurrent NIID and ALS discovered during an autopsy. Abnormal brain MRI findings, including paravermal lesions, could indicate the coexistence of NIID even in patients with ALS showing characteristic clinical phenotypes.

Phenotypic variability in amyotrophic lateral sclerosis

Clinically, ALS phenotypes depend on the areas of the body that are affected, the different degrees of involvement of upper and lower motor neurons, the degrees of involvement of other systems, particularly cognition and behavior, and rates of progression. Phenotypic variability of ALS is characteristic and can be declined on the distribution of motor manifestations but also on the presence of extra-motor signs present in a variable manner in ALS patients. Neuropathologically, ALS is defined by the loss of UMN and LMN and the presence of two representative motor neuronal cytoplasmic inclusions, Bunina bodies and 43kDa Transactivation Response DNA Binding Protein (TDP-43) - positive cytoplasmic inclusions. The distribution of cytopathology and neuronal loss in patients is variable and this variability is directly related to phenotypic variability. Key regulators of phenotypic variability in ALS have not been determined. The functional decrement of TDP-43, and region-specific neuronal susceptibility to ALS, may be involved. Due to the selective vulnerability among different neuronal systems, lesions are multicentric, region-oriented, and progress at different rates. They may vary from patient to patient, which may be linked to the clinicopathological variability across patients.

Phenotypic variability and its pathological basis in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is characterized by its inherent clinicopathological variability. The concurrence of upper and lower motor neuron signs is a common feature in the majority of patients with ALS. However, some patients manifest an atypical clinical course, with only upper or lower motor neuron signs, or various extra-motor symptoms including cognitive dysfunction, parkinsonism, autonomic dysfunction, or ophthalmoparesis. This variability indicates different manifestations of ALS and is reflected by ALS pathology spreading into the central nervous system. The presence of cytoplasmic inclusions positive for transactivation response DNA-binding protein 43 kDa (TDP-43) is a key feature in ALS. Loss of TDP-43 from the nucleus and its subsequent aggregation in the cytoplasm may occur in susceptible regions and may be associated with neuronal loss. However, in some regions, there is no apparent neuronal loss while TDP-43 accumulation is evident; in contrast, in other regions, neuronal loss is apparent without any evidence of TDP-43 accumulation. Therefore, in addition to TDP-43 dysfunction, underlying region-specific cellular vulnerability may exist in the upper and lower motor neurons and frontotemporal system in patients with ALS. The microscopic discrepancy and selective vulnerability may be linked to the macroscopic propensities of the sites of onset, and may also determine the direction and rate of progression of the lesions. Thus, there may be multicentric sites of onset, region-oriented disease development, and different speeds of disease progression across patients with ALS. ALS lesions occur in motor-related areas but may spread to neighboring areas. However, since lesions may spread in a discontinuous manner, and the dynamics of disease propagation have not been able to be identified, it remains controversial whether the stepwise appearance of TDP-43-positive inclusions is based on direct cell-to-cell protein propagation. Further understanding of the phenotypic variability of ALS and its pathological basis may serve as a guide for investigating the underlying pathogenesis of ALS.