A case of neuronal intranuclear inclusion disease with recurrent vomiting and without apparent DWI abnormality for the first seven years

Spatial and Temporal Distribution of White Matter Lesions in NOTCH2NLC-Related Neuronal Intranuclear Inclusion Disease

BACKGROUND AND OBJECTIVES

NOTCH2NLC-related neuronal intranuclear inclusion disease (NIID) is a neurodegenerative disease with characteristic white matter lesions (WMLs) visible on MRI. However, the distribution of WMLs and their clinical correlations remain poorly understood in NIID. This study aims to investigate the spatial and temporal distribution of WMLs in the brain of patients with NOTCH2NLC-related NIID.

METHODS

We retrospectively evaluated patients diagnosed with NOTCH2NLC-related NIID in Zhongshan Hospital, Fudan University. Detailed clinical information, including retrospective MRI data, was collected. Spatial distribution of WMLs with fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI) hyperintensities was quantified, and the relationship between WML distribution and clinical presentations was analyzed by the Fisher exact test. The volume of whole-brain WMLs was quantified using ITK-SNAP software. The relationship between phenotypes and WML volume was analyzed by the Student t test, Mann-Whitney test, or correlation analysis. WML development patterns were summarized based on the longitudinal observation of MRI characteristics.

RESULTS

This study evaluated 45 patients with NOTCH2NLC-related NIID, with a median age of 66 years (range 55-82 years) and consisting of 30 women. Patients exhibited diverse clinical manifestations, with cognitive decline, autonomic dysfunction, and tremor being the 3 most frequent presentations. Severe WMLs were observed in 43 patients, with FLAIR hyperintensities predominantly in the corona radiata, centrum semiovale, and other brain regions. The presence of DWI hyperintensities was common in the corticomedullary junction (91.1%) and corpus callosum (53.3%). Analysis showed significant correlations between FLAIR hyperintensity volume and both age (r = 0.312, p = 0.042) and Montreal Cognitive Assessment scores (r = -0.371, p = 0.048). Longitudinal MRI retrospection in 7 patients over an average of 9.6 ± 2.9 years revealed 3 gradually progressed WML patterns: periventricular-subcortical, periventricular-dominant, and corticomedullary junction-dominant. In addition, 3 patients experienced rapid WML expansion associated with mitochondrial encephalomyopathy with lactic acidosis and stroke (MELAS)-like episodes.

DISCUSSION

Our analysis revealed the radiologic characteristics and spatial distribution of WMLs and demonstrated significant correlations between FLAIR hyperintensity volume and age/cognitive levels in NIID. Long-term retrospection revealed 3 types of gradual WML expansion patterns while MELAS-like episodes cause rapid WML aggravation. Although results should be confirmed in a larger cohort, these insights enhance understanding of NIID's clinical-radiologic relationships and pathogenesis.

Diffusion and functional MRI reveal microstructural and network connectivity impairment in adult-onset neuronal intranuclear inclusion disease

Objectives

Neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disorder lacking reliable neuroimaging biomarkers. This study aimed to evaluate microstructural and functional connectivity alterations using diffusion kurtosis imaging (DKI) and resting-state fMRI (rs-fMRI), and to investigate their diagnostic potential as biomarkers.

Methods

Twenty-three patients with NIID and 40 matched healthy controls (HCs) were recruited. Firstly, gray matter (GM) and white matter (WM) changes were assessed by voxel-based analysis (VBA) and tract-based spatial statistics (TBSS). Then we explored modifications in brain functional networks connectivity by independent component analysis. And the relationship between the altered DKI parameters and neuropsychological evaluation was analyzed. Finally, a receiver operating characteristic (ROC) curve was used to evaluate the diagnostic performance of different gray matter and white matter parameters.

Results

Compared with the HCs, NIID patients showed reduced mean kurtosis (MK), radial kurtosis (RK), axial kurtosis (AK), and kurtosis fractional anisotropy (KFA) values in deep gray matter regions. Significantly decreased MK, RK, AK, KFA and fractional anisotropy (FA), and increased mean diffusivity (MD) values were observed in extensive white matter fiber tracts. Notable alterations in functional connectivity were also detected. Among all DKI parameters, the diagnostic efficiency of AK in GM and FA in WM regions was the highest.

Conclusion

Adult-onset NIID patients exhibited altered microstructure and functional network connectivity. Our findings suggest that DKI parameters may serve as potential imaging biomarkers for diagnosing adult-onset NIID.

Case report: Neuronal intranuclear inclusion disease initially mimicking reversible cerebral vasoconstriction syndrome: serial neuroimaging findings during an 11-year follow-up

Neuronal intranuclear inclusion disease (NIID) is a rare, progressive neurodegenerative disorder known for its diverse clinical manifestations. Although episodic neurogenic events can be associated with NIID, no reported cases have demonstrated concurrent clinical features or MRI findings resembling reversible cerebral vasoconstriction syndrome (RCVS). Here, we present the inaugural case of an adult-onset NIID patient who initially displayed symptoms reminiscent of RCVS. The 59-year-old male patient's initial presentation included a thunderclap headache, right visual field deficit, and confusion. Although his brain MRI appeared normal, MR angiography unveiled left posterior cerebral artery occlusion, subsequently followed by recanalization, culminating in an RCVS diagnosis. Over an 11-year period, the patient encountered 10 additional episodes, each escalating in duration and intensity, accompanied by seizures. Simultaneously, cognitive impairment progressed. Genetic testing for NIID revealed an abnormal expansion of GGC repeats in NOTCH2NLC, with a count of 115 (normal range, <60), and this patient was diagnosed with NIID. Our report highlights that NIID can clinically and radiologically mimic RCVS. Therefore, in the differential diagnosis of RCVS, particularly in cases with atypical features or recurrent episodes, consideration of NIID is warranted. Additionally, the longitudinal neuroimaging findings provided the course of NIID over an 11-year follow-up period.

Neuronal intranuclear inclusion disease with cortical involvement in left hemisphere: a case report

BACKGROUND

Neuronal intranuclear inclusion disease (NIID) is a rare highly heterogeneous disease. In this paper, we present a case of NIID featured in cortical involvement in left hemisphere of brain and the imaging changes in the process of the disease.

CASE PRESENTATION

A 57-year-old female was hospitalized due to recurrent attacks of headache with cognitive impairment and tremor for 2 years. The symptoms of headache episodes were reversible. The characteristic radiologic change was high intensity signal involving the grey matter-white matter junction on the brain diffusion-weighted imaging (DWI), which existed in the frontal lobe and then extended backwards. Atypical features on fluid-attenuated inversion recovery (FLAIR) sequences showing small patchy high signals in the cerebellar vermis. High signals and edema were detected on FLAIR images along the cortex of the left occipito-parieto-temporal lobes, expanding and gradually shrinking in the follow-up visit. Besides, cerebral atrophy and bilateral symmetrical leukoencephalopathy were also detected. Skin biopsy and genetic testing confirmed the diagnosis of NIID.

CONCLUSION

Except for typical radiological change strongly suggesting NIID, it is also necessary to notice the insidious symptoms of NIID combining with some atypical imaging features to make an early diagnosis. Skin biopsies or genetic testing should be carried out early in patients with highly suspected NIID.

Skin biopsy and neuronal intranuclear inclusion disease

Neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disease with variable clinical phenotypes. There is a considerable delay in the definite diagnosis, which primarily depends on postmortem brain pathological examination. Although CGG repeat expansion in the 5'-untranslated region of NOTCH2NLC has been identified as a disease-associated variant, the pathological diagnosis is still required in certain NIID cases. Intranuclear inclusions found in the skin tissue of patients with NIID dramatically increased its early detection rate. Skin biopsy, as a minimally invasive method, has become widely accepted as a routine examination to confirm the pathogenicity of the repeat expansion in patients with suspected NIID. In addition, the shared developmental origin of the skin and nerve system provided a new insight into the pathological changes observed in patients with NIID. In this review, we systematically discuss the role of skin biopsy for NIID diagnosis, the procedure of skin biopsy, and the pathophysiological mechanism of intranuclear inclusion in the skin.

A comprehensive study of clinicopathological and genetic features of neuronal intranuclear inclusion disease

BACKGROUND

The discovery of skin intranuclear inclusions and GGC repeat expansion of NOTCH2NLC has greatly promoted the diagnosis of neuronal intranuclear inclusion disease (NIID). With highly heterogeneous clinical manifestations, NIID patients tend to be underdiagnosed at early stages.

METHODS

This study comprehensively studied clinical manifestations, magnetic resonance imaging (MRI), and peripheral nerve conduction in 24 NIID and 166 other neurodegenerative disease (ND) subjects. The nomogram was plotted using the "rms" package, and the t-distributed stochastic neighbor embedding algorithm was performed. Associations between skin intranuclear inclusions and NOTCH2NLC GGC repeats were further analyzed.

RESULTS

The clinical, MRI, and peripheral nerve conduction features seriously overlapped in NIID and ND patients; they were assigned variables according to their frequency and specificity in NIID patients. A nomogram that could distinguish NIID from ND was constructed according to the assigned variables and cutoff values of the above features. The occurrence of skin intranuclear inclusions and NOTCH2NLC GGC repeats ≥ 60 showed 100% consistency, and intranuclear inclusion frequency positively correlated with NOTCH2NLC GGC repeats. A hierarchical diagnostic flowchart for definite NIID was further established.

CONCLUSION

We provide a novel nomogram with the potential to realize early identification and update the diagnostic flowchart for definitive diagnosis. Moreover, this is the first study to define the association between skin pathology and NOTCH2NLC genetics in NIID.

MRI features of neuronal intranuclear inclusion disease, combining visual and quantitative imaging investigations

OBJECTIVE

To observe the radiological characteristics of Neuronal Intranuclear Inclusion Disease (NIID) on lesion locations and diffusion property using quantitative imaging analysis.

METHODS

Visual inspection and quantitative analyses were performed on MRI data from 31 retrospectively included patients with NIID. Frequency heatmaps of lesion locations on T2WI and DWI were generated using voxel-wise analysis. Gray matter volume (GMV), white matter volume (WMV) and diffusion property of apparent diffusion coefficient (ADC) values of patients were voxel-wisely compared with healthy controls. Moreover, the ADC values within the DWI-detected lesion were compared with those within the adjacent cortical gray matter and white matter. Voxel-based lesion symptom mapping (VLSM) techniques, were used to determine the relationship between DWI lesion location and disease durations.

RESULTS

By visual inspection on the imaging findings, we proposed an "cockscomb flower sign" for describing the radiological feature of DWI hyperintensity within the corticomedullary junction. A "T2WI-DWI mismatch of spatial distribution" pattern was also revealed with visual inspection and frequency heatmaps, for describing the feature of a wider lesion distribution covering white matter shown on T2WI than that on DWI. Voxel-based morphometry comparison revealed that wildly reduced GMV and WMV, both the lesion areas detected by DWI and T2WI demonstrated ADC increase in patients. Furthermore, the ADC values within the DWI-detected lesion were intermediate between the adjacent cortex and the deep white matter with highest ADC. VLSM analysis revealed that frontal lobe, parietal lobe and internal capsule damage were associated with higher NIID durations.

CONCLUSION

NIID features with "cockscomb flower-like" DWI hyperintensity in area of corticomedullary junction, based on a "T2WI-DWI mismatch of spatial distribution" of lesion locations. The pathological substrate of corticomedullary junction hyperintensity on DWI, can not be explained as diffusion restriction. These typical radiological features of brain MRI would be helpful for diagnosis of NIID.

The clinical characteristics of neuronal intranuclear inclusion disease and its relation with inflammation

BACKGROUND

Neuronal intranuclear inclusion disease (NIID) is a great imitator with a broad spectrum of clinical manifestations that include dementia, parkinsonism, paroxysmal symptoms, peripheral neuropathy, and autonomic dysfunction. Hence, it may also masquerade as other diseases such as Alzheimer's disease, Parkinson's disease, and Charcot-Marie-Tooth disease. Recent breakthroughs on neuroimaging, skin biopsy, and genetic testing have facilitated the diagnosis. However, early identification and effective treatment are still difficult in cases of NIID.

OBJECTIVE

To further study the clinical characteristics of NIID and investigate the relationship between NIID and inflammation.

METHODS

We systematically evaluated the clinical symptoms, signs, MRI and electromyographical findings, and pathological characteristics of 20 NIID patients with abnormal GGC repeats in the NOTCH2NLC gene. Some inflammatory factors in the patients were also studied.

RESULTS

Paroxysmal symptoms such as paroxysmal encephalopathy, stroke-like episodes, and mitochondrial encephalomyopathy lactic acidosis and stroke (MELAS)-like episode were the most common phenotypes. Other symptoms such as cognitive dysfunction, neurogenic bladder, tremor, and vision disorders were also suggestive of NIID. Interestingly, not all patients showed apparent diffusion-weighted imaging (DWI) abnormality or intranuclear inclusions, while abnormal GGC repeats of NOTCH2NLC were seen in all patients. And fevers were noticed in some patients during encephalitic episodes, usually with increasing leukocyte counts and neutrophil ratios. Both IL-6 (p = 0.019) and TNF-α (p = 0.027) levels were significantly higher in the NIID group than in normal controls.

CONCLUSION

Genetic testing of NOTCH2NLC may be the best choice in the diagnosis of NIID. Inflammation might be involved in the pathogenesis of NIID.

Clinical and neuroimaging review of triplet repeat diseases

Triplet repeat diseases (TRDs) refer to a group of diseases caused by three nucleotide repeats elongated beyond a pathologic threshold. TRDs are divided into the following four groups depending on the pathomechanisms, although the pathomechanisms of several diseases remain unelucidated: polyglutamine disorders, caused by a pathologic repeat expansion of CAG (coding the amino acid glutamine) located within the exon; loss-of-function repeat disorders, characterized by the common feature of a loss of function of the gene within which they occur; RNA gain-of-function disorders, involving the production of a toxic RNA species; and polyalanine disorders, caused by a pathologic repeat expansion of GCN (coding the amino acid alanine) located within the exon. Many of these TRDs manifest through neurologic symptoms; moreover, neuroimaging, especially brain magnetic resonance imaging, plays a pivotal role in the detection of abnormalities, differentiation, and management of TRDs. In this article, we reviewed the clinical and neuroimaging features of TRDs. An early diagnosis of TRDs through clinical and imaging approaches is important and may contribute to appropriate medical intervention for patients and their families.

First detailed case report of a pediatric patient with neuronal intranuclear inclusion disease diagnosed by NOTCH2NLC genetic testing

INTRODUCTION

Neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disease characterized clinically by eosinophilic hyaline intranuclear inclusions in neuronal and other somatic cells. Skin biopsies are reportedly useful in diagnosing NIID, and the genetic cause of NIID was identified as a GGC repeat expansion in NOTCH2NLC in recent years. The number of adult patients diagnosed via genetic testing has increased; however, there have been no detailed reports of pediatric NIID cases with GGC expansions in NOTCH2NLC. This is the first detailed report of a pediatric patient showing various neurological symptoms from the age of 10 and was ultimately diagnosed with NIID via skin biopsy and triplet repeat primed polymerase chain reaction analyses.

CASE REPORT

This was an 18-year-old female who developed cyclic vomiting, distal dominant muscle weakness, and sustained miosis at 10 years. Nerve conduction studies revealed axonal degeneration, and her neuropathy had slowly progressed despite several rounds of high-dose methylprednisolone and intravenous immunoglobulin therapy. At 13 years, she had an acute encephalopathy-like episode. At 15 years, brain MRI revealed slightly high-intensity lesions on diffusion-weighted and T2-weighted imaging in the subcortical white matter of her frontal lobes that expanded over time. At 16 years, esophagography, upper gastrointestinal endoscopy, and esophageal manometry revealed esophageal achalasia, and per-oral endoscopic myotomy was performed. At 18 years, we diagnosed her with NIID based on the findings of skin specimen analyses and a GGC repeat expansion in NOTCH2NLC.

CONCLUSION

NIID should be considered as a differential diagnosis in pediatric patients with various neurological symptoms.

Clinical-neuroimaging-pathological relationship analysis of adult onset Neuronal Intranuclear Inclusion Disease (NIID)

BACKGROUND

Neuronal Intranuclear Inclusion Disease (NIID) is a degenerative disease with heterogeneous clinical manifestations. We aim to analysis the relationship between clinical manifestations, neuroimaging and skin pathology in a Chinese NIID cohort.

METHODS

Patients were recruited from a Chinese cohort. Detail clinical information were collected. Visual rating scale was used for evaluation of neuroimaging. The relationship between clinical presentations and neuroimaging, as well as skin pathology was statistically analyzed.

RESULTS

Thirty-two patients were recruited. The average onset age was 54.3 y/o. 28.1% had positive family history. Dementia, autonomic nervous system dysfunction, episodic attacks were three main presentations. CSF analysis including Aβ₄₂ and tau level was almost normal. The most frequently involved on MRI was periventricular white matter (100%), frontal subcortical and deep white matter (96.6%), corpus callosum (93.1%) and external capsule (72.4%). Corticomedullary junction DWI high intensity was found in 87.1% patients. Frontal and external capsule DWI high intensity connected to form a "kite-like" specific image. Severity of dementia was significantly related to leukoencephalopathy (r = 0.465, p = 0.0254), but not cortical atrophy and ventricular enlargement. Grey matter lesions were significantly associated with encephalopathy like attacks (p = 0.00077) but not stroke like attacks. The density of intranuclear inclusions in skin biopsy was not associated with disease duration, severity of leukoencephalopathy and dementia.

CONCLUSIONS

Specific distribution of leukoencephalopathy and DWI high intensity were indicative. Leukoencephalopathy and subcortical mechanism were critical in pathogenesis of NIID. Irrelevant of inclusion density and clinical map suggested the direct pathogenic factor need further investigation.

Clinical characteristics of two patients with neuronal intranuclear inclusion disease and literature review

Background

Neuronal intranuclear inclusion disease (NIID) is a rare chronic progressive neurodegenerative disease, with complex and diverse clinical manifestations and pathological eosinophilic hyaline intranuclear inclusions in the central and peripheral nervous systems and visceral organs. Improvements in diagnostic methods such as skin biopsy and gene testing are helpful in revealing the clinical and genetic characters of NIID.

Materials and methods

We presented two cases of NIID diagnosed by using NOTCH2NLC gene testing and skin biopsy. Diffusion weighted imaging (DWI) showed high linear intensity in corticomedullary junction. We also reviewed all the published NIID cases with positive NOTCH2NLC GGC repeat expansion and skin biopsy results in PubMed.

Results

Patient 1 was a 63-year-old male who carried 148 GGC repeats and presented with progressive tremor and limb weakness. Patient 2 was a 62-year-old woman who carried 131 GGC repeats and presented with tremors, memory loss and headaches. The most common clinical manifestation of 63 NIID patients in this study was cognitive impairment, followed by tremors. In our study, almost all the patients were from East Asia, the male to female ratio was 1:1.26, with an age of onset of 54.12 ± 14.12 years, and an age of diagnosis of 60.03 ± 12.21 years. Symmetrical high signal intensity at the corticomedullary junction on DWI were revealed in 80.96% of the patients. For the GGC repeat numbers, the majority of GGC repeats were in the 80-119 intervals, with few GGC repeats above 160. The number of GGC repetitions was significantly higher in patients presented with muscle weakness than in other clinical manifestations.

Conclusion

NIID is a neurodegenerative disease caused by aberrant polyglycine (polyG) protein aggregation. NIID mostly occurs in the elderly population in East Asia, with cognitive dysfunction as the most common symptom. Staging NIID based on clinical presentation is inappropriate because most patients with NIID have overlapping symptoms. In our study, there was no significant correlation between the number of GGC repeats and different phenotypes except for muscle weakness. Abnormal trinucleotides repeat and PolyG protein aggregation maybe common pathogenic mechanism in neurodegenerative diseases and cerebrovascular diseases, which needs to be confirmed by more studies.

Clinical and mechanism advances of neuronal intranuclear inclusion disease

Due to the high clinical heterogeneity of neuronal intranuclear inclusion disease (NIID), it is easy to misdiagnose this condition and is considered to be a rare progressive neurodegenerative disease. More evidence demonstrates that NIID involves not only the central nervous system but also multiple systems of the body and shows a variety of symptoms, which makes a clinical diagnosis of NIID more difficult. This review summarizes the clinical symptoms in different systems and demonstrates that NIID is a multiple-system intranuclear inclusion disease. In addition, the core triad symptoms in the central nervous system, such as dementia, parkinsonism, and psychiatric symptoms, are proposed as an important clue for the clinical diagnosis of NIID. Recent studies have demonstrated that expanded GGC repeats in the 5′-untranslated region of the NOTCH2NLC gene are the cause of NIID. The genetic advances and possible underlying mechanisms of NIID (expanded GGC repeat-induced DNA damage, RNA toxicity, and polyglycine-NOTCH2NLC protein toxicity) are briefly summarized in this review. Interestingly, inflammatory cell infiltration and inflammation were observed in the affected tissues of patients with NIID. As a downstream pathological process of NIID, inflammation could be a therapeutic target for NIID.

Expanding the clinical spectrum of adult-onset neuronal intranuclear inclusion disease

Neuronal intranuclear inclusion disease (NIID) is a heterogeneous neurodegenerative disease with multiple clinical subtypes. Recent breakthroughs on neuroimaging, skin biopsy and genetic testing have facilitated the diagnosis. We aim to investigate the clinical characteristics of Chinese NIID patients to further refine the spectrum. We analyzed the clinical features of 25 NIID patients from 24 unrelated families and performed skin biopsy and/or sural nerve biopsy on 24 probands. Repeat-primed PCR and fluorescence amplicon length PCR were conducted to detect GGC repeats of NOTCH2NLC. Onset age ranged from 24 to 72 years old, and the disease duration ranged from 12 h to 25 years with the mode of onset characterized as acute, recurrent or chronic progressive type. Tremor was a common phenotype, often observed in the early stages, next to dementia and paroxysmal encephalopathy. Symptoms infrequently reported such as oromandibular dystonia, recurrent vomiting, dizziness and headache of unknown origin, as well as pure peripheral neuropathy were also suggestive of NIID. Reversible leukoencephalopathy following encephalitic episodes and the absence of apparent DWI abnormality were noticed. Two genetically confirmed NIID patients failed to be identified intranuclear inclusions, and one patient was simultaneously found significant mitochondrial swelling and fingerprint profiles depositing in lysosomes. All the patients were identified abnormal GGC repeats of NOTCH2NLC. We identify some atypical clinicopathological features and consider that pathological examinations combined with genetic testing is the gold standard for diagnosis. Whether lysosomal and mitochondrial dysfunction is involved in the pathogenesis of NIID deserves further study.

Sporadic adult-onset neuronal intranuclear inclusion disease without high-intensity signal on DWI and T2WI: a case report

Background

Neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disease characterized by eosinophilic hyaline intranuclear inclusions in cells in the central and peripheral nervous system. High-intensity signal in the corticomedullary junction on diffusion-weighted imaging (DWI) is supportive to the diagnosis of NIID. We describe a patient with sporadic adult-onset NIID but without any high-intensity signal on DWI and T2-weighted imaging (T2WI).

Case presentation

A 58-year-old woman without special family history developed mild persistent tremor in the right hand and deteriorated 2 years later. At 60 years of age, the patient began to conceive the bank, police and internet being deceptive, further presented apathy and confusion after two and a half years, as well as fabrication of non-existent things. Despite the treatment of antipsychotic drugs due to a diagnosis of mental disorder, the patient appeared weakness in the right limbs. Neurological examination revealed mutism, resting tremor, cogwheel-like rigidity in upper limbs, and weakness in all limbs. Brain magnetic resonance imaging displayed no cerebral atrophy initially but atrophy of frontal, temporal and parietal lobes 5 years later. No any high-intensity signal on DWI and T2WI was revealed. However, hypometabolism in the cortexes with atrophy and the right putamen nucleus were showed on ¹⁸F-fluoro-deoxy-glucose positron emission tomography/magnetic resonance. On the basis of 107 GGC repeats (normal number <40) in NOTCH2NLC gene and intranuclear inclusions with p62 immunoreactivity in the adipocyte of cutaneous sweat duct by skin biopsy, NIID was finally diagnosed. The symptomatic treatment was given but the patient had no evident improvement.

Conclusions

Our case highlights that despite the lack of high-intensity signal on DWI and T2WI, NIID is still considered for patients with parkinsonism and mental impairment.

Neurodegenerative diseases associated with non-coding CGG tandem repeat expansions

Non-coding CGG repeat expansions cause multiple neurodegenerative disorders, including fragile X-associated tremor/ataxia syndrome, neuronal intranuclear inclusion disease, oculopharyngeal myopathy with leukodystrophy, and oculopharyngodistal myopathy. The underlying genetic causes of several of these diseases have been identified only in the past 2-3 years. These expansion disorders have substantial overlapping clinical, neuroimaging and histopathological features. The shared features suggest common mechanisms that could have implications for the development of therapies for this group of diseases - similar therapeutic strategies or drugs may be effective for various neurodegenerative disorders induced by non-coding CGG expansions. In this Review, we provide an overview of clinical and pathological features of these CGG repeat expansion diseases and consider the likely pathological mechanisms, including RNA toxicity, CGG repeat-associated non-AUG-initiated translation, protein aggregation and mitochondrial impairment. We then discuss future research needed to improve the identification and diagnosis of CGG repeat expansion diseases, to improve modelling of these diseases and to understand their pathogenesis. We also consider possible therapeutic strategies. Finally, we propose that CGG repeat expansion diseases may represent manifestations of a single underlying neuromyodegenerative syndrome in which different organs are affected to different extents depending on the gene location of the repeat expansion.

[A case of neuronal intranuclear inclusion disease with serial MRI changes observed from before onset of forgetfulness]

A 70-year-old woman presented with a 6-year history of cognitive dysfunction, neurogenic bladder, constipation and recurrent vomiting, and gradual worsening of symptoms. At the first admission to our department, she was also found to have hepatic encephalopathy due to intrahepatic portosystemic shunt. Head MRI revealed abnormal signal intensity at the corticomedullary junction, the splenium of the corpus callosum, and bilateral middle cerebellar peduncles on DWI. She was diagnosed with intranuclear inclusion disease (NIID) based on skin biopsy and genetic testing of NOTCH2NLC. In a retrospective review of serial head MRI findings for ten years, abnormal signal intensity at the corticomedullary junction and the splenium of the corpus callosum on MRI existed prior to the onset of cognitive dysfunction, and expanded gradually. For early diagnosis of NIID, it is important to focus not only on the characteristic high signal intensity at the corticomedullary junction, but also on the signal at the splenium of the corpus callosum from the early stage.

NOTCH2NLC-related repeat expansion disorders: an expanding group of neurodegenerative disorders

The NOTCH2NLC gene 5' untranslated region (UTR) GGC repeat expansion mutations were identified as a genetic contributor of neuronal intranuclear inclusion disease (NIID) in 2019. Since then, the number of reported cases with NOTCH2NLC GGC repeat expansion in Asian and European populations has increased rapidly, indicating that the expanded mutation not only leads to the onset or progression of the NIID, but also may play an important role in multiple progressive neurological disorders, including Parkinson's disease, essential tremor, multiple system atrophy, Alzheimer's disease, frontotemporal dementia, amyotrophic lateral sclerosis, leukoencephalopathy, and oculopharyngodistal myopathy type 3. Nevertheless, the underlying pathogenic mechanism of the NOTCH2NLC 5' UTR region GGC repeat expansion in these disorders remains largely unknown. This review aims to present recent breakthroughs on this mutation and improve our knowledge of a newly defined spectrum of disease: NOTCH2NLC-related repeat expansion disorder.

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.