Specific structuro-metabolic pattern of thalamic subnuclei in fatal familial insomnia: A PET/MRI imaging study.

BACKGROUND: Dysfunction of the thalamus has been proposed as a core mechanism of fatal familial insomnia. However, detailed metabolic and structural alterations in thalamic subnuclei are not well documented. We aimed to address the multimodal structuro-metabolic pattern at the level of the thalamic nuclei in fatal familial insomnia patients, and investigated the clinical presentation of primary thalamic alterations. MATERIALS AND METHODS: Five fatal familial insomnia patients and 10 healthy controls were enrolled in this study. All participants underwent neuropsychological assessments, polysomnography, electroencephalogram, and cerebrospinal fluid tests. MRI and fluorodeoxyglucose PET were acquired on a hybrid PET/MRI system. Structural and metabolic changes were compared using voxel-based morphometry analyses and standardized uptake value ratio analyses, focusing on thalamic subnuclei region of interest analyses. Correlation analysis was conducted between gray matter volume and metabolic decrease ratios, and clinical features. RESULTS: The whole-brain analysis showed that gray matter volume decline was confined to the bilateral thalamus and right middle temporal pole in fatal familial insomnia patients, whereas hypometabolism was observed in the bilateral thalamus, basal ganglia, and widespread cortices, mainly in the forebrain. In the regions of interest analysis, gray matter volume and metabolism decreases were prominent in bilateral medial dorsal nuclei, anterior nuclei, and the pulvinar, which is consistent with neuropathological and clinical findings. A positive correlation was found between gray matter volume and metabolic decrease ratios. CONCLUSIONS: Our study revealed specific structuro-metabolic pattern of fatal familial insomnia that demonstrated the essential roles of medial dorsal nuclei, anterior nuclei, and pulvinar, which may be a potential biomarker in diagnosis. Also, primary thalamic subnuclei alterations may be correlated with insomnia, neuropsychiatric, and autonomic symptoms sparing primary cortical involvement.

Neuro-Ophthalmological Findings in Early Fatal Familial Insomnia.

Fatal familial insomnia (FFI) is a rare inherited prion disease characterized by sleep, autonomic, and motor disturbances. Neuro-ophthalmological abnormalities have been reported at the onset of disease, although not further characterized. We analyzed video recordings of eye movements of 6 patients with FFI from 3 unrelated kindreds, seen within 6 months from the onset of illness. Excessive saccadic intrusions were the most prominent findings. In patients with severe insomnia, striking saccadic intrusions are an early diagnostic clue for FFI. The fact that the thalamus is the first structure affected in FFI also suggests its role in the control of steady fixation. ANN NEUROL 2021;89:823-827.

Fatal familial insomnia and Agrypnia Excitata: Autonomic dysfunctions and pathophysiological implications.

Fatal Familial Insomnia (FFI) is a hereditary prion disease caused by a mutation at codon 178 of the prion-protein gene leading to a D178N substitution in the protein determining severe and selective atrophy of mediodorsal and anteroventral thalamic nuclei. FFI is characterized by physiological sleep loss, which polygraphically appears to be a slow wave sleep loss, autonomic and motor hyperactivation with peculiar episodes of oneiric stupor. Alteration of autonomic functions is a great burden for FFI patients consisting in sympathetic overactivation, dysregulation of its physiological responses and disruption of circadian rhythms. The cardiovascular system is the most frequently and severely affected confirming the increased sympathetic drive with preserved parasympathetic responses. Sleep loss, autonomic and motor hyperactivation define Agrypnia Excitata (AE), which is not exclusive to FFI, but it has been canonically described also in Morvan Syndrome and Delirium Tremens. These three conditions present different pathophysiological mechanisms but share the same thalamo-limbic impairment of which AE is one of the possible clinical presentations. FFI, and consequently also AE, is a model for the investigation of the essential role of the thalamus in the organization of body homeostasis, integrating both sleep and autonomic function control.

Losing sleep over mitochondria: a new player in the pathophysiology of fatal familial insomnia.

This commentary highlights the study by Frau-Mendez and coworkers in this issue of Brain Pathology (xxx) in which the authors show evidence for involvement of mitochondria in the pathophysiology of fatal familial insomnia (FFI). Using genetic, biochemical and morphological means, they provide a comprehensive picture of the degree of mitochondrial damage in FFI and show that this leads to increased oxidative stress. This adds FFI to the growing list of dementias with mitochondrial involvement. Future studies will have to address the causality dilemma of which came first, mitochondrial damage and subsequent neurodegeneration or vice versa. Either way, these data provide the basis to devise novel therapeutic strategies for FFI.

Identification of new molecular alterations in fatal familial insomnia.

Fatal familial insomnia is a rare disease caused by a D178N mutation in combination with methionine (Met) at codon 129 in the mutated allele of PRNP (D178N-129M haplotype). FFI is manifested by sleep disturbances with insomnia, autonomic disorders and spontaneous and evoked myoclonus, among other symptoms. This study describes new neuropathological and biochemical observations in a series of eight patients with FFI. The mediodorsal and anterior nuclei of the thalamus have severe neuronal loss and marked astrocytic gliosis in every case, whereas the entorhinal cortex is variably affected. Spongiform degeneration only occurs in the entorhinal cortex. Synaptic and fine granular proteinase K digestion (PrPres) immunoreactivity is found in the entorhinal cortex but not in the thalamus. Interleukin 6, interleukin 10 receptor alpha subunit, colony stimulating factor 3 receptor and toll-like receptor 7 mRNA expression increases in the thalamus in FFI. PrPc levels are significantly decreased in the thalamus, entorhinal cortex and cerebellum in FFI. This is accompanied by a particular PrPc and PrPres band profile. Altered PrP solubility consistent with significantly reduced PrP levels in the cytoplasmic fraction and increased PrP levels in the insoluble fraction are identified in FFI cases. Amyloid-like deposits are only seen in the entorhinal cortex. The RT-QuIC assay reveals that all the FFI samples of the entorhinal cortex are positive, whereas the thalamus is positive only in three cases and the cerebellum in two cases. The present findings unveil particular neuropathological and neuroinflammatory profiles in FFI and novel characteristics of natural prion protein in FFI, altered PrPres and Scrapie PrP (abnormal and pathogenic PrP) patterns and region-dependent putative capacity of PrP seeding.

Clinical, histopathological and genetic studies in a case of fatal familial insomnia with review of the literature.

To explore clinical, histopathological and genetic features of a case with fatal familial insomnia (FFI) and review the related literatures. A middle-aged woman who complained of "insomnia for 9 months and psychosis for 3 months" was suspicious of FFI. The clinical features of the patient were analyzed, and the dead patient was examined by autopsy and the brain tissues were obtained for histopathological studies, and the blood samples from the patient and some of her familial members were collected for the sequencing of prion protein gene (PRNP). The main clinical features included intractable insomnia, psychiatric symptoms and abnormal night sleep behavior, unsteady gait, difficulty swallowing, sudden death, and positive family history. The pathological studies showed neuronal loss and gliosis of multiple brain tissues in the proband, predominated with thalamus; and analysis of PRNP revealed gene D178N mutation, and linkage with 129 methionine (Met) allele in the proband and a relative. FFI patients may manifest as sudden death, and may have prominent psychiatric symptoms; the corresponding gene mutation could occur in the asymptomatic carriers; the data of autopsy and brain tissue pathology is helpful for further understanding of this disease.

Reduced cerebral blood flow in genetic prion disease with PRNP D178N-129M mutation: an arterial spin labeling MRI study.

The D178N mutation in the PRNP gene is associated with fatal familial insomnia and Creutzfeldt-Jakob disease (CJD). Typically, the D178N mutation associated with the 129M genotype is related to fatal familial insomnia while the same mutation associated with the 129V genotype is linked to familial CJD. We describe a D178N-129M haplotype in a patient with early, severe dementia and late-onset minor insomnia, mainly presenting as the CJD phenotype. Cerebrospinal fluid 14-3-3 protein was positive. Diffusion weighted imaging demonstrated widespread cortical ribbon-like high signal intensity, which was also seen in the basal ganglia bilaterally. Arterial spin labeling (ASL) MRI showed severe hypoperfusion in the cerebral cortex, basal ganglia and thalami but this was least marked in the thalami. Neuroimaging abnormalities were more prominent in the cerebral cortex than the thalamus, which was in line with the clinical picture of severe dementia rather than insomnia. ASL-MRI seems to be a useful tool for the detection and follow-up of perfusion changes in patients and asymptomatic carriers harboring the PRNP mutation.

Comparative analysis of gene expression profiles between cortex and thalamus in Chinese fatal familial insomnia patients.

Fatal familial insomnia (FFI) is a special subtype of genetic human prion diseases that is caused by the D178N mutation of the prion protein gene (PRNP). According to the surveillance data from 2006, FFI accounts for about half of all genetic prion disease cases in China. In this study, global expression patterns of the thalamus and parietal cortex from three patients with FFI were analyzed by Affymetrix Human Genome U133+ 2.0 chip. A total of 1,314 genes in the thalamus and 332 ones in the parietal lobe were determined to be differentially expressed genes (DEGs). The percentage of upregulated DEGs is much less in the thalamus (19.3 %) than that in the parietal lobe (42.8 %). Moreover, 255 of those DEGs showed the same altering tendencies in both tested regions, including 99 upregulated and 156 downregulated ones. The reliability of the results was confirmed by the real-time RT-PCR assays. There were 1,152 and 531 biological processes affected in the thalamus and the parietal lobe, respectively, as well as 391 overlapping ones in both regions. The most significantly changed molecular functions included transcription and DNA-dependent regulation of transcription, RNA splicing, mitochondrial electron transport, etc. The changed functions in the thalamus contained more numbers of DEGs than parietal lobe. According to KEGG classification, there were 167 and 115 different pathways changed in the thalamus and the parietal lobe, respectively, while 102 were changed in both. Interestingly, the top three changed pathways in the three groups mentioned above were Parkinson's disease, Alzheimer's disease, and oxidative phosphorylation. These results demonstrate the greater damage in the thalamus than in the parietal lobe during FFI pathogenesis, which is consistent with previous pathological observations. This study aims to describe the global expression profiles in various brain regions of FFI while proposing useful clues for understanding the pathogenesis of FFI and selecting potential biomarkers for diagnostic and therapeutic tools.

Agrypnia excitata.

Agrypnia (from the Greek: to chase sleep) excitata (AE) is a syndrome characterized by loss of sleep and permanent motor and autonomic hyperactivation (excitata). Disruption of the sleep-wake rhythm consists in the disappearance of spindle-delta activities, and the persistence of stage 1 non-rapid eye movement (NREM) sleep. Rapid eye movement (REM) sleep persists but fails to stabilize, appearing in short recurrent episodes, isolated, or mixed with stage 1 NREM sleep. Diurnal and nocturnal motor, autonomic and hormonal overactivity is the second hallmark of AE. Of particular interest is the finding that norepinephrine secretion is extremely elevated at all hours of the day and night whereas the nocturnal melatonin peak is lacking. Oneiric stupor is probably an exclusive sign of AE and consists in the recurrence of stereotyped gestures mimicking simple daily life activities. Agrypnia excitata aptly defines 3 different clinical conditions, fatal familial insomnia (FFI), an autosomal dominant prion disease, Morvan syndrome (MS), an autoimmune encephalitis, and delirium tremens (DT), the alcohol withdrawal syndrome. Agrypnia excitata is due to an intralimbic disconnection releasing the hypothalamus and brainstem reticular formation from cortico-limbic inhibitory control. This pathogenetic mechanism is visceral thalamus degeneration in FI, whereas it may depend on autoantibodies blocking voltage-gated potassium (VGK) channels within the limbic system in MS, and in the sudden changes in gabaergic synapses down-regulated by chronic alcohol abuse within the limbic system in DT.

Comparison of the pathologic and pathogenic features in six different regions of postmortem brains of three patients with fatal familial insomnia.

Fatal familial insomnia (FFI) is an autosomal dominant prion disease clinically characterized by rapidly progressive insomnia, prominent autonomic alterations and behavioral disturbance. The D178N mutation of the prion protein gene (PRNP) on chromosome 20 in conjunction with methionine at codon 129 is a molecular feature. Although the neuropathological characteristics of FFI are well documented, the neuropathologic and pathogenic features of FFI patients remain poorly understood. Six brain regions of postmortem brains from 3 FFI patients were examined using immunohistochemistry, western blot analyses and quantitative real-time PCR. In all 3 brain specimens, reactive astrogliosis was found to be more severe in the thalamus than in the cortex regions. Western blot analyses showed that all three brains expressed PrP, but only 2 were associated with significantly weak proteinase K (PK) resistance. However, the conformational stabilities of PrPSc in the 3 FFI brains were significantly weaker than those presented in a G114V genetic Creutzfeldt-Jakob disease (gCJD) case. Immunohistochemistry and western blot analyses showed comparable amounts of neuron-specific enolase (NSE)-positive stained cells and NSE protein among the different regions in the three brains. In addition, the transcriptional levels of glial fibrillary acidic protein (GFAP) and NSE-specific mRNAs were coincident with the expression of these proteins. In conclusion, in the present study, we described the detailed regional neuropathology of FFI cases.

Thalamic contribution to Sleep Slow Oscillation features in humans: a single case cross sectional EEG study in Fatal Familial Insomnia.

OBJECTIVE: Studying the thalamic role in the cortical expression of the Sleep Slow Oscillation (SSO) in humans by comparing SSO features in a case of Fatal Familial Insomnia (FFI) and a group of controls. METHODS: We characterize SSOs in a 51-year-old male with FFI carrying the D178N mutation and the methionine/methionine homozygosity at the polymorphic 129 codon of the PRNP gene and in eight gender and age-matched healthy controls. Polysomnographic (21 EEG electrodes, two consecutive nights) and volumetric- (Diffusion tensor imaging Magnetic Resonance Imaging DTI MRI) evaluations were carried out for the patient in the middle course of the disease (five months after the onset of insomnia; disease duration: 10 months). We measured a set of features describing each SSO event: the wave shape, the event-origin location, the number and the location of all waves belonging to the event, and the grouping of spindle activity as a function of the SSO phase. RESULTS: We found that the FFI individual showed a marked reduction of SSO event rate and wave morphological alterations as well as a significant reduction in grouping spindle activity, especially in frontal areas. These alterations paralleled DTI changes in the thalamus and the cingulate cortex. CONCLUSIONS: This work gives a quantitative picture of spontaneous SSO activity during the NREM sleep of a FFI individual. The results suggest that a thalamic neurodegeneration specifically alters the cortical expression of the SSO. This characterization also provides indications about cortico-thalamic interplays in SSO activity in humans.

Neuropathology of sleep disorders: a review.

Sleep disorders are important manifestations of neurodegenerativediseases and sometimes are clinically evident well before the onset of other neurological manifestations. This review addresses theneuroanatomical basis and the mechanisms of sleep regulation in humans in relation to the neuropathology of entities associated with sleep disturbances in selected diseases, including Alzheimer disease, progressive supranuclear palsy, Lewy body disorders, multiple-system atrophy, and fatal familial insomnia. This includes abnormalities of circadian rhythm, insomnia, narcolepsy, rapid eye movements sleep behavior disorders, and excessive daytime sleepiness.

The prion diseases.

The prion diseases are a family of rare neurodegenerative disorders that result from the accumulation of a misfolded isoform of the prion protein (PrP), a normal constituent of the neuronal membrane. Five subtypes constitute the known human prion diseases; kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome (GSS), fatal insomnia (FI), and variant CJD (vCJD). These subtypes are distinguished, in part, by their clinical phenotype, but primarily by their associated brain histopathology. Evidence suggests these phenotypes are defined by differences in the pathogenic conformation of misfolded PrP. Although the vast majority of cases are sporadic, 10% to 15% result from an autosomal dominant mutation of the PrP gene (PRNP). General phenotype-genotype correlations can be made for the major subtypes of CJD, GSS, and FI. This paper will review some of the general background related to prion biology and detail the clinical and pathologic features of the major prion diseases, with a particular focus on the genetic aspects that result in prion disease or modification of its risk or phenotype.

Clinical features of sporadic fatal insomnia.

Recent advances in neuropathology, genotyping, and physiochemical characterization of proteins have allowed for the classification and verification of MM2-thalamic Creutzfeldt-Jakob disease (CJD). CJD is a fatal neurodegenerative illness belonging to the transmissible spongiform encephalopathies, also known as prion diseases. Sporadic CJD is generally classified by the genotype at codon 129 of the prion protein gene and the distinct physiochemical features of the pathologic prion protein (PrP(sc)). The entity is characterized by methionine homozygosity at codon 129, type 2 PrP(sc), and, primarily, thalamic pathology (MM2-thalamic CJD). It shares clinical and pathologic similarities with the genetic prion disorder fatal familial insomnia; the MM2-thalamic phenotype has therefore been called sporadic fatal insomnia (SFI). SFI may also present like other neurodegenerative diseases, and common diagnostic findings that are seen in other forms of sporadic CJD may be absent.

Agrypnia Excitata: a microneurographic study of muscle sympathetic nerve activity.

OBJECTIVE: Agrypnia Excitata (AE) is characterized by autonomic over-activity and cardiovascular fluctuations but direct evidence of sympathoexcitation is lacking. AE is a common feature of acquired (i.e. Morvan's syndrome--MS) and genetic (i.e. fatal familial insomnia--FFI) conditions where a dysfunction of the thalamo-limbic system has been suggested. The aim of this study is to report the first microneurographic recordings of sympathetic activity in acquired and genetic AE to investigate the pattern of sympathetic activation. METHODS: We describe two patients presenting acquired AE (MS) as demonstrated by elevated serum antibody levels to voltage-gated potassium channels and one patient with genetically confirmed FFI. Patients and fifteen sex and age-matched healthy controls underwent microneurography from peroneal nerve to assess muscle sympathetic nerve activity (MSNA) and heart rate (HR). RESULTS: Mean level of resting awake MSNA and HR was significantly increased in patients compared to controls. Patients presented a similar pattern of MSNA with a normal cardiac rhythmicity and a very high burst incidence expressed in approximately each cardiac beat. CONCLUSIONS: Acquired and genetic AE presented a resting awake sympathetic over-activity. SIGNIFICANCE: AE patients may develop high blood pressure and/or cardiovascular instability potentially increasing the morbidity/mortality of the underlying disorders.

In vivo detection of thalamic gliosis: a pathoradiologic demonstration in familial fatal insomnia.

BACKGROUND: Increasing evidence supports the usefulness of brain magnetic resonance imaging (MRI) for the diagnosis of human prion diseases. From the neuroradiological point of view, fatal familial insomnia is probably the most challenging to diagnose because brain lesions are mostly confined to the thalamus. OBJECTIVE: To determine whether multisequence MRI of the brain can show thalamic alterations and establish pathoradiologic correlations in a patient with familial fatal insomnia. DESIGN: Radioclinical prospective study. We describe a patient with fatal familial insomnia and normal MRI images. Because the MRI study was performed only 4 days before the patient's death, we were able to compare radiological data with the lesions observed at the neuropathologic level. PATIENT: A 55-year-old man with familial fatal insomnia. MAIN OUTCOME MEASURE: Magnetic resonance spectroscopy combined with the measurement of apparent diffusion coefficient of water in different brain areas. RESULTS: The neuroradiological study showed, in the thalamus but not in the other brain regions studied, an increase of apparent diffusion coefficient of water and a metabolic pattern indicating gliosis. These alterations closely correlated with neuropathologic data showing an almost pure gliosis that was restricted to the thalami. CONCLUSION: Considering fatal familial insomnia as a model of thalamic-restricted gliosis, this case demonstrates that multisequences of magnetic resonance can detect prion-induced gliosis in vivo, as confirmed by a neuropathologic examination performed only a few days after radiological examination.