The Network Structure of Cognitive Impairment: From Subjective Cognitive Decline to Alzheimer's Disease.

It was proposed that a reorganization of the relationships between cognitive functions occurs in dementia, a vision that surpasses the idea of a mere decline of specific domains. The complexity of cognitive structure, as assessed by neuropsychological tests, can be captured by exploratory graph analysis (EGA). EGA was applied to the neuropsychological assessment of people (humans) with subjective cognitive decline (SCD), mild cognitive impairment (MCI), and Alzheimer's disease (AD; total N = 638). Both sexes were included. In AD, memory scores detach from the other cognitive functions, and memory subdomains reduce their reciprocal relation. SCD showed a pattern of segregated neuropsychological domains, and MCI showed a noisy and less stable pattern. Results suggest that AD drives a reorganization of cognitive functions toward a less-fractionated architecture compared with preclinical conditions. Cognitive functions show a reorganization that goes beyond the performance decline. Results also have clinical implications in test interpretations and usage.

Cognitive and Neuropathophysiological Outcomes of Gamma-tACS in Dementia: A Systematic Review.

Despite the numerous pharmacological interventions targeting dementia, no disease-modifying therapy is available, and the prognosis remains unfavorable. A promising perspective involves tackling high-frequency gamma-band (> 30 Hz) oscillations involved in hippocampal-mediated memory processes, which are impaired from the early stages of typical Alzheimer's Disease (AD). Particularly, the positive effects of gamma-band entrainment on mouse models of AD have prompted researchers to translate such findings into humans using transcranial alternating current stimulation (tACS), a methodology that allows the entrainment of endogenous cortical oscillations in a frequency-specific manner. This systematic review examines the state-of-the-art on the use of gamma-tACS in Mild Cognitive Impairment (MCI) and dementia patients to shed light on its feasibility, therapeutic impact, and clinical effectiveness. A systematic search from two databases yielded 499 records resulting in 10 included studies and a total of 273 patients. The results were arranged in single-session and multi-session protocols. Most of the studies demonstrated cognitive improvement following gamma-tACS, and some studies showed promising effects of gamma-tACS on neuropathological markers, suggesting the feasibility of gamma-tACS in these patients anyhow far from the strong evidence available for mouse models. Nonetheless, the small number of studies and their wide variability in terms of aims, parameters, and measures, make it difficult to draw firm conclusions. We discuss results and methodological limitations of the studies, proposing possible solutions and future avenues to improve research on the effects of gamma-tACS on dementia.

Temporal gamma tACS and auditory stimulation affect verbal memory in healthy adults.

Research suggests a potential of gamma oscillation entrainment for enhancing memory in Alzheimer's disease and healthy subjects. Gamma entrainment can be accomplished with oscillatory electrical, but also sensory stimulation. However, comparative studies between sensory stimulation and transcranial alternating current stimulation (tACS) effects on memory processes are lacking. This study examined the effects of rhythmic gamma auditory stimulation (rAS) and temporal gamma-tACS on verbal long-term memory (LTM) and working memory (WM) in 74 healthy individuals. Participants were assigned to two groups according to the stimulation techniques (rAS or tACS). Memory was assessed in three experimental blocks, in which each participant was administered with control, 40, and 60 Hz stimulation in counterbalanced order. All interventions were well-tolerated, and participants reported mostly comparable side effects between real stimulation (40 and 60 Hz) and the control condition. LTM immediate and delayed recall remained unaffected by stimulations, while immediate recall intrusions decreased during 60 Hz stimulation. Notably, 40 Hz interventions improved WM compared to control stimulations. These results highlight the potential of 60 and 40 Hz temporal cortex stimulation for reducing immediate LTM recall intrusions and improving WM performance, respectively, probably due to the entrainment of specific gamma oscillations in the auditory cortex. The results also shed light on the comparative effects of these neuromodulation tools on memory functions, and their potential applications for cognitive enhancement and in clinical trials.

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.

Sarcopenia in subjects with Alzheimer's disease: prevalence and comparison of agreement between EGWSOP1, EGWSOP2, and FNIH criteria.

BACKGROUND: Sarcopenia is an age-related clinical syndrome characterized by the progressive loss of muscle mass and muscle strength. It appears to be closely linked to dementia, particularly Alzheimer's disease (AD); however, its prevalence among AD patients remains unclear. In this study, we assessed differences in sarcopenia prevalence between non-demented individuals and AD patients. Moreover, we assessed sex-specific differences in sarcopenia prevalence and explored the diagnostic value of the Muscle Quality Index (MQI) for diagnosing sarcopenia among AD patients. METHOD: Cross-sectional study including 145 patients with probable AD and 51 older adults with normal cognition. Sarcopenia was diagnosed according to the criteria of the European Working Group on Sarcopenia in Older People (EWGSOP1 and EWGSOP2) and of the Foundation for the National Institutes of Health (FNIH). The MQI was computed as the ratio of handgrip strength to skeletal muscle mass. RESULTS: No significant difference in sarcopenia prevalence was observed between AD patients and controls. Prevalence ranged from 3.4 to 23.4% in AD patients and from 2 to 11.8% in controls, depending on diagnostic criteria. Prevalence was higher using EWGSOP1 and decreased using EWGSOP2 and FNIH. Prevalence was higher in males than in females with AD. The MQI was lower in AD patients than in controls (95%CI: - 0.23, - 0.05, p < 0.001), but displayed poor diagnostic accuracy in identifying sarcopenia cases. CONCLUSIONS: AD patients and controls show comparable sarcopenia prevalence. Sarcopenia prevalence is higher in males than females among AD patients and higher when using EWGSOP1 compared to FNIH and EWGSOP2 criteria.

Sleep and circadian rhythm disruptions in behavioral variant frontotemporal dementia.

INTRODUCTION: Sleep and rest-activity rhythm alterations are common in neurodegenerative diseases. However, their characterization in patients with behavioral variant frontotemporal dementia (bvFTD) has proven elusive. We investigated rest-activity rhythm alterations, sleep disturbances, and their neural correlates in bvFTD. METHODS: Twenty-seven bvFTD patients and 25 healthy controls completed sleep questionnaires and underwent 7 days of actigraphy while concurrently maintaining a sleep diary. Cortical complexity and thickness were calculated from T1-weighted magnetic resonance (MR) images. RESULTS: Compared to controls, bvFTD patients showed longer time in bed (95% confidence interval [CI]: 79.31, 321.83) and total sleep time (95% CI: 24.38, 321.88), lower sleep efficiency (95% CI: -12.58, -95.54), and rest-activity rhythm alterations in the morning and early afternoon. Increased sleep duration was associated with reduced cortical thickness in frontal regions. DISCUSSION: Patients with bvFTD showed longer sleep duration, lower sleep quality, and rest-activity rhythm alterations. Actigraphy could serve as a cost-effective and accessible tool for ecologically monitoring changes in sleep duration in bvFTD patients. HIGHLIGHTS: We assessed sleep and circadian rhythms in behavioral variant frontotemporal dementia (bvFTD) using actigraphy. Patients with bvFTD show increased sleep duration and reduced sleep quality. Patients with bvFTD show rest-activity alterations in the morning and early afternoon. Sleep duration is associated with reduced cortical thickness in frontal regions. These alterations may represent an early sign of neurodegeneration.

Chromatic Pupillometry in Isolated Rapid Eye Movement Sleep Behavior Disorder.

BACKGROUND: Melanopsin retinal ganglion cell (mRGC)-mediated pupillary light reflex (PLR) abnormalities have been documented in several neurodegenerative disorders including Parkinson's disease. Overall, isolated rapid eye movement (REM) sleep behavior disorder (iRBD) represents the strongest prodromal risk factor for impending α-synucleinopathies. OBJECTIVES: To quantitatively compare PLR and mRGC-mediated contribution to PLR in 16 iRBD patients and 16 healthy controls. METHODS: iRBD and controls underwent extensive neuro-ophthalmological evaluation and chromatic pupillometry. In iRBD, PLR metrics were correlated with clinical variables and with additional biomarkers including REM atonia index (RAI), DaTscan, and presence of phosphorylated-α-synuclein (p-α-syn) deposition in skin biopsy. RESULTS: We documented higher baseline pupil diameter and decreased rod-transient PLR amplitude in iRBD patients compared to controls. PLR rod-contribution correlated with RAI. Moreover, only iRBD patients with evidence of p-α-syn deposition at skin biopsy showed reduced PLR amplitude compared to controls. CONCLUSION: The observed PLR abnormalities in iRBD might be considered as potential biomarkers for the risk stratification of phenoconversion of the disease. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The importance of social zeitgeber in paediatric type 1 narcolepsy: What we can learn from the COVID-19 restrictions adopted in Italy?

The lockdown due to the new coronavirus pandemic (COVID-19) has led to unparalleled changes in several aspects of human behaviour. During the lockdown, the general population delayed sleep timing and spent more time in bed; however, little is known on the effects of COVID-19 restriction on children and adolescents suffering type 1 narcolepsy. In the last months of 2019, we performed follow-up actigraphy in 18 type 1 narcolepsy children and adolescents under stable pharmacological treatment with sodium oxybate. We contacted these patients for a follow-up actigraphy during the first Italian lockdown. Actigraphs and the Epworth Sleepiness Scale for children and adolescents (ESS-CHAD) have been sent to participants' homes. Differences in motor activity were analysed through functional linear modelling. During lockdown, type 1 narcolepsy children and adolescents went to bed and woke up later, slept more during the daytime and napped more frequently. No difference emerged in time in bed, estimated total sleep time and nocturnal sleep quality. Similarly, no difference emerged in ESS-CHAD and body mass index. The time-series analysis of motor activity documented reduced activity during the early morning and in the evening during the lockdown period compared with pre-lockdown. Our study objectively showed that type 1 narcolepsy children and adolescents delayed the sleep phase and slept more during the daytime during the lockdown. The analysis of type 1 narcolepsy children and adolescents' behaviour during the lockdown has provided new information that could pave the way to a personalized school programme.

Being creative during lockdown: The relationship between creative potential and COVID-19-related psychological distress in narcolepsy type 1.

The national lockdown imposed in several countries to counteract the coronavirus disease 2019 (COVID-19) pandemic led to an unprecedented situation with serious effects on mental health of the general population and of subjects affected by heterogeneous diseases. Considering the positive association between narcoleptic symptoms and creativity, we aimed at exploring the psychological distress associated with COVID-19 restrictions and its relationship with depressive symptoms and creativity in patients with narcolepsy type 1 (NT1). A total of 52 patients with NT1 and 50 healthy controls, who completed a previous study on creativity, were contacted during the first lockdown period to complete an online survey evaluating psychological distress related to the COVID-19 outbreak, sleep quality, narcolepsy and depressive symptoms, and creative abilities. The patients with NT1 showed an improvement in subjective sleepiness while controls reported worsening of sleep quality during the lockdown. Depression and NT1 symptom severity proved significant predictors of COVID-19-related distress. Creative performance, namely generative fluency, turned out to be a favourable moderator in the relationship between depression and patients' distress, reducing the detrimental effect of depression on the patients' wellbeing. On the contrary, creative originality proved to be a disadvantageous moderator in the relationship between NT1 symptom severity and the distress associated with this traumatic event indicating a higher vulnerability to developing COVID-19-related distress, particularly evident in patients displaying higher originality. Overall, these results highlight a crucial role of creativity in patients with NT1, suggesting that creative potential could be used as a protective factor against the development of distress associated with the lockdown.

Sarcopenia screening in elderly with Alzheimer's disease: performances of the SARC-F-3 and MSRA-5 questionnaires.

BACKGROUND: The 3-item SARC-F (SARC-F-3) and the 5-item Mini Sarcopenia Risk Assessment (MSRA-5) questionnaires have been recently proposed to screen elderly people regarding the risk of sarcopenia. However, no studies have investigated their performances in Alzheimer's disease (AD). METHODS: We conducted a single-center observational study, including 130 consecutive AD patients (mean age: 70.71 ± 8.50 y, 54.6% women) who attended a center for neurodegenerative diseases. Sarcopenia was diagnosed using the European Working Group on Sarcopenia in Older People of 2010 (EWGSOP1) and of 2018 (EWGSOP2) criteria. Sensitivity, specificity, positive and negative likelihood ratio, and the area under the receiver operating characteristic curve (AUC) were used to assess the diagnostic performance of SARC-F-3 and MSRA-5. RESULTS: SARC-F-3 showed a sensitivity of 9.7%, a specificity of 82.8% and an AUC of 0.41 using EWGSOP1, whereas the sensitivity was of 16.7%, specificity of 84.7% and AUC of 0.58 using EWGSOP2. The MSRA-5 displayed a sensitivity of 3.2%, a specificity of 89.9% and an AUC of 0.41 using EWGSOP1, whereas sensitivity was of 0%, specificity of 91.1% and the AUC of 0.55 using EWGSOP2 criteria. The questionnaires showed a moderate agreement (Cohen's k = 0.53). CONCLUSIONS: In our sample of AD patients, a sizable number of sarcopenic individuals were misidentified by SARC-F-3 and MSRA-5, making those questionnaires unsuitable for sarcopenia screening. Considering that sarcopenia has a high prevalence in dementia and that its correct and timely identification is paramount for optimal management of patients, the development and validation of an ad-hoc sarcopenia screening tool for AD patients is highly desirable.

(Not so) Smart sleep tracking through the phone: Findings from a polysomnography study testing the reliability of four sleep applications.

An increasing number of sleep applications are currently available and are being widely used for in-home sleep tracking. The present study assessed four smartphone applications (Sleep Cycle-Accelerometer, SCa; Sleep Cycle-Microphone, SCm; Sense, Se; Smart Alarm, SA) designed for sleep-wake detection through sound and movement sensors, by comparing their performance with polysomnography. Twenty-one healthy participants (six males, 15 females) used the four sleep applications running on iPhone (provided by the experimenter) simultaneously with portable polysomnography recording at home, while sleeping alone for two consecutive nights. Whereas all apps showed a significant correlation with polysomnography-time in bed, only SA offered significant correlations for sleep efficacy. Furthermore, SA seemed to be quite effective in reliable detection of total sleep time and also light sleep; however, it underestimated wake and partially overestimated deep sleep. None of the apps resulted capable of detecting and scoring rapid eye movement sleep. To sum up, SC (functioning through both accelerometer and microphone) and Se did not result sufficiently reliable in sleep-wake detection compared with polysomnography. SA, the only application offering the possibility of an epoch-by-epoch analysis, showed higher accuracy than the other apps in comparison with polysomnography, but it still shows some limitations, particularly regarding wake and deep sleep detection. Developing scoring algorithms specific for smartphone sleep detection and adding external sensors to record other physiological parameters may overcome the present limits of sleep tracking through smart phone apps.

Excessive daytime sleepiness in narcolepsy and central nervous system hypersomnias.

PURPOSE: Excessive daytime sleepiness (EDS) is the core complaint of central nervous system (CNS) hypersomnias. In this mini-review, we summarized EDS features in CNS hypersomnias to provide a guide for differential diagnosis purposes. METHODS: A review of recent literature was performed to provide an update in CNS hypersomnias. RESULTS: At clinical evaluation, narcolepsy patients report a good restorative potential of sleep together with the frequent occurrence of dreaming even during short-lasting naps. These features are mirrored by the neurophysiological evidence of REM sleep at sleep onset (SOREMP) during the Multiple Sleep Latency Test (MSLT), a specific marker. Conversely, patients with idiopathic hypersomnia (IH) complain sleep inertia and prolonged nocturnal sleep. Polysomnographic studies show high sleep propensity on the MSLT or high 24-h total sleep time during continuous monitoring. Patients with insufficient sleep syndrome (ISS) can present with variable clinical EDS features in between narcolepsy and IH. ISS diagnosis is based on the clinical evidence of nocturnal sleep curtailment (weekdays versus vacations) associated with the disappearance of EDS complaint after sleep extension. Polysomnographic data are not required, but when the MSLT is performed, ISS patients can present with SOREMP arising from non-REM stage 2 sleep (vs narcolepsy patients entering into SOREM most frequently from wakefulness). Kleine-Levin Syndrome is characterized by recurrent episodes of enormously prolonged sleep time lasting days associated with abnormal cognition and behavior intermixed by asymptomatic periods, a sleep pattern that can be well documented by actigraphy. CONCLUSIONS: Different CNS hypersomnias present with specific features of EDS are useful to guide the clinician to apply and interpret appropriate neurophysiological investigations.

The spectrum of REM sleep-related episodes in children with type 1 narcolepsy.

Type 1 narcolepsy is a central hypersomnia due to the loss of hypocretin-producing neurons and characterized by cataplexy, excessive daytime sleepiness, sleep paralysis, hypnagogic hallucinations and disturbed nocturnal sleep. In children, close to the disease onset, type 1 narcolepsy has peculiar clinical features with severe cataplexy and a complex admixture of movement disorders occurring while awake. Motor dyscontrol during sleep has never been systematically investigated. Suspecting that abnormal motor control might affect also sleep, we systematically analysed motor events recorded by means of video polysomnography in 40 children with type 1 narcolepsy (20 females; mean age 11.8 ± 2.6 years) and compared these data with those recorded in 22 age- and sex-matched healthy controls. Motor events were classified as elementary movements, if brief and non-purposeful and complex behaviours, if simulating purposeful behaviours. Complex behaviours occurring during REM sleep were further classified as 'classically-defined' and 'pantomime-like' REM sleep behaviour disorder episodes, based on their duration and on their pattern (i.e. brief and vivid-energetic in the first case, longer and with subcontinuous gesturing mimicking daily life activity in the second case). Elementary movements emerging either from non-REM or REM sleep were present in both groups, even if those emerging from REM sleep were more numerous in the group of patients. Conversely, complex behaviours could be detected only in children with type 1 narcolepsy and were observed in 13 patients, with six having 'classically-defined' REM sleep behaviour disorder episodes and seven having 'pantomime-like' REM sleep behaviour disorder episodes. Complex behaviours during REM sleep tended to recur in a stereotyped fashion for several times during the night, up to be almost continuous. Patients displaying a more severe motor dyscontrol during REM sleep had also more severe motor disorder during daytime (i.e. status cataplecticus) and more complaints of disrupted nocturnal sleep and of excessive daytime sleepiness. The neurophysiological hallmark of this severe motor dyscontrol during REM sleep was a decreased atonia index. The present study reports for the first time the occurrence of a severe and peculiar motor disorder during REM sleep in paediatric type 1 narcolepsy and confirms the presence of a severe motor dyscontrol in these patients, emerging not only from wakefulness (i.e. status cataplecticus), but also from sleep (i.e. complex behaviours during REM sleep). This is probably related to the acute imbalance of the hypocretinergic system, which physiologically acts by promoting movements during wakefulness and suppressing them during sleep.

24-h actigraphic monitoring of motor activity, sleeping and eating behaviors in underweight, normal weight, overweight and obese children.

PURPOSE: Within a chronobiological perspective, the present study aimed to describe 24 h of sleep-wake cycle, motor activity, and food intake patterns in different body mass index (BMI) categories of children through 7 days of actigraphic recording. METHODS: Height and weight were objectively measured for BMI calculation in a sample of 115 Italian primary schoolchildren (10.21 ± 0.48 years, 62.61 % females). According to BMI values, 2.60 % were underweight, 61.70 % were of normal weight, 29.60 % were overweight and 6.10 % were obese. Participants wore a wrist actigraph continuously for 7 days to record motor activity and describe sleep-wake patterns. In addition, participants were requested to push the event-marker button of the actigraph each time they consumed food to describe their circadian eating patterns. RESULTS: BMI group differences were found for sleep quantity (i.e. midpoint of sleep and amplitude), while sleep quality, 24-h motor activity and food intake patterns were similar between groups. Regression analyses showed that BMI was negatively predicted by sleep duration on schooldays. BMI was also predicted by motor activity and by food intake frequencies recorded at particular times of day during schooldays and at the weekend. CONCLUSIONS: The circadian perspective seems to provide promising insight into childhood obesity, but this aspect needs to be further explored.

Effects of dawn simulation on attentional performance in adolescents.

PURPOSE: This study aimed at examining the effects of 2 weeks of dawn simulation on attentional performance in adolescents. METHODS: On the whole, 56 adolescents (24 females and 32 males) took part to the study, with a mean age of 17.68 ± 0.97 years (age ranging between 15 and 20 years). Each adolescent was requested to participate for 5 consecutive weeks and the research design included the baseline and two counterbalanced conditions, dawn simulator and control (no dawn simulator). Attentional performance of adolescents was measured through the attention network test (ANT) that allowed assessing the efficiency of three separable attentional networks, namely alerting, orienting and executive. Overall, participants performed the ANT three times (i.e., one time for each condition), while sleep quality, sleep duration and sleep timing were concurrently monitored by means of actigraphy and were treated as potential confounders. RESULTS: The only improvement of the attentional performance attributable to the use of dawn simulator was observed for the efficiency of alerting network (45.97 ± 32.76 ms) that significantly increased in comparison to the baseline (31.57 ± 26.97 ms) (p < 0.05). On the contrary, the sleep quality, sleep quantity and sleep timing did not significantly change. CONCLUSION: These results show for the first time that, controlling for sleep quality, sleep duration and sleep timing, the use of dawn simulator across 2 weeks is able to determine an alerting effect in adolescents.

Deep Learning-based Approach for Brainstem and Ventricular MR Planimetry: Application in Patients with Progressive Supranuclear Palsy.

Purpose To develop a fast and fully automated deep learning (DL)-based method for the MRI planimetric segmentation and measurement of the brainstem and ventricular structures most affected in patients with progressive supranuclear palsy (PSP). Materials and Methods In this retrospective study, T1-weighted MR images in healthy controls (n = 84) were used to train DL models for segmenting the midbrain, pons, middle cerebellar peduncle (MCP), superior cerebellar peduncle (SCP), third ventricle, and frontal horns (FHs). Internal, external, and clinical test datasets (n = 305) were used to assess segmentation model reliability. DL masks from test datasets were used to automatically extract midbrain and pons areas and the width of MCP, SCP, third ventricle, and FHs. Automated measurements were compared with those manually performed by an expert radiologist. Finally, these measures were combined to calculate the midbrain to pons area ratio, MR parkinsonism index (MRPI), and MRPI 2.0, which were used to differentiate patients with PSP (n = 71) from those with Parkinson disease (PD) (n = 129). Results Dice coefficients above 0.85 were found for all brain regions when comparing manual and DL-based segmentations. A strong correlation was observed between automated and manual measurements (Spearman ρ > 0.80, P < .001). DL-based measurements showed excellent performance in differentiating patients with PSP from those with PD, with an area under the receiver operating characteristic curve above 0.92. Conclusion The automated approach successfully segmented and measured the brainstem and ventricular structures. DL-based models may represent a useful approach to support the diagnosis of PSP and potentially other conditions associated with brainstem and ventricular alterations. Keywords: MR Imaging, Brain/Brain Stem, Segmentation, Quantification, Diagnosis, Convolutional Neural Network Supplemental material is available for this article. © RSNA, 2024 See also the commentary by Mohajer in this issue.

Neurophysiological indices for split phenomena: correlation with age and sex and potential implications in amyotrophic lateral sclerosis.

Background: Split phenomena (SP) are characterized by patterns of differential muscle wasting and atrophy, which are highly prevalent in amyotrophic lateral sclerosis (ALS) patients. Several neurophysiological indicators, including the split-hand index (SHI), split-leg index (SLI), and split-elbow index (SEI), have been proposed to assess SP. Nevertheless, their cutoff values and the impact of age and sex on these measures remain unclear. Methods: We prospectively collected neurophysiological data from 300 healthy adult subjects. The following indices were measured from compound muscle action potentials (CMAPs): SHI [abductor pollicis brevis (APBcmap) x first dorsal interosseous (FDI)cmap/adductor digiti minimi (ADMcmap)], SEI (BICEPScmap/TRICEPScmap), SLI (extensor digit brevis (EDB)cmap/abductor Hallucis (AH)cmap), and the neurophysiological ratios APBcmap /ADMcmap and FDIcmap/ADMcmap. Multiple linear regression analysis was used to investigate the association between age, sex, CMAPs, and neurophysiological indicators. Results: The median SHI was 10.4, with a median APBcmap/ADMcmap ratio of 0.9 and a median FDIcmap/ADMcmap ratio of 1.2. The median SEI was 1.6 (IQR:1.1-2.4) and the median SLI was 0.7 (IQR:0.5-1.0). Negative associations were observed between age, most of the CMAPs, and all the neurophysiological indices, except for SLI. The male subjects exhibited significantly higher CMAP values for the first dorsal interosseous (FDI), biceps, and SHI compared to the female participants. Conclusion: Our findings highlight the importance of age- and sex-adjusted normative data for SP indices, which could enhance their diagnostic accuracy and clinical utility in patients with ALS. The SL index appears to be the most reliable indicator, as it showed no significant association with age or sex.

Mapping lower-limbs muscle vulnerability in patients with ALS: The role of upper and lower motor neurons.

BACKGROUND: Several studies have reported disproportionate wasting of the flexor muscles of the lower limbs (LL) compared to the extensors in patients with amyotrophic lateral sclerosis (ALS). However, these studies have involved small sample sizes (n ã€ˆ100), and their findings have been inconsistent. Thus, it remains uncertain whether a distinct pattern of LL muscle weakness is specific to ALS. AIMS: To investigate the muscle weakness pattern in the LL at the knee, ankle, and toes in a large cohort of ALS patients and evaluate the relationship between the pattern of muscle strength and the extent of upper (UMN) and lower (LMN) motoneuron impairment. MATERIAL AND METHODS: The strength of flexor and extensor muscle was evaluated in 1250 legs of newly diagnosed ALS patients at the knee, ankle, and foot toes. UMN and LMN burden were assessed using validated scores. Within-subjects ANOVA considering the type of muscle (flexor/extensor) and anatomical sites (knee/ankle/toes) and mixed-factorial ANOVA were conducted to explore the impact of UMN and LMN impairments on the muscle weakness pattern. RESULTS: Muscle strength showed a significant decline from proximal to distal regions. Indeed both flexor and extensor muscles at the knee outperformed those at the ankle and toes. Within each site, extensor muscles exhibited less strength than flexor, except at the knee. Patients with heightened UMN impairment showed a more marked difference between flexors and extensors within each site, with extensor muscles being more compromised at the ankle and toes. Higher LMN impairment corresponded to a more pronounced weakness in flexor muscles at the ankle and toes compared to those at the knee. CONCLUSIONS: The extensor muscle at the knee and the flexors at the foot and toes displayed relative resistance to ALS disease. UMN impairment amplified the differences between flexor and extensor muscles within each site, while LMN impairment demonstrated a clear distal-to-proximal vulnerability.