Early Onset Inherited Peripheral Neuropathies: The Experience of a Specialized Referral Center for Genetic Diagnosis Achievement.

BACKGROUND: Charcot-Marie-Tooth disease (CMT) is a heterogeneous group of inherited peripheral neuropathies. Although the typical disease onset is reported in the second decade, earlier onsets are not uncommon. To date, few studies on pediatric populations have been conducted and the achievement of molecular diagnosis remains challenging. METHODS: During the last 24 years we recruited 223 patients with early-onset hereditary peripheral neuropathies (EOHPN), negative for PMP22 duplication, 72 of them referred by a specialized pediatric hospital. Genetic testing for CMT-associated genes has been carried out with a range of different techniques. RESULTS: Of the 223 EOHPN cases, 43% were classified as CMT1 (demyelinating), 49% as CMT2 (axonal), and 8% as CMTi (intermediate). Genetic diagnosis was reached in 51% of patients, but the diagnostic yield increased to 67% when focusing only on cases from the specialized pediatric neuromuscular centers. Excluding PMP22 rearrangements, no significant difference in diagnostic rate between demyelinating and axonal forms was identified. De novo mutations account for 38% of cases. CONCLUSIONS: This study describes an exhaustive picture of EOHPN in an Italian referral genetic center and analyzes the molecular diagnostic rate of a heterogeneous cohort compared with one referred by a specialized pediatric center. Our data identify MPZ, MFN2, GDAP1, and SH3TC2 genes as the most frequent players in EOHPN. Our study underlines the relevance of a specific neurological pediatric expertise to address the genetic testing and highlights its importance to clarify possible unexpected results when neuropathy is only a secondary clinical sign of a more complex phenotype.

Navigating the complexities of encephalocraniocutaneous lipomatosis: a case series and review.

INTRODUCTION: Encephalocraniocutaneous lipomatosis (ECCL) is a rare congenital syndrome with complex skin, eye, and central nervous system (CNS) symptoms. Diagnosis and treatment are challenging due to its rarity and diverse manifestations. It often involves issues like porencephalic cysts, cortical atrophy, and low-grade gliomas in the CNS, resulting in developmental delays. The spinal cord is frequently affected, leading to problems like medullary compression and radiculopathy, causing back pain and sensory/motor deficits. Surgical interventions are reserved for symptomatic cases to address hydrocephalus or alleviate spinal lipomas. This article reviews a case series to assess surgical risks and neurological outcomes. CASE SERIES: We present a case series ECCL, focusing on the diffuse lipomatosis of the spinal cord and the intricate surgical procedures involved. A multi-stage surgical approach was adopted, with continuous neuromonitoring employed to safeguard motor pathways. We discuss clinical characteristics, imaging studies, and indications for neurosurgical interventions. DISCUSSION: ECCL is a complex syndrome. Diagnosis is challenging and includes clinical evaluation, neuroimaging, and genetic testing. Treatment targets specific symptoms, often requiring surgery for issues like lipomas or cerebral cysts. Surgery involves laminectomies, spinal fusion, and motor pathway monitoring. Thorough follow-up is crucial due to potential CNS complications like low-grade gliomas. Hydrocephalus occurs in some cases, with endoscopic third ventriculostomy (ETV) preferred over ventriculoperitoneal shunt placement. CONCLUSION: Neurosurgery for ECCL is for symptomatic cases. ETV is preferred for hydrocephalus, while the treatment for lipoma is based on the presence of symptoms; the follow-up should assess growth and prevent deformities.

A novel de novo variant in POLR3B gene associated with a primary axonal involvement of the largest nerve fibers.

BACKGROUND AND AIMS: POLR3B gene encodes a subunit of RNA polymerase III (Pol III). Biallelic mutations in POLR3B are associated with leukodystrophies, but recently de novo heterozygous mutations have been described in early onset peripheral demyelinating neuropathies with or without central involvement. Here, we report the first Italian case carrying a de novo variant in POLR3B with a pure neuropathy phenotype and primary axonal involvement of the largest nerve fibers. METHODS: Nerve conduction studies, sympathetic skin response, dynamic sweat test, tactile and thermal quantitative sensory testing and brain magnetic resonance imaging were performed according to standard procedures. Histopathological examination was performed on skin and sural nerve biopsies. Molecular analysis of the proband and his relatives was performed with Next Generation Sequencing. The impact of the identified variant on the overall protein structure was evaluated through rotamers method. RESULTS: Since his early adolescence, the patient presented with signs of polyneuropathy with severe distal weakness, atrophy, and reduced sensation. Neurophysiological studies showed a sensory-motor axonal polyneuropathy, with confirmed small fiber involvement. In addition, skin biopsy and sural nerve biopsy showed predominant large fibers involvement. A trio's whole exome sequencing revealed a novel de novo variant p.(Arg1046Cys) in POLR3B, which was classified as Probably Pathogenic. Molecular modeling data confirmed a deleterious effect of the variant on protein structure. INTERPRETATION: Neurophysiological and morphological findings suggest a primary axonal involvement of the largest nerve fibers in POLR3B-related neuropathies. A partial loss of function mechanism is proposed for both neuropathy and leukodystrophy phenotypes.

Asynchronous combined central and peripheral demyelination (CCPD) in a girl with anti-MOG positivity: A case report and review of the literature.

The occurrence of combined central and peripheral demyelination (CCPD) is rare, data are limited to small case and cohort studies, mainly concerning adults. In few patients positivity to anti MOG antibody is reported, thus widening the spectrum of anti-MOG associated disorders (MOGAD). We describe a 7-year-old girl with optic neuritis followed 8 years later by peripheral demyelination, with fluctuating anti-MOG antibody positivity at cell-based assay. From the review of the literature, MOGAD-CCPD appear very rare in childhood, especially with asynchronous course. Clinicians should keep this possibility in mind to better define diagnosis in atypical demyelination syndromes, with therapeutical implications.

Recurrent Sensory-Motor Neuropathy Mimicking CIDP as Predominant Presentation of PDH Deficiency.

INTRODUCTION: Pyruvate dehydrogenase complex (PDH) deficiency (Online Mendelian Inheritance in Man # 312170) is a relatively common mitochondrial disorder, caused by mutations in the X-linked PDHA1 gene and presenting with a variable phenotypic spectrum, ranging from severe infantile encephalopathy to milder chronic neurological disorders.Isolated peripheral neuropathy as predominant clinical presentation is uncommon. RESULTS: We report on a patient, now 21 years old, presenting at the age of 2 years with recurrent symmetric weakness as first symptom of a PDH deficiency. Neurophysiological evaluation proving a sensory-motor polyneuropathy with conduction blocks and presence of elevated cerebrospinal fluid proteins, suggested a chronic inflammatory demyelinating polyneuropathy. The evidence of high serum lactate and the alterations in oxidative metabolism in muscle biopsy pointed toward the final diagnosis. After starting nutritional supplements, no further episodes occurred. A hemizygous mutation in PDHA1 (p.Arg88Cys) was identified. This mutation has been previously described in five patients with a similar phenotype. A three-dimensional reconstruction demonstrated that mutations affecting this arginine destabilize the interactions between the subunits of the E1 complex. CONCLUSION: We summarize the clinical and genetic characteristics of one patient with PDH deficiency presenting isolated peripheral nervous system involvement. This study highlights that the diagnosis of PDH deficiency should be considered in children with unexplained peripheral neuropathy, even with features suggestive of acquired forms, especially in case of early onset and limited response to treatment. A simple analysis of lactic acid could help to target the diagnosis.In addition, we suggest that the residue Arg88 is the most frequently involved in this specific phenotype of PDH deficiency.

The SPTLC1 p.S331 mutation bridges sensory neuropathy and motor neuron disease and has implications for treatment.

AIMS: SPTLC1-related disorder is a late onset sensory-autonomic neuropathy associated with perturbed sphingolipid homeostasis which can be improved by supplementation with the serine palmitoyl-CoA transferase (SPT) substrate, l-serine. Recently, a juvenile form of motor neuron disease has been linked to SPTLC1 variants. Variants affecting the p.S331 residue of SPTLC1 cause a distinct phenotype, whose pathogenic basis has not been established. This study aims to define the neuropathological and biochemical consequences of the SPTLC1 p.S331 variant, and test response to l-serine in this specific genotype. METHODS: We report clinical and neurophysiological characterisation of two unrelated children carrying distinct p.S331 SPTLC1 variants. The neuropathology was investigated by analysis of sural nerve and skin innervation. To clarify the biochemical consequences of the p.S331 variant, we performed sphingolipidomic profiling of serum and skin fibroblasts. We also tested the effect of l-serine supplementation in skin fibroblasts of patients with p.S331 mutations. RESULTS: In both patients, we recognised an early onset phenotype with prevalent progressive motor neuron disease. Neuropathology showed severe damage to the sensory and autonomic systems. Sphingolipidomic analysis showed the coexistence of neurotoxic deoxy-sphingolipids with an excess of canonical products of the SPT enzyme. l-serine supplementation in patient fibroblasts reduced production of toxic 1-deoxysphingolipids but further increased the overproduction of sphingolipids. CONCLUSIONS: Our findings suggest that p.S331 SPTLC1 variants lead to an overlap phenotype combining features of sensory and motor neuropathies, thus proposing a continuum in the spectrum of SPTLC1-related disorders. l-serine supplementation in these patients may be detrimental.

Comparison of Qualitative and Quantitative Analyses of MR-Arterial Spin Labeling Perfusion Data for the Assessment of Pediatric Patients with Focal Epilepsies.

The role of MR Arterial-Spin-Labeling Cerebral Blood Flow maps (ASL-CBF) in the assessment of pediatric focal epilepsy is still debated. We aim to compare the Seizure Onset Zone (SOZ) detection rate of three methods of evaluation of ASL-CBF: 1) qualitative visual (qCBF), 2) z-score voxel-based quantitative analysis of index of asymmetry (AI-CBF), and 3) z-score voxel-based cluster analysis of the quantitative difference of patient's CBF from the normative data of an age-matched healthy population (cCBF). Interictal ASL-CBF were acquired in 65 pediatric patients with focal epilepsy: 26 with focal brain lesions and 39 with a normal MRI. All hypoperfusion areas visible in at least 3 contiguous images of qCBF analysis were identified. In the quantitative evaluations, clusters with a significant z-score AI-CBF ≤ −1.64 and areas with a z-score cCBF ≤ −1.64 were considered potentially related to the SOZ. These areas were compared with the SOZ defined by the anatomo-electro-clinical data. In patients with a positive MRI, SOZ was correctly identified in 27% of patients using qCBF, 73% using AI-CBF, and 77% using cCBF. In negative MRI patients, SOZ was identified in 18% of patients using qCBF, in 46% using AI-CBF, and in 64% using cCBF (p < 0.001). Quantitative analyses of ASL-CBF maps increase the detection rate of SOZ compared to the qualitative method, principally in negative MRI patients.

On the role of REM sleep microstructure in suppressing interictal spikes in Electrical Status Epilepticus during Sleep.

OBJECTIVE: Non-Rapid Eye Movement (NREM) sleep promotes the spread and propagation of Interictal Epileptiform Discharges (IEDs), while IEDs are suppressed during REM. Recently, it has been shown that the inhibitory effect on epileptic activity is mostly exerted by the phasic REM (PREM) microstate. This study aims at assessing if this holds true even in the extreme condition of IEDs activation during sleep represented by Electrical Status Epilepticus during Sleep (ESES). METHODS: eight patients affected by ESES, who underwent long-term EEG were included. REM was subdivided into phasic and tonic microstates along with the sleep scoring. IEDs count was carried out using a semi-automatic method and a Spike Index (SI) was calculated. RESULTS: The SI was significantly higher in NREM sleep than in REM. Within REM, the SI was significantly lower in PREM than in tonic REM (TREM). The SI was reduced by 84% in TREM with respect to NREM and by 97% in PREM with respect to NREM. Moreover, the SI was reduced by 87% in PREM with respect to TREM. CONCLUSIONS: PREM has a greater suppressive effect on epileptic activity even in the extreme IEDs activation during sleep typical of ESES. SIGNIFICANCE: Understanding the protective effect of PREM sleep on epileptic activity might be relevant for future therapeutic approaches.

Longitudinally Extensive Transverse Myelitis (LETM) and Myopericarditis in a 7-Month-Old Child with SARs-CoV-2 Infection.

INTRODUCTION: In the last few months, some pediatric cases with neurological and neuroradiological pictures related to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections have been reported, often associated with multisystem inflammatory syndrome (MIS-C). The most frequently encountered pediatric neurological complications seem to be postinfectious immune-mediated acute disseminated encephalomyelitis (ADEM)-like changes of the brain, myelitis, neural enhancement, and splenial lesions. Concomitant neurological and cardiac involvement has been reported only in MIS-C, although specific clinical details are often not fully available. METHODS: In this case report, a very young child infected with SARs-CoV-2 and diagnosed as longitudinal extensive transverse myelitis with concomitant myo-pericarditis is presented. RESULTS: A previously healthy 7-month-old girl presented with abrupt onset of generalized weakness with inability to sit up. She had had mild respiratory symptoms 1 week earlier. Spinal magnetic resonance imaging (MRI) showed a T2-hyperintense intramedullary lesion extending from C4 to T2, compatible with acute longitudinally extensive transverse myelitis (LETM). Cerebrospinal fluid analysis was negative.Echocardiography and blood tests were suggestive for myo-pericarditis. Real time polymerase chain reaction for SARS-CoV-2 on nasopharyngeal swab sample tested positive. She was promptly treated with high dose of steroids and immunoglobulin with satisfactory clinical response. CONCLUSION: To the evolving literature of neurological complications of SARs-CoV-2 infection, we add the youngest patient described to date with isolated LETM and concomitant cardiac involvement. Our case suggests that clinicians should be aware of this association, although difficult to recognize in infants. Practitioners are encouraged to consider aggressive first-line immunotherapies with the final aim to prevent permanent disability.

Sleep disturbances in craniopharyngioma: a challenging diagnosis.

Craniopharyngiomas are rare solid or mixed solid and cystic tumors that arise from Rathke's pouch remnants along the pituitary-hypothalamic axis, from the sella turcica to the brain third ventricle. Both the tumor and its treatment can lead to significant neurological and endocrinological complications. Due to the essential role of the hypothalamus in the complex neurophysiologic process of sleep, tumors involving the hypothalamic area may be responsible for disturbances in sleep-wake regulation with alterations in the circadian rhythm, sleep fragmentation, and increased daytime sleepiness. We report two cases of patients with craniopharyngioma, who came to our attention due to the occurrence of episodes characterized by psychomotor slowing and afinalistic limb movements, temporal and spatial disorientation, psychomotor agitation, and oneiric stupor like episodes. A comprehensive clinical data collection and a targeted diagnostic work-up led to a diagnosis of severe sleep disorder characterized by hypersomnia, altered sleep-wake rhythm, and sleep-related breathing disorder. In addition, the polysomnography revealed peculiar alterations in the sleep structure. The diagnostic work-up lead to an accurate differential diagnosis between epileptic seizures and episodes expressions of sleep disturbances. These clinical features can be challenging to diagnose and can lead to misdiagnosis and inappropriate treatment. Diagnosis of sleep disorders is crucial, considering the impact of sleep on general health, cognition, and neuropsychological functioning. These findings support the need to incorporate a comprehensive sleep evaluation in childhood brain tumor involving the suprasellar/hypothalamic region.

Multimodal approach in the pre-surgical evaluation of focal epilepsy surgery candidates: how far are we from a non-invasive ESI-based "sourcectomy"?

The management of drug-resistant patients with focal epilepsy is often challenging. Surgery is recognised as a useful and effective treatment option. The identification of the epileptogenic zone relies on the integration of clinical, neurophysiological, and neuroimaging findings. The role of non-invasive functional neuroimaging techniques has been reported to add diagnostic accuracy to first-line evaluations, avoiding invasive presurgical examinations in selected cases. In this view, we report the case of a 16-year-old male suffering from drug-resistant focal epilepsy with episodes rarely evolving to a bilateral tonic-clonic seizure. Conventional 1.5T and 3T MRI were considered uninformative. Based on electro-clinical data, focal cortical dysplasia was suspected. The epileptogenic zone was identified with the integration of further non-invasive functional neuroimaging techniques ([18F]-fluorodeoxyglucose positron emission tomography and arterial spin labelling), where electrical source imaging played the main role. All techniques pointed towards a cortical region, where a 7T brain MRI identified a signal alteration consistent with focal cortical dysplasia. A tailored resection of the lesion located in the inferior frontal sulcus was performed, guided by intraoperative electrocorticography (strip and depth electrodes). Postoperative seizure freedom was achieved. The histopathology confirmed the suspicion of focal cortical dysplasia type IIa. With this case report, we highlight the importance of a multimodal approach in the presurgical evaluation of candidates for epilepsy surgery, which, in selected cases, may allow invasive procedures, such as stereo-EEG, to be avoided in the investigation of the epileptogenic zone. Moreover, we underline the pivotal role of EEG source imaging, especially when focal cortical dysplasia is suspected.

Sleep disorders in Prader-Willi syndrome, evidence from animal models and humans.

Prader-Willi Syndrome (PWS) is a complex genetic disorder with multiple cognitive, behavioral and endocrine dysfunctions. Sleep alterations and sleep disorders such as Sleep-disordered breathing and Central disorders of hypersomnolence are frequently recognized (either isolated or in comorbidity). The aim of the review is to highlight the pathophysiology and the clinical features of sleep disorders in PWS, providing the basis for early diagnosis and management. We reviewed the genetic features of the syndrome and the possible relationship with sleep alterations in animal models, and we described sleep phenotypes, diagnostic tools and therapeutic approaches in humans. Moreover, we performed a meta-analysis of cerebrospinal fluid orexin levels in patients with PWS; significantly lower levels of orexin were detected in PWS with respect to control subjects (although significantly higher than the ones of narcoleptic patients). Sleep disorders in humans with PWS are multifaceted and are often the result of different mechanisms. Since hypothalamic dysfunction seems to partially influence metabolic, respiratory and sleep/wake characteristics of this syndrome, additional studies are required in this framework.

Musculoskeletal Features without Ataxia Associated with a Novel de novo Mutation in KCNA1 Impairing the Voltage Sensitivity of Kv1.1 Channel.

The KCNA1 gene encodes the α subunit of the voltage-gated Kv1.1 potassium channel that critically regulates neuronal excitability in the central and peripheral nervous systems. Mutations in KCNA1 have been classically associated with episodic ataxia type 1 (EA1), a movement disorder triggered by physical and emotional stress. Additional features variably reported in recent years include epilepsy, myokymia, migraine, paroxysmal dyskinesia, hyperthermia, hypomagnesemia, and cataplexy. Interestingly, a few individuals with neuromyotonia, either isolated or associated with skeletal deformities, have been reported carrying variants in the S2-S3 transmembrane segments of Kv1.1 channels in the absence of any other symptoms. Here, we have identified by whole-exome sequencing a novel de novo variant, T268K, in KCNA1 in a boy displaying recurrent episodes of neuromyotonia, muscle hypertrophy, and skeletal deformities. Through functional analysis in heterologous cells and structural modeling, we show that the mutation, located at the extracellular end of the S3 helix, causes deleterious effects, disrupting Kv1.1 function by altering the voltage dependence of activation and kinetics of deactivation, likely due to abnormal interactions with the voltage sensor in the S4 segment. Our study supports previous evidence suggesting that specific residues within the S2 and S3 segments of Kv1.1 result in a distinctive phenotype with predominant musculoskeletal presentation.

A novel approach to estimate trabecular bone anisotropy using a database approach.

Continuum finite element (FE) models of bones have become a standard pre-clinical tool to estimate bone strength. These models are usually based on clinical CT scans and material properties assigned are chosen as isotropic based only on the density distribution. It has been shown, however, that trabecular bone elastic behavior is best described as orthotropic. Unfortunately, the use of orthotropic models in FE analysis derived from CT scans is hampered by the fact that the measurement of a trabecular orientation (fabric) is not possible from clinical CT images due to the low resolution of such images. In this study, we explore the concept of using a database (DB) of high-resolution bone models to derive the fabric information that is missing in clinical images. The goal of this study was to investigate if models with fabric derived from a relatively small database can already produce more accurate results than isotropic models. A DB of 33 human proximal femurs was generated from micro-CT scans with a nominal isotropic resolution of 82 µm. Continuum FE models were generated from the images using a pre-defined mesh template in combination with an iso-anatomic mesh morphing tool. Each element within the mesh template is at a specific anatomical location. For each element within the cancellous bone, a spherical region around the element centroid with a radius of 2mm was defined. Bone volume fraction and the mean-intercept-length fabric tensor were analyzed for that region. Ten femurs were used as test cases. For each test femur, four different models were generated: (1) an orthotropic model based on micro-CT fabric measurements (gold standard), (2) an orthotropic model based on the fabric derived from the best-matched database model, (3) an isotropic-I model in which the fabric tensor was set to the identity tensor, and (4) a second isotropic-II model with its total bone stiffness fitted to the gold standard. An elastic-plastic damage model was used to simulate failure and post failure behavior during a fall to the side. The results show that all models produce a similar stress distribution. However, compared to the gold standard, both isotropic-I and II models underestimated the stress/damage distributions significantly. We found no significant difference between DB-derived and gold standard models. Compared to the gold standard, the isotropic-I models further underestimated whole bone stiffness by 26.3% and ultimate load by 14.5%, while these differences for the DB-derived orthotropic models were only 4.9% and 3.1% respectively. The results indicate that the concept of using a DB to estimate patient-specific anisotropic material properties can considerably improve the results. We expect that this approach can lead to more accurate results in particular for cases where bone anisotropy plays an important role, such as in osteoporotic patients and around implants.