New Insights into the Neuropsychological Profile and Intellectual Quotient Variability in Joubert Syndrome Compared to Other Congenital Cerebellar Malformations.

The neuropsychological characteristics of the cerebellar cognitive affective syndrome (CCAS) in congenital, non-progressive malformations of the cerebellum have been scarcely investigated, and even less is known for Joubert syndrome (JS), an inherited, non-progressive cerebellar ataxia characterized by the so-called molar tooth sign. The few studies on this topic reported inconsistent results about intellectual functioning and specific neuropsychological impairments. The aim of this research is to examine the neuropsychological profile of JS compared to other congenital cerebellar malformations (CM), considering individual variability of intellectual quotient (IQ) in the two groups. Fourteen patients with JS and 15 patients with CM aged 6-25 years were tested through a comprehensive, standardized neuropsychological battery. Their scores in the neuropsychological domains were inspected through descriptive analysis and compared by mean of MANOVA and ANOVA models, then replicated inserting IQ as covariate. The two groups showed a largely overlapping neuropsychological profile, consistent with CCAS. However, the JS group showed worse performance in visual-spatial memory compared to CM patients, although this difference was mitigated when considering IQ. These findings highlight a divergence between JS and other CM in visual-spatial memory, which might suggest a critical role of the cerebellum in recalling task-relevant memories and might inform rehabilitative interventions.

Cerebellar Heterotopia: Broadening the Neuroradiological Spectrum of KBG Syndrome.

KBG syndrome is a rare genetic disorder caused by heterozygous pathogenic variants in ANKRD11. Affected individuals have developmental delay, short stature, characteristic facial features, and other dysmorphic findings. To date, a spectrum of unspecific neuroradiological defects has been reported in KBG patients, such as cortical defects, white matter abnormalities, corpus callosum, and cerebellar vermis hypoplasia.Deep clinical and neuroradiological phenotyping and genotype of a patient presenting with mild cognitive and behavioral problems were obtained after written informed consent.We herein describe the first KBG patient presenting with cerebellar heterotopia, a heterogeneous malformation characterized by the presence of clusters of neurons within the white matter of cerebellar hemispheres.This novel association broadens the neuroradiological spectrum of KBG syndrome, and further prompts to investigate the potential functions of ANKRD11 in cerebellar development.

Recurrent, founder and hypomorphic variants contribute to the genetic landscape of Joubert syndrome.

BACKGROUND: Joubert syndrome (JS) is a neurodevelopmental ciliopathy characterised by a distinctive mid-hindbrain malformation, the 'molar tooth sign'. Over 40 JS-associated genes are known, accounting for two-thirds of cases. METHODS: While most variants are novel or extremely rare, we report on 11 recurring variants in seven genes, including three known 'founder variants' in the Ashkenazi Jewish, Hutterite and Finnish populations. We evaluated variant frequencies in ~550 European patients with JS and compared them with controls (>15 000 Italian plus gnomAD), and with an independent cohort of ~600 JS probands from the USA. RESULTS: All variants were markedly enriched in the European JS cohort compared with controls. When comparing allele frequencies in the two JS cohorts, the Ashkenazim founder variant (TMEM216 c.218G>T) was significantly enriched in American compared with European patients with JS, while MKS1 c.1476T>G was about 10 times more frequent among European JS. Frequencies of other variants were comparable in the two cohorts. Genotyping of several markers identified four novel European founder haplotypes.Two recurrent variants (MKS1 c.1476T>G and KIAA0586 c.428delG), have been detected in homozygosity in unaffected individuals, suggesting they could act as hypomorphic variants. However, while fibroblasts from a MKS1 c.1476T>G healthy homozygote showed impaired ability to form primary cilia and mildly reduced ciliary length, ciliary parameters were normal in cells from a KIAA0586 c.428delG healthy homozygote. CONCLUSION: This study contributes to understand the complex genetic landscape of JS, explain its variable prevalence in distinct geographical areas and characterise two recurrent hypomorphic variants.

Get Your Molar Tooth Right: Joubert Syndrome Misdiagnosis Unmasked by Whole-Exome Sequencing.

Joubert syndrome (JS) is a recessively inherited ciliopathy, characterized by a specific cerebellar and brainstem malformation recognizable on brain imaging as the "molar tooth sign" (MTS). Clinical signs include hypotonia, developmental delay, breathing abnormalities, and ocular motor apraxia. Older patients develop ataxia, intellectual impairment, and variable organ involvement. JS is genetically heterogeneous, with over 40 ciliary genes overall accounting for 65-75% cases. Thus, in recent years, the genetic diagnosis of JS has been based on the analysis of next-generation sequencing targeted gene panels. Since clinical features are unspecific and undistinguishable from other neurodevelopmental syndromes, the recognition of the MTS is crucial to address the patient to the appropriate genetic testing. However, the MTS is not always properly diagnosed, resulting either in false negative diagnoses (patients with the MTS not addressed to JS genetic testing) or in false positive diagnoses (patients with a different brain malformation wrongly addressed to JS genetic testing). Here, we present six cases referred for JS genetic testing based on inappropriate recognition of MTS. While the analysis of JS-related genes was negative, whole-exome sequencing (WES) disclosed pathogenic variants in other genes causative of distinct brain malformative conditions with partial clinical and neuroradiological overlap with JS. Reassessment of brain MRIs from five patients by a panel of expert pediatric neuroradiologists blinded to the genetic diagnosis excluded the MTS in all cases but one, which raised conflicting interpretations. This study highlights that the diagnostic yield of NGS-based targeted panels is strictly related to the accuracy of the diagnostic referral based on clinical and imaging assessment and that WES has an advantage over targeted panel analysis when the diagnostic suspicion is not straightforward.

Challenges and resources in adult life with Joubert syndrome: issues from an international classification of functioning (ICF) perspective.

BACKGROUND: Joubert Syndrome (JS) is a rare inherited neurodevelopmental disorder defined by a characteristic cerebellar and brainstem malformation (i.e. the molar tooth sign) and variable organ involvement. The aim of the present study was to describe functional limitations and disabilities in a large sample of adult patients with a diagnosis of JS. METHODS: We administered the International Classification of Functioning (ICF) checklist to thirty-six adult Italian patients with JS or their caregivers through telephone calls. RESULTS: None-to-mild impairment was documented for basic cognitive and mental functions, whereas severe deficit emerged for higher-order skills and language. A mismatch between individuals' capacity for daily activity and social participation and the actual performance in these fields emerged, suggesting that adults with JS may greatly benefit from external support from the caring environment. Indeed, specific facilitators were highlighted, including communication technologies as well as family members, healthcare professionals and peers support. Mild-to-severe barriers have been identified by adult patients with JS in the domains of services, systems and policies. CONCLUSIONS: These findings highlight challenges and barriers for adults with JS in areas of daily functioning that may be improved by investing in rehabilitation care models that embed social support programs and policies into clinical interventions.IMPLICATIONS FOR REHABILITATIONChildren with Joubert Syndrome, a child-onset rare inherited neurodevelopmental condition, are growing up and becoming adults; a life course approach in rehabilitation is needed;There is a substantial lack of information on the long-term adaptive daily functioning of children with a diagnosis of Joubert Syndrome;In this paper, the International Classification of Functioning (ICF) was applied to assess the daily functioning in people with JS;Severe deficits emerged for high-order skills and language, whereas the use of communication technologies and the engagement of family members were highlighted as key facilitators;These findings highlight the need for a change of paradigm in the care model of subjects with JS, with the embedding of social support in rehabilitation programs.

Cognitive rehabilitation in a child with Joubert Syndrome: Developmental trends and adaptive changes in a single case report.

We report the clinical and rehabilitative follow up of M, a female child carrying a compound heterozygous pathogenic mutations in the TCTN1 gene and affected by Joubert Syndrome (JS). JS is a congenital cerebellar ataxia characterized by "the molar tooth sign" on axial MRI, a pathognomonic neuroradiological malformation involving the cerebellum and brainstem. JS presents with high phenotypic/cognitive variability, and little is known about cognitive rehabilitation programs. We describe the therapeutic settings, intensive rehabilitation targets and outcome indexes in M's cognitive development. Using a single case evidence-based approach, we attempt to distinguish the effectiveness of the intervention from the overall developmental trend. We assume that an adequate amount of focused, goal directed treatment in a relative short period of time can be at least as effective as one provided in longer time, and much less interfering with the child's everyday life. We conclude by discussing specific issues in cognitive development and rehabilitation in JS and, more broadly, in cerebellar malformations.

Delineation and diagnostic criteria of Oral-Facial-Digital Syndrome type VI.

Oral-Facial-Digital Syndrome type VI (OFD VI) represents a rare phenotypic subtype of Joubert syndrome and related disorders (JSRD). In the original report polydactyly, oral findings, intellectual disability, and absence of the cerebellar vermis at post-mortem characterized the syndrome. Subsequently, the molar tooth sign (MTS) has been found in patients with OFD VI, prompting the inclusion of OFD VI in JSRD. We studied the clinical, neurodevelopmental, neuroimaging, and genetic findings in a cohort of 16 patients with OFD VI. We derived the following inclusion criteria from the literature: 1) MTS and one oral finding and polydactyly, or 2) MTS and more than one typical oral finding. The OFD VI neuroimaging pattern was found to be more severe than in other JSRD subgroups and includes severe hypoplasia of the cerebellar vermis, hypoplastic and dysplastic cerebellar hemispheres, marked enlargement of the posterior fossa, increased retrocerebellar collection of cerebrospinal fluid, abnormal brainstem, and frequently supratentorial abnormalities that occasionally include characteristic hypothalamic hamartomas. Additionally, two new JSRD neuroimaging findings (ascending superior cerebellar peduncles and fused thalami) have been identified. Tongue hamartomas, additional frenula, upper lip notch, and mesoaxial polydactyly are specific findings in OFD VI, while cleft lip/palate and other types of polydactyly of hands and feet are not specific. Involvement of other organs may include ocular findings, particularly colobomas. The majority of the patients have absent motor development and profound cognitive impairment. In OFD VI, normal cognitive functions are possible, but exceptional. Sequencing of known JSRD genes in most patients failed to detect pathogenetic mutations, therefore the genetic basis of OFD VI remains unknown. Compared with other JSRD subgroups, the neurological findings and impairment of motor development and cognitive functions in OFD VI are significantly worse, suggesting a correlation with the more severe neuroimaging findings. Based on the literature and this study we suggest as diagnostic criteria for OFD VI: MTS and one or more of the following: 1) tongue hamartoma(s) and/or additional frenula and/or upper lip notch; 2) mesoaxial polydactyly of one or more hands or feet; 3) hypothalamic hamartoma.