Neuropsychological phenotypes of 76 individuals with Joubert syndrome evaluated at a single center.

Joubert syndrome (JS) is a genetically heterogeneous ciliopathy characterized by hypo-dysplasia of the cerebellar vermis, a distinct hindbrain/midbrain malformation (molar tooth sign), and intellectual disability. We evaluated the neuropsychological profiles of 76 participants with JS in the context of molecular genetics and clinical covariates. Evaluations included neuropsychological testing, structured parental interviews, DNA sequencing, brain magnetic resonance imaging (MRI), electroencephalography (EEG), ophthalmologic examination, and assessment for renal and hepatic disease. On average, participants manifested Full Scale Intelligence Quotients (FSIQ) in the moderately to profoundly low range (M = 64.3 ± 15.3). Of the Wechsler index scores, verbal comprehension was least affected and processing speed was most affected. Receptive language was rated as better than expressive language on the Vineland Adaptive Behavior Scales-Second Edition. Those with abnormal EEG had a significantly lower FSIQ (n = 15; M = 50.7 ± 12.9) compared to participants with normal EEG (n = 39; M = 64.7 ± 16.3; p = .004). Participants taking psychiatric medications manifested a lower FSIQ (n = 20; M = 54.8 ± 13.2) than those not taking them (n = 42; M = 65.0 ± 17.2; p = .022). These correlations were also present in the TMEM67-related JS sub-cohort (n = 14). Based on parental assessment, psychiatric and behavioral problems were significantly more common than in the general population for all measures (p < .004 for all). The majority (65%) of individuals with JS have some degree of intellectual disability. Abnormal EEG is associated with lower neuropsychological function. Processing speed is a weakness, while verbal comprehension and receptive language are relative strengths. These findings may guide parents, teachers, therapists, and doctors to determine appropriate therapies, accommodations, and academic goals for individuals with JS.

Mutations in CEP120 cause Joubert syndrome as well as complex ciliopathy phenotypes.

BACKGROUND: Ciliopathies are an extensive group of autosomal recessive or X-linked disorders with considerable genetic and clinical overlap, which collectively share multiple organ involvement and may result in lethal or viable phenotypes. In large numbers of cases the genetic defect remains yet to be determined. The aim of this study is to describe the mutational frequency and phenotypic spectrum of the CEP120 gene. METHODS: Exome sequencing was performed in 145 patients with Joubert syndrome (JS), including 15 children with oral-facial-digital syndrome type VI (OFDVI) and 21 Meckel syndrome (MKS) fetuses. Moreover, exome sequencing was performed in one fetus with tectocerebellar dysraphia with occipital encephalocele (TCDOE), molar tooth sign and additional skeletal abnormalities. As a parallel study, 346 probands with a phenotype consistent with JS or related ciliopathies underwent next-generation sequencing-based targeted sequencing of 120 previously described and candidate ciliopathy genes. RESULTS: We present six probands carrying nine distinct mutations (of which eight are novel) in the CEP120 gene, previously found mutated only in Jeune asphyxiating thoracic dystrophy (JATD). The CEP120-associated phenotype ranges from mild classical JS in four patients to more severe conditions in two fetuses, with overlapping features of distinct ciliopathies that include TCDOE, MKS, JATD and OFD syndromes. No obvious correlation is evident between the type or location of identified mutations and the ciliopathy phenotype. CONCLUSION: Our findings broaden the spectrum of phenotypes caused by CEP120 mutations that account for nearly 1% of patients with JS as well as for more complex ciliopathy phenotypes. The lack of clear genotype-phenotype correlation highlights the relevance of comprehensive genetic analyses in the diagnostics of ciliopathies.

Pre- and Postnatal Neuroimaging of Congenital Cerebellar Abnormalities.

The human cerebellum has a protracted development that makes it vulnerable to a broad spectrum of developmental disorders including malformations and disruptions. Starting from 19 to 20 weeks of gestation, prenatal magnetic resonance imaging (MRI) can reliably study the developing cerebellum. Pre- and postnatal neuroimaging plays a key role in the diagnostic work-up of congenital cerebellar abnormalities. Diagnostic criteria for cerebellar malformations and disruptions are based mostly on neuroimaging findings. The diagnosis of a Dandy-Walker malformation is based on the presence of hypoplasia, elevation, and counterclockwise upward rotation of the cerebellar vermis and cystic dilatation of the fourth ventricle, which extends posteriorly filling out the posterior fossa. For the diagnosis of Joubert syndrome, the presence of the molar tooth sign (thickened, elongated, and horizontally orientated superior cerebellar peduncles and an abnormally deep interpeduncular fossa) is needed. The diagnostic criteria of rhombencephalosynapsis include a complete or partial absence of the cerebellar vermis and continuity of the cerebellar hemispheres across the midline. Unilateral cerebellar hypoplasia is defined by the complete aplasia or hypoplasia of one cerebellar hemisphere. Familiarity with these diagnostic criteria as well as the broad spectrum of additional neuroimaging findings is important for a correct pre- and postnatal diagnosis. A correct diagnosis is essential for management, prognosis, and counseling of the affected children and their family.

Vestibular impairment in patients with Charcot-Marie-tooth disease.

OBJECTIVE: This case-control study aimed to determine whether the imbalance in Charcot-Marie-tooth (CMT) disease is caused only by reduced proprioceptive input or whether the involvement of the vestibular nerve is an additional factor. METHODS: Fifteen patients with CMT disease (aged 48 ± 17 years; 8 women) underwent cervical vestibular-evoked myogenic potentials, which reflect otolith-spinal reflex function, and quantitative horizontal search-coil head-impulse testing, which assesses the high-acceleration vestibulo-ocular reflex of the semicircular canals. RESULTS: Relative to healthy age-matched control subjects, cervical vestibular-evoked myogenic potentials were found to be impaired in 75% of patients (average p13 latency: 23.0 ± 2.7 milliseconds, p = 0.01; average n23 latency: 29.0 ± 1.8 milliseconds, p = 0.01) and the quantitative head-impulse test in 60% of patients (average gain ± 1 SD: 0.67 ± 0.24, p < 0.001). All patients with head-impulse test impairment also showed cervical vestibular-evoked myogenic potential abnormalities, while the reverse was not true. CONCLUSIONS: We conclude that the neuropathic process in patients with CMT disease frequently involves the vestibular nerve and that cervical vestibular-evoked myogenic potentials may be more sensitive than quantitative head-impulse testing for detecting vestibular involvement, in particular at an early disease stage.

Phenotypic spectrum and prevalence of INPP5E mutations in Joubert syndrome and related disorders.

Joubert syndrome and related disorders (JSRD) are clinically and genetically heterogeneous ciliopathies sharing a peculiar midbrain-hindbrain malformation known as the 'molar tooth sign'. To date, 19 causative genes have been identified, all coding for proteins of the primary cilium. There is clinical and genetic overlap with other ciliopathies, in particular with Meckel syndrome (MKS), that is allelic to JSRD at nine distinct loci. We previously identified the INPP5E gene as causative of JSRD in seven families linked to the JBTS1 locus, yet the phenotypic spectrum and prevalence of INPP5E mutations in JSRD and MKS remain largely unknown. To address this issue, we performed INPP5E mutation analysis in 483 probands, including 408 JSRD patients representative of all clinical subgroups and 75 MKS fetuses. We identified 12 different mutations in 17 probands from 11 JSRD families, with an overall 2.7% mutation frequency among JSRD. The most common clinical presentation among mutated families (7/11, 64%) was Joubert syndrome with ocular involvement (either progressive retinopathy and/or colobomas), while the remaining cases had pure JS. Kidney, liver and skeletal involvement were not observed. None of the MKS fetuses carried INPP5E mutations, indicating that the two ciliopathies are not allelic at this locus.

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.